FulanoDetail-
Project Log 90: "Final" Project Log.
12/03/2024 at 20:39 • 2 commentsI started this project log on a Sunday, 08/09/2024, at 07:59.
However, for the last 3 months, I've been both procrastinating and slowly making progress on the project.
Still, I feel like in the entire last month I kept doing a whole bunch of nothing, literally doing anything else, avoiding at all costs this project since I have absolutely no energy to continue the project (for now).
Well, my intention was to finish the project and 3D model everything before the end of November, because day 24 would be the anniversary of 2 years of this damned project.
Well, that didn't happened.
Even so, the google document that I initially intended on post here ended up with 368 pages.
I literally cannot post here in Hackaday, but I had the intention of making a summary (which I also didn't finish).I feel like everything I've been doing so far was just rambling useless things that won't add anything substantial to the project, and again, the text ended up a gigantic mess.
I do intend on continuing the project, but goddamn, I don't feel like I can actually finish it right now.
In any manner, I will leave the link here, so you can check right now and hopefully find something useful on it:Google Doc: DIY Mech/Exoskeleton suit: Project Log 90.
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Project Log 89: Screw it, let's freaking do it.⁹
09/07/2024 at 23:51 • 0 commentsThe project log 87 got so long that I had to split it into project log 88 and 89, sorry for that, lol.
Manufacturing The Mech parts:
I still need to make the 3D model, calculate weight and all that stuff, but I just want to get this out of the way first.
Obviously, I will run into more details when I actually start building, linking all the proper tutorials that I followed, precise steps that I took and the like (yes, on the details I say this is more of a guide, but being frank, this way I will be forced to actually organize my stuff, lol).
For the Coils of stator, bearings and couplings:
- Find a soda can for aluminum scrap.
- Triturate all of it, take out the paint, clean it up as much as possible.
- Take the proper weight of aluminum welding rods 4043 and 2024, fluxes etc.
- Make the microwave kiln with sodium silicate and silicon carbide.
- Use the same materials to make an aluminum wire extruder (first I thought of doing that idea of pouring paraffin wax in sand for a wire mold, but that would take too long.
- Purify the aluminum scrap as much as possible, taking out dirt, humidity and the like (I don’t want an aluminum steam explosion in my face).
- Buy all the safety equipment for forging aluminum (I want to DIY everything, but molten metal is risky).
- Make a pile of dirt sacks around the kiln and the extruder for extra safety.
- Heat both the kiln and the extruder so there isn’t a thermal shock explosion.
- Make the process of manufacturing aluminum wire at a safe distance.
- Then use a cheap Carbide Wire DrawPlate to smooth out any imperfections on the surface.
- Anodize the aluminum wire for insulation, just like enameled wire, it will serve for protection and avoid short-circuits.
- Make the aluminum coils into the desired shapes using 3D printed molds and the like.
- Heat treats the aluminum coils in an artificial aging process for hours or days.
- Infuse the coils with a mixture of polymer (such as HDPE) composite with thermal paste for heat dissipation (DIY or not) and a thermochromic paint (DIY or not if possible) in order to make the visualization of heat easier.
- You can add a ferrite polymer composite core or not to the center of these coils for a slightly better magnet field.
- Position the wired coils into the stator’s molds, connect them with the 3 phase correctly (check and recheck multiple times, any mistakes will be hard to correct) and inject the mold with structural polymer for stator completion.
- Then I would use good insulating materials around the motor housing to avoid frost build up.
- That also applies to bearings, couplings, servos etc.
I was thinking of making the mold using glass panels, they are made with incredible tolerances (in the micrometer range) and thus, the rotors would also have those tolerances if made with the same surface.
The space between the coils, magnets and the like would be dependent on the precision of the mold, which on another hand, would be limited by the method of fabrication.
I was thinking of using resin 3D printing (in this case, hire a 3D printing business for this specific case).
But in hindsight, I feel that it would be unnecessarily troublesome, I could do it with laser printed plastic schematics with measurements glued to a glass and align the parts with it.
I was even thinking of using an DIY light/shadow projector, the bigger the projected shadow/light, the higher the precision. But you would need a lot of space for that.
For the permanent magnet rotors:
- Find and/or buy Alnico/Neodymium magnet powder or turn Alnico/Neodymium magnets into powder. Do that in some oil because neodymium is highly reactive with oxygen.
- Mix it with a 95% magnet powder to 5% polymer composite, just like the coils, the polymer, thermal paste and thermochromic paint. Some magnets can survive from up to hundreds of degrees celsius, but not the plastic.
- Do that under a strong magnetic field, so the particles will align properly during injection and curing.
- Use a magnetizer to turn these magnets into permanent magnets.
- Position the magnets into the rotor's molds (check and recheck multiple times, any mistakes will be hard to correct) and inject the mold with structural polymer for rotor completion.
- Then I would use good insulating materials around the motor housing to avoid frost build up.
- That also applies to bearings, couplings, servos etc.
A halbach array is an interesting manner of increasing the magnetic field strength of a permanent magnet rotor and the like, even with the possibility of building personalized magnets, I don’t think it is worth the trouble.
For the Assembly:
I still didn’t 3D model it, but I was thinking of separating the motor and the hydraulic pump in two separated chambers, and both would be coupled together with an electromagnetic clutch.
There are many types of electromagnetic clutches out there, but, depending on how easier it is to calculate, predict and build, I would use eddy current clutches and/or bearings. The rotor would have an induction coil for wireless power transmission to power its electromagnets for its contactless electromagnetic bearings and clutches mechanisms, then the pump would have either an aluminum plate for the eddy current formation or an DC current electromagnet with a full bridge rectifier to follow the electric motor.
Either way, both would be floating in their respective chambers, the electric motor being cooled by its -70ºC coolant and the pump cooled by the water it is pumping.
For a clutch or a bearing to work, they need a power that can resist the forces they are receiving, which would be really powerful. 10 pieces of 1000 volts 20 amps cost 50 reais (10 dollars), so depending on the importance of the piece in question, I could make an AC to DC conversion using a full-bridge rectifier for the system.
For the Cooling System:
Well, it ends up that I won’t need to cool down aluminum wires to -70ºC as explained in the 3D modeling section.
Observation: Although the system doesn’t use flammable products, it is still extremely dangerous to touch a liquid at -70ºC (imagine being splashed by it).This, of course, is just to make Aluminum as conductive/resistive as copper while being as light a possible. If -70ºC is too much (and I do believe it is too much), you should increase the size/weight by 1.54 times in order to compensate for the resistivity at ambient temperature.
When I actually 3D model everything and calculate its weight, I will decide whether or not I should mix the aluminum coils with copper and use a conventional freezer cooler (-17ºC).
Just like I linked before, I would use the pulse tube cryocooler system built by Hyperspace Pirate’s channel.
However, since I don’t have access to the same copper tubing he uses (because it is expensive and a little hard to mess with), I will be using the equivalent sizing and tubing made using plastic parts mixed with thermal paste for heat exchange, either for cooling or dispersing heat.
I would actually attempt to make a radial piston system also driven by the motor and/or hydraulic pump, either with an electromagnetic or physical clutch/coupling.
This time, however, I wouldn’t care much about maximum efficiency, as long as it performs really well, I don’t care that much.
If there is more than one electric motor chamber, the coolant will be pumped through insulated hoses around the body of the mech.
The heat exchanger would be an hybrid of liquid cooled that would be pumped through a radiator with a pump integrated on the electric motor itself and a section for stacked peltier cooling. The peltier plates would be only used during highly demanding moments for super fast cooling at the cost of efficiency, in fact, you can cool things to about -40ºC to -50ºC using stacked peltier plates in a very compact and light manner.
But that can change if I ever find a better way of getting rid of the heat generated by the system in a way that is faster, like having a bigger mass of coolant.
The cooling system will also be used to cool down the electronic parts.
About Liquid Metal Magnetohydrodynamic Generator (LMMHDG): Not Practical, back to Molten Carbonate Fuel Cell.
Since last project, I was in doubt on how to make it an efficient and inductive system, but a good way of doing it would be to attach a flipping valve at the end of the air blower that switches between two vacuum ejectors-gas chamber hybrids.
This way the liquid would go back and forth, creating an inducting current on the coils.
One thing that concerns me is that the fuel and oxygen would eventually contaminate the molten metals since it would constantly be at 700ºC, I would need a really non-reactive metal.
Well, it seems like I either find a way of this working or I need to change back to Molten Carbonate Fuel Cells.
Because no metal would stay non-oxided with oxygen being blown into it while molten. ChatGPT suggested platinum, gold and silver however.
Other chatgpt suggestion:
“At temperatures between 400°C and 700°C, some materials, including certain molten salts and carbonates, can be conductive and molten. Here are a few examples:
Conductive Molten Carbonates:
Sodium Carbonate (Na₂CO₃):
Melting Point: ~851°C
State at 400°C to 700°C: Solid (but molten above 851°C)
Conductivity: In its molten state, sodium carbonate is ionic and conductive. However, it is not molten within the 400°C to 700°C range.
Potassium Carbonate (K₂CO₃):
Melting Point: ~891°C
State at 400°C to 700°C: Solid (but molten above 891°C)
Conductivity: Similar to sodium carbonate, it is conductive when molten but remains solid in your specified temperature range.
Lithium Carbonate (Li₂CO₃):
Melting Point: ~723°C
State at 400°C to 700°C: Close to its melting point; it may begin to melt near 700°C.
Conductivity: When molten, lithium carbonate is conductive due to its ionic nature.”
Ironic that I would rely on fricking carbonates to escape from the molten carbonate fuel cell.
It also suggested adding other materials to the molten thing in order to make it more conductive, such as Silicon Carbide, Tin Oxide and Indium Oxide.
Well, this presents another problem.
On the molten carbonate fuel cell you don’t care too much if the carbonates are actually in liquid state, you just need them to be ionically conductive.
But here, with the LMMHDG, you actually need materials to be in liquid state.
But then you would need temperatures ranging from 700ºC to 1600ºC.
When I think of a high temperature binder material, I think of sodium silicate. But it melts at 1000ºC, even binders for ceramic fibers only survive until 1200ºC.
I was thinking of even using the manufacturing technique of NASA's thermal tiles of fused silica fibers, but they can only survive until 1200ºC also.
Which binding materials could survive temperatures up to 1600ºC?
At this point isn't it better to just make a turbine engine using these insane materials?
ChatGPT suggested calcium aluminate cement and phosphate binders, I couldn’t find either to buy, but I found a tutorial on how to make a phosphate.
The maximum refractory cement I found was 1400ºC…
I did find plates that can easily reach 1600ºC or more, but the problem is that I need to make something in a customized shape and size that will contain molten metal.
You know what? Screw it, I will just add a thermometer to start cooling the whole structure at 1300ºC.
However, the more I stop talking about it, the more I think the molten carbonate fuel cell seems more attractive… I just started to wonder about using liquid metal magnetohydrodynamic generators because the molten fuel cell has a maximum efficiency of 50% and slow power spikes on demand.
I’m assuming that all of this trouble will allow the LMMHDG to achieve efficiencies over 70% or even more. All of that because of this blasted article:
https://www.mdpi.com/2071-1050/15/16/12619
But according to other sources, the maximum efficiency achieved using the carnot cycle is 60%.
Then how can the system reach 70% of efficiency?
There is the Brayton Cycle, the Rankine Cycle and the Carnot Cycle, one consecutively more efficient than the other 40% and 45%. Although the Carnot is a hypothetical thermal engine, it only calculates the maximum amount of efficiency achievable without any kind of losses.
So, since I was thinking of using something similar to a turbine engine, but using the liquid metal, it would be safe to assume that at the best possible performance, I would still only reach 40% with this system.
Even a Rankine-Brayton Combined Cycle (and other types of combined cycles) can still only reach a maximum 60% of efficiency.
That, of course, is the upper limit of thermal engines, like piston engines, gas turbine engines, steam engines etc. So these values may not apply to other types of energy generation, like hydro-electrical turbines and Fuel Cells.
Now that I think about that, since I can make a hydraulic pump/actuator 95% efficient using the diaphragm piston thingie, then why wouldn’t that work with combustion engines?
Of course, you would need a really temperature resistant material for that, but I mean… If the combustion chamber is a good insulator for a high temperature combustion chamber, the piston rod has almost no friction, it has a heat exchanger and a regenerator… That would be the closest possible engine to a Carnot Engine.
Of course, that would be a stretch, especially because the Carnot Engine is the more efficient the higher the difference between the cold and the hot part. Which you would have a hard limit to maximum 1000ºC for flexible things.
Wouldn’t that be just a Stirling Engine tho?
Since the maximum efficiency of Stirling Engines is 40%, then maybe you could surpass that limit if you had a vacuum ejector turbine engine. The combustion chamber would take both microwave, fuel and high pressure air, the combustion channel would make even more heat and thus, even more air flux, creating a vacuum. You could add electric turbines to the system, which would both rotate the compressors and the electric generators.
The incoming air would be both used on the coolers, on the heat-exchange/regenerator and as the air supply for the combustion.
I feel like I already talked about this on this project before…
It also got me wondering: would you be able to make an electromagnetic field around the turbine blades to protect against the plasma generated?
This also got me wondering:
Thermoelectric Generators (TEG) have low efficiency (<10%), but by stacking multiple layers, the heat generated by the heat source and the electrical resistivity (that would also turn into heat) would eventually be converted into electricity with enough layers, no? Wouldn’t that increase efficiency?
Edit: Accordingly to this article, kinda yes, kinda no. They only achieved 15%.
I couldn’t find any paper that explored this possibility, so I'm probably wrong. Especially if you take into consideration that the bigger the heat difference between the hot part and the cold part, the higher the efficiency/performance of the system.
If the system is completely solid, wouldn’t that mean that the difference in heat between the cold and hot parts is so minuscule that no energy would be produced?
The only way I could think that this could be somewhat “solved” would be to have as many many cooling and heat systems as possible to maintain the difference between each layer as practical as possible, even if that means diverting heat from the heat source to more distant layers in order to increase their heat difference.
Making a solid 3D system like that already makes a knot on my brain tho…
I said that, but I was thinking of it more like a “river” with two parallel “liquids” with different temperatures, the more the “rivers” flow, the more equal the temperature starts getting. When equilibrium is reached (aka both sides have the same temperature) the two “rivers” separate, what was the hot one goes back into the heat source and what was the cooler one goes to the outside for dissipating its heat. Then both “rivers” unite again until equilibrium is reached again, repeating the process.
You could literally have “rivers” doing that with liquids in insulated tubes, or you could have solid materials spiraling around the heat and cooling sources.
Or am I just thinking too much? You could get the same result with a spiral style cooling system, where the inner wall is hotter than the outer side of the wall because the heat source already distributes its heat to the cooling flow.
Kinda like Joule-Thompson cooling and/or cascade cooling, but on the reverse.
If Hyperspace Pirate is correct, then this system has 0.1% of efficiency, because this is just a reverse heat engine, just like the carnot cycle. And the most efficient type of heat engine is the Pulse Tube Cooler or Stirling Heat Engine, with an efficiency of 40%.
Huh, the carnot cycle is useful both for heating and cooling… hm
See? That is why I like to write down everything about my thought process. I learn a bunch just thinking about why certain things work or don’t work (even though they are obvious things for everyone with 2 working brain cells, not my case).
That may also explain why the idea of a vacuum ejector-turbine hybrid may not work: you can’t use the same working system to cool down systems.
… But that is even accurate, tho? Turbo Compressors are a thing, and they are part of the Carnot Cycle.
About Molten Carbonate Fuel Cells:
Embarrassingly, only now I saw the comments made by latinflavorxd on my project logs about fuel cells (damn, it took me 1 entire year to answer him, sorry for that).
He suggested using methane to reform into hydrogen gas to feed into a Solid Oxide Fuel Cell. Solid Oxide Fuel Cells are really hard to DIY and really expensive to buy, as far as I could search on the subject, of course. About the hydrogen since it is 20% hydrogen by weight, but unfortunately, reforming or using any solid hydride storage of hydrogen gas with anything below 40% of hydrogen per weight is really not viable (as far as I could actually calculate).
As I answered him, I also thought of using the hydrogen and carbon released from the Methane reforming to react in an hydrogen alkaline fuel cell and in a carbon molten carbonate fuel cell.
I would get 31 megajoules per kg of liquid methane (around 2.3 liters), and since Methane is 55 megajoules per kilogram, that would make the whole system have an efficiency of 56%.
Of course, assuming the carbon fuel cell will take the carbon released from the reforming process and the plasmatron reforming wouldn't require too much energy, which I'm not very confident that it would work.
Taking into consideration the difficulty of storing methane (in a DIY method), reforming it and consuming it, I don't think this would be much practical in a DIY system. But it could be really interesting in other scenarios.
By the way the materials used to make solid oxide fuel cells:
“The main materials used in the different components of a solid oxide fuel cell (SOFC) are:
Electrolyte: Yttria-stabilized zirconia (YSZ) is the most commonly used electrolyte material in SOFCs. It is a solid oxide material that conducts negative oxygen ions from the cathode to the anode. [1][2]
Cathode: Strontium-doped lanthanum manganite (LSM) or a composite of LSM and YSZ is typically used as the cathode material. The cathode is responsible for the reduction of oxygen into oxygen ions. [1]
Anode: Nickel-YSZ cermets (a composite of nickel and YSZ) are the most common anode material. The anode must be porous to allow fuel flow and must conduct both electrons and ions. It is also often the structural support layer. [1][2][3]
Interconnect: Metallic alloys such as chromium-based alloys or lanthanum strontium manganite (LSM) are used as the interconnect material. The interconnect provides electrical connection between the individual cells in an SOFC stack. [2]
Sealant: Glass-ceramic or glass-based materials are typically used as sealants to prevent gas leakage between the different components of the SOFC. [2]
https://www.sciencedirect.com/science/article/abs/pii/S0955221901001200
https://www.fuelcellstore.com/fuel-cell-components/sofc-materials
https://en.wikipedia.org/wiki/Solid_oxide_fuel_cell”
Off-topic:
I just want to get this thing out of my brain.
I don’t remember if I talked about this before, but essentially, if you heat copper acetate or copper formate, it turns into pure copper and liberates flammable gasses (which you can carefully burn in a chimney), formaldehyde gas (which you can neutralize with hydrogen peroxide aka oxygenated water) and a little bit of copper vapor (which you definitely need to vent through activated carbon).
These reactions can be used to make metallic copper mirrors, which are good at reflecting infrared light.
(the same goes to silver acetate)
Also, quite useless thing, but I was thinking: if you use that idea of using really powerful incandescent filament for light bulbs on the kilowatt range to make an infrared emitter “melter”, maybe you could make an energy blade of some sorts.
The idea would be to use reflective articulated tubes (like I said in the previous project log) like optical fibers and direct the output in some edge or knuckle style weapon in order to make a heat blade/power gauntlet.
Some materials are invisible in the infrared spectrum while opaque in the visible light, like potassium chloride (KCL) and sodium chloride (table salt), so that is what you could make the tip out of (but both melt around 700-800ºC). But if you mix it with sodium silicate… Maybe it would be able to last longer.
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Completely useless to anything in real life, but so cool tho…
I just don’t know if you would need to make it a pulsed infrared emitter (like the laser) or a continuous infrared emitter. If you need to make it a pulsed one, you need to make the filament as thin/resistive as possible, so the pulses can have enough time to emit infrared radiation. If it is continuous, maybe you would need a really thick incandescent filament?
Oh, by the way, about the laser thruster:
I still don’t know how much energy it would require for a given amount of thrust, but maybe the Kinetic energy calculator would help?
If you accelerate, let’s say, 1000kg at the same speed of the gravity (9,807 m/s²), you would need around 50,000 joules of energy. Even though gravity is measured in acceleration, not speed.
So I guess that’s the amount of energy per second required to keep something into the air? Since the speed is measured in meters per second…?
ChatGPT agrees with me, but I’m not very confident about it anyway…
On the Wikipedia article about ablative laser propulsion it has 5000 seconds of specific impulse, then I asked GPT to calculate with this information. It said it would either need 35 megajoules or 240 megajoules.
Poe on Quora answered:
“To calculate the energy required to provide 500 lbs of thrust on an aircraft, we can use the relationship between thrust, fuel flow rate, and the energy content of the fuel.
Assuming the aircraft is using a hydrogen-oxygen rocket engine, the energy required can be calculated as follows:
Thrust (F) = 500 lbs
Specific Impulse (I_sp) for a hydrogen-oxygen rocket engine is typically around 450 seconds.
The relationship between thrust, mass flow rate (m_dot), and specific impulse is:
F = m_dot * I_sp * g_0
where g_0 is the acceleration due to gravity (9.81 m/s²)
Rearranging this equation, we can solve for the mass flow rate:
m_dot = F / (I_sp * g_0)
m_dot = 500 lbs / (450 s * 9.81 m/s²)
m_dot = 0.1136 kg/s
The energy content of hydrogen is approximately 141.8 MJ/kg.
The energy required per second to provide 500 lbs of thrust is:
Energy = m_dot * Energy content of hydrogen
Energy = 0.1136 kg/s * 141.8 MJ/kg
Energy = 16.1 MJ/s”
Therefore, it takes approximately 16.1 megajoules (MJ) of energy per second to provide 500 lbs of thrust on an aircraft using a hydrogen-oxygen rocket engine.”
If you replace the 500 lbs by 2200 lbs (1000kg) and the specific impulse with 5000 seconds it gives 6.3 MJ/s.
Of course, that is assuming the energy density of said laser is the same as liquid hydrogen (141.8), but I don’t quite know what should be the energy density of an infrared laser made using incandescent filaments. 😐
Besides, is this equation even correct? If I use something with 1000 MJ/kg, the consumption only increases.
So how the hell do I calculate how much energy I would need for 1000kg of thrust using a pulsed laser thruster similar to a pulsejet?
In any manner, the whole idea of the laser guns and laser thrusters is that before every “shot” of infrared emission, a tunnel of ionized air will be made using a Nd:glass donut tube. After that, the infrared light will be emitted through this ionized tunnel at its target, like an optical fiber.
But that gave me the idea of using it as an energy shield instead.
You would make the ion optical tunnel in the shape you want, in this example, a cone, and then the infrared light would be emitted inside of it. Reflecting until its energy is dispersed as heated plasma, then you repeat the process billions of times per second.
The only shape that I could think of realistically making was a cone/pyramid shape, unfortunately, I couldn’t think of a way of making an ion tunnel using lasers with a more convenient shape, like an actual shield of some sorts.
On top of that, it would also need to be really, really precise on its timing, or else all the infrared light (and visible light) would be emitted in every direction instead of being fully absorbed by the plasma bubble.
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There is also the possibility of making the laser curve using the thermal lensing effect, but I really don’t know how that would work in such a short path (neither in a long path, lol).
You can bend a laser’s path using a gradient of sugar content on water, I just don’t know how you would do that in the middle of the air using the heat gradient of a laser.
I asked this on quora, but people keep ignoring the gradient part and straight up saying “that is just a trick, you can’t bend a laser outside of a black hole”, and I can only judge in silence.
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Project Log 88: Screw it, let's freaking do it.⁸
09/07/2024 at 23:41 • 0 commentsThe previous project log got so full I had to split it up to this one.
I added more information to the bot:
“To determine whether the characteristics of a brushless motor with a specific magnetic flux density are considered good or bad, you can evaluate several factors that influence motor performance. Here's how you can approach this:
Magnetic Flux Density Values: For brushless motors, the magnetic flux density (B) typically ranges from 1 to 1.7 teslas (T) for efficient designs. Your calculation of 1 to 2.5 T for an 80 kW motor at 4000 RPM and 300 Nm of torque indicates that you might be targeting higher performance levels. However, while NdFeB magnets can achieve values above 1.0 T, exceeding the recommended limits can lead to issues such as irreversible demagnetization, especially under high thermal stress or external demagnetizing fields [1][5].
Torque and Current Relationships: The torque produced by the motor is directly related to the magnetic fields in the air gap, which are influenced by the current flowing through the windings. When designing your motor, you should consider the maximum current that your motor can handle without overheating. For instance, typical current densities for brushless motors can be around 16 A/mm² [1]. If your design requires higher current densities, it may affect the thermal management of the motor and ultimately its performance.
Torque Ripple and Performance Consistency: Low torque ripple is desirable in brushless motors. A torque ripple of about 2% is considered very low and indicates a smooth operation of the motor [4]. You should aim for designs that minimize fluctuations in torque to improve overall performance.
Thermal Considerations: The performance of magnets, particularly the residual flux density and coercivity, is temperature-dependent. The temperature coefficients for NdFeB magnets indicate that the residual flux density can decrease by approximately 0.10% per °C [6]. Therefore, it is critical to account for the operating temperature range of your motor to ensure that it can maintain performance without demagnetizing.
Design Innovations: Consider innovative rotor designs that can help minimize leakage flux and maximize torque density. Structures like flux barriers can help concentrate the magnetic flux and reduce unwanted leakage, thus enhancing the overall output power density [5].
The maximum magnetic flux for neodymium magnets, particularly the NdFeB (neodymium-iron-boron) type, is a critical factor in the design and performance of brushless motors. The residual flux density (Br) for these magnets is typically around 1.12 T (teslas) at room temperature (20 °C) [1].
Flux barriers in the stator yoke of an electric machine are typically made from non-magnetic materials or air gaps. The primary purpose of these barriers is to increase the magnetic resistance (reluctance) in specific areas, thereby controlling the magnetic flux path and reducing unwanted harmonics.
Here are some common materials and methods used to create flux barriers:
Air Gaps: Simple air gaps are often used as flux barriers. By cutting specific shapes or slots into the stator yoke, designers can create regions where magnetic flux is impeded or redirected.
Non-Magnetic Materials: Materials such as plastics, ceramics, or composites with low magnetic permeability can be inserted into the stator yoke to serve as flux barriers. These materials do not conduct magnetic flux, effectively creating a high reluctance path.
Non-Magnetic Metals: In some cases, non-magnetic metals like stainless steel or aluminum may be used. These materials are structurally strong but have low magnetic permeability, making them suitable for certain designs.
The choice of material depends on factors such as the specific application, cost, structural requirements, and the desired magnetic properties.”
So, magnetic flux around 1 tesla on each slot, the flux barriers are already part of the design since I plan to make everything out of plastic. Of course, the 1 tesla per slot can change if you use an electromagnet on the rotor…
But I’m feeling like this won’t be that simple to achieve, especially because of the shape of the coil.
Too thin and long or too wide and short and the magnetic flux density will suffer…
But assuming that I make a coil/slot too large, is that really bad? The density will be lower, but that would only be an issue if you were using conventional heavy materials. Here it would only be a matter of size.
“Increasing the size of an existing motor while maintaining its power input would indeed lead to a significant reduction in magnetic flux density. This is because magnetic flux density (B) is defined as the magnetic flux (Φ) per unit area (A). If you increase the area (by enlarging the motor) while keeping the magnetic flux the same (since power input remains unchanged), the magnetic flux density will decrease accordingly. Specifically, doubling the area will halve the flux density, as indicated by the formula B = Φ/A [2].
Now, regarding the implications of this reduction in magnetic flux density, there are a few key points to consider:
Output Power: If the motor's power input remains constant, theoretically, the output power could stay the same. Power is the product of torque and speed (P = T × ω). However, increasing the motor size might affect the torque and speed characteristics due to the change in design and operational parameters. This means that while you may maintain the same input power, the efficiency of converting that power into useful work could change due to alterations in the torque-speed relationship [3].
Lower Losses: The reduction in magnetic flux density could potentially lead to lower losses, especially if the motor operates in a regime where higher flux densities cause increased iron losses (core losses). As mentioned, with a lower flux density, the chances of saturation in the iron core decrease, which could lead to improved efficiency [4][5]. Additionally, a larger motor may allow for better heat dissipation, reducing thermal losses.
Impact of Coil Weight: If the weight of the coils remains constant, but the overall size of the motor is increased, the coil's current density may decrease, leading to lower copper losses. This is beneficial since lower current density can mean less heat generation in the coils, which is advantageous for the motor's longevity and performance [1]. However, it is essential to consider that the overall design must still effectively utilize the available magnetic flux.
Magnetic Path Considerations: Increasing the size of the motor can also affect the magnetic path length and the design of the stator and rotor. A longer magnetic path can lead to increased reluctance, which may require higher magnetizing current to maintain the same level of performance. This could negate some of the benefits gained from reduced losses due to lower flux density”
I can attempt to 3D model it on my computer, but I have a feeling that I would only know it for sure by making a mockup version in real life…
For example, I assumed that the wires were 22mm thick and so on, but I also said on the “Manufacturing” section of this project log (way below) that I would change the production of aluminum wires to be as thin as possible for the sake of spreading them around the slots as efficiently as possible.
I’m not so sure how I could do that in a 3D model.
In a way or another, the best I can do is at least try to do it, right?
I will try first the way I know: making the slot geometry and then slowly making the coils as spreaded as possible.
Boi, I’m taking so long to make these I sure hope I can miniaturize the electric motors to fit inside the 35 joints… I’m still in doubt if it will be worth it since all of them are supposed to be at -70ºC.
I’m really procrastinating tho? I want to do something, something that I enjoy, and I can’t pull myself to do it. I just stare blankly at the computer and the music keeps going on. I heard something about “Executive Dysfunction” or something like that.
Which would explain why this project never goes forward…
Look at these cool 80’s/90’s mech animes:
(not mech, but cool anyway)
Damn, that was really cool. I wish I wasn’t this stupid so I could finish this project already.
Am I really stupid or this project is just difficult?
Anyway, first 3D model attempt:
From smaller to bigger electric motors:
- 18 slots and 12 poles
- 24 slots and 20 poles
- 30 slots and 26 poles
- 36 slots and 30 poles
- 99 slots and 66 poles
Now modeling the coils on each combination and calculating its weight:
![]()
23 wires with 1mm of thickness, allows for 1000 amps in total, but you would need around half of it for the 500 amps 600 volts 300 kilowatts motor.
Just pretend every hexagon is a 1mm thick wire, obviously, it is not a wire that is complying with the shape of the coil, but this is an approximation.
1 - 18 slots 12 poles:
I’m only doing this one because the evolito’s brushless axial flux motor 3d model/image has this number of slots and poles.
I made the 3D model of the coil and it resulted in 30.48743cm³ of volume area with 110mm of height, around 30mm of width and 40mm of length, 24 turns of wire in total.
30487.4058 x 18 = 548773.3044 mm³
Inserting on the density to weight calculator :
1.852 kilograms in total for aluminum wire if you add 1.7x (or 2x for simplicity) more aluminum wire in order to compensate for its lower resistivity at room temperature: 3.1484 kilograms.
6.146 kilograms in total for copper wire.
So it seems like I was actually overthinking the weight issue…?
Now calculating the magnetic flux density, inputting these dimensions, number of turns etc into a magnetic field calculator, it said the magnetic flux density at the air gap between the permanent magnet and coils would be:
57,3356 milliteslas, or 0.0573 teslas.
A common magnetic flux density for brushless motors is around 0.7 teslas, so I don’t know if this would mean the motor is too inefficient or the like.
You still need to take into consideration that ferrite magnets have 0.5 teslas of magnetic field flux, not to mention that you can still use ferrite soft cores for the coils.
So maybe all of this stuff will add up?
In the end, if you need to add 10 times more turns, you would also weigh a little more than 10 times, but it would solve the issue. I think.
If I were to risk, I’d risk it with the 99 slot motor.
2 - 24 slots 20 poles:
For some reason, now the coil has 83mm of height, 30mm of width and 82mm of length. Also 24 turns.
45632 x 24 = 12343582.2384 mm³
Inserting on the volume weight calculator:
2.957 kg for aluminum, double it for compensation at room temperature.
9.813 kg for copper.
Magnetic flux density calculation:
65,2469 millitesla or 0.065 tesla.
3 - 30 slots 26 poles:
Coil has 94.3357 mm of height, 31.4mm of width and 43.4 of length. 24 turns.
26093.9144 x 30 = 782817.432 mm³
2.1136kg for aluminium, double for compensation.
7.014kg for copper.
60,6145 millitesla or 0.065 tesla.
4 - 36 slots 30 poles:
Coil has 264.596mm of height, 23.4mm of width and 9.48mm of length. 24 turns
21921.6888 x 36 = 789180.7968 mm³
2.131 kg for aluminum, double for compensation.
7.071 kg copper.
19,8961 millitesla or 0.019 tesla.
5 - 99 slots 66 poles:
Since I could only fit a single turn until I had the coil to go really tall, its height ended up being 848.3112mm of height, 7.97mm of width and 18.4 length.
22013.0712 x 99 = 2179294.0488 mm³
5.884 kg for aluminum, double for compensation.
19.526 kg for copper.
3,9578 millitesla or 0.003 tesla.
Remembering that these 23 wires with 1mm of thickness allows for 1000 amps, if you cut it by half for 500 amps, the weight is reduced by half.
Also, the amount of tesla increases to 0.009. lol
There is still the 3D model for the ferrite soft core for the coils; according to ChatGPT, the magnetic flux density is so small it is unlikely to go into saturation.
I’m also kinda done with this Project Log in specific, so any further 3D models will be done when I actually start building this thing.
Which… Yeah. From now on, I need to actually start building stuff.
Gearboxes Talk:
I didn’t want to work with gearboxes… But there is a possibility that this may be actually useful for someone that is not interested in the direct drive part, and also because I want to take this subject out of my mind. I won’t stop thinking about it until I write this stuff somewhere.
Yes, I went through all that trouble of making the coilgun actuators, the REB 90 3D model and the countless, countless gearboxes I came up with and all that stuff… BUT, I’m more knowledgeable right now, and I’d like to give a try at finding a good reduction box for a DIY project.
I saw this “explosive” electric actuator for robots, and it is essentially a planetary gearbox with an extra motor outside of it rotating the outer ring of the first planetary gear.
https://ars.els-cdn.com/content/image/1-s2.0-S2095809921005282-gr1.jpg
I think these videos can be easier to understand:
I need to figure out how much each motor changes the output, it would be nice to divide the power input between two equally sized motors tho.
ChatGPT explained that you would need the primary motor and secondary motor to have a 2:1 power ratio, if that is accurate I’m not sure.
This is essentially a continuously variable transmission (CVT) and there are many, many designs out there that wouldn’t need a secondary motor with equal or similar output power as the first one.
While looking for articles on the subject, I finally found the goddang inception-drive, the news articles that talked about it never linked the original article:
If I understood it correctly, the inner gear-belt has a tooth with a certain radius and the outer gear-belt is like a big gear, so when the outer gear-belt contacts the further part of the triangle, the bigger is diameter, and thus, bigger the gear ratio.
No, I definitely didn’t grasp how the hell it works…
![]()
https://journals.sagepub.com/doi/full/10.1177/17298806231193891
He uses a conventional v-belt CVT drive as an example, where the output/input pulleys are like a rotating arm, so I just need to imagine it as one in order to understand it. Right?
https://i.imgur.com/SlVzO74.png
As you can see in this crappy drawing I’ve made, you just need one input shaft and one output shaft, while the pulleys can slide around the v-belt. Just like in the conventional CVT v-belt.
Now, why in tarnation do you need four pulleys and all that weird stuff?
I think I finally understood how it works.
If you keep both pulleys fixed, even if they are bigger or smaller than the other, they will rotate in the same direction.
Since only one pulley is fixed and the other is rotating, if you change their sizes, the rotating pulley will rotate in an opposite direction from the fixed pulley.
From what I could understand, it is because if the rotating pulley is at a distance from the fixed pulley, it is like the rotating pulley is attached to a bigger wheel.
So, if you fix one of the three, the bigger pulley, the smaller pulley or the imaginary wheel that is rotating one of the pulleys, then the output of the other two will change.
Actually, I remember seeing something that works kinda like this, it is an orbital drive:
I guess it could work with a variable diameter pulley for an orbital drive CVT.
Like these two.
The simplest continuously CVT that I could find was this one here:
Essentially, the idea is to have two parallel disks with ropes attached, the attachments in both disks can move, essentially changing the size of the “virtual disks”.
If the attachments on the driving disks are closer to the center, while the driven disk has its attachments far away from the center, they are working like if a small gear is driving a bigger gear. Exchanging speed for torque.
If the reverse is done, then it will be like a bigger gear is driving the smaller gear, exchanging torque for speed.
But this thing is limited by the size difference between the two disks…
You could add more disks to increase the difference tho…
I think you would either need springs or linear actuators to actively change the gear ratio of these disks, but if you are thinking of something as insane as a 3 ton lifting actuator for a mech, I don’t think these two options would be very practical.
They aren’t infinitely variable, but they would be easier to 3D model and build.
Just found this one that seems quite simple in principle, but I think it would be kinda hard to fit the clutches into the system.
Bearings, couplings and screws:
You know what? On top of all of that, I will make the bearings electromagnetic and instead of screws/bolts I will have electromagnetic couplings/locks. I was thinking of making the metal core slightly porous so it can be embedded into the plastic structure. This is me on the next day, the electromagnetic locks replacing screws sounds kinda stupid to be honest. Electromagnetic locks are heavy and need iron cores.
Nah, it is stupid, a 14 ton holding electromagnet that I found on Aliexpress has 60cm of diameter and uses 1.2 kilowatts to work continuously. Even if I somehow made it smaller, it would still consume as much and be as heavy. Although I could have sensors and the like to proportionally input energy based on the load it suffers.
By the way, what garbage is pumped into my brain guts, but what made me think that electromagnetic bearings wouldn’t face the same problem of size and power input?
If the entire weight of the mech is applied to a electromagnetic bearing, then the bearing MUST be able to make that much weight to float.
Although I could use electromagnetic bearings and couplings on the connection between the electric motor and the hydraulic pump.
Interesting video, related to the subject.
Electro-hydraulic actuators:
I intended on making this part because I thought the weight of the electric motors would be too much, but in the end it wasn’t that big of a deal.
Between DIY electric motors and DIY hydraulic actuators, I think I prefer electric motors.
Although I talked about how not very useful it would be to make the hydraulic mech, I do want to check one last time this idea. Especially now that I’m aware that multiple independent actuators would be too heavy.
… Now that I look at it, the output values don’t seem that absurd to be honest.
On Project Log 81 I reached the conclusion that even a hydraulic mech with 1.5 or 1.2 times more force for every consecutive actuator would need around 4000 to 5000 liters per minute or 260 horsepower to 350 horsepower.
A brushless motor with 80 kilowatts/106 horsepower weighs 20 kilograms, so around 60 to 80 kilograms for the driving motor.
About the Hydraulic Vane pumps:
I could use a Vane Pump 3D model to be as thin as possible, but one interesting thing I thought of: you could hire laser cutting of metal plates based on how thin these things are.
This website shows some graphs on the efficiency proportional to pressure and flow of vane pumps.
The highest efficiency was 87% at 1800 RPM and 1000 PSI/68 bar according to the final graph, but for the highest efficiency, you would maintain the pressure at 500 PSI/34 bar and around 1000 RPM. … But I don’t know the dimensions of the vane pump in question.
According to this article, the most efficient would be around maximum 20 bar, 1600 RPM and 6 liters per minute of fluid flow. But I don’t know how reliable that is, because the article discusses a unique pump integrated into a bldc motor.
One thing that I absolutely hate about hydraulic pumps is that the components touch each other. Piston pumps (the most efficient), gear pumps, vane pumps, internal gear pumps, all of them have to be in direct contact with the walls, O-rings, seals and bearings.
Everything is beginning to overheat and deteriorate over time.
The only pumps that don't have that problem are centrifugal/impeller pumps, but those are the worst for high pressure applications.
I searched for hours and found nothing about a centrifugal pump with either high pressure nor good efficiency, the same is applied to axial-flow pumps.
I could only think of an archimedes screw pump, but those are used to transport water, not pump hydraulics.
Ok, I think I found a solution: diaphragm pumps.
https://d3i71xaburhd42.cloudfront.net/001140ff5c269ac326f1b9d8afdaa358b020601f/2-Figure2-1.png
The image actually shows a diaphragm actuator, but using it as a pump would work just the same.
It is at least 95% efficient and it won’t care if I use oil or water, which makes things easier.
I could also make the actuators like that.
By the way:
“In a water hydraulic system, to reduce the creation of air bubbles and prevent corrosion, you can consider the following additives and treatments:
Antifoaming Agents (Defoamers)
Purpose: These reduce the formation of air bubbles and foam within the hydraulic fluid.
Examples: Silicone-based antifoams or polyalkylene glycols (PAGs).
Corrosion Inhibitors
Purpose: These protect the metal components of the system from corrosion by forming a protective layer on the metal surfaces.
Examples:
Sodium Nitrite: Commonly used in water systems, it forms a passive oxide layer on metal surfaces.
Sodium Benzoate: Acts as a corrosion inhibitor and is less toxic than some other inhibitors.
Boron-based additives: Effective in preventing corrosion in ferrous metals.
Biocides
Purpose: Prevent the growth of microorganisms that can lead to biofilm formation and subsequent corrosion or blockages.
Examples:
Isothiazolinones: Commonly used in water treatment to control microbial growth.
Glutaraldehyde: An effective biocide for hydraulic systems.
Demineralized or Deionized Water
Purpose: Using purified water helps reduce the presence of dissolved gases and minerals that can contribute to corrosion and bubble formation.
Dissolved Air Removal
Purpose: Remove dissolved air from the water before it enters the hydraulic system.
Methods:
Vacuum Degassing: Exposing the water to a vacuum to release dissolved gases.
Deaeration Tanks: Allowing water to sit in a tank where air can escape before being used in the system.”
It would also be better to make BLDC servo valves instead of solenoid valves, this way the system wouldn’t need to be as heavy (and expensive) as the actual solenoid valves used on hydraulic systems.
https://en.wikipedia.org/wiki/Rotary_valve
This would allow you to simulate spring action on the hydraulic actuators by opening and closing the valves accordingly. You can program that with conventional bldc motors, but this time you would need encoders and other sensors.
Another detail is that I don’t think I will keep up with the idea of using Stewart platforms for the limbs, it would indeed be stronger and studier, but it would also require even more fluid flow, even more actuators and even more weight.
By the way, I was wondering if it would be a good idea to have the hydraulic actuators be hydraulic motors.
More specifically, radial piston hydraulic motors.
They seem to be very torque dense (and ChatGPT agrees), although I wouldn’t make it a fully rotating motor precisely because of the way the fluid is supplied. It is normally fed through the axis of rotation, which adds friction losses.
Although I fail to see that much difference between a radial piston engine/pump.
Why does the radial piston hydraulic motor have moving pistons pointing inwards and pushing a wobbly surface instead of having fixed pistons pushing a wobbly rotor?
Guess that answers the question: the rotor would be too small.
Still, I think I could keep the inner part where the pistons are fixed and let the wobbly surface move.
Looking at gifs and videos on how it works, I have no idea if I will be able to pull it off.
I don’t know how I would time correctly which piston would receive fluid.
I could only think of having various sets of pistons in different positions compared to the curves of the walls and simply activate each set/disk when it is at the best position for maximum torque.
Almost like a 3 phase BLDC motor.
Not like what I said, but pretty close.
… But that would require a LOT of fluid flow to compensate, no? I would need to make a valve system into the motor so that the exhaust of the previous “ring phase” helps power up the next “ring phase”. A regenerative system, like a turbocompressor of some-sort.
That could also be applied to the electric system of a motor, no?
I was just not paying attention to the details, I rewatched the first video I linked here about radial piston motors and essentially, the ports for each individual piston are holes on the rotor structure, and the feeding and exhaust of the working fluid are fixed holes too instead of a sliding opening like in the axial piston pumps/motors.
You need to get the position of each port very carefully aligned with the wobbly surface so every time the pistons expand or compress, the whole thing will rotate.
Some radial piston hydraulic motors work more like vane pumps, where you can change the distance between the walls and the rotor by moving a disk. Just like swash disk axial pistons.
This is about a radial piston pump, but it can be used as a motor anyway.
If I’m going to make linear actuators/pump pistons with membranes for as low friction as possible, then why not use that idea of flexible hydraulic cylinder artificial muscles that I suggested?
Although not as incredible as the axial piston hydraulic motor, these would be easier to manufacture.
Anyway, I need to figure out the linear speed of the pump, the cylinder diameter, pressure, fluid flow speed and thus, port size, cavitation production etc.
Should I change the actuator?
Pneumatic/hydraulic Artificial muscles:Out of curiosity, I don’t remember posting these two artificial muscles, but these two redesigns of a McKibben artificial muscle achieved 45% and 65% of efficiency while working with Pneumatics.
https://www.mdpi.com/2076-0825/10/5/100
https://www.science.org/doi/10.1126/sciadv.adi7133
I think that is relevant because it could be a good option for the hydrolysis driven pneumatic system or a hydraulic system altogether.
Of course, I don’t see how I could mass-produce those (at the moment), but boi.
OH BOI, all this electric motor hydraulic motor talk is driving me CRAZY.
I’m willing to bet that if I simply stuck with the simple approach, with the pros and cons, I would've finished this project already.
Homemade Shape Memory Alloy:
By the way, I also saw this new video from NileRed where he shows an arc-melting furnace that is meant for melting highly reactive metals. It is simply a chamber with inert gas (like argon) with a conventional arc-tig setup where the arc is formed through the target material, instantly melting it. He uses it to make metallic glass, actually.
The interesting part, however, is that you could literally make Nitinol wire in bulk with this thing by constantly injecting material and melting it through a tube.
Even though Nitinol is not the most efficient, it is certainly the simpler and highest performance one. I would only need a dozen kilograms for an entire mech instead of hundreds of kilograms and complex systems without the risks of electrocution, frostbite and instant combustion.
Yes, both nickel and titanium are expensive as hell, the other shape memory alloys that use cheaper materials are less efficient and less energetically dense than Nitinol. But that could be so much easier to handle...
These actuators are less than 10% efficient, so the weight they are saving on themselves is compensated by the extra weight they will need to actuate, defeating the point all together.
I try to check for shape memory alloys with higher efficiency, but they never outright measure the actual efficiency. They only say that the efficiency is 10 to 15% and never try to check the energy input, contraction speed, distance, force and the time all of those things took in place.
So, if you input X amount of joules of heat for 1 second and then the whole thing takes 10 seconds (or even a minute) to fully contract with a given force, speed that in total would be 60% of the initial energy, then is it really 10 to 15% efficient?
This article claims “energy savings of up to 80% (80% of 90% is 72% +10% to 15% = 82% to 87% efficiency):
Nickel/Titanium free SMAs:
https://www.intechopen.com/chapters/67075
https://link.springer.com/article/10.1557/s43578-021-00444-7
https://www.sciencedirect.com/science/article/abs/pii/S0141029618305030
https://www.mdpi.com/1996-1944/15/22/8089
I don’t know if this one is a rare-metal free shape memory alloy, but it showed a method to make it actuate 35 per second (35 hz): https://www.nature.com/articles/srep21118
(maybe I just missed it, but they didn’t write which alloy was used)
Also, a detail about the SMA’s: you need to allow them to fully return to their original state (or “contract”, if you will) or else they will degrade rapidly.
I did think on making the wires as coiled as possible, so even though they try to contract, they would never fully restore their initial shape, making absurdly strong contractions. But that extra tension would also increase the degradation of the SMA through fatigue and deformation.
I also thought of braiding and/or twisting the SMA wires in order to increase the force output and resistance, just like real ropes. And just like real ropes, if you always use these actuators with the lowest force possible with a safety factor, you can extend their life cycle. But I’m not very sure how much that would extend its lifetime.
I would copy-paste a paragraph from ChatGPT explaining all of that, but it would be too long. Just know that for now, the average life-cycle of SMA’s are around:
“The values of the displacement drift generated after 1, 1000, 2000, 3000, 4000, and 5000 such cycles as measured using a Talbot interferometer are 0, 0.875, 1.275, 1.459, 1.720, and 1.859 mm, respectively.” Source: https://opg.optica.org/ao/abstract.cfm?uri=ao-57-20-5779
So I’d assume that you would lose 4mm of contraction every 10,000 cycles. 4cm after 100,000 cycles and 40cm after 1 million.
In this other article it is said that the faster the cooling of the SMA’s, the better. Longer cooling cycles increase fatigue. Although they are talking about nickel based SMA’s, maybe that would be true to other shape memory alloy types.
Why does every freaking option sounds good and viable?
Everything looks so simple yet so complex, so practical yet so impractical…
Mandatory Armored Core reference:
This project log got so full I had to split it up to the next project log. (holy crap, I'm sorry)
-
Project Log 87: Screw it, let's freaking do it.⁷
09/07/2024 at 23:27 • 0 commentsFriday, 16/08/2024, 16:19
I feel like my passion for this project is just fading away. I liked spending time researching and theorizing and all that stuff, but I feel like I never make any progress.
I mean… I don’t know. Pretty funny how I’m feeling down so close. And even funnier how everything seems so close and so distant at same time.
I talk, I talk and talk, but I really don’t know what to do…
I feel like I don’t know what to do, I feel totally lost
I’m really undecided on what to do next? Or am I just trying to procrastinate?
You know what? I just promised to myself I will only post this project log when I actually finish 3D modeling something.
It is funny to me that every day I’m either “this project is stupid, I’m a joke” or “f*ck yeah, this project is awesome”
Also, have you guys seen the teaser for “Secret Level”? There will be a f*cking animation from Armored Core!
It seems that this project log is so long it won’t fit in a single post, sorry for that.
The one time I actually do something in this project and the posts are completely overwhelmed.
Also, for some reason I decided to make a wargame tabletop with a friend of mine. I’m definitely not good with my life choices… Because it will also take years to just study the already existing wargames systems and rules.
About Electromechanical Rheostat Servos:
In the previous project log I talked about how the electrical actuator mech with electromechanical rheostat-switches wouldn’t be practical because I would need a lot of brushless motors.
Obviously I was wrong, although I don’t have the precision to make tiny brushless motors on mass, I can actually make something closer.
- I can make linear brushless motors that can rotate crankshafts.
- I can make solenoid that also can rotate crankshafts.
- I can make bigger, less efficient DIY brushless motors.
For some reason the obvious never crosses my mind on the first try.
I will list here some videos I found about making DIY brushless motors, there are many, so I will just put the links:
- https://youtu.be/0j2epmD4MYs
- https://youtu.be/VQu7KKK3qXo
- https://youtu.be/OZarwftUh8w
- https://www.youtube.com/shorts/Vtm_HCDdENM?feature=share
- https://youtu.be/FxmJE8zcoZg
- https://youtu.be/HaURynfTqqo
- https://youtu.be/bE5CMq7bSZk
- https://youtu.be/TFQrXbMy84c
- https://youtu.be/1K8LQPfMmJk
- https://youtu.be/w25OAqQk_9g
Anyway, I need to start 3D modeling this piece of crap that I call mech, and then I will need to actually build something.
And my first doubt is: how should I make the direct drive brushless motors for the mech?
I mean, I’m thinking of just going “frick it, we ball” and 3D modeling every option of actuator for the mech. The linear brushed motor, the linear brushless motor and then the rotary brushless motor.
… And maybe the exoskeleton I talked about before.
High Torque Density motor:
Before I finally go with the hydraulic/hydrostatic route, let me at least try to find a super high torque to weight ratio actuator. Maybe this way I can still keep it fully electric.
Being honest, I doubt I will be able to pull it off, but even if I reach a pretty close value to those ultra light high power motors, it is still going to make the electro-hydraulic mech lighter.
Anyway, what number of poles and slots would I need for a direct drive brushless torque motor?
I always use the REB-90 as the reference and I also posted that excel document on which shows the best ratio of slots and poles, but none of them talks about the number of slots/poles based on the power output you want.
The “best” approach I have for now is to “just” increase the AWG of the wires, since changing the wires of a brushless motor for a thicker one also increases its torque while decreasing its output speed.
I already 3D modeled the REB-90 copy ages ago, so maybe I just need to cut the number of poles and slots by half and significantly increase the thickness of the aluminum wires.
You know the drill by now, no?
I will talk about direct drive motors, then I will talk about torque motors and how none of the manufacturers tell how many poles and slots they have, yara yara yara…
Some relevant links for this task:
- Before anything, the previous Project Logs about DIY electric motors are still valid, but I believe that what I talk about here wasn’t discussed on those logs. On those I was more concerned with practical construction techniques instead of the high density to weight ratio part.
- https://electronics.stackexchange.com/questions/590217/quasi-direct-drive-actuator-slot-pole-combinations-for-high-torque-motor They show the spreadsheet I talked about talking about the number of slots and poles. They said that for a torque motor, the more poles/slots, the better. So, I’m assuming that it should be 108 slots and 74 poles based on the spreadsheet. But you could have some combinations even reaching 132 slots. Unfortunately, the Bavaria Winding Scheme calculator doesn’t allow for the number of slots above 99, so I have no idea of which winding factor (ABCabc) you need for this combination. The closest one would be 99 slots and 66 poles.
- https://www.moog.com/products/motors-servomotors/brushless-motors/high-performance-direct-drive-brushless-dc-motors.html https://ph.parker.com/br/pt/product-list/frameless-direct-drive-torque-motors-tk-series https://catalog.wholesalesupply.us/brand-siemens/torque-motor-1000nm170rpmaxial-cable/sku-V4319-1fw61600wb072jc2 https://emrax.com/e-motors/ Lists of available Direct Drive Brushless DC Frameless Torque Motors that these manufacturers produce, their output torque, size and weight. For reference.
- https://electronics.stackexchange.com/questions/562402/how-to-select-bldc-motor-for-high-torque-applications/562459#562459 Torque motors perform the best the wider it is, because the torque is generated between the electromagnet tips and the permanent magnets. And so, the smaller the distance between the edge of these two and the lever/arm that will apply work, the better. But you can’t realistically make it infinitely wider. Although, you could take a smaller motor that has an output of 100 kw or more and make it wider. (by the way, I took the 3D model of the REB-60/90 I’ve made and basically, if it had 2.5cm of thickness, it would be 1 meter wide. The most compact that I could make it without these absurd sizes was giving it 10cm of thickness and 50cm of diameter)
- It could help to make the wires as flat as possible (or have as many parallel wires as possible) to make the coil as small as possible.
- https://youtu.be/PMma3OJUHhs I think it is interesting, it shows that I can’t “just” add a random piece of iron to block magnetic fields, the magnetic field must be either fully absorbed by a really thick piece of iron or redirected to the other magnetic poles in order to close the loop.
- One thing that I noticed: some motors have peak torque of the same value, bigger or lower even though they are of the same or bigger wattage. I would guess that a way of actually getting the power/force you want from the torque besides the number of poles, slots, diameter and wire thickness is to take the input watts of an electromagnet, solenoid and the like and multiply its weight in wire between the electromagnets of a motor. For example, the linear solenoid motor that I was thinking of using has an output force up to 10 tons. What if you took the input, 200,000 watts and divided it by the number of electromagnets (slots) in a brushless motor? Every active slot would output a smaller version of that power, but together would be 200,000 watts. 200,000 divided by 20 active slots = 10,000 watts. How do you want to divide that amount of watts? 500 amps x 20 volts? 500 volts x 20 amps? So on and so forth.
With those parameters established, the first thing that comes to mind when talking about high torque density are axial flux brushless motors, but I don’t like one aspect of them. The bigger the electromagnets, the more distant they are from the edge of the motor, which means that not all electromagnetic fields are being used to its full extent. So I was thinking of making a wobbly axial flux style axial flux motor.
In fact, you could actually make multiple stators and rotors with the axial flux brushless motors in order to increase their power output without increasing the weight too much, no?
Found this article: https://ntnuopen.ntnu.no/ntnu-xmlui/bitstream/handle/11250/258043/759964_FULLTEXT01.pdf?sequence=2&isAllowed=y
“By stacking more discs in series, higher torque can be obtained. Doing this will not increase the efficiency of the machine, because the arrangement is made up of several machines with the same efficiency. The losses will increase proportionally with the torque increase. The end coil volume for each stator disc will also remain the same.”
I've seen an axial flux motor called “D500 1x3”, which has around 350kw of output power while only weighing 30kg.
I couldn't find any other motor with this absurd output, what is their secret?
I see that a lot of these high power low weight brushless motors normally need water cooling… I would guess that they are sacrificing efficiency by using lighter windings and using the cooler to keep it from melting itself…
Being honest, with all this headache over motor weight and power output, I’m starting to not worry about 90%+ efficiency.
It seems I’m mistaken, they actually have high efficiency and the reason they need liquid cooling is because 10% to 5% of energy converted into heat starts being a problem when you have 200,000 watts, which would be around 2000 to 1000 watts of energy converted into heat. That is enough to melt metals by the way.
About how they are so light, I received an answer:
“Brushless motors may be powered by DC but they turn that DC into high frequency (kHz range) PWM (Pulse Width Modulation) energy that drives the coils in the motor, effectively creating a multi-phase rotating field. This allows the field coils to have lower inductance than a conventional 50 or 60Hz motor. We're talking 1 to 10% of the copper required.
Because of the small motor size, the gaps between the coils and the armature can be very small, enhancing efficiency.
There are many more reasons but these are the big ones: high frequency PWM drive and efficiency.”
I asked chatgpt:
“PWM, or Pulse Width Modulation, is a technique used to control the speed and power of electric motors. Here's a more detailed explanation:
PWM refers to both the input signal and the method used by motor controllers to control motor speed. The basic principle is that the controller varies the perceived input voltage to the motor by rapidly turning the power on and off in a series of pulses. [1]
The width (duration) of these pulses is modulated to control the average power delivered to the motor. A wider pulse means more power, while a narrower pulse means less power. [1][2]
This works because motors have inductance, which allows them to "smooth out" the pulsed power and respond to the average voltage rather than the instantaneous voltage. As long as the pulse frequency is high enough, the motor will run at a speed proportional to the average voltage. [2]“
Well, I don’t see that being easy to implement in a fricking 300 kw motor using mechanical switches like I was planning.
The best way I could think of doing such an absurd thing right now would be to: spread the transmitting wire as thin as possible (like a foil), divide it in two, submerge it into a dielectric solution and then force the connection of both thin plates using electromagnets.
That would work exactly like a relay, but as small as possible.
A 100 amps 80 volts (8 kilowatt) transistor costs around 15 reais (3 dollars), but in order to deal with 300,000 watts I would need 38 of these, so 570 reais (around 100 dollars) in total.
But the idea of this project is to be as “DIYable” as possible and cheap as possible, if I simply go the route of buying high power components, I will easily surpass the 5000 reais (1000 dollars) limit.
One idea that I had would be to use a cheap low power high resolution pulse modulator to take the sensor input and then control the high power electromechanical system.
… I should’ve thought of that before…
Also, I found something interesting.
This article shows how to reduce the resistivity of aluminum metal using “simple” tricks, but nothing that will make aluminium super duper mega conductive. It was intended to make it more competitive compared to copper.
Essentially, to make the aluminum less resistive, you need to make it as pure as possible and reduce surface/internal defects as much as possible. You would do that by heat treating the aluminium wire, probably with thermal shock followed by aging (exposing it to around 200ºC to 400ºC for a couple of hours).
A way that ChatGPT suggested to achieve that by recycling soda cans:
“In summary, the overall aluminum alloy composition in soda cans is approximately 97% aluminum, 0.65% manganese, 2.75% magnesium, and up to 0.5% other impurities.
The amount of fluxes and refining agents needed to remove impurities from aluminum soda cans would depend on the specific impurities present and their concentrations. However, I can provide some general guidelines based on typical refining practices.
Fluxes: For removing oxides and other surface impurities, a flux mixture containing 75-85% chloride salts (such as NaCl and KCl) and 15-25% cryolite (Na3AlF6) is commonly used. The amount of flux needed would be around 1-2% of the weight of the aluminum.
Refining Agents:
Sodium (Na): To remove magnesium and iron impurities, the amount of sodium needed would typically be around 0.1-0.2% of the weight of the aluminum. However, this can vary depending on the concentration of impurities present.
Magnesium (Mg): To remove silicon impurities, the amount of magnesium needed would typically be around 0.2-0.5% of the weight of the aluminum. Again, this can vary depending on the concentration of impurities present.
Calcium (Ca): To remove hydrogen gas, the amount of calcium needed would typically be around 0.02-0.05% of the weight of the aluminum.
Flux Reactions: The chloride salts and cryolite in the flux will react with the aluminum oxide and other surface impurities to form a molten slag layer on top of the molten aluminum. This slag layer will float to the top of the melt and can be skimmed off to remove the impurities.
Refining Agent Reactions:
Sodium (Na): When sodium is added to the molten aluminum, it will react with magnesium and iron impurities to form sodium magnesium aluminate (NaAlMg4) and sodium iron aluminate (NaFeAl4), respectively. These compounds will float to the top of the melt and can be skimmed off along with the slag layer.
Magnesium (Mg): When magnesium is added to the molten aluminum, it will react with silicon impurities to form magnesium silicide (Mg2Si). This compound will sink to the bottom of the melt and can be drained away to remove the silicon impurities.
Calcium (Ca): When calcium is added to the molten aluminum, it will react with hydrogen gas to form calcium hydride (CaH2). This compound will float to the top of the melt and can be skimmed off along with the slag layer.”
It would be easier to “just” at ⅓ of recycled soda cans to a high purity aluminum crucible… But high purity aluminum is expensive.
I asked again, but using aluminium alloys to make the slag instead of flux:
“New Mixing Proportions:
Soda Can Alloy (100g): Aluminum: 97g Manganese: 0.65g Magnesium: 2.75g
Addition of Aluminum-Copper Alloy (e.g., 2024):
Add 10g of 2024 alloy (which contains around 0.44g of Cu).
This may reduce the Mn content by forming Cu-Mn intermetallics.
Addition of Aluminum-Silicon Alloy (e.g., 4043):
Add 15g of 4043 alloy (to react with magnesium and some manganese).
Expected Outcome:
Manganese: Partially removed through Cu-Mn compounds and silicide formation.
Magnesium: Reacts with silicon to form Mg2Si, which can be removed.
Silicon: Should be controlled by not adding too much 4043 alloy.”
And the most obvious way of all to reduce resistivity: reduce its temperature.
To make it have the same conductivity/resistivity of copper, you need to reduce its temperature to -65ºC (according to ChatGPT). According to the actual paper, it seems like you would need to reduce the temperature to between 100 to 150 kelvin, or -173ºC to -123ºC. Unless the motor is encased in a liquid nitrogen, I don’t see this being possible. Besides, if I were to use liquid nitrogen at all, it would still be better to use copper.
According to this article (that is actually accessible), ChatGPT was correct. However, it depends on the type of aluminum alloy, the 1100 is the purest aluminum. Which also proves the resistivity of materials based on their purity.
Well, you could “just” add a little bit of copper, reducing the resistivity and in turn also increasing the cooling from -65ºC to something that even a freezer could handle (-17ºC).
Of course, that would slightly increase the density (and weight) of the aluminium.
“To determine the amount of copper that should be added to pure aluminum to achieve the same resistivity as copper at -17°C, we need to consider the following factors:
Electrical resistivity of copper and aluminum at -17°C:
The electrical resistivity of copper at -17°C is approximately 0.0174 μΩ·m [1].
The electrical resistivity of pure aluminum at -17°C is approximately 0.0265 μΩ·m [2].
Calculating the required copper content:
The resistivity of a copper-aluminum alloy can be approximated using the rule of mixtures:
ρ_alloy = x * ρ_Cu + (1-x) * ρ_Al
Where x is the weight fraction of copper in the alloy.
To achieve the same resistivity as copper at -17°C, we need to solve for x:
0.0174 = x * 0.0174 + (1-x) * 0.0265
Solving for x, we get x ≈ 0.34 or 34% copper by weight.
Therefore, to make a copper-aluminum alloy with the same resistivity as pure copper at -17°C, you should add approximately 34% copper by weight to the pure aluminum.
Adding 34% copper by weight to aluminium would increase the density of the aluminium in the following ways:
Copper has a higher density than aluminium. The density of pure copper is around 8.96 g/cm³, while the density of pure aluminium is around 2.70 g/cm³. [1][2]
When copper is added to aluminium, it forms an aluminium-copper alloy. The addition of the higher density copper increases the overall density of the aluminium alloy.
The density of an aluminium-copper alloy increases approximately linearly with the amount of copper added. With 34% copper by weight, the density of the aluminium alloy would be significantly higher than pure aluminium, likely around 3.8-4.0 g/cm³.”
On Quora answers however, some people pointed out that aluminum’s resistivity increases with the addition of copper. Source: https://www.sciencedirect.com/science/article/abs/pii/S0925838817328852
Either way, I will just let these two links here:
List of additives that reduces the freezing point of water: https://www.researchgate.net/figure/Chemical-materials-able-to-lower-the-freezing-temperature-of-water-solutions-if_tbl1_273362118
Accordingly to this patent, potassium acetate only reduces the freezing point of water to -95ºC when it is mixed with potassium formate: https://patents.google.com/patent/US5104562A/en
Hyperspace pirate’s pulsetube cryocooler: https://youtu.be/GjRoThMyNGA https://youtu.be/WOmjJFk8rl0 https://youtu.be/cy8aGMH8Tz4 https://youtu.be/vC2it8LHKSQ
The idea is to use the R410A gas (or Helium, depending on how cheap it is) coolant in the pulse tube cryocooler to reach -70ºC and keep the protected electric parts submerged on the water+additives at -70ºC. So the whole system will be as efficient as possible.
Observation: Although the system doesn’t use flammable products, it is still extremely dangerous to touch a liquid at -70ºC (imagine being splashed by it).
This, of course, is just to make Aluminum as conductive/resistive as copper while being as light a possible.
If -70ºC is too much (and I do believe it is too much), you should increase the size/weight by 1.54 times in order to compensate for the resistivity at ambient temperature.
And yes, this also introduces more complexities into the system, and unfortunately, you would need contact seals to maintain the cryo liquid inside the motor.
But you would need to do something similar anyway, we are talking about 2 to 20 kilowatts of heat generated by the entire system.
You need a robust cooling system.
By the way, HDPE starts cracking at -120ºC. I got worried about the integrity of the whole system.
But it does mess up PVA, so the graphene polymer composites would need to also be mixed with HDPE.
I’m even considering making a DIY magnetizer for DIY permanent magnets, but although there are many tutorials on the internet, I’m so sure what I can use to make the material that will be turned into a magnet…
Well, now I need to figure out how to make the primer material for a permanent magnet.
For this, I even thought of buying neodymium magnets in bulk (from scrap or normal ways) , smash them up, mold into the way I want and then redo the magnetization process.
But… A 600 gram Neodymium magnet costs fricking 500 reais (100 dollars), even when I try looking for smaller pieces in high quantities it is still 100 reais (20 dollars) for every 400 to 500 grams. I think I would need around 10kg of this stuff for the motor…
“Neodymium magnets are not made of pure neodymium metal; instead, they are composed of an alloy known as NdFeB, which stands for Neodymium (Nd), Iron (Fe), and Boron (B). The typical composition of a neodymium magnet is about 65-75% iron, 15-20% neodymium, and 1-2% boron, with small amounts of other elements like dysprosium or praseodymium added to improve specific properties, such as resistance to demagnetization and high-temperature performance.”
But Some time ago I heard about iron nitride permanent magnets and how they would outpace neodymium magnets:
“Based on the search results, here is a detailed response about iron nitride magnets:
Iron nitride (specifically the Fe16N2 phase) is a promising non-rare earth permanent magnet material that could potentially outperform neodymium-based magnets. The key points about iron nitride magnets are:
“Iron nitride magnets do not contain any rare earth elements, making them less susceptible to supply chain constraints and geopolitical issues compared to neodymium magnets [1].
Iron nitride has a theoretical maximum magnetic energy product (a measure of magnetic strength) of 130 MGOe, which is more than twice the maximum for commercial neodymium magnets [1].
Iron nitride has a very high saturation magnetic flux density of 2.9 Tesla, significantly higher than neodymium magnets [1].
Iron nitride has a much lower temperature coefficient of coercivity (0.4 Oe/°C) compared to neodymium magnets (-81.9 Oe/°C), meaning it maintains its magnetic properties better at higher temperatures [1].
However, current iron nitride magnets produced by companies like Niron Magnetics can only reach around 10 MGOe, well below the theoretical maximum. More research and optimization is needed to unlock the full potential of iron nitride [2].
Niron Magnetics aims to commercialize iron nitride magnets with an energy product above 10 MGOe in 2024, and above 30 MGOe in 2025, which could make them competitive with neodymium magnets for applications like electric vehicle motors [2][3].”
That is cool and all, but how do I make one of these?
https://hackaday.com/2022/09/01/iron-nitrides-powerful-magnets-without-the-rare-earth-elements
“Low-temperature nitridation is also possible, using iron oxide nanoparticles as a starting material. In this method, the particles are treated with ammonia gas to get the nitrogen into the crystal structure. Alternatively, iron oxide can be mixed with ammonium nitrate in a planetary ball mill; after a few days of milling at 600 rpm, the stainless steel balls decompose the ammonium nitrate into elemental nitrogen, which diffuses into the iron nanoparticles. The resulting α”-Fe16N2 is then separated by a magnet and can be formed into solid shapes. This method seems like it would easily scale up to an industrial process.
High-temperature nitridation of iron foils and wires is also possible. This method uses ribbons of an iron-copper-boron alloy and exposes it to an atmosphere of ammonia and hydrogen at 550°C for 28 hours, followed by a rapid treatment at 700°C and an ice-water quench. A variation on this method is the strained-wire approach, where high-purity iron is melted in a crucible with urea. The nitrogen that decomposes from the urea diffuses into the iron, and the mixture goes through heat treatment and quenching steps before being hammered flat and cut into strips. The strips are put into a straining device and stretched during an annealing step, which serves to elongate the crystal structure and trap the diffused nitrogen.”
Well, time to look for 32892389328 scientific articles about iron nitridation synthesis just to find a better alternative too late, like every time that I research these subjects.
Aaaaand I was right, if it was that easy, some random science youtuber would’ve done it. I mean, there are literal fricking particle accelerator tutorial videos on youtube:
With that put aside, I don’t think that permanent magnets would make that big of a difference, that 500 grams neodymium magnet I talked about before. It could “only” lift 300kg. While a holding electromagnet’s coil wouldn’t weigh nearly as much (the metal core definitely would weigh more), its holding force would be around 15 tons.
Wouldn’t that mean that if you want absolute performance instead of maximum efficiency, you would want electromagnets instead of permanent magnets? I mean, the magnets would always save some weight because they are already magnetized…
To Be honest with you, I think I will stick with the cheap and weak permanent magnets just because I don’t want to make an induction coil to power up the rotor’s electromagnets.
Ferrite is fairly cheap and I can buy kilograms of the stuff.
Now I need to find out how the hell ferrite permanent magnets are made, because the information I find is always mixed up. For example, the ferrite core that is made by mixing a polymer/resin with ferrite powder is used for transformer cores, but then, there are injection molding ferrite permanent magnets that are made in the same exact manner, but somehow they are permanent magnets. Then there are sintered ferrite transformer cores and sintered ferrite permanent magnets, somehow? The sources keep saying “magnetic field” this, “magnetic field” that, but the word is always used in both cases of a magnetic core and as permanent magnet. For some fricking reason…
I keep asking and explaining while giving links to WebGPT (it can access and read links you send it) and this stupid goddang piece of overhyped vaporwave keeps telling me the same exact thing without explaining the difference between a ferrite transformer core and a ferrite permanent magnet. Bonded by resin/polymer or sintered.
It keeps saying Barium ferrite and Strontium ferrite, but it keeps using these two to talk about both ferrite permanent magnets and ferrite transformer cores.
I can only suppose that the difference is that in the resin/polymer bonded transformer was made by binding ferrite powder without an external magnetic field and the resin/polymer bonded ferrite permanent magnet was done by injection molding under a stronger magnetic field to align the ferrite powder and after it, make it go through a magnetizer.
You can kinda turn a common piece of steel or iron into a weak permanent magnet by rubbing it with a permanent magnet, which aligns its crystalline structure with the magnetic field direction. But I’m not very confident it could survive the varying magnetic field of an electric motor.
(it is actually called the “stroke method”, either way it makes me chuckle, lol)
I just know that ferrite permanent magnet made by bonded powder works because there are companies that sell drone motors that use them:
I saw this video on my youtube feed, but never bat an eye on it, and ironically enough, he explains all of my questions (although the bonded magnet he shows is made out of neodymium).
However, there is a really important piece of information, there are “soft” and “hard” ferrite powders. The “soft” ferrite powder is for transformer cores, the “hard” ferrite powder is for permanent magnets.
Unfortunately, I can’t find ferrite powder of the latter.
The only way I could think of was to do the process I was thinking of doing for the Neodymium magnets: buy kilograms of the stuff, smash them up, mix with a bonding material and magnetize them.
I just found out you can’t use Ferrite magnets at temperatures below -40, but as a core, it loses a lot of magnetic flux at -180ºC.
“The exception is that ferrite magnets experience permanent magnetisation loss at temperatures below -40 degrees Celsius, and magnetic tapes and sheets can lose magnetic force at below -20 degrees Celsius, and should not be exposed to significant cold temperatures.”
Source: https://e-magnetsuk.com/how-does-temperature-affect-magnets/
However, Alnico magnets can survive until -100ºC.
However², even though Alnico magnets aren’t rare-earth magnets, they are even more expensive than Neodymium magnets (in my country).
I researched so much, and in the end I will need to work with neodymium anyway.
Just… Bruh.
Also, almost forgot about this:
https://www.youtube.com/watch?v=NX7GHqq28uU&list=PLzP6_DqZoxc3qNnCqWT7R58rQC3nV30PN&index=1
I obviously won’t build PCB motors specifically because of the resistivity of the copper deposited in their surface not being the best, but they share relevant information about axial motors.
This one about electromagnets.
I’m still in doubt on how to proceed, by the way.
I’m still checking other super high power density motors, and maybe the idea of using as many poles as possible for super high torque is not a good idea…?
The D250 1x3 from evolito is on itself an example, it has 220 kilowatts of power, but it only weighs 8 kilograms because it is a high speed, low torque motor.
While the other high torque motors are 3 times heavier.
… But that pattern doesn’t repeat itself on other motors, like the Freerchobby MP240150 that outputs 100 kilowatts, half of that and weighing double of that (16kg).
I can’t make heads of why, I ask on forums and no one answers.
I even searched for the datasheet for the D250: https://evolito.aero/media/2024/07/D250_210724.pdf
It doesn’t show much tho, it just shows the information already provided and the efficiency graph of the motor.
Calculating it - Dubious result:
Sorry for procrastinating so much, I don’t know why, I always feel a wall on my mind every single step of the way.
Also, these last 2 to 3 weeks I’ve been very sick. First I had a high fever, then I started having a lot of coughing and now one of my ears is so inflamed that I can’t hear anything and my jaw can’t completely close. 😐
Anyway, I will attempt to calculate the weight of the coils even though I didn’t make any 3D model.
I’m also thinking of changing the electric motor from a super high torque direct drive motor to a high energy dense motor, like I talked about the D250 Evolito brushless axial motor.
So, assuming 300 kilowatts of nominal power and maybe a possible 600 kilowatts of nominal power, I would need to divide the 300 kilowatts between 4 stators with 99 slots and 5 rotors with 66 poles. So 396 slots in total with 330 poles. I want to make this with 5 rotors and 4 stators because Axial Flux motors are known for having bad heat dissipation due to its unique structure, so I want to spread the motor’s surface area as much as possible for maximum heat dissipation. Of course, this will come at the cost of efficiency.
Since it is a 3 phase BLDC motor, when one of the three phases is deactivated, other two are reaching peak, so it would be safe to take that ⅓ of the total power and add to the full system, so all the slots are at full power at any moment.
So, 300 kw / 3 = 100 kw + 300 kw = 400kw.
400,000 watts/396 slots = 1010.1010101 watts per pole.
(yes, I’m assuming all the phase windings are divided in parallel)
I’m also assuming that whatever is the actual voltage and amperage that you use, the coils will always have the same weight when taking into consideration the thickness of the wire and the number of turns (which, if it was true, the D250 Evolito wouldn’t be a thing).
What should be the thickness of an aluminum wire with the same conductivity/resistivity of copper in order to transmit 1010.1010101 watts through a given distance?
I asked ChatGPT to calculate the required thickness of the copper wire to transmit 1010.1010101 amps and 1 volt across 10 cm (I’m just guessing this length for the single-turn wire, but it could be less and it could be more), with energy losses of 5%, 3%, 1% and less than 1%.
… And obviously, it was useless because it kept giving completely different values every time. 😐
So, based on copper awg charts based on amperage, the diameter of copper wires aren’t universal. Essentially, each wire thickness can have a maximum amperage and frequency before the wires heats up to 60ºC, 75ºC, 90ºC and so on. So I’d assume that if you double the thickness for a given amperage based on the 60ºC, you would have a wire that barely heats up above ambient temperature.
So that could be the 5%, 3%, 1% and >1% of efficiency loss on wire thickness.
Based on various different types of charts (they always give a different values for some reason), for copper wire with AWG of 1000, having 11.684 mm of thickness and 107 mm² of area, it allows 300 to 455 amps at 60ºC, 545 amps to 75ºC and 615 amps to 90ºC
Like I said, in some charts you have up to 900 amps to heat a 1000 AWG copper wire to 60ºC, so this list isn’t universal. You would need to actually test yourself, but until then, here we go.
So, for each amount of efficiency loss that would turn the energy into heat, the modified aluminum wire would need to be:
- 5% = 107mm² of area for every 615 amps = 14,96 mm of thickness.
- 3% = 107mm² of area for every 545 amps = 15,89 mm of thickness.
- 1% = 107mm² of area for every 450 amps = 17,487 mm of thickness.
- >1% = 107mm² of area for every 300 amps = 21,417 mm of wire thickness.
Using a cylinder volume calculator and adding the length of 10cm for every thickness, adding the volume to a Density to Weight calculator, I would get:
- >1% = 22mm diameter = 38,01 cm³ of volume = 0,10263 kg of weight per slot 0,10263kg x 396 slots = 40.64148 kilograms in total for the 300kw axial brushless motor.
- 1% = 18mm = 25,45 cm³ = 0,06872 kg x 396 = 27.21312 kilograms.
- 3% = 16 mm = 20,11 cm³ = 0,0543 kg x 396 = 21.5028 kilograms.
- 5% = 15 mm = 17,67 cm³ = 0,04771 kg x 396 = 18.89316 kilograms.
I rounded the numbers up because I’m really not that interested in making it in microgram precision, but you can already see that unless you have a really chonky cooler for -70ºC, you would considerably run into more and more weight saving at the cost of efficiency.
Out of curiosity, I took the value of 10% with the density of copper just to see how heavy it would be if I were absolutely certain that I wanted to go with the full electric route: it would weigh 43.53624 kilograms in total per motor. If it was aluminum, it would weigh 13kg.
You could, in fact, reduce the efficiency until it reaches just 10 to 5 kilograms of weight per motor. Reaching a maximum 30% of energy converted into heat for the 5 kilogram heavy motor. However, this is assuming the coils are at -70ºC. And if you keep converting all that energy into heat, it will quickly heat up to ambient temperature and exponentially increase the resistivity until you have a pile of molten metal.
This one is a bit tempting to me, to be honest, having 5kg of weight per motor…
… But you would need a really powerful cooler to run through all these motors…
Now I need to figure out how much it would weigh if the motor in question had an average torque and a high rpm, just like the D250 Evolito’s brushless motor.
Again, the 40kg motor I calculated above is for high torque density, this one is for high power density.
Well, I literally asked WebGPT to search and calculate a high power density:
Based on the search results, here are the key points regarding the ideal number of slots and poles for a high power density motor instead of an axial flux motor:
“For fractional-slot motors with high power density, the selection of both the number of magnetic poles and the slot-pole combinations is crucial. This choice significantly determines the motor's parameters and operating capabilities. [1]
The best slot-pole combination in terms of power density is 24-pole, 27-slots, although this results in a very high operating frequency of 960 Hz. This combination achieved a power density factor of 6.0 kW/kg, which is much better than other combinations. However, the high frequency may make control and powering the motor difficult, especially at high current loads. [1]
The slot-pole combinations with q = 0.5 (where q is the number of slots per pole per phase) are characterized by the lowest rotor losses. The 20-pole, 30-slot combination (q = 0.5) had 2.6-2.8 times lower rotor losses compared to other combinations. [1]
Slot-pole combinations where the number of stator slots Qs is smaller than the number of magnetic poles 2p should be avoided, as they can have large amplitude subharmonics in the magnetomotive force (MMF) distribution, which negatively impacts the motor's performance. [1]
While q = 0.5 combinations have favorable winding factors, the selection of the number of poles must also consider the motor's overall dimensions and operating conditions, as this affects the output parameters and rotor losses. The target solution cannot be predicted solely based on the q value and winding factor. [1]
In summary, for a high power density motor, the ideal number of slots and poles appears to be in the range of 20-24 poles and 24-30 slots, with a slot-pole ratio q around 0.5. However, the final selection should consider the tradeoffs between power density, efficiency, rotor losses, and ease of control at the high operating frequencies involved.
Learn more:
1: https://www.mdpi.com/1996-1073/15/1/215
2: https://things-in-motion.blogspot.com/2019/01/selecting-best-pole-and-slot.html
3: https://www.anttilehikoinen.fi/technology/electrical-engineering/pole-count-good-bad-ugly/”
Well, I will at least find some documents to feed to a new AI bot on the Poe website.
I did it, but I don’t think it helped a lot… As expected for ChatGPT. But since this is the only free option to reach that conclusion, then we ride with it.
It suggested a motor with 10,000 rpm, 300 Nm, 30 slots to 26 poles configuration with 400 volts DC and 750 amps, suggesting 4 turns per pole for some reason?
Just like before, I will only assume the number of turns, its length and size.
Assuming each slot has 4 turns and 750 amps, it would probably be 40 cm of length with the 22mm of thickness, it would weight:
- 40cm of length 22mm of diameter = 0,4105kg per wire.
- 0,4105 kg x 30 slots = 12.315 kilograms in total.
Well, this is an interesting result, but being honest, I don’t quite feel satisfied.
I’m not really sure if this result is correct, and another detail is that the higher the rpm, the lower the torque. So it wouldn’t deliver 300 nm of torque at 10,000 rpm.
The torque, density and efficiency map of the D250 Evolito’s motor shows that. It also says it uses cobalt based core material and permanent magnet materials.
I changed the base AI that this trained bot is supposed to use and it gave me a completely different answer:
“Summary:
In summary, for your 300 kW brushless motor:
Slots: 24
Poles: 20
Voltage: 600 V
Amperage: Approximately 500 A
Summary:
In summary, for your 300 kW brushless motor:
Wire Thickness: Approximately 2 AWG (2.588 mm diameter) to handle 500 A effectively.
Number of Turns per Pole: Approximately 150 to 200 turns depending on the specific design and magnetic characteristics of the motor.
Summary:
The estimated weight of the winding using 2 AWG wire with approximately 175 turns per pole and a total of 20 poles would be around 154.4 kg. This weight includes the wire used in the winding and contributes to the overall weight of the motor design [4][6].
Keep in mind that this is a rough estimate, and actual weight may vary based on additional factors such as insulation, end-windings, and the specific configuration of the motor. Further optimization may be needed during the design and prototyping stages.”
I just copy pasted the summaries or else this section would be needlessly long.
Literally one message after this, it suggested 12 to 24 turns per slot for a 24 slot configuration. 😐
So, it would reduce the weight from 154kg to 24kg if using copper, with a further reduction of weight using pure aluminum cooled to -70ºC. And as such, 7.45kg in total.
Or maybe not.
It incorrectly assumed that the thickness of the AWG 2 copper wire is around 2.588 mm of thickness, when in fact you would need a 1000 AWG wire for the 500 amps, which would be 22mm as I calculated before. Making it around 10 times thicker, increasing the weight by 10 times.
So, 74.5 kilograms for the 300 kilowatt axial brushless motor.
In any case, I feel like this was a dubious result. I don’t know for sure if the result ChatGPT reached is correct, if the result I reached is correct, so on and so on.
The obvious choice would be to go back to the REB-90 brushless motor and slightly modify it in order to make it reach 300 kilowatts of power instead of 80 kilowatts.
But it has the same problem when it comes to the number of turns of wire per stator.
Either way I need to make a 3D model and learn how to make those electromagnetic simulations in order to check the validity of what I calculated here. 😐
… Which I should’ve done ages ago…
… So all these calculations were useless…? Bruh.
3D modeling:
I’m still procrastinating… Still Procrastinating…
I’m still not in the best of health right now, but even so… I feel I should post this Project Log already.
I feel like I really reached a point where I need somebody’s help (I mean, the whole project was like that already).
I will just make a few simple 3D models of the electric motors that I proposed and then I will check how to make the electromagnetic simulations.
I still remember how I tried to make a mechanical simulation of 3D objects on FreeCAD and my potato computer could barely do anything.
The WebGPT says:
“The formula to calculate the number of turns of copper wire on slots from brushless motors is:
Turns per phase = (Voltage * 60) / (4.44 * Flux density * Stator area * Frequency * Kv)
Where:
Voltage is the desired motor voltage
Flux density is the maximum flux density in the stator, typically around 0.78-1.2 Wb/m^2
Stator area is the cross-sectional area of the stator
Frequency is the motor's electrical frequency
Kv is the desired motor Kv (rpm/V)
This formula allows you to determine the optimal number of turns per phase to achieve your desired motor specifications, such as voltage, Kv, and flux density. 1: https://endless-sphere.com/sphere/threads/motor-winding-calculations-cooling-design.122425/
2: https://www.instructables.com/Rewinding-a-Brushless-Motor/
3: https://fishpepper.de/2017/11/10/tutorial-brushless-motor-rewinding-based-on-a-br1103b/”
While the trained bot says:
“To calculate the number of turns per slot in brushless motors (BLDC), you need to consider several factors, including the slot area, the slot fill factor, and the desired torque characteristics of the motor. The formula used to calculate the number of turns per coil (T_C) is derived from the relationship between the slot area (A_slot), the slot fill factor (SF_g), and the current flowing in the coils.
The general formula can be expressed as:
Aslot⋅SFg=2⋅TC⋅ISP
- Aslot is the area of the slot,
- SF g is the slot fill factor (commonly around 0.4 for round copper wire),
- TC is the number of turns per coil,
- ISP is the current flow through the coils.
To break it down further, you first need to calculate the slot area, which is typically provided by design software or can be estimated based on the dimensions of the motor. Next, you multiply the slot area by the fill factor to determine the effective copper area available in the slot. After that, you can rearrange the formula to solve for T C :
Tc = Aslot*SFg/2*ISP
This calculation allows you to estimate how many turns of wire can fit within each slot while optimizing for maximum torque output. The number of turns impacts the back electromotive force (back EMF), which is crucial for the performance of the motor.
For example, if you have:
- Aslot=10mm2
- SFg=0.4
- ISP=10A
You would calculate:
You would calculate:
Calculate the effective copper area:
10 mm^2 ⋅ 0.4 = 4 mm^2
Solve for T C T C :
TC = 4mm²/2*10A = 4/20 = 0.2
Since the number of turns must be an integer, you would round this value based on practical considerations and further calculations on the motor’s torque requirements.
This formula and approach allow engineers to optimize the design of brushless motors effectively, balancing the number of turns with the physical constraints of the motor and the desired performance characteristics.”
Either way, I need to model it…
Well, the REB-90 is already modeled, so I will start with it.
Using an Area calculator, it seems it has around 24 cm² of area.
Well, in one of the calculations it gave me around 7 turns. But this is the calculation for flux density, not number of turns. The calculation should take the number of turns and then the magnetic flux to see if it has the appropriate force.
When I said the number of turns, it gave me around 1.5 to 2.5 teslas of magnetic flux.
… I have absolutely no idea the impact of this value 😐.
This project log got so full of text that I had to split it up to the next project log.
-
Project Log 86: Screw it, let's freaking do it.⁶
08/08/2024 at 22:40 • 2 commentsMonday, 05/08/2024, 14:19
Well, it seems like I talked too much useless stuff in the previous project log, because it ran out of space for new text to be added to it.
- First: find a relatively good alternator’s diagram in order to copy it.
- Second: list every part of it and the resistivity, inductance, etc. of each part and find a good enough DIY substitute.
- Third: actually build it for once?
Maybe make the 3D model of the parts?
Well, I didn’t do sh1t and just procrastinated, so I will just post this thing incomplete.
Maybe this way I will take some shame in my face and actually work on this project (brazilian expression).
I'm still procrastinating, but I asked ChatGPT how to make a 700ºC inverter and he just said it would be impossible. 💀
"I'm afraid it's not feasible to create a 1 kilowatt inverter that operates at 700 °C from scratch, as the temperatures you're mentioning are far beyond the capabilities of typical electronic components and materials. Even advanced ceramic semiconductors used in high-temperature applications usually have a maximum operating temperature of around 200-300 °C."
The only reason I wanted to make an DC to AC inverter would be to wireless transfer power to the rest of the mech without need to cool the power cable down and maintain as high efficiency as possible. If I can't make the goddang inverter to survive 700ºC, then what is the point?
The only way I thought of making it work would be using a mechanical switch, a literal electric motor connected to a disk/lever that would mechanically change the flow of electricity.
I could only think of electromagnetic coupling.
And finally, I need to build it up in order to see what is the energy output of the Molten Fuel Cell in order to convert it to the appropriate voltage/amperage.
But alas, I could do it with the induction coil, so it acts both as a wireless power transfer and as a transformer.Wouldn't that mean that I could make the 3-phase brushless linear motor for the actuators without a ESC controller, but just a mechanical switch controlled by a smaller electric motor?
huh... 😐
This is a 400 amps 15,000 volts switch, by the way:
![]()
This one costs 2000 reais (360 dollars), btw.
I just remembered about rheostats/potentiometers.
A potentiometer just changes the resistance for signal transmission control, a rheostat changes the resistance of the conduction of power.
This is a rheostat for power transmission:
This one is for a 3 phase 10 kilowatt rheostat:
![]()
I feel like this is so stupid...
Should I stay with the MHDG?
About the Inductive Magnetohydrodynamic Generator (IMHDG):
I was wondering how would be another way of making this generator efficient and compact with a somewhat certainty that it would actually work, the only thing that I could find that is similar to what I’m thinking of was to mix a liquid metal MHDG with an ejector in order to make it work without the problem of electrodes simply melting.
The idea would be to mix a vacuum ejector:
![]()
With this thing here:
![]()
Source: https://www.mdpi.com/2071-1050/13/23/13498
It is a molten metal MHDG for a radioisotope power source for a satellite, according to the simulation/calculations in the paper, it is said that the higher the temperature and intensity, the higher the efficiency. Achieving a maximum 50% efficiency.
This is the same author that made this article about a liquid metal disk MHDG:![]()
Source: https://www.mdpi.com/2071-1050/15/16/12619
And according to him, the efficiency can reach around 70%.
Now it is the part that I talk about the problems:
First off, I already talked about a similar design, but for a combustion driven water turbine because a conventional combustion turbine would require really expensive materials.
And this idea is essentially that, but with liquid metal and a less efficient way of converting kinetic energy into electricity.
Besides, the Vacuum Ejector has different efficiencies based on the type of fluid it interacts with.In both designs a thermoacoustic engine is required, even if the MHDG on itself is efficient, the thermoacoustic engine is not.
You would need to literally have a piston style engine to make this work, and I don’t know how long it would last with liquid metal nor how efficient it would actually be.
Essentially it would be just a Stirling engine with more complexity.
I could literally replace the MHD/Stirling Engine with a two way pulsed turbine.
Source: https://journal.hep.com.cn/fie/EN/10.1007/s11708-020-0702-3
All this shenanigans about universal fuel engines started because conventional generators and combustion engines aren’t that efficient and still are heavy and expensive…
![]()
Maybe I’m overreacting?
The liquid metal MHDG with vacuum ejector would be more efficient than a pulsed LMMHDG and more efficient than the combustion hydroturbine that I talked about, especially because of the heat in the system.
The adiabatic combustion engine would be more efficient than conventional engines because of the extra heat, and on top of that, the liquid metal passing through the coils would indeed have lower efficiency than a conventional dynamo/alternator, but it would be extremely light and easily out-perform the latter.
Using the liquid metal magnetohydrodynamic generator and the adiabatic system, maybe you could reach really high efficiencies.
1- The idea is to take a small portion of liquid metal, such as tin, aluminium or other low melting point metals.
2- Then to take an air blower with a heat exchanger, inject the air in a vacuum ejector that would also work as a combustion chamber like in a turbine engine.
3- The combustion and air flow would move the liquid metal in a system with electromagnetic coils, permanent magnets and electrodes similar to a tokamak and the previous examples of MHDG.
4- Since the air and fuel are both absorbing heat and combustion in the presence of molten metal, it would work just like a heat-exchanger and regenerator at same time, increasing the heat, and thus, the energy in the system to really extreme levels. The more heat the air and fuel absorb before combustion, the better. But the limiting factor of turbine engines is the heat that the turbine part can survive, which wouldn’t be a problem in this molten metal mess.
5- I don't know how efficient the system would be, but the idea would be to take the general efficiency of liquid metal magnetohydrodynamic generators, the efficiency of the heat and kinetic transfer of the combustion chamber/vacuum ejector hybrid and the added efficiency of the heat-exchanger/regenerator hybrid and attempt on finding a final efficiency on generating electricity.
6- That would be a rough estimate, but it would still be an estimate nevertheless.
… Or maybe I’m just talking out of my ass? If you assume the REB-90 to be a reference, that motor only weighs around 30kg, if we assume that it would be as efficient as a generator (90%), I would need it to be around 100 kg of weight for 300 kilowatts of power.
I even got myself wondering if it would be feasible to just switch to liquid hydrogen altogether. You would “just” need 15 liters of liquid hydrogen for every kilogram of it, and every kilogram of liquid hydrogen would contain 142 Megajoules of energy, you would need 2kg of it for every hour under 100 horsepower. So, 20kg in total, which would be 300 liters of liquid hydrogen for 10 hours of use at 100 horsepower.
![]()
This 150 liter liquid nitrogen tank weighs 100kg and costs around 2000 dollars (10,000 reais). The liquid hydrogen is too cold for this tank.
(you can actually freeze liquid hydrogen into “ice” cubes, but its density only increases by 10%, so 30% of 300 = 30, total amount of liters = 270)
Surprisingly enough, there are cryocoolers that can reach 4 kelvin, which is 10 degrees below the 14 kelvin required to solidify hydrogen.
The cheapest pulse-tube cryocooler that I could find is around 4000 reais (700 dollars), but I don’t know how to make a DIY cryocooler to reach those insane temperatures. The only tutorial I found on making cryocoolers was in Hyperspace Pirate’s channel, and that guy made some insane stuff that would instantly kill him if anything went wrong. Plus, the Pulsetube cryocooler that you see is just one part of the system, you still need a compressor, heatsink etc etc etc.
… At this point I’m reaching such levels of insanity that I think it would be the best for me to just shut the f*ck up and work on the Molten Carbonate Fuel Cell.
![]()
About the Actuators:
I didn’t want to write this here because my brain is weird, so when I try to forget something, it just keeps me remembering said stuff.
I still worry about those things. In fact, I always keep rolling all the details of this project in my mind during the day, trying to find a detail that I missed or easier/better ways of doing something.
That is one of the reasons I repeat myself so many times through the project logs.
Well, the thing is, now that I know I can make both the linear electric motor and the conventional electric motor by using mechanical switches, I do wonder if the linear ones are actually the best choice.
For example, I had the idea of using linear motors because:
- The normal rotary motors would need an ESC controller to work, which I can’t make out of scrap.
- The stewart platform would divide the loads between all actuators, making the system more efficient.
Well, we both learned that neither is completely true.
The ESC controller can be made using mechanical switches and the Stewart platform doesn’t exactly divide all the loads between all actuators at all times.
(This is a lighter version of the AMP suit on the upcoming game called "Avatar: Frontiers of Pandora", it is kinda interesting to see how everything kinda works under the protection)
On top of that, the stewart platform needs to be extremely redundant, with each actuator actually outputting the power required (100 kilowatts), which increases weight and also the number of mechanical switches the whole mech will need.
An electric motor with the same output (100 kw) wouldn’t weigh as much (supposedly) and would have a bigger area that the electromagnetic coils would be able to support, further reducing the weight/size of the coils and switches.
Of course, that wouldn’t be completely true for every part of the body, each shoulder needs 5 degrees of freedom using rotary actuators, which means 5 actuators for every degree. While the thighs would only need 3, since these “only 3” would sustain the whole body, they would need to be heavier/bigger.
But, each electric motor would need bearings and shafts that would need to be very precise, while the linear actuators wouldn’t necessarily need to be that precise. I will try my best to be as precise as possible using tubes for the molds, and I don’t know if the rotary ones would be easier to make/find “references” like that.
(I couldn't find an humanoid robot with the same degrees of freedom as a human body)
Every shoulder has 5 degrees of freedom, torso has 3, every thigh has also 3, 1 for every biceps, 1 for every knee, each foot has also 3, each wrist has 3 and the fingers are another nightmare. So, around 35 motors in total. While the Stewart platform would have around 6 per limb, 30 in total for shoulders, torso and thighs, while having another 24 for both feet and wrists. 54 in total.
I don’t exactly want to work with rotary actuators, but, like I said, just putting it out of my brain to free up space.
Unrelated, but look at this cylindrical robot, it is so cute. lol
![]()
Source: https://www.artstation.com/artwork/PmgNnn
I too keep wondering if there is another way of making the switches rotate and/or going back and forth in a purely mechanical manner. Without the use of brushless motors that would require a system.
For example, I thought of maybe using hydraulic mechanisms that would physically move the rheostat of an actuator without the need of an encoder, brushless motor, ESC controller and circuit board. Literally, all using mechanisms. No programming, all made using recycled parts, just like the rest of the mech.
I’m not very confident in the idea, however.
How actually everything would work? How would every detail be done? How robust would the system be? What about getting dirty? What about impacts messing up the mechanical system?
The hydraulic ones sound the most practical ones, you simply move your body and pads or syringes full of oil would be pressed, pushing the fluid to move the switches either in a linear or rotary manner. I’m tired of using this example, but it is just like one of those hydrostatic excavator toys.
![]()
As any other system, it has problems.
What if the pressure made by the movement of the pilot’s body isn't strong enough to move the switches? What if there is a leak? What if there is something loose? How well, fast and/or practical would it be fixed? How safe would it be to fix it?
The idea is to maintain the pilot’s body moving as little as possible, which I genuinely can’t see being done in a practical manner using the hydrostatic system. But I can see it being done with the hall effect sensors.
But maybe it would be more responsive than the idea of using the haptic-skin to transmit the sensation of touch to your body, of course, assuming that there is a mechanical encoder.
The encoder on the actuators would give feedback to the system on the position of the limbs, if the encoder is mechanical, then while moving your body, you would physically feel the resistance the actuator is experiencing. With an equally electro-mechanical working system, the power source would increase the output based on the force you are applying, only stopping when you stop.
Speaking of which, I still didn’t think how the system would increase output based on the power the system requires it to output.
In an electrical system it is easy, you increase torque and rpm, the system increases amperage and voltage, the battery/generator increases the energy output.
Now, with a dumb-down electromechanical system, how can I command the power source to generate more power?
If I’m using an electronic command and an electronic feeding system, then the increase in force would be detected by the system, and thus, it would make the electronic fuel feeding system increase the fuel input.
The system would then calculate and compensate how much electricity is being fed to the other actuators and automatically change the rheostat’s position to lower electricity transmission.
On a mechanical system however… How would you do that?
This is a mechanical speed controller from the 80’s, it is not as complex as the thing I’m talking about, however.
With all of that in mind, I do wonder: are electric actuators even worth it at this point?
The electromechanical switches and rheostats are really interesting to me, don’t get me wrong.
But would all of that fit into the mech?
Everything must take space, cost, weight and complexity into consideration, among other things. But every actuator would need 3 switches/rheostats, and every rheostat-switch would need 3 servo motors and every servo motor would need its own control board.
I don’t think the servo motor would be a cheap one, and even if it were, I would need 54x3 = 162 motors in total, even if I take the cheapest one that costs around 50 reais (10 dollars), I would need 8100 reais/1620 dollars.
And I don’t think it would be practical to DIY build every single servo motor just so they can work as rheostat switches.
I guess that in the end, the best choice would in fact be the hydrolysis activated artificial muscles, no?
Of course, I can still stay with the brushed/sliding contact railgun I was thinking of until now.
But... I would still need around a single rheostat switch with a servo motor for every actuator in this case, around 54.
... Assuming the mechanical rheostat switches aren't hydraulically actuated, as I suggested above.
Off-topic:
About the laser stuff:
(I wrote this part after I wrote the part about the nd:glass and so on, so it will look like I’m contradicting. Why don't I simply add it under all the text? I don’t know.)
I try asking about cheap and efficient high power alternatives of laser emitters to web-search gpt, but it always says these don't exist and always list the same diode lasers, plasma lasers etc.
Then I learn that there are nd:glass lasers, a glass rod with a chemical mixture, which is cheaper than synthetic ruby (a fortune) and things like lead-salt diode lasers, which, although it needs to be at cryogenic temperatures to work, it is still way cheaper than a conventional laser diode that is basically made out of fricking gold.
Could the chat gpt help me once to find something like this?
I just found this article about Lead Halide Perovskite Nanowire Lasers which reached something more than 90% of efficiency.
The problems are:
- I don’t know how easy these are to make in a DIY setup.
- I don’t know how expensive the materials used are.
- I don’t know how to make a macroscale perovskite crystal, assuming it is even possible.
Well, I just started all this babbling about DIY laser mediums because I was afraid of not being able to make the photon gun made out of incandescent light bulb filaments to work for pulsed detonation propulsion.
If I’m going to lose 50% of the energy input that the light bulbs filaments would output anyway, then what is the point?
An idea I shared with chatGPT:
Me:
If I have a plasma dense enough to reflect light, what would be the efficiency of infrared light reflection?
Would it just absorb the light?
I'm asking this because most laser gain mediums are expensive and inneficient, so it would be easier to have high efficiency near-infrared and short-infrared LEDs emitting their light in a optical fiber made up of laser induced plasma until it reaches its target.
Both would work with ultrafast pulses.Its answer:
The efficiency of infrared light reflection in a dense plasma can be quite high, but it depends on the specific properties of the plasma.
Here's a more detailed explanation:
When a dense plasma is formed, the free electrons in the plasma can act as a reflective surface for electromagnetic radiation, including infrared light. This is known as the "plasma mirror" effect. [3]
The reflectivity of the plasma mirror depends on the plasma density. For a plasma with an electron density above the critical density for the infrared wavelength, the reflectivity can be very high, often over 90%. [1][3]
The critical density for infrared light is quite high - around 10^21 cm^-3 for 1-5 μm wavelengths. So to achieve high reflectivity, the plasma needs to be very dense, on the order of 10^22-10^23 cm^-3. [2]
At these high plasma densities, the infrared light would not be absorbed, but rather efficiently reflected by the plasma. The reflected light could then potentially be coupled into an optical fiber and guided to a target. [1]
Using a laser-induced plasma as the reflective medium in an optical fiber setup could indeed be more efficient than traditional laser gain media, especially for ultrafast pulses in the near-infrared to short-infrared range. The plasma-based approach avoids the limitations and inefficiencies of solid-state laser materials. [1][2]By the way, in a previous chat, Web-searchGPT said it would only have 30% of efficiency. lol
It seems like I was asking too much and didn't read properly.
The QUANTUM efficiency of Ruby lasers is 80%, but its optical to optical-to-optical efficiency conversion (aka from scattered light source to coherent laser source) is around 17% maximum using laser emitting diodes.
Nd:Yag, nd:glass and other laser materials more expensive of cheaper also achieved a maximum of around 50% to 60% using Laser Emitting Diodes, which on themselves are as expensive as gold.
So, asking for a high efficiency laser material on the cheap is kinda asking too much.
Also, the search results always give me conflicting answers, one article says their efficiency is on 80% without specifying in which way is it efficient, other articles say these materials only achieve 10-17%.
So... I wish there was a chart explicitly explaining all that stuff...
Just a heads up, in the previous project log I calculated I would need 25 megajoules of laser power for 1000kg of thrust based on the candy-rocket fuel, but that is probably too much, because a tank cannon has 30,000kg of recoil and the projectile has around 20-30 megajoules.
ChatGPT on the other hand, keeps saying I would need an energy output that always varies between 20 kilowatts to 200 megawatts of power [more or less 20 kilojoules to 200 megajoules.
Well, unfortunately I couldn’t say what I recently found out: you can just mix the oxide of certain materials with glass and the glass will become a laser emitting material.
I’m not really sure on which size I should make the laser rod based on the output in watts, but basically, it has a range of efficiency between 40% to 60%. Although the efficiency is lower compared to Ruby rods and Diode lasers, it can actually take and survive way stronger pulses than the other two.
Assuming that I would use DIY incandescent light bulbs to pump the gaining medium (the doped glass), I made this aberration of a graph:
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The number of squares is the percentage of the total energy that is absorbed of each wavelength, reaching this list based on neodymium dopant.
Since neodymium absorbs from 800nm wavelength to 1064nm wavelength, I need to make both ends meet in this range. “Downconversion” and “upconversion”, as the ChatGPT puts it.
“For 800 nm to 1400 nm (mid-range absorption percentages): Use Upconversion Materials: Ytterbium (Yb), Erbium (Er) for converting longer NIR to near-visible or NIR ranges.
For 1400 nm to 3000 nm (lower percentages of absorption): Use Downconversion Materials: Phosphors, Quantum Dots for converting UV or visible light to longer IR wavelengths suitable for Nd-doped glass.
NaYF4+, Yb3+ (Sodium Yttrium Fluoride: Erbium, Ytterbium) Absorption: NIR light (around 980 nm) Emission: Visible to NIR (around 800-1500 nm)
LiYF4+, Yb3+ (Lithium Yttrium Fluoride: Erbium, Ytterbium) Absorption: NIR (e.g., 980 nm) Emission: Visible to NIR (e.g., 800-1600 nm)
Er3+/Yb3+ Co-doped Glass Absorption: Yb3+ absorbs around 900-1000 nm. Emission: Er3+ can emit around 800 nm when co-doped with Yb3+, as the energy transfer from Yb3+ to Er3+ can facilitate this emission.
Pr3+/Yb3+ Co-doped Glass Absorption: Yb3+ absorbs around 900-1000 nm. Emission: Pr3+ can emit in the range of 800-850 nm when co-doped with Yb3+, thanks to the energy transfer process.
Tb3+ (Terbium-doped Glass) Absorption: Tb3+ absorbs in the range of 800-1000 nm. Emission: Emits in the range of 490-550 nm. Tb3+ is not a direct choice for 800 nm, but it can be used in systems that involve other dopants or non-linear processes.
LaF3+ (Lanthanum Fluoride doped with Cerium) Absorption: Ce3+ can absorb in the range of 900-3000 nm. Emission: The emission can occur around 400-500 nm. Ce3+ is typically used in combination with other materials for specific applications.”
I’m pretty sure I won’t find any of these materials to be bought, and they can, they won’t be cheap. I asked for a list with other dopant materials to cover for the full range of the incandescent light-bulb.
“Visible to Near-Infrared (400 nm - 1400 nm)
400 nm (1.04%) Dopant: Samarium (Sm) Absorption/Emission: 400-450 nm
500 nm (1.04%) Dopant: Praseodymium (Pr) Absorption/Emission: 440-485 nm
600 nm (2.08%) Dopant: Praseodymium (Pr), Dysprosium (Dy) Absorption/Emission: 485-605 nm, 572-670 nm
700 nm (3.13%) Dopant: Dysprosium (Dy) Absorption/Emission: 572-670 nm
800 nm (5.21%) Dopant: Neodymium (Nd) Absorption/Emission: 740-870 nm
900 nm (6.25%) Dopant: Ytterbium (Yb) Absorption/Emission: 900-980 nm
1000 nm (7.29%) Dopant: Ytterbium (Yb), Neodymium (Nd) Absorption/Emission: 900-1030 nm
1100 nm (7.29%) Dopant: Neodymium (Nd), Erbium (Er) Absorption/Emission: 980-1060 nm
1200 nm (7.29%) Dopant: Erbium (Er), Thulium (Tm) Absorption/Emission: 980-1200 nm
1300 nm (7.29%) Dopant: Erbium (Er) Absorption/Emission: 980-1600 nm
1400 nm (6.25%) 1500 nm (6.25%) 1600 nm (5.21%) 1600 nm (5.21%) Dopant: Erbium (Er) Absorption/Emission: 1530-1600 nm
1700 nm (5.21%) 1800 nm (4.17%) 1900 nm (4.17%) Dopant: Thulium (Tm) Absorption/Emission: 1700-1900 nm
2000 nm (3.13%) 2100 nm (3.13%) Dopant: Holmium (Ho) Absorption/Emission: 2000-2100 nm”
(After this it keeps repeating holmium for higher wavelengths from until it reaches 3000nm)
And again, I doubt I would find any of these materials for cheap, nor even find them.
The best way to make this laser as efficient as possible would be to use LEDs that emit light in the absorption of the laser dopant.
And I don’t know if the other dopants would absorb the infrared light of the previous dopants.
… Or maybe that is a lot of bullcrap, because there is this graph of erbium doped glass and it absorbs and emits light in a pretty close wavelength:
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Thulium and Neodymium:
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Only Neodymium:
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Source: https://www.samaterials.com/n31-nd-glass.html
Yttrium:
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Holmium:
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Thulium + Holmium:
Source: https://opg.optica.org/prj/fulltext.cfm?uri=prj-4-6-214&id=350876
Ytterbium:
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Needless to say, I didn’t read sh1t.
I just found the first result and copy-pasted it.
Probably none of them are useful and in some cases it is said that it is about “luminescence”, which may or may not be related to laser emission.
On top of that, they use very, very specific types of glasses for each approach. Which may or may not work for sodium silicate.
It seems like the infrared wavelength that is “invisible to the atmosphere” is around 8000 nm to 15000 nm, and that is long-infrared and the light bulb emission is in the near infrared to the short infrared, unlike what I wrote before.
As you can guess, it seems I am as unreliable as the chatgpt’s AI, lol.
Something interesting that I found:
For some reason, nd:glass has only 40 to 60% of efficiency, but an optical fiber made of nd:glass is 92% efficient.
According to WebGPT, it is because the fiber has a super high surface area in which the light pumping has optimal transfer rate.
Even using sodium silicate for the neodymium oxide, I don’t think it would be practical to make a DIY optical fiber. I mean, you would need a really thin, long and super perfect hollow tube so you could cast the sodium silicate.
Besides, I don’t fully understand how fiber amplification works within lasers.
And according to this article that WebGPT linked to me, fiber lasers aren’t meant for high power outputs.
In any manner, the method used for optical fiber pumping is called a “cladding pump”, which I found on this website explaining it with images. It could be used as a basis for designing Nd:glass rod for lasers. Maybe this way will reach 90% efficiency.
I still don’t know what is the optimal size of laser rods based on the output power desired, pulse duration, pulse intensity etc.
But if I were to make an optical fiber, I would at least try to make something more like articulated optical pipes. Basically, the inner laser rods would be made with articulation in mind and all of the outside of the nd:glass rod would be reflective, then there would be a section for the pumping source and finally the outside layer.
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This is a microscope articulated arm, but imagine the nd:glass parts shaped like this.
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Other articulated pipes as an example.
Actually, I’m skeptical about that value. WebGPT is not the best source for anything, it could have shown a whatever value based on its generative bullshittering.
I still don't know what is the optimal size for laser rods based on the power output, but I found something interesting that may help:
While searching for conventional Nd:Yag laser rods, I saw this website were they say that the amount of power that can end up damaging the material is around 800 MW/cm².
A watt-second is equal to a joule-second, but a watt-hour is equal to 3600 joules, however, WebGPT told me that it would be around 800 joules per cm² for the laser rod.In another website it says that their Nd:Yag lasers are a few dozen joules per cm² and then in other wavelengths they use the value of kilowatts per cm².
This website at least has some explanation to it, but I can't make heads of it."Pulsed Lasers
As previously stated, pulsed lasers typically induce a different type of damage to the optic than CW lasers. Pulsed lasers often do not heat the optic enough to damage it; instead, pulsed lasers produce strong electric fields capable of inducing dielectric breakdown in the material. Unfortunately, it can be very difficult to compare the LIDT specification of an optic to your laser. There are multiple regimes in which a pulsed laser can damage an optic and this is based on the laser's pulse length. The highlighted columns in the table below outline the relevant pulse lengths for our specified LIDT values.
Pulses shorter than 10^-9 s cannot be compared to our specified LIDT values with much reliability. In this ultra-short-pulse regime various mechanics, such as multiphoton-avalanche ionization, take over as the predominate damage mechanism [2]. In contrast, pulses between 10^-7 s and 10^-4 s may cause damage to an optic either because of dielectric breakdown or thermal effects. This means that both CW and pulsed damage thresholds must be compared to the laser beam to determine whether the optic is suitable for your application."Another something that took my attention:
"Beam diameter is also important to know when comparing damage thresholds. While the LIDT, when expressed in units of J/cm², scales independently of spot size; large beam sizes are more likely to illuminate a larger number of defects which can lead to greater variances in the LIDT [4]. For data presented here, a <1 mm beam size was used to measure the LIDT. For beams sizes greater than 5 mm, the LIDT (J/cm2) will not scale independently of beam diameter due to the larger size beam exposing more defects"
Well, I need to compare a lot of things that probably needs super expensive instruments to measure and then make the thing.
... Like in the rest of the project logs, it would be easier to find a laser rod that already exists and then copy its dimensions with cheaper materials in order to approach its performance.
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Disk lasers work like this, like a mirror, then maybe I can make a high power laser without the risk of melting/exploding it with so much power.
By the way, there is a thing called "Q-switch", which is basically a thing that pulsed lasers use to reflect the emitted laser multiple times in the gaining medium (like the laser rod) and then release it all at once in a stronger pulse.
Imagine it like one of those bouncing castles of some sort, but instead you add one above and one below, and every time you bounce you do an extra kick, adding more and more speed the longer you keep bouncing on both platforms.
And once you have significant speed, someone takes out the up bouncing castle and you go full ballistic into the sky.That's kinda it.
But there are various ways you can do this q-switching thing, you can have a mechanical mirror that goes up and down with a motor for example.
The other example is of a saturable absorber/reflector, that only reflects the laser's light until a certain point.
You can do that using specific Dye lasers, crystals and the like.But I really can't wrap my head around on how the electronic ones work.
The only one that ChatGPT explained to me as a crystal with a refractive index that can be changed based on the electricity you put into it, but I couldn't find whenever or not I can DIY such a thing.
The only way I could think of actually pulling this off would be if you instead of pumping the light directly to the laser medium, you would pump a smaller laser that then would point at another bigger laser medium.
So, since you don't have to worry about if the Q-switch would work or not with the full scale of the power input.But that strongly depends on the type of laser medium you're using, if it is the Nd:glass laser with 50% of efficiency, you would only transmit half of half of your input power.
There is such a thing as a Plasma Mirror.
In the wikipedia article it is said that the plasma is made in fused silica (quartz) by applying a really intense laser pulse that will ionize the material.
I... Just don't understand how it is ionized or why it needs to be a laser that ionizes it. Wouldn't a kilovolt pulse ionize its surface and make plasma or something like that?
It can also be used for plasma lensing, but I don't know how to do neither.
What WebGPT said:
"Based on the search results, here are the key details for the energy and duration requirements of an ultrafast laser pulse to create a plasma mirror:
The laser pulse needs to have enough energy to convert the surface of a highly polished mirror into a highly reflective plasma. This is typically achieved with pulse energies in the range of a few millijoules [1].
The pulse duration should be in the femtosecond (10^-15 s) to picosecond (10^-12 s) timescale [1][2]. This ultrashort pulse duration is necessary to generate the high intensity required to create the plasma mirror.
Specifically, the search results mention that the researchers used a chain of plasma mirrors, where the first two mirrors were used to clean up the laser contrast by reflecting only the main ultrashort pulse and not the nanosecond-scale prepulse [2].
The third plasma mirror was then used as the basis for high-order harmonic generation, where the intense laser field drives the surface of the plasma, causing the electrons to oscillate at relativistic speeds [2].
In summary, the ultrafast laser pulse needs to have an energy of a few millijoules and a duration in the femtosecond to picosecond range in order to effectively create a plasma mirror for applications like high-order harmonic generation [1][2]."
I found this article here:
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Source: https://link.springer.com/article/10.1140/epjs/s11734-023-00909-2
They always use the words "relativistic plasma mirror", and it is always about using the laser to focus on a really, really small point (as in the image).
So I'm guessing it is some "quantum-quacky-stuff" that makes it work.Whatever it is the working method, it does look like some really complicated stuff that I honestly can't grasp.
Well, first: it seems like if you have a vacuum chamber with electrodes mirroring the shape of a lens, when making plasma, it will have similar properties to that of a conventional lens.
And yes, I know this is not what plasma lenses are normally about, but it is an easy work-around without too much complexity.
On top of that, I saw this experiment with lasers using water. If you have any material with a certain refractive index, depending on the angle, the material will act like a reflector, but not a mirror.
So, maybe, you could have a plasma chamber that acts as a reflector that directs the laser beam to an actual mirror in order to make the q-switch.
Accordingly to this simulation: https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_all.html
I would need something with a refractive index of at least 1.3 (water) or 1.5 (glass) at an angle of 45 degrees from the light source in order to fully reflect it, or else the beam would just split in two, dividing the whole laser.
I asked chatgpt and it said that:
"So, the plasma density required to achieve a refractive index of 1.5 should be in the range of 10^9 to 10^12 cm^-3, with an angular frequency of 0.746ω.
An electron density of 1010 cm−310^{10} \text{ cm}^{-3}1010 cm−3 is 1014 m−310^{14} \text{ m}^{-3}1014 m−3. To give you a sense of scale, it's roughly:
10^10 electrons per cubic centimeter, which is a high density but not extreme. It's comparable to some conditions in lower-density plasmas found in laboratory settings.
Electron Density: Approximately 1.7 × 1 0 10 cm − 3 1.7×10 10 cm −3 to achieve a refractive index of 1.5.
Power Density: Typically in the range of 0.1 W/cm 2 0.1 W/cm 2 to 1 W/cm^2 1 W/cm^2 to maintain such an electron density in a low-pressure plasma system.
The exact power density will depend on the specifics of the plasma generation system and the conditions in your vacuum chamber.I asked on quora if this is a big type of plasma or not, but I doubt I will receive any answer.
Also, about the rechargeable explosive pulsed power generator:
Needless to say: don’t try this at home, not even I will try this insanity.
I was having a little difficulty finding out how to calculate it, but after asking around it was said that I would need to just check the amount of joules needed to heat water.
So, you need 4.1 Joules to heat 1g of water to 1ºC.
Since I want to heat up 1 liter of water to 2000ºC in a steam explosion, I would supposedly need:
- 2000ºC - 25ºC (room temperature) = 1975 ºC
- 1975 x 4.1 = 8097.5 joules in total for 1 gram
- 1kg = 1000 grams = 8097.5 x 1000 = 8,097,500 joules
So, in order to output, let’s say, 30 megajoules of power, I would need around what?
“In your case, aluminium is said to have a specific heat of 0.90Jg∘C . So, what does that tell you? In order to increase the temperature of 1 g of aluminium by 1∘C , you need to provide it with 0.90 J of heat.”
So, taking a look at the specific heat list on wikipedia, the most promising materials to work with would be molten salt and aluminum. Although molten salt melts at 220ºC and boils at 1200ºC while aluminum melts at 660ºC while it boils around 2200ºC.
Actually, the lithium would be the best, but I would need to use another fluid since water explosively reacts with lithium. But screw lithium.
So, assuming that I inject the water in the highest amount of injectors as possible in order to increase the efficiency of heat exchange as much as possible, reaching an efficiency of around 90%, I would need around:
- 2000ºC - 25ºC = 1975 ºC
- 1975 x 0.90 = 1777.5 joules
- 1777.5 joules x 1000 grams = 1,777,500 joules.
- 1kg of aluminum = 1,7 MJ
- 30 MJ / 1.7 MJ = 17.6 kg
Obviously, I doubt this would occur, for a lot of different reasons.
If the water steam absorbed 90% of this heat, the aluminum would immediately solidify since it lost 90% of its heat. So I’m willing to bet that the efficiency of heat transfer would be maximum 30% (even though ChatGPT says it would have 90% of efficiency, 99% even).
So I would need around 3.33 times more mass of aluminum, around 58.6kg. On top of that, Explosive pulsed power generators have really low efficiency, around 30% to 20%, so I would need even more water to absorb 3.33 times more heat.
So, 195kg of aluminum and 9 liters of water in total.
Not as portable than I thought, but more portable than a building sized capacitor bank.
For molten salt it would be:
- 1200 ºC - 25 ºC = 1175ºC
- 1175 x 1.56 = 1833 joules
- 1000 x 1833 = 1,833,000 joules per kg
- 30 / 1.8 = 16kg of molten salt
- 16kg x 3.33 of efficiency of heat transfer x 3.33 of efficiency of generator = 177kg in total.
But if I want to “just” have a pulse of 10 kilojoules, then I would need around 5.8 grams of molten aluminum reacting with around 11 grams of water, and 5.4 grams of molten salt to react with the same amount of water.
To separate the molten liquid from the steam, I would use a liquid vapor separator, like this one:
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The steam would go through a radiator and turn back into liquid while the molten metal/salt would go back to the molten tank.
I did think of making the moving part being an air piston with an electromagnet inside of it, while the outer coil is the stator that catches the energy, the air piston being able to go back and forth a few times after the steam explosion.
This maybe would make the system slightly more efficient.
But I was wondering if the most efficient and portable option would be to make the moving part a turbine, just like in the flywheel systems. But google didn’t show anything similar to an explosive turbine pulsed generator, so I can’t say for sure if it would be efficient or practical.
I also thought of making the structure more similar to a magnetized target fusion reactor, lol.
Lithium and glycol (it doesn’t react with lithium, unlike water, and it has the same specific heat as water) would both be better options than the water+molten metal/salt, but lithium is highly toxic and dangerous to humans. But of course, if you are crazy enough to put an explosive pulsed power generator on your backpack, you wouldn’t mind the extra hazard. I bet the system would be 3 to 4 times lighter than the molten aluminum/salt.
If you use the hydrolysis of water to generate hydrogen and oxygen, then the weight might become more acceptable.
For example, 1 liter of water converted into 900 grams of oxygen or 629,8 liters and 100 grams of hydrogen or 1194 liters of hydrogen, you would need around 13.2 MJ of energy, and assuming 100 bar (or 10 MPa) gas tanks, you would need a tank of at least 11 liters of hydrogen and another with 6 liters of oxygen for that.
However, the efficiency of hydrolysis is around 70% and the efficiency of the explosive driven pulsed power generator is 30%, you would need 3.33 times more liquid/gas, for the same 13.2 megajoules, totalling 82.5 liters of hydrogen at 10 MPa and 45 liters of oxygen at 10 MPa for the 30 megajoule threshold.
I just don’t know how you would detonate around 8250+ liters of hydrogen and 4500+ liters of oxygen at same time in this generator.
Just now I remembered that you would either need a really powerful pump for that, or make the hydrolysis in a really tough gas tank.
“It's a question I had also and if I remember well I read somewhere that this process is pressure insensitive, which makes no sense to me ! But from what I understand it seems to be the case, and here is an application of this similar to your idea of high pressure ocean water electrolysis : http://en.wikipedia.org/wiki/High_pressure_electrolysis Does it make sense ?”
Source: https://www.physicsforums.com/threads/effect-of-pressure-on-electrolysis-of-water.179504/
I was thinking here: this is really a convoluted process of generating electric pulses, why not just use the fuel directly?
Well, the only problem is that you would need an air compressor and an air tank.
And these have terrible efficiency, or maybe not, I mean, you would need a little compressor to get just the right amount of air.
Also, I said that you could use a turbine flywheel hybrid, but I don't know how simple that would be.
We are talking about a detonation engine, not a conventional turbine. You would need really precise calculations and really thick blades to avoid it being absolutely destroyed.
I had the thought of using a dual way counter rotating turbine, just like steam turbines, where they convert the extreme pressure and speed of steam into rotational motion.
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The stator (yes, they have stators) always takes some amount of efficiency out of the equation, so, for absolutely maximum efficiency, it could be interesting to make what would be stators into counter rotating turbine blades also.
Making the entire counter rotating turbine would be really complex and difficult, but since the electromagnetic bearing would also be the generator and shaft, then it would be "easier" to make every disk rotate independetly.
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Of course, I'm thinking of the blades to be as thick as a screw thread because of the explosion, although, the more it travels through the blades, the less powerful the wave would be.
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Source: https://www.mdpi.com/1996-1073/15/24/9353
Just now crossed my mind that you could actually use steam instead of coal or hydrolysis to power this thing, heating steam electrically is 90% efficient.
-
Project Log 85: Screw it, let's freaking do it.⁵
07/30/2024 at 14:09 • 2 commentsTuesday, 09/07/2024, 16:11
I’m writing this here on google docs first.
Well, soon or later I would need to figure out how to make a PCB for controlling the mech.
I kept avoiding it because I really don’t know how I would wrap my head around these concepts. In fact, I already tried multiple times to learn how to make the control board, but with no success…
Depending on the result of this “serious” attempt may or may not result in the possibility of a brushless linear actuator instead of a sliding contact one like I was babbling about in the previous project log. After all, both the ESC and the energy supply would do basically the same thing, changing the voltage, amperage, frequency and which actuators receive it.
Also, I don’t know if all this work I had making a rough estimation of the coils strength would actually be useful, since, you know, the energy would be divided by all actuators and rarely a single one would actually use all the 200,000 watts of power.
And I also doubt the system would even survive such energy input… Maybe I’m really over-engineering this thing with all these 40 ton cylinders.
… Bruh, 9 days in and I still didn’t even start to research this subject. I’m procrastinating too much…
Bruh² my drawing table with a display from Huion stopped working out of nowhere. 😐
Luckily I’m still within the time duration for a refund.
Now I don’t know what to do… Do I try to buy another table from a different seller or just… Keep going with this project…?
I bought a used one for ⅓ of the price, lol.
… I've been procrastinating for so long, and this project has already taken so uselessly long that I’m wondering if I should hire someone to design this garbage can for me.
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Oh yeah, I tried it before, they asked for AT LEAST 30,000 reais (5400 dollars).
ACTUAL WORK:
Goddang it, I hate how I procrastinate so much, but I think I can trick my mind into properly working right now.
Basically, I was literally saving a bunch of videos explaining the literal basics to advanced concepts involved in electronic systems, so it was a daunting task for me from the beginning. SO, my “brilliant” idea was to actually take already existing units of what I need and find a DIY material that can survive the insane temperatures I need it to withstand.
For example, the first system I was thinking of studying/designing/building is the DC to AC inverter for the molten fuel cell.
The molten fuel cell will be at around 400ºC to 650ºC, so I can’t just buy a commercial inverter. However, I could copy the system schematic of a commercial one and replace the materials with high melting point ones.
On top of that I can only predict so much without actually building anything, and that applies to the molten fuel cell.
For example, this article states that its 10 kilowatt fuel cell produced 56 volts without stating its amperage, but doing the math, you can find that it is 178.5 amps. But it uses cells in a well produced cell, not this amalgamation of inconel and stainless steel that I intend on making.
And I NEED to make the cell this way, because if I’ve made it the traditional way, it would be the size of a truck.
… Now that I think about it… In a molten carbonate fuel cell, how the amount of electrolyte is determined by the amount of energy I need for it to output? What is the calculation for this?
WebGPT keeps saying out of its butt that the Molten Carbonate Fuel Cell needs around 0.1 to 1 liters of electrolyte per kilowatt, but never gives a source for that.
So, 300 liters of electrolyte = 660 kilograms, 0.1 x 30 = 30 liters = 66kg.
Of course, ASSUMING it is correct, which probably isn’t.
In other GPT’s available on the same website they tend to say that the higher the temperature, the less electrolyte is required. But I don’t know how true is that, since the truck-sized 250 kw molten fuel cell is also at 650ºC
However, in all articles the power generated both in watts, amps and volts are based on the SURFACE AREA, not the amount of VOLUME, nor WEIGHT. So I’m PROBABLY alright as long I allow the fuel cell to have as much surface area as possible proportional to the output energy.
“The peak current density achieved was 120 mA/cm2 at 0. 8 V and 800 °C (96 mW/cm2 power density, 80% efficiency) with furnace black. This power density is of the same order as gas fed molten carbonate fuel cells that generally operate around 120 mW/cm2 [180], however, the efficiency of DCFC is significantly higher. The results also showed that nano-structured (crystallographic) disorder of the carbon particles, electrical conductivity and reactive site density control the rate of electrochemical oxidation and efficiency of the cell with the purity of carbon fuel being less critical”
Source: https://www.sciencedirect.com/science/article/abs/pii/S0360128512000044
Since the wattage is 120 mW/cm2, then I would need
In the Project Log 80 I calculated that the hydroxide fuel cell (which works just like molten carbonate fuel cell) would need 1kg of inconel/stainless steel wire with 0.8mm of thickness to fulfill the 20 square meters of surface area.
Since the value of 250 m² is around 13 times more than the previous calculation, I would need 13kg worth of wire. And I was intending on using the wire because I would organize everything in an hexagonal pattern.
BUT, if we take the density of 120 milliwatts per square centimeter, and divide it by 300,000 watts, then the size in square meters would be around 4774m². Well, at first this seems like a lot, but if you take the value of 250x250 meters in an area calculator, it gives 62,500m².
If you add the 4775 m², it will give 69,1 meters on each side (nice).
In the truck-sized molten fuel cell I talked about it is stated that the closer to peak power the cell produces, the higher its efficiency and performance. So maybe it would be interesting to have a cell for every 100 kilowatts of output power.
so, each one of the 3 cells will have an area of 1.600 m², which would be around a square of 40x40 meters.
If we take the rectangle volume calculator and add the 40x40 meters and 1mm of thickness (like this is a supersized cell), it will have around 1,6 m³. Taking this volume and the density of lithium carbonate and inserting on the density to weight calculator, I would need around 3,376 kg of electrolyte.
The same goes for the stainless steel cathode/anode, which would weigh 12,800 kg or 25,600 in total for both.
I was thinking of using an hexagonal pattern for maximum usage of surface area with the 0.8mm wires, so I would “just” need 477.5 kilograms of wire to reach that desired surface area.
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Source: https://www.sciencedirect.com/science/article/abs/pii/S0378775316316214
I would need to reduce the thickness of both by at least 100 times, or 10 micrometers. And I inserted the new values in the density to the weight calculator, and it would still weigh 33kg and the cathode/anode would weigh 256 together. I would need literally 1 micrometer for this to be “just” 3.3kg and 25kg.
And that is from a single 100 kw cell, the three cells would weigh 84.9 kg.
I would need one of these to check its thickness:
Good thing they aren’t that expensive, now the problem is: would the cathodes and anodes even survive the extreme conditions of a molten fuel cell while having just 0.01/0.001 mm of thickness?
Should I just switch back to the charcoal engine or keep going?
… The fact that I procrastinated this much just to understand how much I screwed up is just…
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Well, I do intend on incasing everything into silicates such as sodium silicate, potassium silicate, lithium silicate etc.
So, maybe by spreading the powder of either material inside the silicates, then you wouldn't need to worry that much about thickness as long you have the powder proportional to the surface area you want to achieve.
I would need to measure it by its weight and/or amount of volume (milliliters, milligrams etc) and then spread the cursed paste as thinly as possible.
... But I don't know...
Whatever I have to do with this piece of crap to make it work is way simpler and easier than making the charcoal engine.
I guess I will just keep going and see where it leads me...
I don't know if this idea would work, but I was wondering: what about high surface area materials?
Sponges, 3D printed materials or whatsoever, they could be used to make this work, no?
For example, since I intend on mixing everything up in sodium silicate, then everything is technically a liquid coating.
I could dilute the silicates and the materials in a really thin liquid and switch between baths covering a 3D printed high surface area object.
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Source: https://www.sciencedirect.com/science/article/pii/S2352710224011999?dgcid=rss_sd_all
If you add an electrode to each end, and each bath will only touch one of the endings, then you could make it work, no?
Although, it would be a pain in the ass to continuously switch between baths and drying periods. Because I do think that if you just dip it in sodium silicate without first heating up the layer, the coatings would mix.
The problem is: how the fuel will travel through these microscopic channels?
Maybe you could make the two channels in a factral pattern, or just a conventional spiral pattern with the surface area that you require (4775 m²), this way you could maybe make both the coatings in a practical manner and the channels too?
I'm just brainstorming here.
I Just checked the area of cylinder calculator, and a channel with 1mm of inner diameter would need around 150 meters of length in order to reach the surface area of 4775 m².
Obviously, this is assuming that all the area of the wire is used, but in reality you would need around 3 times more wires to make 3 or more coils of wires connecting on each other.
So, the steps:
- Make a 3D model of the air and fuel channels in spirals that can be moved around.
- 3D print it with a resin printer or a fdm printer.
- Use the Silicate bath to cover the cathodes and anodes with their respective layer of conducting material + catalyser + stabilizers.
- Once dried, cover both in a layer of silicate with the electrolyte or just shove both of these in a bath of silicate with electrolyte.
- Dry the silicate again.
When I say "dry it up" I mean heat treat it, once sodium silicate solidifies you need to further heat it to 100ºC so the structure.
My only issue with this idea is that I have no idea how effectively will the powdered materials stick to the tubes/channels. I suggested dilluting it first, but I'm not so sure right now.
But do I really need to make it a 1mm thick wire tho? I could "just" make it a 1mm thicker plate/cylinder and so on...
I also made a mistake, it seems like the 1kg of 0.8 mm stainless steel wire for the electrodes would indeed just weight 1kg for each electrode.
So there is that...
… BUT I don’t think the steel will survive, being honest with you.
I think that maybe it will be better to use the magnetohydrodynamic generator, it only has an efficiency of 30%-20%, unlike the Molten Carbonate fuel cell, which can reach around 60% or even 80% depending on the design.
So, how would that be better?
Because of the key phrase here: “depending on the design”
My design is literally made out of scrap and trash, made with no regards to precision, durability or long-term use.
And the high 80% efficiency is achieved through carefully planned heat recovery in steam systems, on by itself you can expect a maximum efficiency of 40%-45%.So, why bother with a charcoal engine that will be super complex, a molten carbonate fuel cell that will be a hell of a labor-intensive work instead of “just” working with the plasma-furnace that is the MHD generator?
The only thing that kinda gives me hope on this design for the molten fuel cell is this paper that states that their corrugated plates are made in the micrometer thickness, literally reaching the same conclusion I reached about the ideal thickness of the components for the fuel cell.
However, this other article shows what the corrosion can do, specially in the oxygen electrodes.
They literally oxide really fast because of the presence of oxygen in a high temperature environment, meaning that I will need to either find another material for the oxygen side or scrap the idea all together.I say this because anything containing nickel is AT LEAST 5 times more expensive than stainless steel, even nichrome, which is cheaper because only contains around 30%-20% nickel is already 5 times more expensive.
I could use graphite+sodium silicate as the electrode... I'm stupid.
Wait, I'm stupid², the graphite electrode would run the risk of being consumed while working.
No, I'm being stupid³, the article in which I linked stated that their cell experienced rapid deterioration AFTER they started doing electrolysis, not the regular work.
"The possibility of producing hydrogen from molten carbonate steam electrolysis using the well-established Molten Carbonate Fuel Cell (MCFC) technology was explored in this work. For this purpose, a 81 cm2 MCFC single cell assembled with conventional cell materials was operated under alternated fuel cell/electrolysis conditions at 650°C in a binary eutectic Li2CO3-K2CO3 electrolyte for about 400 h after an initial period of 650 h in which the cell worked only in the usual MCFC mode. A rapid cell performance loss in terms of cell internal resistance and electrode polarization was observed as soon as the cell started to work in the alternated fuel cell/electrolysis mode. "
It is literally in the introduction, but I didn't pay attention.
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Now I'm absolutely in doubt.
The response time to change in wattage output of the Molten carbonate fuel cell can range from seconds to minutes. Essentially, if I'm adding a certain amount of fuel and out of nowhere rapidly increases its input due to higher demand in energy, the fuel cells would take whole seconds or even minutes to deliver that extra energy.
You could use lead-acid batteries and capacitors in order to deal with these spikes, but we are talking about 100,000 watts of power and peak power outputs into 300,000 to 400,000 watts. That is around 300 kilojoules of power spikes.
Lead-acid batteries are expensive and equally heavy, I literally cannot fit a power pulse system of such size magnitude of power in a mech.
I could use a flying wheel system, but that would also increase another loss of efficiency...
I mean, even a normal capacitor/battery system would decrease its efficiency...
Maybe I should actually work with the MHD generator...
Well, assuming an efficiency of around 30% and the energy density of charcoal being 30 megajoules per kilogram, if I want to output 100 horsepower for an entire hour, I would need 30kg of fuel, in a total of 300kg of fuel for 10 hours of continuous output of 100 horsepower.
In 1 minute, I would need to insert 5kg of charcoal, and in 1 second, I would need to input 0.083 kg of fuel.
This means that the MHD generator would instead need to be really, really tiny.
Of course, this is just taking into consideration that this would be the space required to react 83 grams of fuel in a stellarator configuration.
The stronger the magnetic field, the more efficient the MHD generator, and the smaller the distances between everything, the stronger the magnetic field.
Wouldn’t that mean that I could get away by buying and using smaller magnets or just electromagnets for high tesla magnetic fields?
For example, this video teaches how to reach that:
However, if you take the principle of a MHD generator, it is indeed required to have a large surface area for its electrodes. Since it is how it is able to convert the heat and flow into electricity.
Google didn’t show me much about something like an electrodeless MHD generator, which would be just perfect for this. The idea of an electrodeless MHD generator would be that the ripples on plasma itself would make ripples on the coils and magnetic field, just like an alternator/dynamo, and that is how you would extract energy.
I still need to get a grasp on it in order to check if it is efficient or even possible to do that.
Well, my gut feeling is telling me that is not possible.
If we use the alternator/dynamo analogy, either the coils or the magnets are the ones rotating while the other is stationary. This means that for the perspective of either the stationary or the rotating part, the other part is rotating its magnetic fields. These magnetic fields traveling through the coils, a potential difference is produced into the coils. Like ripples or waves that go through a hydro turbine.
If the coils are stationary and the magnetic field is also stationary, what would change in the system? If you assume the plasma to work like the coils, it will rotate and ripple, but it needs to be connected to the system somehow to transfer that energy, thus the electrodes.
If there is no electrode, then how will the plasma transmit its energy?
I could only think of turning the plasma in an induction coil, just like a wireless induction energy transfer.
But how would you make this work?I tried to search for induction magnetohydrodynamic generators, because that is exactly what it is. But…
This article says that this generator is not viable.
“The observed response of the generator is in accord with the theory. The fairly close agreement indicates that the assumptions made in the analysis were justified. It has been found that this generator is not a practical power generator. An output power of 10W is very low in comparison with that which has been obtained from electrode-type MHD genera-tors, for example by PAIN and SMY.”
Another way I could think of making this work would be if the plasma mirrors the magnetic field in the chamber, creating the ripple into the magnetic field without moving other parts.
But I’m really not sure how that would work.
Google only showed me a couple of papers about inductive MHDG’s.
This one is just a simulation of a proposed design that SEEMS to work fine without the extreme conditions found inside conventional MHD generators, but they didn’t talk about its expected efficiency:
https://www.researchgate.net/publication/320431128_Simulink_model_of_an_iductive_MHD_generator
This other paper states that a 300 kilowatt version of the proposed MHDG would have 70% of efficiency, but you would need really high speed gases with equally high temperatures.
https://www.rand.org/content/dam/rand/pubs/papers/2008/P3837.pdf
This one uses an arc generator of 2000 amps and 500 volts (1 megawatt) to make the system work, and I’m not very sure if I understood the efficiency of the whole system.
https://apps.dtic.mil/sti/pdfs/AD0403369.pdf
These two articles discusses the simulation of a inductive MHDG just like the first option, but with higher performance, slightly above ambient pressure and speeds below and above sonic speeds.
https://ieeexplore.ieee.org/document/5544810
https://fupubco.com/futech/article/download/119/88/654
I think it is best for me to stick with the Molten Fuel Cell, the MHD is way too complex for me.
(I mean, both types are super complex and I'm just taking a simplified approach)
I hate how indecisive I am…
Off-topic:
On a unrelated note, I just saw this artwork of a car cockpit, but for some reason I can only think of it as a mech cockpit. Maybe I will use that as inspiration, lol.
But now that I stopped to think about it… I think in the end the mech will be heavier than the target I wanted. For example, in the previous project log I talked about the weight of the 14mm thick coils, and they would weight 150kg in total, then you add the weight of the polymer structure of the actuator +90kg (or a little less), then the pilot +100kg (more or less), then the fuel +200kg, then the fuel cell + 50kg, then extra structure to keep everything together, I didn’t design it yet, but I’m willing to bet around +100kg.
So, 150+90+100+200+50+100 = 690kg. Almost 700kg.
I could change the sizes, reduce the weight here and there, like cutting the fuel to 100kg and reducing the shapes of the actuators to around 40% less weight depending on what you do, like adding graphene fibers etc. Well, with all of that, it could be reduced to around 500kg or less. I could further reduce it by reducing the number of actuators per limb, instead of 6 per limb, just 4.
On a similar note, I still think about the possibility of using continuum robot limbs (tentacle Dr. Ock style arms), I do wonder if making the tubes slightly flexible would allow them to be used just like artificial muscles. But what always keeps me away from this option is precisely the lack of simple predictability. I can copy hydraulic actuators and linear motors, but what can I copy a continuum robot from?
Well, after thinking about it all afternoon instead of doing what I’m supposed to do, I think the continuum robot could be used for the fingers instead… I think…
But I have to admit, continuum robots always keep my imagination active, I can’t help but wonder how a mech with this mechanism would work/look like. You could make them extend and contract just like Dr.Ock’s robot arms, but what if you wanted them to be as short as a human being’s limbs? Wouldn’t that essentially be a hybrid between mech and exosuit? Could you do the same thing with the rigid telescopic actuators I previously suggested?
I just saw this video here, I really can’t see a mechanism like this lifting a ton of weight or doing anything remotely strong at all.
And on top of that, if I were to build something like a continuum robot meant for heavy duty applications I can’t think of it as a safe to be around machine. It would need to be really, really rigid and heavy.
A good example is him showing how the continuum robot would just fall without any stiffness, but you could avoid it by pulling another cable in the opposite direction, forcing a compression load. However, if you do that, how much of the force applied would be just fighting against its own weight? How much of the force applied would be just fighting against the opposite actuator? How much of the remaining force would be enough to lift something heavy?
An ideal scenario would be to have a pulling and pushing actuator on opposite sides, but the problem is that you can’t really make a flexible pushing actuator, can you? You would need to make it absurdly stiff, no?
The only ones that I could find that would work like that would be articulated/spine-like continuum robots, which wouldn’t allow for a human-safe machine.
Perhaps attaching the actuators proportionally to the limb’s length would help, for example: making the diameter of the tentacle ⅓ of its length, this way it would work just like a lever. If not for its entire length, at least for the majority of it, getting smaller at the tip and wider at the tip to compensate for the distribution of loads (you need to apply more force the farther away from the tip, just like a lever).
Maybe you could do a segmented continuum robot using non-extensible ropes/knots, but I couldn’t find anything like that to copy/use as an example.
I mean, imagine one of those super thick naval ropes, they are so thick that they are almost rigid. You could achieve the same with a really, really dense knot, no?
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I mean, there are basket ropes that seem quite solid:
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But I still have difficulty imagining it sustaining around 1000kg of weight and maintaining its shape…
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Pneumatic jacks exist and I could totally see those lifting something as heavy as this target in a continuum configuration, but they are pneumatic and inherently inefficient…
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MAYBE one could make use of a pneumatic syringe compressor/pump (or just that hydrolysis pneumatic muscles), just like those syringe robot arms. I don’t know if it would be efficient or practical though, it works in hydraulics because of the non compressibility of liquid. With a gas, maybe you would need to make it high pressure for increased efficiency in power transmission.
However… Do I really need a pneumostatic transmission or anything that crazy? I could literally just have a balloon-like segmented body and insert the electric flexible actuators inside/around its body.
… But even if I make it like this, would it even be a stable mechanism? The idea is to make a low-mass and flexible body for safety around humans, so any impact would be like being hit by a pillow Wouldn’t that mean the entire mech/exosuit would be super wobbly and unstable?
And in the end, whatever design I choose, a Baymax balloon-like mechanism or a solid spinal mechanism, why would I choose this continuum mech instead of the conventional one?
The only benefits that I can think of would be:
- If you imagine it as a very long stewart platform, you only need to worry about the position of the base and the position of the top-base. So it could be simpler to make the fingers while keeping them safe to humans, I THINK. I also thought that it could be interesting to add a balloon-like outer shell to the mech to avoid injury to humans nearby.
- The segments would be exactly the same shape, but in different sizes, so it would be easier to mass-produce them with fewer molds.
- Since the actuators would be in a different place to the body, I think it would be simpler to produce them, keep them safe and to maintain them.
- I wouldn’t make them a telescopic linear coil, like that radial sliding contact motor I talked about in the previous project log. Such a motor would rotate a hoist-like mechanism that in turn would pull the “ligaments” to the continuum limbs. But in such configuration I would need to add the balloon segments for extension and compression…
I feel like I talked about this so many times and I’m already repeating myself needlessly in this project log…
Kinda unrelated, but I asked a friend of mine why the hell someone would want a mech/exosuit with continuum arms and he suggested that it would be a good mechanism for climbing buildings. I thought it was a really interesting idea.
Also, look at this cool snake/tentacle/continuum-tank
https://www.flickr.com/photos/lord_dane/48785087506
Well, I made up my mind, an exoskeleton with the same power output as this mech (or rather, mini-mech, since it “just” has 3 meters of height) would be insanely cramped. Imagine fitting 6 actuators with 10 to 20 cm of diameter in each shoulder and thigh?
I hate to admit it, but the only reason I never truly get over the idea of making an exoskeleton like that is because of the terminator in Warhammer 40k.
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Source: https://www.artstation.com/artwork/g0VOdP
Look at how cool this thing is!
They’re like the middle-man between exoskeletons and mechsuits, lol.
(accordingly to ~le lore~, the terminator armor was originally an exoskeleton used for working in hazardous environments [and it is also nuke-proof])
Only power armor that can be more power armor than the ones in Warhammer 40k is this one, lol:
Ok, I’m done procrastinating. I need to finish this project log asap.
… But before that, I just want to say that I was wondering about artificial/synthetic cells. Essentially, I wonder if it would be possible to make biomimetic machines that imitate cells, not necessarily nanorobots and the like.
https://en.wikipedia.org/wiki/Artificial_cell
The closest thing that was actually built in real life was the “xenobot”, that thing scientists made using frog cells to make organic materials work in artificially pre-programmed ways.
https://en.wikipedia.org/wiki/Xenobot
It would really be convenient if we could “just” grow robots and machines in a tank instead of building everything from the ground up.
This really tempts me into researching the subject and even maybe starting a project on its own, actually, every idea I have is kinda like that. Unfortunately, I’m not knowledgeable, skilled, nor dedicated enough to make such things.
Maybe a matryoshka machine would work? Essentially, it would be a machine that makes a smaller copy of itself, and that copy makes an even smaller copy, until it reaches a maximum practical point (you can’t really build things smaller than atoms). And it got me wondering how I would make a 3D printer that could make smaller versions of itself, including electronics, actuators, filaments, etc.
… But maybe I’m overthinking this?
For example, there is a thing called “Pantograph” that is a mechanism that can be used to make smaller copies of a drawing:
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Maybe you could use it to build micro-machines/synthetic cells.
Obviously, the already most used approach is lithography. Which is used in the production of microchips and the like, but these need a ton of chemicals that may not be accessible/practical to make half a ton of micromachines.
Unfortunately I kept thinking about it instead of doing what I’m supposed to do…
Well, I thought on the subject, and maybe the idea of “simply filling a tank with chemicals and letting the synthetic cells do all the work” wouldn’t work as simply as that. You would need to literally make a synthetic parallel for every part of the human body down to its very DNA, which would result in a synthetic human clone and not necessarily a robot. And if anyone ever makes an actual conscious “syntheth” human using this absurdly complex method, I just hope they don’t enslave the poor creature.
The “best” idea I had would be to keep the “Pantograph machine” mass-producing the micromachines necessary for every major function and another class used specifically and only for organizing these micromachines in place.
The micromachines would essentially be like those origami micro-robots used in medical applications.
Imagine every single micro-machine a “cell”, and those cells would be built for a single, limited role with the most basic function possible.
Essentially separating between actuator “cells” (used as muscles), energy storage “cells”, energy transmission “cells”, energy generation “cells” (if you use fuel cells instead of batteries), control pathways “cells” (essentially neurons/nerves that directly connect to a USB port or anything like that, maybe system board cells would be needed), structural “cells” (various types of machines/materials that would act as different types of binders and insulators for bones, ligaments, tendons, muscles, nerves etc) and finally the “organizer cells”. By the way, I was thinking of the energy generation cells being micro molten fuel cells that take the fuel around it (like charcoal powder, mineral oil, etc) and provide energy to surrounding cells.
Every type of synthetic cell would need to perform a function and have a sensor array for position feedback and function feedback, while the organizer cells would need to consume the energy-cells in some way and be remotely connected to the program controlling everything. I have no idea how the energy would be transmitted and how the cells would be powered, either you would remotely power/control everything using electromagnetic waves or every cell would have a wireless transmission coil to transmit power to everything. Basically, the outer surface of the “cell” would have these coils, and unless they are using it, they re-transmit to the other cells around it. It would be very inefficient to just allow the waves to travel everywhere until they find a cell that actually needs it, so you would need another cell to specifically connect to the central system and transmit that energy where it is needed. Either using it or storing it.
The computer would need to painstakingly monitor and control every organizer cell position and state, constantly changing malfunctioning cells of any type. I don’t really think that it would be possible to make the synthetic organism system recycle and replace these malfunctioning cells by itself with a built-in factory or something. So you would need to collect the malfunction cells (like poop, lol) and feed it more healthy cells.
Ideally, you would let the system board and control be a decentralized group of cells completely encased into the synthetic organism. But being honest, I’m not really sure how you would make such a thing in a viable way.
I just saw this hacksmith video where they use a coating that is so strong it can withstand the tensile force of around 4444 pounds (2 tons), and they showed it being tested:
It is a “proprietary alloy”, so unfortunately, I have no idea how it is made. And if I knew how, it would probably be super mega expensive and complex…
In the company's website it is said that it is something made out of cobalt and phosphorus, but without giving any details, of course.
https://www.integran.com/electroformed-alloys-and-components
So yeah, definitely expensive, anything with cobalt, that is.
Now that I calmed down about the subject, I can confidently say that I’m insultingly talking out of my ass and insultingly oversimplifying a very, very complex science. Everything I said is probably useless.
(just now that I finished writing all this crap I remembered that the actual name is photon propulsion)
One thing that I just saw these days was laser propulsion.
There are a lot of ways of ways that you can use lasers for propulsion, but I’m talking specifically about pulsed laser propulsion:
In the video, a really powerful laser pulses multiple times per second, the little aircraft model focuses the light in certain points, ionizing the air in what are essentially tiny explosions.
So, the idea is that if you have a sufficiently powerful energy source, and a sufficiently powerful (and efficient) lasers, you could propel any aircraft with it from earth to space without the need for ejecting mass. Fusion rockets and Fission rockets are the absolute option when it comes to efficiency and power output, but they need to eject mass. Either ionized gas (plasma) or steam. Increasing the weight/size of the spacecraft and limiting its range based on the amount of ejectable mass. And in the end, this would be a really strong weapon since photons can push stuff (which is the first way laser propulsion is planned to be used for [I do wonder which is more efficient: a coilgun or a laser propelled gun]).
However, if it was that simple to make something like this to work, then it would’ve been done.
First problem is that the on-board laser would need to work with nozzles for maximum efficiency. On top of that, these nozzles would work more like a pulsejet, where air comes in and it is detonated. You could use it to make a rotating detonation engine for more efficiency, but it would still need an air intake, be it through check valves or compressors (the latter which would be a waste of weight, and thus, energy). There are valveless pulsejets, but these are even less efficient than the already inefficient pulsejet. For precise numbers you would require research specifically for thrust efficiency, and I couldn’t find any.
The second problem is that, even though I talked about “no mass required”, the laser on the vacuum of space would PROBABLY have super, super low thrust (I say probably because I couldn’t find a single article talking about such possibility). So, to truly escape a planet’s gravity, you would need to either go super, super fast, or take some mass with you (be liquid, solid or gaseous) to eject in the pulsed laser thruster. Once you are in space, then you don’t really need that. But again, the thrust would be really, really, really small (I think). So, unless someone finds a solution to that, you would still need to eject mass.
From a forum that I found:
“Light propulsion does not give much thrust for the energy input. The formula is: F=P/c F is the force in newtons P is the power of the light beam in watts c is the speed of light in meters per second If you had a laser with 299,792,458 watts it would give a propulsion force of one newton. A newton is the amount of force required to accelerate a mass of one kilogram by one meter per second per second. This is equal to about 100 grams. To equal the Falcon Heavy thrust of 5.13 million pounds you would need a source of power equal to 7x10^15 watts. This is about 1400 times the currently installed electrical generating capacity of the world.”
The third problem would obviously be the efficiency of the laser, which is directly linked to its cost. Only diode lasers can reach efficiencies around 90%, and those are stupidly expensive. The only cheaper laser that can be easier to deal with would be the CO2 gas laser, but that one is infrared with an efficiency of 20%. Those 80% are converted into heat, something you really don’t want in a spaceship. Also, the best laser to ionize air in bursts are ultraviolet lasers. Not even to mention the cost, efficiency and weight of a nuclear fission reactor itself to keep this thing working.
Maybe in the end such spacecraft wouldn’t be useful for deep space exploration, but from earth to orbit operations/delivery/transport, which is already more than good enough in my meaningless opinion.
If your objective is just that, you don’t need to use a fission reactor with a 1 megawatt diode laser, you could still use conventional electrical generation units for heavy air travel.
Why would you want to do that? I don’t know.
I WOULD BECAUSE SPACESHIPS ARE FRICKING RAD
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But seriously thought, I do think that we will find a way to make warp drives work by using lasers. If you focus enough energy in a spot the size of an electron, you can make a black hole, or a kugelblitz. But I’m probably talking out of my ass, because you can use any kind of energy, such as electromagnetic fields.
So, if you can create a subatomic blackhole with that, a natural phenomena in which you bend space and time, then you would need that to warp space and time.But maybe I’m talking out of my ass, because of the way lasers work. In order to excite the gain medium (the thing responsible for making the laser beam), you need a way of converting electricity into light. Wouldn't it be more efficient to just skip the conversion and just use pure, brute electrical power to make the detonations?
The only thing that makes me think that the electrical discharges wouldn’t be as viable is the fact that they literally destroy the electrodes over time, while the laser could work continuously without much wear. I mean, you eventually need to replace the gas, but it would be easier than changing the entire structure.
Speaking of photon drives and photon weapons, I just saw this video:
I don’t know how one could make a weapon out of that thing, but I’d suppose that you could use really small leds continuously adding to a beam using mirrors and/or prisms.
But I always wondered if it would work by “simply” adding a mirrored tube and then the lenses?
Well, he posted a link for a light simulator and that just shut me up, lol. You really can’t focus it in a proper manner, just like he said (and I didn’t listen).
I found this other link where they added the equation for the fresnel lens: https://phydemo.app/ray-optics/gallery/fresnel-lens
And it still can’t make a single focal point, but a weird line.
I just found this article: https://www.mdpi.com/2076-3417/10/9/3257
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The easiest way to do an infrared laser would be to use a solid gaining medium such as Ruby rods or optical fibers, both are beyond my monetary reach.
In the end I think I would need an approach similar to the Webb Telescope system…And I was confused about the difference between a laser and a photon:
“So in summary, the key differences are that laser weapons use a coherent, monochromatic beam of light that can be tightly focused, while photon weapons use a broader, less coherent beam of visible light. Lasers are generally more powerful and precise, but photon weapons can still be effective in some applications.”
I was wondering/calculating how many LED lights I would need to reach those 10 kilojoule rates for laser weapons, and it ends up that I would need 10,000 to 20,000 watts in LED lamps. It would cost around 1500 reais (275 dollars).
However… One thing that I forgot is that incandescent lights and metal vapor lights are more efficient in making invisible infrared light instead of the 75% of visible light the LEDs make, and they are SIGNIFICANTLY cheaper. Around 10 times cheaper.
This means that I don’t need the super complex CO2 laser that only has 20% of efficiency, just around… what? 10 to 20 incandescent/metal vapor 1000 Watt lamps and find a way of converting scattered light into coherent light. :|
Do I even need to buy it tho? The first filament light bulb was a fricking carbon filament made out of bamboo.
Well, I guess I would need to ink print a myriad of filaments with conductive graphite with the correct resistivity and then embed it in sodium silicate.
“The search results do not provide the specific length or diameter of a typical carbon filament light bulb. However, the example calculation [3] shows that for a 4 cm long tungsten filament with a resistance of 0.350 Ω, the diameter is around 0.09 mm.
Assuming a similar geometry for a carbon filament, we can estimate the ideal resistivity per meter as follows:
Resistivity per meter = Resistivity / Length
Resistivity per meter = 3.5 × 10^5 Ω·m / 0.04 m = 8.75 × 10^6 Ω/m
Therefore, the ideal resistivity per meter of a carbon filament light bulb is approximately 8.75 × 10^6 Ω/m.”Well, I asked what would be the energy required to make the air detonation in order to generate 1000kg of thrust, and it said I would need around 1 trillion joules. :|
So much work for nothing I guess…
Actually, no.
I searched for the 1000kg thrust sugar rocket and took its weight (45 kg), energy density (17 MJ/kg) and the amount of time it keep flying (30 seconds) and it resulted in 25.5 megajoules.
So I “just” need to double or triple the energy output of said laser assuming the infrared laser has a 90% efficiency of converting electricity to emission, 90% of efficiency in converting the emission into an explosion and 90% of that explosion being converted into thrust.
If you need this little energy to make 1000kg of thrust, why then use legs? lol
Out of curiosity, a 50.cal BMG bullet has 10 kilojoules of energy. So this is not just blindingly dangerous, but super dangerous.
Out of curiosity², a tank gun (120mm) armor-piercing round has around 25 megajoules of kinetic energy.The national ignition facility’s laser used for Laser Inertial Fusion reactor has 3 megajoules of power, while 1kg of TNT has 4 megajoules.
Of course, it is not that simple, a pulsed laser can divide all of that absurd energy between multiple sources and lenses without damaging the system, the National Ignition Facility delivers ALL of the 3 megajoules of power in a single millisecond pulse.
If achieving a 10 kilojoule laser was that easy… Wouldn’t it be even easier to make a 3 megajoule laser?
That is why I think I’m talking out of my ass.
By the way, I was looking for a 10 megajoule capacitor bank, it is the size of a entire room:
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It is insane to think that gasoline has 4 times that energy in a single liter.
Also, the fusion was done using UV lasers with 2 megajoules in total for the fusion shot, it uses 100 times more energy because it is only 1% efficient, and the pulse duration is 1 nanosecond. I was searching and it seems like they use gold capsules for the fuel so it transforms the UV lasers into X-rays, huh.
“According to the search results, the conversion efficiency from the laser energy to x-rays in the National Ignition Facility (NIF) is around 15%:
The NIF laser generates 3 MJ of infrared laser energy, of which about 1.5 MJ remains after conversion to UV light. [1]
Another 15% of the UV light is then lost in the hohlraum (the metal cylinder surrounding the target capsule). [1]
This means that about 15% of the resulting UV light, around 150 kJ, is absorbed by the target's outer layers and converted into x-rays. [1]
So in summary, the NIF's UV lasers have a conversion efficiency of around 15% to x-rays that are then used to drive the implosion of the fusion target.“
I looked on google and if one day they actually make a inertial confinement fusion reactor that doesn’t use lasers with shitty 1% efficiency, they intend on making from 1 to 10 shots per second, so, around 1 to 10 megajoules per second, which would generate 10,000,000 watts in a hour.
Just a post-note: the pellets cost millions of dollars because they are made with super-ultra-duper-mega precision in order to make the fusion occur efficiently.
There are other approaches to inertial confinement fusion, like magneto-inertial fusion, which literally uses plasma railguns to shoot the magnetized target, resulting in an explosion without all the insane requirements for the laser type.
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Source: https://www.researchgate.net/publication/284228265_Magneto-Inertial_Fusion
But the problem as everything else is tests and data, the National Ignition Facility was built in 1993 and only in 2022 it was able to generate fusion. Around 30 years of testing and development in order to just get that result.
Now think about all of these crazy fusion reactor concepts around the world/internet, how many of those are going to have millions of dollars invested in them? And if they do, will they live long enough to generate results? How many of the ones that lived long enough are going to be practical or even efficient?
I asked WebGPT and you could indeed suspend individual electrons in a magnetic field and once the magnetic field is deactivated, if they end up hitting an electrode, they would indeed make an electrical current through the system.
Wouldn’t that mean that you could use this system as some kind of capacitor? A super high density capacitor?
Well, this thing is essentially a particle accelerator and you would need a really, really strong magnetic field. In fact, equally proportional to the force of the electrons, because they would have the same charge and repel each other.
But I do wonder: would the increased speed of the electrons cause more charge? If so, wouldn’t it be possible to trap just a few electrons on a permanent magnet field in a vacuum? I just now remembered that electrons/particle accelerators need much more energy to make the electrons/particles to curve, that is why the bigger the particle accelerator the better. On such a note, I do wonder if instead of hitting an electrode, the electromagnetic field would contain the electrons spinning and once the electromagnetic field collapses, all those electrons start pushing against the field, generating a current…
Would I even need electrons for that though? The collapsing field would generate a ton of eddy current anyway and it would work just like a capacitor.
That is just an inductor. I’m stupid. lolFrom what I readed only, the inductor outputs most of its energy in a high voltage pulse, while the capacitor outputs most of its energy in a high amperage pulse.
A Flywheel would be better than the capacitors and inductors
There are also explosive pulsed power generators, these use high explosives and the like. But I was wondering if you could use low-explosives like a gasoline/hydrolisis powered shock turbes or pulsed detonation engine or "just" compressed air.
But in both cases, I think flywheel may be the safest option.Hackaday has a page about that: https://hackaday.com/2017/01/11/pulsed-power-and-its-applications/
Just now I remembered that if you add drops of water into liquid aluminium, the water will turn into steam so fast it can actually cause an explosion with the same power as C4.
It is just like droping water into boiling oil.
I say this, because if you control the amount of mass of liquid aluminium and water, you could have a "rechargeable explosive" for the explosive pulsed power generator.Needless to say: don't try this at home.
... Wait a minute. If you can generate such strong explosion, wouldn't that mean that you could make a inertial confinment fusion reactor that uses this steam-liquid metal explosion to reach the same explosion the laser fusion does, but without the laser part?
But if it all these ideas were so easy to make, then why no one made them?
What I'm missing?
By the way, although I don't have the money to buy synthetic Ruby laser rods, it seems like you can "just" take neodymium oxide and/or yttrium oxide and mix with phosphate glass in order to make a gain medium for near infrared or short infrared lasers.
You can also use silicate glass for this, meaning you can literally "just" melt both in order to create it. Although I don't know if it would work with sodium silicate.
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Project Log 84: Screw it, let's freaking do it.⁴
06/21/2024 at 16:43 • 6 commentsTuesday, 18/06/2024, 19:06
Well, I’m writing this in a google docs first and then later posting on hackaday.io because it is having a lot of trouble staying up.
Power Source:
So I will write what is in my mind right now:
So, I’m kinda pissed off because it seems like the molten carbonate fuel cells and molten hydroxide fuel cells kinda fricking suck and are equally dangerous. Plus, I don’t really need lithium carbonate in a lot of quantities because it is more of a catalyser for the carbonate solution. Most of the articles that I could find on the subject said that they used a nickel anode and a cathode with a layer of lithium while only using potassium carbonate and sodium carbonate.
On top of that, one of the recurring problems is that the molten carbonate fuel cell also needs the CO2 from the exhaust of its own reaction to be mixed back for whatever reason. And it also can suffer from layer separation, since the carbonates have different densities (akin to what happens to water and oil).
And well, I also revisited the idea of using magnetohydrodynamic generators, but I’m really not confident on its resulting performance and on its viability while building it homemade.
The idea is simple:
- First, using the plasma jet engine to power a tip-jet rotor.
- The tip-jet rotor will rotate an axial compressor.
- The air from the air compressor will go to a plasma jet rocket engine.
- On top of the plasma, a fuel (gaseous, liquid or powder) will be introduced, increasing the performance of the plasma jet rocket engine.
- On the combustion chamber and nozzle there will be a Magnetohydrodynamic generator coil that will turn the flow of air and combustion into electricity.
- The electricity will be used to maintain the reaction going just like in a conventional jet engine and the excess used to power the other systems.
- This will be an Air-Breathing Plasma Jet Magnetohydrodynamic Rocket Engine Generator (ABPJMREG).
- The plasmatron turns hydrocarbons into hydrogen and CO/CO2, so MAYBE the plasma can end up doing something similar on either making more complex reactions and/or more toxic byproducts.
- Another problem is the amount of noise, heat, vibration, fumes etc.
Obviously there will be a LOT of variables and a LOT of thought on the type of material required to make this beast to work continuously, and on top of that, dealing with this kind of machine can easily cause my own death.
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And although ChatGPT (that f*cking stupid chat bot) keeps saying the efficiency of the MHD systems is “90%” the own sources it shows to me prove otherwise, this article (which gpt itself sent to me as the said source) said the magnetohydrodynamic generator on the rocket engine achieved a maximum of:
“There are energy losses in the MHD channel. These include friction with the wall, heat transfer, electrical resistance of the gas, and electrical losses at the ends of the channel and the conductor walls (17:331). These losses give linear MHD channels using gases at 2000-3000K only a 15% efficiency (35:31).“
The pancake type is more efficient, but it is said to be 30% efficient. I don’t see the appeal of working my butt off on a glorified plasma furnace that will blow up in my face, melting years of work and thousands of moneys into a giant pile of molten slag.
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Source: https://en.wikipedia.org/wiki/Magnetohydrodynamic_generator
This image is from a supposedly “optimized Stellarator fusion reactor”, only god can tell me if any fusion reactor structure would be practical/useful for MHD generators…
This article is about a nuclear enchanced MHD generator which uses molten metal, and it still only achieves maximum 30% alone. The metal it uses is Rubidium, but I could use Tin, Indium, Bismuth and Lead. And through that, I would increase the surface area in which the liquid moves, probably increasing the efficiency.
Actually, this gave me the idea of using a molten metal magnetohydrodynamic heat engine. The liquid metal would be heated by a furnace and move through some piping, turning the motion into electricity. I found this article about an open cycle coal powered MHD generator that is said to achieve 60% of efficiency, however, the thing was designed for 1.5 Megawatts (1,500,000 watts). Five times more power than the peak power designed for the mech. The magnet used in this was 5000 tons alone (dunno if it is a typo mistake or it is actually 5 million kilograms), so you can imagine how heavy this thing would’ve been.
It would be really fucking nice (and cool) if I could fit a MHD generator in my backpack and produce enough energy to power up a city, but unfortunately, reality isn’t that convenient.
The Molten Fuel Cells aren’t any better and the safer solution would be to use a conventional combustion engine generator.
And a conventional hydrogen fuel cell would be my first choice in ages, but there is absolutely no practical way of storing hydrogen gas in any shape or form. Even the best metal hydrides can only store 10% of its own weight in hydrogen, and assuming an efficiency of 50% in conversion to electricity, I would need 4,2kg of hydrogen per hour at 100hp. This would require 400kg of metal hydrides for 10 hours of activity.
What made me think of using molten fuel cells and magnetohydrodynamic generators in the first place is fuel cost and accessibility.
100 liters of fuel (whatever type) to make this mech going would be the cost of a minimum salary (or more), and the only fuels that are somewhat possible to make at home are Wood-Methane, Methanol and Ethanol. Unless I suddenly find a charcoal powered piston engine or a way of making “liquid charcoal”, I don’t think that the combustion engine will be a good option.
And yes, there are “charcoal” engines that were popular during the war, but in reality, those engines had a SynGas generator using wood or charcoal, which has half of the energy density of butane.
There is liquid coal or “coal to liquid” process in which coal is converted into diesel or gasoline using a huge fricking plant.
Lastly, the only combustion engine that I could find that uses charcoal without a chemical process or extra steps are turbine engines. And those aren’t as simple and cheap as making a piston engine.
I like all the ideas I presented, but when it comes to power-to-weight ratio, practicality, efficiency, cost, complexity and safety, all of them fall short.
Well, personal note: if it was this simple to make a portable power source, there wouldn’t be a concept such as “world energy crisis”.
And all of this fucking sucks.
However, before we delve into the next and last option, let me try to check the possibility of making the thermoelectric generators one last time.
The only reason that I got the will to try to design a TEG with around 30% to 40% is because I didn’t care enough to understand how it works at the first time because it used gold.
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Source: https://www.nature.com/articles/s41586-022-04473-y
The gold is used because it is a great reflector of infrared light, that is why the hobbes telescope uses it. And the materials were tuned to both work as a thermoelectric device and as a photovoltaic device, a literal solar cell-TEG hybrid. That is why it uses germanium and GaAs (gallium arsenide) and other types of materials, they are meant to filter all other frequencies and only let infrared radiation pass through.
The article says that it achieved higher efficiency because of this filtering, but I want to understand why only allowing infrared to pass and not other bandwidths, I mean, the more sources the better, no?
Well, the idea for now is to do the following:
- Make a thermoelectric and thermophotovoltaic using cheaper materials.
- Make reflectors with cheaper materials
- Structure the TEG/TPV materials in a way that maximizes absorption of heat and radiation (there are a lot of papers on that).
- Add a magnetohydrodynamic generator and a plasma source to make it as hot as possible (3000 to 5000ºC). The MHD will stop the flames/plasma from destroying the materials.
- Use a blanket of air between the heat source and the actual contact with the TEG/TPV.
- Make a really long path for both MHD, TEG and TPV to absorb as much as possible.
- Add tin as a liquid metal coolant in the primary radiators.
- Connect the primary radiator to TEG/TPV and then connect to the secondary oil radiators (the oil/liquid could be conductive to allow MHD generation).
- Connect the secondary oil radiators with TEG/TPV to the tertiary air radiators.
- Vent the heat from the tertiary radiators into the air input, recycling heat into the system.
- Pass the already heated air through the exhaust heat exchanger to recycle even more heat.
- Introduce the heated air into the turbocharger into the combustion chamber and add a plasma source for the MHD generator.
- And maybe making everything in a circle, just like the stellarator.
I also need to find what would be the best size for the plasma flame, too big and it may not allow the TEG/TPV/MHD to fully absorb the energy, too little and numerous and the heat source may not be hot enough to make the system work.
And then make it 3D printable…
All of this is starting to sound more complicated than the charcoal engine, to be honest…
Well… I was expecting to find cheaper materials that have similar properties to the ones that the article has, like using aluminium and/or tin as the heat/infrared reflector (because mirrors can reflect infrared too), but… Well, the problem is that there really isn’t any other material that can reach the heights of the ones used in the TPV (thermophotvoltaic) with 40% of efficiency.
MAYBE by using a little more expensive materials like silicon carbide, boron based compounds, nitride related materials and sulfide materials (like Lead Sulfide), I could increase the efficiency from less than 5% to around 15% that is the normal efficiency of non-precious materials TEG/TPV cells using optimized surface area for better absorption (which I was able to find articles saying they reached even 23% efficiency only doing that).
Then, MAYBE by using the MHD would add another 15% of efficiency, with pseudo-photovoltaic cells (like DIY solar panels) and any other type of thermoelectric generation device, just MAYBE I could increase the efficiency to a maximum 30% or even 40%.
And I did find out that plasma is a type of “blackbody” that can absorb any kind of wavelength/frequency and emit it as thermal radiation, but it needs to be really opaque in order to work, unlike in a Tokamak which works in near vacuum. So, maybe an additional 2% of efficiency? lol
Taking into consideration all the nuisances that would come with a charcoal engine electric generator and the compound thermoelectric generator (this aberration I’m suggesting), I don’t really know which to choose.
- An experimental never tested thermal to electrical energy conversion/generation
- A well understood diesel converted to charcoal engine with a conventional electric generator.
Just now I discovered that there are other thermoelectric effects that can be used to generate power:
- Thermionic Converter:
A thermionic converter consists of a hot electrode which thermionically emits electrons over a potential energy barrier to a cooler electrode, producing a useful electric power output. Caesium vapor is used to optimize the electrode work functions and provide an ion supply (by surface ionization or electron impact ionization in a plasma) to neutralize the electron space charge.
Maybe this is a simpler example to understand, you don't necessarily need to make the gaseous media to be some weird exotic chemical or vacuum, just working on air/plasma can work.
It is said that Thermionic Converters have higher effiicencies (around 20%) than TEGs, but need higher temperatures and a medium of vacuum, rarefied conductive gases (like mercury) or plasma to work properly. - Pyroelectric generator:
Pyroelectricity is a property of certain crystals which are naturally electrically polarized and as a result contain large electric fields. Pyroelectricity can be described as the ability of certain materials to generate a temporary voltage when they are heated or cooled. The change in temperature modifies the positions of the atoms slightly within the crystal structure, so that the polarization of the material changes. This polarization change gives rise to a voltage across the crystal. If the temperature stays constant at its new value, the pyroelectric voltage gradually disappears due to leakage current. The leakage can be due to electrons moving through the crystal, ions moving through the air, or current leaking through a voltmeter attached across the crystal.
There was actually more designs and machines designed to convert heat to electricity, but the google results lead me to weird websites and videos. That is how I found out about the "blackbody" property of plasma, because it lead me to a scam/conspiracionist website of a guy that claimed making a 100% efficient way of converting infrared radiation into electricity by using plasma.
... Which would break the laws of thermodynamics... And the author/weird fans were convinced that the "scientist groups" were "persecuting" him because they did not accept his "free energy generator". :|Anyway, the idea would be to add mutiple types of thermal to electric generators/converters in order to squeeze as much electricity as possible from the heat source.
... But I feel like this is just an stupid idea for some reason... My guts tell me that I can't simply add up the efficiency of different types of generators in order to absorb more power... Well... MAYBE stacking the copper/copper oxide photovoltaic cells with the thermoelectric generators would work, since you don't necessarily need the TEGs to be in direct contact with the heat source. So stacking them would actually work.
But I don't know about the pyroelectric and thermionic generators, not to mention that I don't know crap about a cheaper way of making thermophotovoltaic cells.Also, I forgot to say, but I saw a few articles that had some charts about thermoelectric, magnetohydrodynamic and stirling engines that had really high efficiencies based on the temperature.
So all of these generators actually had effiicencies increasing from a single number to even 40% with higher temperatures.
Diesel Engine to Charcoal Engine:
Well, well, well, look at that, after 2 days looking at random crap spilled by google, it finally shows what I wanted.
There is research on the performance of diesel engines using charcoal/coal slurry, now I “just” need to read all the 29032993232 pages.
“Charcoal emulsification
In order to be pumped, the charcoal powder had to be mixed into an emulsion of diesel and fatty acids to produce a slurry. The target of these studies was to obtain a charcoal slurry with viscosity less than 100 cP at 25 C and high calorific value.
Charcoal Charcoal type: cedar.
The particle’s median diameter 10.33 microm, Fig. 5
Water Distilled water
Diesel Summer type, 6.5 cSt at 25 C
Weight ratio: Charcoal:diesel:water 25:72.2:2.8 (with surfactant)
Mix speed Mixed by homogenizer at average speed: 6000 rpm, Fig. 5
Viscosity For measurements, a rotor type viscometer was used.
Viscosity was measured at spindle’s speeds: 60 rpm, 6 rpm, 0.3 rpm. Temp.
Both production and measurements took place at room temperature.”In the end the project said that it would be more efficient to use indirect injection of charcoal powder instead of slurry.
Well, since we are already here, then why not use compression ignition anyway?
It still needs a spark plug for controlled ignition.
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Now, I need to learn it and find a 4 stroke diesel engine that is best for this job, especially if it is a single cylinder. Just like one of those super high compression ratio engines for ships. On top of all that, building it to be an adiabatic engine.
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Well, it seems like compression ratio isn’t everything when it comes to engine horsepower… It is possible to double the output of a combustion engine by simply increasing the air input pressure with a few PSI.
I was intending on making the engine with the fastest rpm possible, so the piston would need to be as small as possible, but… It is said that the maximum speed diesel engines can is 5500 rpm because diesel doesn’t burn fast enough, although I would like to doubt that if the engine in question is adiabatic (and using charcoal), which could lead to fast combustion… Maybe?
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Obviously, I’m not going to simply coat a polymer engine with ceramic, but make an insulated composite base material for the engine and then add the polymer on the outside.
The electric generator will be just like I was planning before:
A brushless stator and an electromagnetic rotor, the brushless stator will increase its amperage, thus, its resistance to torque gradually until the speed of the motor is slightly reduced, then, through that you can tune it whenever you like. For example, you could lower the amperage when the motor is rising and increase it when it is descending, allowing the motor to only experience resistance on its power stroke.
Well, f*ck.
As always, it took me a while to figure out the obvious: It is really fricking hard to design an engine and generator from scratch, so now I need to find a diesel engine that can output 100 to 300 horsepower with as few cylinders as possible. I was thinking of a single cylinder because (supposedly) it would be easier to make, but I doubt I will find a single cylinder engine (and a generator at that) with 300hp that isn’t as big as a building…
Well, I kinda found it, but it is not that simple (as always).
The thing is: I’m going after the biggest engines out there and divide the number of cylinders by the output power, and even if a single cylinder produces too much power, then I will “just” reduce its size. Or take an already existing engine and increasing its size x amount of times
I'm still procrastinating, but for some reason I went to check on batteries and the like.
Not because I found a crazy battery that has thousands of watt-hours, but because I went calculating its weight based on the amount of joules it would provide.
Wattage is like kilometers per hour and Joules are the exact distance you travelled, so even though you went to 100 km/h, you only went that fast for around 100 meters. If you were to keep going for 100 km/h for an entire hour, then yes, you would have travelled 100 kilometers.
The same apply to wattage and amount of joules.So, an Iron Air battery that could supply around 1,000 watt-hour per kilogram, would store around 1000 x 3600 joules per hour in each kilogram.
So, 3,600,000 or 3 MJ per kilogram (gasoline can provide 46 MJ/kg).- 100 horsepower hour = 268,451,953 joules, or 268 MJ
- 268,451,953 joules / 3,600,000 joules = 74.5699869444
- I would need an iron air battery with at least 74 kilograms for every hour consuming 100 horsepower.
However, my interest peaked because I was wondering if I could throw away the oxided iron in order to be lighter and consume less energy for every moment.
Then, I also thought about supercapacitors and my little research that I've made with dielectric elastomers, which are the same thing.
For some reason unknown to me, supercapacitors use an electrolyte to store the charge as both ions and electrons, unlike dielectric elastomers.
And it got me wondering:
How much energy I could store with those dielectric materials?
I was talking about materials with dielectric strength/voltage breakdowns around 50 KV or even more, with dielectric constants around 80 to 300 using titanium dioxide and lead zirconate titanate (which have 500 to 6000).
So I got to a capacitance calculator and I inserted these values, however, I don't know how correct these values are.
So, I found this:
"And so, the dielectric constant for teflon is 2.1, and we multiply that by permittivity of free space 8.85 times ten to the minus 12 farads per meter. And then, multiply by the area of five square meters and divided by 0.01 millimeters, which is 0.01 times ten to the minus three meters. And, this gives 0.93 microfarads as the capacitance."
So, doing the same thing with the supposedly material with 300 as dielectric constant:
- 300 x 8.85x10^-12 = 2.655e-9 farads per meter
- Capacitance calculator: 0.00000331875 farads
The area was around 1.25 m² because I took a cylinder volume calculator and made a cable with 10cm of length and 4cm of thickness, which would be a cable for 1000 amps. Then I've input the values of a rectangle volume caculator and matched the volume from teh cylinder with the rectangle with 1mm of length, 10cm of height and around 125cm ofwidth.
Which when I've inputed on the rectangle area calculator, gave me around 1.25 m² of surface area.
(this thing would weight around 10kg btw)I inserted then the separation distance of 1mm and the calculator gave me a capacitance of 0.00000331875 Farads.
When I inserted the capacitance and the voltage (50,000 volts) on the capacitor energy calculator, it gave me the value of: 4,148.4 joules for every 10 kilograms of capacitor.
Even if I changed it from copper to conductive polymer, it would still be 4 kilojoules per kilogram (10 times lighter). :|
By the way, 8.85x10^-12 = 0.00000000000885.
So I would need to increase the capacitance by 112,994,350,282 times in order to increase its capacitance to 1 farad per meter. :|
Well, now I know why the electrolyte is required alright...
A conventional supercapacitor stores around 20,000 Joules of energy per kilogram, and it normally uses aluminium oxide as the dielectric material, which in turn, has a dielectric constant of around 10.
Assuming that I use the diamond powder to increase the dielectric constant to 1000, then I would store 100 times more energy, which would be around 2 MJ (2 million joules) per kilogram.
The dielectric consant is related to the temperature of the material, some increase with heat, some decrease with heat.
Maybe using these changes could increase the energy density of supercapacitors, although, the electrolyte would need to be comfortable in these conditions in order to work.
Well, I don't know if I can even approximate how much energy it would be stored, since the thickness of the aluminium oxide layer in aluminium supercapacitors is around 4 nanometers (or 0.00004 millimeters). And on top of that, it is highly porous to increase its surface area without increasing its size.
It is really a complex science and at the moment google doesn't show me a single article about the effect of temperature and dielectric material on the energy density of supercapacitors. :/
... And I doubt this would change too much, a graphene supercapacitor (the most energy dense supercapacitor) was able to achieve 88,1 wh/l, or 317,160 joules per liter (which is probably per kilogram too).
... So, another useless detour. lol
Well, I was mentioned in a Mech video (not as this account's name) and I saw a bunch of comments talking about a variety of different manners of storing energy.
For example, there are molten batteries and molten-air batteries. Which I never heard about.
Molten-air battery's storage capacity among the highest of any battery type (phys.org)
Accordingly to this news article, a carbon molten air battery would have around 28 MJ (megajoules = 1 million joules) per kilogram of mass.
I would need around 10 kilograms of this stuff for every 100 horsepower-hour that I would consume.The page links to an article on the subject, I gotta study about it to check if is going to work in a practical manner.
I do hope they don't need some acidic/toxic electrolyte to work tho...
Well, too bad, in this specific article they use lithium carbonate and barium carbonate for both the iron and carbon battery (I didn't care about the vanadium battery because it is expensive).
So, if I'm going to use molten lithium carbonate at 800ºC at the risk of losing charge to the formation of CO2, then why not just use the Molten Carbonate Carbon Fuel Cell?
(I just checked, most articles still use molten carbonates based on lithium, sodium and potassium, just like molten carbonate fuel cells)
... For some reason I feel less pro-active these days, I don't have energy for anything at the moment. Maybe I should stick with Molten Carbonate or Molten Hydroxide fuel cells instead of making the adiabatic carbon-diesel engine with the brushless generator.
Before writing about the new coil actuator down below the off-topic section, I do think this project log in specific is pretty useless, I just complain that other methods aren't that viable and jump straight to a combustion engine. Which is the one of the most complex systems I suggested.
Besides, I could also use the TEG generators to recycle some of the wasted heat of the Molten carbonate fuel cells.
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I just found this concept for a molten carbonate fuel cell, it looks just like a conventional fuel cell and I do think this way it could allow for a system to properly control the electricity output.
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While looking for other molten carbonate fuel cell structures I found out you can literally use anything that is carbon based, even wood and hydrocarbons, but I'm not really going to test inserting gasoline in a 700-800 ºC furnace, lol
Actually, if I'm not mistaken, they process the fossil fuels in order to take out elements like sulfur and then insert into the fuel cell just like that. :|
Now I'm doubt which one I should choose: molten air carbon battery or molten carbonate fuel cell.
- Both need to be at 650-800ºC to work
- Both need carbon.
- Both need energy heat itself up and mantain functionality
- Only Molten carbonate needs air intake and co2 recycling
- I would need to find an energy source to charge the batteries
- I would need need to find fuel for the carbonate
- The molten battery could have multiple cells around the body, both risky and redundant
- The molten carbonate would only need a single cell
- The battery needs to carry all the 200kg of carbon while the fuel cell consumes it
Oh well, I guess this is settled
Just found this video, common table salt can become a ionic liquid until its molten (around 800ºC). So maybe this could be an useful material for the carbonate fuel cell, of course, assuming that the carbonates aren't working as an ionic fluid already, since these are considered "salts".
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Source: https://www.sciencedirect.com/science/article/abs/pii/S0378775301009429
This is a 250 KW Molten Carbonate Fuel Cell that uses hydrocarbon gas fuel by the way...
Is the idea of maintaining the electrolyte solution in a ceramic bucket even remotely viable?
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I was even thinking on mixing the carbonates with their equivalent carbonates: sodium silicate, potassium silicate and lithium silicate and using a sacrificial fiber material, so it becomes some kind of huge sponge-like cell.
Why do they need such immense sizes for a 250 KW fuel cell?
Hydrogen fuel cells can be this smaller too:
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I also just found out about molten chloride fuel cells, which use things like table salt (sodium chloride). Dunno what is the difference between these two in the matter of performance and efficiency, but I suppose there are many, many types of molten fuel cells.
Off-topic:
So, I just scrolling on youtube shorts (definitely not procrastinating) and I saw this little video here:
The spheres are magnetic (can lift 9 kilograms), which is interesting, but anyway.
I was thinking: could you make a "disactivation" coilgun with this?
I've made a rough estimative with that by inputing the weight of a possible projectile and the thrust required to accelerate it towards mach 4 in 0.001 seconds (the length of a 60cm barrel), and basically, it would need a thrust of 6000kg.
Well, I don't necessarily need to start with 6 tons of electromagnetic force, but you you get what I mean.
Basically, I thought on lining up those holding electromagnets (since they are just like permanent magnets) launch the electromagnetic projectile in its direction and once it gets more or less in the middle of each section, the electromagnet is disactivated and its remaining electricity is pumped into the next electromagnet until the thing is launched.
A 100kg holding electromagnet only uses 14 watts, but I do know that I would probably need to increase its output power severely, since the "trick" to these electromagnets is that they complete the magnetic field using the ferromagnetic target (the object it attaches itself to).
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However, the idea would be to put the nort and south poles of electromagnets in a "C" along the tube of the gun.
Kinda like this:
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Insert a tube in the air gap and it is pretty much what I thought.
I just couldn't find any kind of coilgun like that, the closest I found was a "quench coilgun" that instead of disactivating the coils, it quenches/heats up superconductors in a sequence.I just said that, and it seems this is a "reluctance coilgun", which would be better with aircore solenoids instead of iron core electromagnets because the core has a limit on the amount of magnetic flux it can allow to pass through itself.
Source: https://4hv.org/e107_plugins/forum/forum_viewtopic.php?id=83108
There is a lot of interesting concepts would there, for example:
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Wait a minute, wouldn't this be actually great for pilebunkers?
The magnetic rod wouldn't scape the solenoid's insane electromagnetic field and would go back and forth just like the first video of the magnetic sphere.
Pilepunkers are always depicted as a combustion/detonation machine, but I don't think anything would be able to survive the detonation and be cheap enough for its use.
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... But if that is the case, then why not just use it to push a projectile really fricking fast instead of launch it with a coil gun?
There was actually a silenced projectile/gun like that, but with combustion instead.
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It is called a "captive piston cartridge".
Not Off-topic - Revisiting Actuators:
Now that I ended up procrastinating and researching about railguns, I found out that the lower the speed of the railgun, the higher its efficiency.
So, a 1000 m/s (Mach 2.9) railgun has efficiencies around 40% while a 3500 m/s (Mach 10) to 5000 m/s (Mach 14) has efficiencies around 30% to 20%.
So, this made me think: what if the speeds were actually 1.33 meters per second just like the mech needs?
If the efficiency raises up to 80% to 90% at these speeds, then I could make an actuator that is super light, effiicent, strong, cheap, simple and fast.
Even better than artificial muscles and electric motors.
Just now I found out that the maximum efficiency would be 50%, but I asked chatGPT to make the calculation on how efficient it would be for a railgun to push a 3000kg projectile at 2 m/s and it said it would be around 1% to 0.2%...
I went asking around to see if there is something like this, but people normally just scoffs at the question, just says it is idiot or plainly ignores it.
... Which is kinda frustrating... I just want to understand if it works or not... And I don't think I have the resources to test this out...
I just found a few articles about it, and they don't even mention the efficiency of the system...
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Do I really need a railgun actuator tho?
The coilgun actuator could do the same work, an 1 ton solenoid holding magnet uses around 1 to 3 kilowatts of power and weighting 3kg to 5kg.
Of course, the holding solenoid isn't that powerful because it needs a ferromagnetic material to close its magnetic loop, but would a solenoid be able to pull up this much power by also using an electromagnetic inner rod/plunger?
... But the solenoid rod has less moving force the further it is from the center, so you would need it to be stronger X amount of times.
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... No matter how much I feel I learned with this project, I always learn that I know nothing.
I'm in the right path? I'm making real progress? I actually checked every option properly?
I should've been in an engineering college or something like that... Or else I can't see this project being completed... 🤔
I just now found something similar to the railgun-coilgun hybrid, but for actuation porpuses.
And stopping to think about it, I don't think this is an "hybrid" like the templin institute said, but just a coilgun with a commutator...
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Source: https://lifeboat.com/em/chapter.4.pdf
As you can imagine, the idea is pretty simple: make the sliding contact coilgun, but use it as an actuator instead.
Could this finally mean that I could have an efficient, simple, cheap, practical that outputs force proportional to the energy input?
You could also built it with flexible tubes/fibers in order to work just like a muscle, which would be a pain in the butt to maintain and verify for defects and wear. But at least you would have the first and only electric artificial muscle with efficiencies above 80%.
Well, the only problem would be the wear and friction of the commutator/sliding contact, which is also a source of inefficiencies and cost of maintenance on normal brushed motors.
MAYBE this time it will be easier to find the energy input and efficiency because both are coils/solenoids.
... But I think I'm looking at it in the incorrect manner... Should I make it brushless instead?
You see, the first idea I had for this was the linear brushless motor... And I discarded it because it would be too heavy and expensive.
Maybe it didn't work at first because I've made a brushless motor with a rotor (the moving part) with too many slots? Just like in the image above?
... And also because I couldn't possibly make an ESC controller with hundreds of amps and hundreds of volts.
... Which I wouldn't worry about while building the brushed linear motor.
Sorry for not calculating this thing right now.
For some reason I'm feeling indisposed...
But goddang it, it kinda a pain in the butt to convert joules to watts.
Supposedly, accordingly to kinect energy calculators, I woud need around 2,665 joules to move the 3000kg load at 1.33 m/s target. But the problem is that joules can't be directly converted to watts because watts is a matter of work over time.
So I can't just convert joules to watts and watts to volts and amps. It would be so much easier this way tho...
So, basically, I need to make coils on Blender and measuring their height, diameter, number of turns and thickness of wires in order to use a solenoid force calculator.
And even then it is not that easy, because the calculator probably only shows the force at the center of the solenoid, not on its outside.... But I could just use a back iron plate to redirect the electromagnetic field...
I guess one way of looking at it would be thrust to move an object to certain speed.
If we use a speed calculator to move something at 1.33 m/s with a 30 cm distance, it would take 0.22556 seconds.
If we take an acceleration calculator, to move from 0 to 1.33 m/s would need an acceleration of 5.896 m/s².
If we take a thrust to acceleration calculator, to move a 3000kg mass to 1.33 m/s with an acceleration of 5.896 m/s², it would need a thrust of 17,688 newtons or 1,803.8 kg-force.
If we want to quadruple the speed (let's say, when jumping), you would need 7,215.2 kg-force.
Obviously, the transmission of power isn't perfect and it would require more energy, but at least I think it will be easier to find a result for said brushed coil actuator.
Also, let's remember that the reduction in the transfer of the lever limbs (aka, where the actuator is attached to the limbs in the body will work like a lever) will be 3:1, an increment of 3 times the speed and decrease of 3 times in its strength, reaching the speeds the human body reaches.
From stationary to even 12 meters per second or 43 km/h while carrying 1 ton of weight.
A kind soul told me that I should start calculating the inductance first and then calculate how the solenoid should be.
Well, I roughly calculated the inductance, magnetic field strength etc. And I still can't tell how strong the electromagnet would be, neither if this electromagnet would be strong enough to lift 3 to 10 tons.
I'm mcfuckin losing it my guy, I can't find a way of predicting the force output of the coils no matter how much I look into it.
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Also, I think the previous estimative that the actuators would need to accelerate masses to 1,33 m/s is incorrect because I didn't take into consideration the gravity of earth, which is 9,8 m/s².
So, essentially I need to counter that acceleration of gravity and then add the 1,33 m/s to the mix.
No matter what, the results are never consistent.
I ask to chatgpt and it says it will have less than a single newton of force, I go to solenoid force calculators and they say my coil would have 10 million newtons of force.
Here is the question that I copy paste for every ChatGPT:
I need an electromagnet solenoid coil to pull up an outer electromagnetic with an X amount of force.
How I can calculate its force?
The outer diameter of the inner coil is 190mm, the inner diameter is 110mm, the space between the turns is 1mm, the height is 82mm, number of turns is 2, the length of the wire itself is 1193.8mm, the ampearge is 1000 amps, the voltage 200 volts, it has a distance of 1mm between this coil and the outer coil and is at 10mm above the inner electromagnet.
The outer coil has a wire thickness of 40mm, a spacing of 1mm between the turns, 2 turns and an inner diameter of 194mm, so an outer diameter of 274mm, the amperage is 1000 amps, the voltage is 200 volts, the length of the wire itself is 1721.6mm
Mistra-medium from PoeGPT said the following:
Sure, here are the calculations for the force exerted by each solenoid coil with 400 V and 500 A:
For the inner solenoid coil:
The cross-sectional area of the inner solenoid is:
A = π * (190/2)^2 - π * (110/2)^2 = 14,094 square millimeters
The force exerted by the inner solenoid can be calculated using the formula:
F = (μ₀ * N * I^2 * A) / (2 * g^2)
F = (4π × 10^-7 * 2 * 500^2 * 14,094) / (2 * 1^2)
F = 88,220 Newtons
For the outer solenoid coil:
The cross-sectional area of the outer solenoid is:
A = π * (274/2)^2 - π * (194/2)^2 = 39,377 square millimeters
The force exerted by the outer solenoid can be calculated using the same formula as above:
F = (μ₀ * N * I^2 * A) / (2 * g^2)
F = (4π × 10^-7 * 2 * 500^2 * 39,377) / (2 * 11^2)
F = 37,364 NewtonsNow, let's try the same thing again:
If you increase the voltage to 500 volts and the amperage to 400 amps in both coils with the 40mm wire thickness, the force exerted by the solenoids will increase significantly due to the increased current flowing through the coils.
The force exerted by an electromagnetic solenoid is proportional to the square of the current, so doubling the current will result in a four-fold increase in the force. Using the same calculation as before, the force exerted by the inner solenoid coil at 500 volts and 400 amps would be:
F = (μ₀ * N * I^2 * A) / (2 * g^2)
F = (4π × 10^-7 * 2 * 400^2 * 14,094) / (2 * 1^2)
F = 352,880 Newtons
Similarly, the force exerted by the outer solenoid coil at 500 volts and 400 amps would be: F = (μ₀ * N * I^2 * A) / (2 * g^2)
F = (4π × 10^-7 * 2 * 400^2 * 39,377) / (2 * 11^2)
F = 149,456 NewtonsWell, this value is unnusually high, so I asked it to recalculate with an wire with the proper diameter for 400 amps, but it got way less force, so I asked why that was the case.
And the answer from the Mistra-medium was:
I apologize for the confusion in my previous responses. You are correct that the forces I calculated earlier for the 40mm thick coils were much higher than the forces I calculated in my latest response for the 14mm thick coils.
The force exerted by an electromagnetic solenoid coil is proportional to the current flowing through the coil, the number of turns in the coil, and the cross-sectional area of the coil. Since the current and number of turns are the same in both cases, the difference in force can be attributed to the difference in cross-sectional area.
For the 40mm thick coils, the cross-sectional area of the inner coil was approximately 14,094 square millimeters, while the cross-sectional area of the outer coil was approximately 39,377 square millimeters. In contrast, for the 14mm thick coils, the cross-sectional area of the inner coil is approximately 1,848 square millimeters, while the cross-sectional area of the outer coil is also approximately 1,848 square millimeters.
Therefore, it is not surprising that the forces exerted by the 14mm thick coils are much lower than the forces exerted by the 40mm thick coils. In general, larger coils with more turns and a larger cross-sectional area will be able to produce a stronger magnetic field and exert a greater force.
I hope this clarifies any confusion. Please let me know if you have any further questions or concerns.No, seriously, this doesn't make any sense. I asked around and people told me I'm stupid.
I mean, they aren't wrong, but I guess it is useful tho...
Dunno if this is useful at all, but I was only expecting an approximation, not an absolute answer. But I guess it is better than start with absolutely nothing.
Just now I decided to calculate the weight.
The weight of a single aluminium coil actuator in the molds I just talked about would weight around 28kg.
840kg in total for all 30 actuators.The 14mm thick wire would weight around 5kg per actuator, 150kg in total.
Maybe sticking with the HASEL artificial muscles is a better idea?
Of course, that is the weight of all actuators that can output 10 tons to 50 tons (accordingly to the chatbots), I could make the upper limbs lighter (and weaker).
It took me almost an entire month just to figure this idea wouldn't work...🥲
(assuming ChatGPT is correct)
I think that the slip contact coilgun turned actuator could be used in a round planar format for certain axis.
![]()
The image is from a coreless axial flux motor, but you could turn it in a single coil/solenoid and maike a rotary brushed coilgun turned actuator.
Now what?
What I do now?
Also, like I said before: I can't buy anything for the next 7 months because that is how much I divided the cintiq style table.
So I don't know if I will be able to continue this project until next year. In fact, I don't even know how to start.
I guess a good start could be making the 3D model of the linear actuators and parts that I would need to make/print.
Another thing is that now that I look at it, I don't feel confident with the Stewart Platform's range of motion. But I will only know for sure when I at least make a non-colision simulation.
(I think I need to figure out a way of turning this linear motor into a telescopic one)
Actually I figured out how to make telescopic, but it hard to explain without a proper picture, and I couldn't find a proper picture.
Just imagine a linear motor's stator and its moving rod, if you "simply" puts the hollow stator in the middle, a moving rod in the center and hollow rod outside of the stator, you can move both rods at the switching of the electromagnets of the hollow stator in opposite directions if both have opposite poles.
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Just replace the gears and teeth with electromagnetic coils.
Also, I was wondering if a dual solenoid coil would work for an electric artificial muscle.
Basically, a center solenoid has a fixed length and the outer solenoid is all stretched out, both have opposite polarities, forcing the outer stretched solenoid to "contract" in the direction of the fixed length solenoid.Dunno if it would work tho...
I was just going to test it on my adjustable power source that I bought a time ago and the plug literally broke its teeth.
![]()
Well, I made a quick fix and tested it anyway.
It didn't work, probably because I'm stupid.
Behold, the utimate mech:
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Source: https://www.p
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Project Log 83: Screw it, let's freaking do it.³
06/10/2024 at 12:56 • 2 commentsMonday, 10/06/2024, 09:44
(is Hackaday.io going down to all of you or just me? Some times I need to wait an entire day for the website to be accessible)
Well, I feel like it is a bit too soon to be worrying about design, and specially since I literally didn't start working on it at all even though I name the project logs exactly to do that. :|
But here we go again with my shenanigans...
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Design of the Artificial muscles:
Materials for dielectric elastomers:
Well, since I'm intending on making dielectric elastomer fibers with 1mm of thickness, I can't really just make it whatever way I want and leave at it.
I could simply connect a single fiber and be done, since very high voltages and very low amperages can travel kilometers in materials without any loss, but if any fiber is damaged, well, you could have the entire thing stop working. Of course, I still could make the fibers slightly bigger and just connect new muscles whenever some fiber is damaged, and I do intend on doing that if this idea shows itself to not be viable.
(I want to make it as small as possible because I'm afraid that the contraction ratio of the muscle will force me to change the proportions, right now the idea is that the muscle is attached to 1/3 of the limbs length, if I'm reguired to increase it, then it would make the muscles even heavier)
I need polymers that are soluale in a material, but not in other. At least for the outside layer.
Polyvinyl alcohol is soluable in water and alcohol, but not in acetone or gasoline.
Polystyrene (styrofoam) is soluable in acetone and gasoline, but not in alcohol or water. (Funnily enough, polystyrene is even cheaper than PVA)
Poly(methyl methacrylate) (PMMA) is soluable in acetone, but not in alcohol, water or gasoline.
Polyvinyl chloride (PVC) is soluable in acetone, but not in alcohol, water or gasoline.
So, if my brain isn't being stupid: for half of the outer layer of PVC/PMMA that dissolve in acetone and for another half, I would need a material that dissolves in gasoline, but not in acetone, alcohol or water. I could only find a few forum questions saying that PET and LDPE can be damaged by gasoline over time, but not something that can actually dissolve.
I found out that if I mix PVA with dielectric silicone grease, it becomes resistant to water, but also that there are waterproof PVA glues in the market. So I "just" need to mix it with PVA and make it hydrophobic.
So, the design of the actuator:
Outer layer of negative electrode side = Dielectric Soluble Polymer 1 + low friction material + other additvies if required. Negative Compliant Electrode = fumed silica powder + graphene + polymer. Dielectric Elastomer Layer = Dielectric Elastomer Polymer + titanium dioxide + other additives if required. Positive Compliant Electrode = fumed silica powder + graphene + polymer. Outer layer of positive electrode side = Dielectric soluble Polymer 2 + low friction material + other additvies if required. I don't know what polymer to use on the electrodes yet, I was thinking on just using PVA. I also don't know which low friction material I should use for the outer layers, I was thinking that they should have low friction for better actuation of the artificial muscles...
So the idea is to:
- Make a 1 mm (less or more) fiber with this structure.
- when deciding to attach to a limb, over the attachment places of the skeleton/limb with dielectric material.
- Roll the dielectric elastomers up in a loop.
- Hold them in place with a really tight cable.
- Making the "tendons" by going with another rope through the loops.
- Use one solvent in one tip of the muscles and the other solvent in the other tip.
- Cover the tips in a conductive polymer (probably PVA) with the negative and positive electrodes.
- Connect everything to the electronic system.
- Then wrap everything in another layer of dielectric material to avoid the electrical current to arc.
- Done.
- Optional: I also thought on surrounding the muscles with a plastic bag and fill it up with a dielectric liquid, grease or gel for extra safety if any fiber muscle comes to be damaged.
"Just" that, god, I whish there was an electric artificial muscle that didn't need a positive and negative end...
You could just have a dielectric elastomer in which you just insert the electricity, but doesn't need the other electrode to be connected to anything, the difference in energy potential alone would make the dielectric elastomer actuate. However, I do think that the difference in voltage of the powersource is bigger than the difference in voltage of the material alone. But I don't know who to ask.
For some reason I can't find the goddang dielectric values of polyvinyl alcohol, it is said it is high, but never how much.
And I'm not talking about dielectric constant, but dielectric strength and breakdown voltage.
Well, after 2 hours I actually found it, in this paper it says that:
"The dielectric strength of polyvinyl alcohol (PVA) is potentially very high i.e >1000 kV/mm. "
Ok... But I think that using cheap off-the-shelf PVA glue with waterproof PVA glue mix won't give such insane results, I guess that I will literally need to buy the equipment and test it to failure...
Now I need to find out how to make a power source that reaches high values of Kilovolts and high values of Hertz...
Actually, I found power supplies like that, but they cost thousands of bucks, so I will need to build everything homemade, which I'm not capable right now since I bought a new table and a new drawing tablet...
Just now GPT actually answered me other materials that actually are soluable in different solvents than PVA and Polystyrene.
Like Polyoxymethylene (POM) or Polyacetal that aren't soluable in acetone nor water or alcohol, but it is soluable in Benzyl Alcohol, but although I couldn't find how it affects PVA and Polystyrene, it probably dissolves one of them.
In any case, I will keep trying to find new options.
On a side note, the dielectric constant is the value of how much charge a given material can store, so the higher the dielectric constant, the higher the energy density of the material.
HOWEVER, this can also decreases its breakdown voltage (depending on the material), so you can't just take a material that has insane high dielectric breakdown voltage if it can't store that much charge...
So, making a list:
I will make it later, right now I'm reading manga, lol
The manga is a generic tutor isekai crap, it is not that big of a deal, I just like to read something silly and dumb to forget a little about our burning world full of horros beyond our comprehension.
Now I finished it:
Name (for some reason this part of the table is squished): Dissolves in: Insoluble in (for some reason this part of the table is squished): Dielectric Breakdown Voltage: Dielectric Constant (it can change severely based on hertz): Tensile strength: Polyvinyl Alcohol Water, Ethanol Acetone 45 (source), 420 (source) to 1000 (source) KV/mm 1.01 8-40 MPa depending on the source. Polystyrene Acetone, Gasoline Water, Ethanol 24, 25, 400–600 KV/mm 2.6 5-50 MPa Polyoxymethylene (POM) or Polyacetal Benzyl Alcohol Water, Ethanol, Acetone 19.5 to 50 KV/mm 3.02 69 MPa Titanium dioxide Not required Not required 12-270 KV/mm (Depending on the source 1, 2) 85-173 Not required Aluminium Oxide/alumina not required not required 14 KV/mm (source) 8.6-10 not required FiberGlass Not required not required 2,000 KV/mm 6.2 not required Silicone Rubber Acetone, Mineral spirits, tuolene, white vinegar, Isopropyl Alcohol, Methyl Ethyl Ketone (MEK) Water, Ethanol 39.5 KV/mm 3 3-5 MPa Dielectric Silicone Grease Same ones Same ones 0.350-1.5 KV/mm 2.6-2.9 Not required Polyurethane rubber Acetone, toluene, xylene or MEK Water, Ethanol 70-90 KV/mm 13.5 3-5 MPa Polyethylene (HDPE/LDPE etc) Tuolene, Xylene Water, Ethanol, Acetone 50, 500–700, 18 KV/mm 2.2 20-45 MPa Polypropylene Xylene, Tetralin and Decalin Water, Ethanol, Acetone 30-40 KV/mm 2.1 30-45 MPa ABS Ester, Acetone, Chloroform Water, Ethanol 20-25 KV/mm 20-25 30-60 MPa Nylon Phenols, calcium chloride-saturated methanol solution and concentrated formic acid Water, Ethanol, Acetone 25 KV/mm 3.5 85 MPa Polycarbonate Ethylene chloride, chloroform, tetrachloroethane, m-cresol, and pyridine Water, ethanol, acetone 15-67 KV/mm 2.9 39-120 MPa Teflon Virtually none Virtually all 60 KV/mm 2.05 41 MPa Lead zirconate titanate not required not required 25 KV/mm 500-6000 Not required Talc Powder not required not required 200-500 KV/mm 3-15 not required Cellulose Acetate acetone, spirits and ethanol. water 11-15 KV/mm 3.6 26-33 MPa Polyvinyl Acetate acetone, spirits and ethanol. water (not found) 3-15 3-10 MPa Now that I finally finished the list I end up finding this PDF archive that pretty much lists all of the polymers out there... There is also this textbook and this one.
There is also this list of the highest dielectric constant (aka permitivity) materials.
Funnily enough, I could find Lead-Zirconate-Titanate piezoelectric devices in a reasonable price on aliexpress. Even if I bought them and broke them back to powder, I don't know how much of their original properties would be left...
I also thought on adding diamond powder to the composite of the dielectric layer, since it has such high breakdown voltage. But I don't know if the diamond powders out there are really diamond or just zirconia.
Well then... I've made this huge list, now what?
Hum...
First:
maybe the 1mm thick fibers aren't a realistic goal for this project, maybe I should aim for a dielectric elastomer layer with 1mm of thickness.
Second:
I need to find a way of making the restrained DEA with the mesh, I mean, I don't know how to mass-produce at home these braided mesh for a 1mm of thickness dielectric elastomer actuator.
I also don't know if other shapes could work, for example, the McKibben muscle works in a similar way with the braided mesh, but they also use linear meshes. If the linear meshes are viable, then would them work in the fiber 3D printed DEA?
Restricted DEA with a braided mesh:
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McKibben muscle with a similar mesh:
![]()
McKibben muscle with linear mesh:
Would any of these work with the fibrous 3d printed DEA?
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If this was to work, then it woud way easier to make the actuator in a mass-produced manner, and it would probably be possible to make it smaller than 1mm.
Although the dissolving the opposite electrodes idea will be in the trashcan after this... Or maybe not, the image shows that you could print the fibers without one of the electrodes, so every X meters I would go switching which electrode can be accessed by simply not printing one of the four parts (outer dielectric layer > outer electrode > Inner dielectric layer > inner electrode)
Also, I was considering making the electrodes liquid (or even a gel), so it would be easier to simply remove the extra fluid of one of the concentric tubes. Some even use room temperature liquid metals like galinstan.
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Source: https://www.mdpi.com/2073-4360/13/24/4310
The use of liquid electrodes also doesn't solve the problem that I would need to connect thousands of fibers, I really need to solve this problem, even if it where the conventional sandwich of dielectric elastomer layers, it would still be a problem to wire thousands of fibers.
Just now I remembered that there is the option of a spiral fiber dielectric elastomer actuator:
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Maybe with this design I could turn the inner hole a continuous connector and the outer tube also a continuous connector, let's say, you can only access the negative electrode from the outside and the positive through the inner side. Although... I still don't know how well this would work... I can still use the idea of covering the different electrodes with different plastics that dissolve in different solvents.
There is also this design:
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I know that I simply never stop adding more and more designs that could pottentially work, but I do think this is it. This one allows the fibers to be actually around 1mm to 2mm thick while also allowing the separation between the electrodes to be also 1mm without making the electrodes too thick.
My only gripe with this design is that the center contracts more than the borders, so how exactly would it reduce its length if the entire border of the actuator is connected to something?
The only reference I have are these two videos of dielectric elastomer actuators:
The first is just like the 3 dimensional version of this planar electrode, while the second doesn’t seem to have the same issue because it doesn’t seem to have the outside electrodes.
The only problem remaining is that I kinda want to use PVA because of its price, but there isn't anything that doesn't dissolves in something PVA does… I guess that I could simply mix it with waterproof PVAc (wood glue) to make the core water-proof but not the electrode protection, or even hydrophobic materials like fumed silica.
So, a drawing of how I intend on doing it:
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Obviously, this will be a continiously printed dielectric elastomer actuator.
Also, I didn't talk about it because I didn't want to bloat the project log more than it already is, but taking into consideration the thickness of everything, a lot of these options for fiber DEA's ended up being half a centimeter of thickness (or even wider) when you stop to think its dimensions. Besides, I do think this version would also be easier to print without some crazy DIY setup. I could even use a rolling printer for this.
Oh yeah, I forgot to write about the efficiency of dielectric elastomer actuators. They work through the Maxwell stress, so a lot of energy is wasted just to overcome the resistance of the material for bending. So, the efficiency is around 18%-20% and maximum 60% while recycling the energy that comes out of the muscle, they are a kind of capacitor anyway.
Okay guys, this is the last time, I swear.
I'm not satisfied with the hypothetical performance of this dielectric elastomer, I'm not very confident on its actuation strain and efficiency. And after some consideration, I do believe that the best material to continue with this endeavour is the HASEL actuator. They don't neeed an elastomeric material, only a flexible one.
They can also be tuned to have higher contraction ratios as shown in the video.
I also tried to find a dielectric elastomer and HASEL hybrid only for the sake of not throwing the design away, but I couldn't find any.
And finally, I will need to figure out how to extrude this thing. I was thinking of even using a 3D printer… Initially I was against the idea because I was thinking of making everything as thin as possible, since this is not the objective anymore, dimensions of millimeters are really within any 3D printer. After all, 3D printers have a precision of 0.2mm or even smaller. And for that I would need multiple nozzles and a multi-material screw extruder for mixing all the materials together.
And at this point, I’m not even sure if I will use PVA glue for the plastic or HDPE/UHMWPE + PE wax for the core materials…
Third:
Now I "just" need to start modelling the skeleton and "simply" making the muscles.
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This is that moment that deep down in my lizard brain that makes me think:
"This thing might kill me"
We are taking about kilovolts that could easily make my heart stop.
Although the thickness of the materials will differ, and thus, the input voltage may be lower, we are still talking about inserting 81 Kilowatts of power in the shape of high voltage low amperage.
And on top of that, it will require the same mechanical brakes as the other artificial muscles, so I'm starting to ask myself it is worth the trouble...
Shouldn't I instead work with the thermal artificial muscles...?
Well, this is me from the future, and I finally went to check the price of mechanical/electromagnetic brakes and winches with the lifting capacity closer to the intended input force (3000kg), and guess what?
It is too expensive and heavy. :|
With the exception being the manual winch brakes, which would need to be modified for higher load and also for the insertion of a encoder:
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Mech design:
I want to make some of the parts of the mech biomimetic, I was thinking on making artificial cartillage (gels attached to the joints of the skeleton), artificial ligments (cables/ropes attached to the skeleton) and tendons (ropes covered in pva).
I'm just not that confident on my skills, neither in how long/strong will these parts actually hold on. I say this because some parts of the human body can reach 1 GPa of tensile strength. That is close to carbon fiber, now imagine an elefant or a horse...
You know what? I will "study" (look at videos) the anatomy of elefants, horses, rhinos, hippos and all sort of heavy animals in order to take inspiration/copy their structure for the mech. By the way, elefants can weight from 2700kg to 6000kg depending on the race, horses can weight from 150kg to 1500kg depending on the race, hippos range from 1300kg to 1800kg and rhinos 2500kg to 3200kg. These values are the average, the elefants can even get up to 10 tons.
In both cases, what concerns me is the relaxation of the artificial tendons, ligments and muscles.
This video is about a reduction pulley that uses ropes, and after a while, the ropes start creep. The guy was forced to use Dyneema for it, which has the lowest extension in the market, but it is also very expensive. However, his actuator is a precision actuator, not a biomimetic artificial tendon made in the trash (like mine), so I don't know how much it would affect my project.
Accordingly to this document, irreverssible rope creep can happen after a few years. Well, it sounds good to me, gears and bearings have the same issue of degradation over time. https://www.samsonrope.com/docs/default-source/technical-bulletins/tb_understanding-creep_mar2012_web.pdf?sfvrsn=1e71fc4e_2
Bruh, the idea that every couple of years I will need to make a "surgery" in a mech to fix its arthritis, arthrosis, tendinopathy and strains.
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Articles that I think are interesting for biomimetic human robot:
- "Bone has yield strength of 51–66 MPa in tension and 106–131 MPa in compression when tested along its transverse axis. The Young's modulus of cortical bone is 17–20 GPa along the longitudinal axis and 6–13 GPa along the transverse axis (Toma et al., 1997)." https://www.researchgate.net/publication/336821961_Rapid_prototyping_technology_for_bone_regeneration
- "Tensile strength of the extensor tendons averaged 13,392 psi (88 MPa) while that of the flexor tendons was less, with an average of 10,944 psi. These results indicate that, of the tendons tested, the extensors are about 20 per cent stronger than the flexors." https://www.sciencedirect.com/science/article/abs/pii/0021929068900389
- "The tensile strength of cartilage from the deep zone did not show an increase in the early years but decreased continuously with age. The tensile stiffness of the superficial layer at stresses of 5 MN/m2 (5 MPa) and 10 MN/m2 (10 MPa) increased to maximum values in the third decade and thereafter decreased with increasing age." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1001032/
- " Ultimate tensile strengths for tendons and ligaments range from 50 to 150 MPa (for comparison, recall that the tensile strength of bone is about 150 MPa)." https://musculoskeletalkey.com/mechanical-properties-of-ligament-and-tendon/
- "The 'overall' strain in the ligament was calculated from the outermost pairs of markers along the ligament length. The average tensile strength, the 'overall' tensile modulus and the 'overall' strain of the ALL at failure were 27.4 MPa (S.D. 5.9), 759 MPa (S.D. 336) and 4.95% (S.D. 1.51)" https://pubmed.ncbi.nlm.nih.gov/1400518/
- https://asmedigitalcollection.asme.org/mechanismsrobotics/article/15/1/014503/1140488/Experimental-Verification-of-Kinematics-and
- https://onlinelibrary.wiley.com/doi/full/10.1002/aisy.202200126
- https://www.mdpi.com/2313-7673/9/3/151
- https://www.semanticscholar.org/paper/Design-of-a-highly-biomimetic-anthropomorphic-hand-Xu-Todorov/a4a9eff18b74cd9c2518c9f3ef164b4aab3ac276
- https://www.researchgate.net/publication/343115388_3D_Printing_an_Assembled_Biomimetic_Robotic_Finger
- https://www.researchgate.net/publication/261479910_Design_of_an_anthropomorphic_robotic_finger_system_with_biomimetic_artificial_joints
- https://arxiv.org/html/2404.06740v1/
- https://arxiv.org/pdf/2310.18283
- https://www.semanticscholar.org/paper/Design-concept-of-detail-musculoskeletal-humanoid-a-Nakanishi-Asano/91e00abaee60fd39bf9317f94338864fc9701666
- https://www.semanticscholar.org/paper/Human-mimetic-musculoskeletal-humanoid-Kengoro-real-Asano-Kozuki/afba83157286c9892a8715511b6b9d0ce99ac506
- https://www.mdpi.com/2072-666X/12/9/1124
- https://arxiv.org/pdf/2012.10981
- https://salford-repository.worktribe.com/preview/1503213/T_RO_2%20%28003%29.pdf
- https://www.semanticscholar.org/paper/Fluid-Lubricated-Dexterous-Finger-Mechanism-for-Kim-Yoon/94cb1c73b7eff9ed8af0bf07e95f1d3297774169
- https://www.semanticscholar.org/paper/On-the-Optimal-Design-of-Underactuated-Fingers-Boisclair-Lalibert%C3%A9/0d132d7f3dff8da409ca2bb096f973ed5cb3ac38
- https://engineering.stackexchange.com/questions/19547/what-is-this-kind-of-bearing-called
- https://www.researchgate.net/publication/346997961_A_flexible_self-recovery_finger_joint_for_a_tendon-driven_robot_hand
- https://josr-online.biomedcentral.com/articles/10.1186/s13018-019-1234-6
- https://www.semanticscholar.org/paper/The-DLR-hand-arm-system-Grebenstein-Albu-Sch%C3%A4ffer/571c8c6aa4a0da330c7266ba2f0d951d1775922b
- https://elib.dlr.de/93329/1/Wolf2014_VIA_PPRIME.pdf
- https://www.sciencedirect.com/science/article/abs/pii/S0029801822011465
- https://www.semanticscholar.org/paper/Biomimetic-design-of-musculoskeletal-humanoid-knee-Asano-Mizoguchi/bc767a23d95de2cce4514020533bbf23eaf590e2
- https://www.sciencedirect.com/science/article/pii/S1751616123001613
- https://www.mdpi.com/2313-7673/9/3/164
- https://www.researchgate.net/publication/304190275_An_Overview_of_the_Ongoing_Humanoid_Robot_Project_LARMbot?_tp=eyJjb250ZXh0Ijp7ImZpcnN0UGFnZSI6Il9kaXJlY3QiLCJwYWdlIjoiX2RpcmVjdCJ9fQ
- https://www.researchgate.net/publication/304190275_An_Overview_of_the_Ongoing_Humanoid_Robot_Project_LARMbot
- https://www.researchgate.net/publication/286342185_Actuation_Principles_for_the_Bioinspired_Soft_Robotic_Manipulator_SpineMan
- https://www.cureus.com/articles/9512-the-barrow-biomimetic-spine-comparative-testing-of-a-3d-printed-l4-l5-schwab-grade-2-osteotomy-model-to-a-cadaveric-model#!/
- https://josr-online.biomedcentral.com/articles/10.1186/s13018-022-03012-9
- https://www.semanticscholar.org/paper/Biomechanical-study-of-lumbar-spine-with-artificial-Han-Lee/4790928247fd6b5604e475a8d1133c6a171f4525
- https://www.researchgate.net/publication/228086806_Finite_element_analysis_of_artificial_disc_with_an_elastomeric_core_in_the_lumbar_spine
- https://www.researchgate.net/publication/258359443
- https://tensegritywiki.com/index.php?title=Spine
- http://www.biotensegrity.com/resources/tensegrity-truss-spine.pdf
- https://www.researchgate.net/publication/322280616_Design_and_kinematics_analysis_of_a_novel_six-degree-of-freedom_serial_humanoid_torso
- https://www.researchgate.net/publication/253241653_Dual_Arm_and_Multi-segment_Spine_Motion_Control_for_Assistive_Humanoid_Robots
- https://www.researchgate.net/publication/221710009_A_Musculoskeletal_Flexible-Spine_Humanoid_Kotaro_Aiming_at_the_Future_in_15_Years_Time
- https://www.researchgate.net/publication/272922007_Design_Approach_of_Biologically-Inspired_Musculoskeletal_Humanoids
- https://www.sciencedirect.com/science/article/pii/S2405844023007478
- https://www.researchgate.net/figure/The-LAB-human-and-dummy-models-BAUDRIT-HAMON-SONG-ROBIN-and-LE-COZ-1999-LIZEE_fig10_292731361
- https://www.lsoptsupport.com/documents/papers/robustness/2010-earlier/test-paper
- https://www.semanticscholar.org/paper/Analysis-of-using-an-active-artificial-spine-in-a-Kuehn-Dettmann/661cd2797d9582ebf68f2a248f3288df621d52e7
- https://www.semanticscholar.org/paper/Design-of-upper-limb-by-adhesion-of-muscles-and-%E2%80%94-Kozuki-Motegi/63b81a6cd95cba47851ed7bcf5b4dfdc2c02ade2
- https://www.semanticscholar.org/paper/Design-of-a-biologically-inspired-humanoid-neck-Barker-Fuente/512e22a3efdd64558daf12c083c8fe21368b6383
- https://homes.cs.washington.edu/~todorov/papers/XuICRA16.pdf
- https://tbirehabilitation.wordpress.com/2018/08/23/review-moving-toward-soft-robotics-a-decade-review-of-the-design-of-hand-exoskeletons-full-text-html/
- https://www.semanticscholar.org/paper/Design-of-a-3D-printed-hand-prosthesis-featuring-Cuellar-Plettenburg/8a34cdad7d408beaaa27ad2969b8fb346f9be629/figure/4
- https://www.researchgate.net/figure/5-The-skeleton-of-the-3D-printed-finger-connected-by-crocheted-ligaments-and-laser-cut_fig3_338912205
- https://www.researchgate.net/figure/A-the-CAD-assembly-of-the-proposed-biomimetic-human-index-finger-design-B-the-design_fig2_343115388
- https://www.science.org/doi/pdf/10.1126/scirobotics.aaq0899
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1571305/
- https://pubs.rsc.org/en/content/articlelanding/2021/bm/d0bm01852j
- http://davidbuckley.net/RS/HandResearch.htm
- https://www.semanticscholar.org/paper/On-the-Optimal-Design-of-Underactuated-Fingers-Boisclair-Lalibert%C3%A9/0d132d7f3dff8da409ca2bb096f973ed5cb3ac38
- https://www.frontiersin.org/articles/10.3389/frobt.2023.1164660/full
- https://www.researchgate.net/figure/Biaxial-Compliant-Rolling-contact-Element_fig2_267837075
- https://h2t.iar.kit.edu/pdf/Beil2018a.pdf
- https://www.researchgate.net/publication/365216860_Bio-inspired_design_of_a_self-aligning_lightweight_and_highly-compliant_cable-driven_knee_exoskeleton
- https://www.researchgate.net/figure/Proposed-1-DoF-joint-mechanism-using-the-rolling-joint_fig4_370924703
- https://www.researchgate.net/figure/Rolling-contact-articulations-can-be-employed-instead-of-standard-revolute-joints-to_fig4_326398115
- https://ras.papercept.net/images/temp/IROS/files/2632.pdf
- https://www.cs.cmu.edu/~cga/c/0749.pdf
- https://www.researchgate.net/publication/282389660_Design_Considerations_for_a_Hyper-Redundant_Pulleyless_Rolling_Joint_With_Elastic_Fixtures
- https://srl-ethz.github.io/get-ball-rolling/
- High tensile poly(vinyl alcohol)/Carboxymethyl cellulose sodium/Polyacrylamide/Borax dual network hydrogel for lifting heavy weight and multi-functional sensors | Cellulose (springer.com) (Mixing borax with polyvinyl alcohol turns it into a really good viscoelastic material that could be used as the biomimetic artificial cartillage for the mech, I do enjoy how PVA can be so versatille)
- https://link.springer.com/article/10.1007/s10853-023-09061-7
- Even though I suggest so many types of biomimetic hands, maybe the safer approach would be to turn the fingers into stewart platforms:
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https://arxiv.org/html/2310.05266v2
A rubber pad for hydraulic jack with a diameter of 115mm and thickness of 35mm can withstand 2500kg, and accordingly to compressive strength calculator, the force in MPa would be around 2.3 MPa. So a compressive strength of 8 MPa would be 3.47 times that value (assuming the same diameter of 11.5cm), so: 8695.6kg. Obviously, I do intend on using other materials for the composite and increasing its strength, like starch, cellulose fibers, borax and even sodium hydroxide with fumed/fused silica powder. The addition of 1:1:0.1 of PVA, starch and cellulose alone can double or even triple its tensile strength.
I said "biomimetic", but boy, do I say BOY, the idea of simply going full anatomical copy of the human body is extremely tempting.
The reason why this is a bad idea:
- Human body has 206 bones
- More than 650 skeletal muscles (muscles attached to the skeleton)
- 900 ligaments
- 4,000 tendons.
So, I was wondering which should be the height of the mech. Well, I actually found proportional human height calculator:
https://hpc.anatomy4sculptors.com/
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And as such, you could insert the height of a person in a determined position in order to check how tall the mech should be in order to fit the pilot inside of it.
For example, if the pilot has 185 cm of height (1.85 meters), its thigh/femur would have around 46cm long, and if you assume this person is in a sitting position, then you just need to reduce the length of the thigh by the total length 185-46 = 139cm. If you insert this length in one of the parts, the other measurements will be in proportion to that. For example, if you add this length of 139cm to the square where it says "from shoulder line to navel", the total height including head would be around 6,6 meters tall (5.7 meters without the head).
By the way, if you assume the leg of the Mech in the art of this project has around 1,9 meters of height, the total height of the mech would be around 7,5 meters tall.
Well, I settled for the height of this 185cm tall person in a crouch position to be a little more than 90cm, so the entire height including the head of this mech would be around 3,8 meters tall (without the head).
Of course, you could change this whatever way you want to, but it would stil give an idea on how big the mech should be in order to fit the pilot and on top of that, all of the equipment. And I do think this is too tall since the floor to the ceiling of my room is just 2,5-2,6 meters tall, and I don't see the reason for a mech that needs to be crouched to fit in a room.
By the way, using the square cube law and assuming that a 1,80 meter tall human weights around 80kg to 100kg, a 3,6-3,8 meter tall human would weight around 640kg to 800kg.
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So you can have an idea on how much weight this mech would weight in this scenario.
Obviously, I don't know yet what are the exact dimensions of the pseudo-bones/endoskeleton of the mech, since they are meant to be biomimetic and not a 1:1 scale.
Besides, the human skeleton is capable of enduring 30 times its own weight, so i would need to make it around 10 times thicker/stronger in order to survive the thousands of kilograms I intend on making it lift.
It just occurred to me that I could just make cylinders actuated by the HASEL/DEA actuators instead of a biomimetic mess that would be harder to build and maintain…
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That is a way of doing that alright. Obviously I’m not gonna do this way, but you get the ide
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Also, links relevant for heavy animal anatomy:
- https://www.turbosquid.com/pt_br/3d-models/asian-elephant-anatomy-3d-model-1387620
- https://wellcomecollection.org/works/g9646xnk
- https://archaeonewsnet.com/elephants-sixth-toe-discovered/
- https://globalelephants.org/rambas-feet/
- https://www.reed.edu/biology/courses/BIO342/2011_syllabus/2011_websites/Stu_Sara/mechanism.html
- https://www.researchgate.net/publication/360938306_AN_INVESTIGATION_INTO_MANAGEMENT_METHODS_TO_PROMOTE_FOOT_HEALTH_AND_LOCOMOTION_IN_CAPTIVE_ASIAN_ELEPHANTS_ELEPHAS_MAXIMUS
- https://pressbooks.umn.edu/largeanimalanatomy/chapter/distal-limb/
- https://pressbooks.umn.edu/largeanimalanatomy/chapter/thoracic-limb-forelimb/
- https://www.researchgate.net/publication/8371421_Musculature_of_the_crus_and_pes_of_the_African_elephant_Loxodonta_africana_Insight_into_semiplantigrade_limb_architecture
- https://animaltherapeutics.com.au/stifle-injury-in-horses/
- https://www.semanticscholar.org/paper/Osteology-of-the-pelvic-limb-of-the-African-Smuts-Bezuidenhout/08100c84e73bc4d8a7de5501ec98132c36310e2d
Off-topic:
While I was reading manga, it got me wondering:
Wouldn't it be cool if there was a mathematical system and/or a programming system based on magical circles and the like?
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I'd say that they would need to be intuitive, dynamic and work with the already stablished system in order to work properly...
You may think it too much of a difficult task, but just look how Japanese people makes multiplication:
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Don't tell me this doesn't look like a magic circle, lol.
Also, while image searching, I just found out that there is a mathematical "magic circle" made by a chinese named Yang Hui.
I do wonder what else strange mathematical systems one could find while digging around history... huh
Adding this here because I'm afraid of the project log deleting some things:
I just found out that there are graphene fibers that are made either using graphene oxide or dissolving them into polyvinyl alcohol and water while extruding.
I don't know how exactly they are done, but I do think the PVA and electrospinning (that method of making nanofibers) would be the easier method and the simplest.
Source: https://www.sciencedirect.com/science/article/pii/S0950061820316524
Plus, the continuous method of making flash graphene is by either using a plasma torch with neutral gases such as argon or helium or simply making an automatically self-charging flash tube.
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Project Log 82: Types of mechs that may be viable/practical.
06/05/2024 at 11:33 • 6 commentsWednesday, 05/06/2024, 07:36
Well, the previous project log had so much text that it started deleting new text.
I really don't want to go 2812838218 project logs into the part I actually start building something...
I also bought a new table and one of those drawing tablets with screen on it, because, if you don't know, I like to draw things (even though I'm bad at it [hey, I make a mech project, even though I'm bad at it too]), so I won't be able to buy anything for the project for the next... What? 6 to 10 months. lol
I do hope I can make some extra money with my drawings tho... Hopefully...
Well, Anyway, starting from where we left:
Wattage consumption:
(81 kilowatts is the energy required to move 1 ton of weight at the speed of the human body)
- Arm + Shoulder + Torso + Leg of one side of the mech.
- 81 + ((81x3)x6) + ((81x3x3)x6) + ((81x3x3x3)x6) = 19,035 kilowatts = 25,380 horsepower.
- 81 + ((81x2)x6) + ((81x2x2)x6) + ((81x2x2x2)x6) = 6,885 kilowatts = 9,180 horsepower.
- 81 + ((81x1.5)x6) + ((81x1.5x1.5)x6) + ((81x1.5x1.5x1.5)x6) = 3,543.75 kilowatts = 4,725 horsepower.
- 81 + ((81x1.2)x6) + ((81x1.2x1.2)x6) + ((81x1.2x1.2x1.2)x6) = 2,203.848 kilowatts = 2,938.464 horsepower.
- 81 + ((81x1.1)x6) + ((81x1.1x1.1)x6) + ((81x1.1x1.1x1.1)x6) = 1,769.526 kilowatts = 2359.368 horsepower.
Assuming that there is no biceps/arm actuator, but a shoulder-arm stewart platform:
- (81x6) + ((81x3)x6) + ((81x3x3)x6) = 6,318 kilowatts = 8,424 horsepower.
- (81x6) + ((81x2)x6) + ((81x2x2)x6) = 3,402 kilowatts = 4,536 horsepower.
- (81x6) + ((81x1.5)x6) + ((81x1.5x1.5)x6) = 2,308.5 kilowatts = 3,078 horsepower.
- (81x6) + ((81x1.2)x6) + ((81x1.2x1.2)x6) = 1,769.04 kilowatts = 2,358.72 horsepower.
Well, let's try a non-exponential aproach then:
- 81 + ((81x2)x6) + ((81x3)x6) + ((81x4)x6) = 4,455 kilowatts = 5940 horsepower
- (81x6) + ((81x2)x6) + ((81x3)x6) = 2,916 kilowatts = 3888 horsepower
- 81 + ((81x1.5)x6) + ((81x2)x6) + ((81x2.5)x6) = 2997 Kilowatts = 3996 horsepower
Okay, this is just getting stupid.
Needless to say, screw actuator, hydraulics or pneumatics, I don't think it will be possible to continue with this insane amount of power required.
I guess this is another wall that I've stumbled upon and I need time to think on how to preoceed...
The first obvious thing that probably anyone with a lizard brain bigger than mine notice: I'm assuming that all the actuators in the stewart platform are using power, which would not occur.
And being honest, I don't know how to properly calculate that...
It is always relevant to remember myself that all of this problem comes from the fact that I'm trying to make a humanoid mech, a walker mech wouldn't need to worry about lifting weight, in fact, this project would've already been in actual construction if it wasn't for this detail... (I think).
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Types of mechs that are viable/practical or not:
As you will notice, no option has a "✅" on them, that is because if they were the obvious, easy and correct option, Mechs would already be built using said options and actually viable to use.
So the "❓" means: it seems viable and practical, but I'm not sure it will work until I actually build it.
Screw Actuator Mech: ❌
I still need to calculate those, but even though it would supposedly be lighter and practical with a direct electric motor driver, unfortunately it is not as simple.
As you could see, it requires 81,000 watts (100 horsepower) to move the limbs with a force of 1000kg at a speed of 4 meters per second, and even though I'm inputting 3000kg at 1.33 meters per second, it is the same amount of energy, but transformed.
And since the electric motor would be that 80 kilowatt Reb 90 for every limb, which weights around 30kg and probably costs hundreds of dollars if you're not in the mood to build it from scratch. And don't think this is viable... For the mech.
If you are making an exoskeleton, then this value wouldn't be that high (8 kilowatts/10 horsepower), but it would still require considerable planning.
Coilgun Actuator Mech: ❓
On project log 84 I found out that there are brushed/sliding contact coilguns that are simpler and cheaper but not that better than conventional coilguns, but still better than railguns.
The thing is, what if you used them as actuators instead of guns?
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And just like that, you could make an electric mech that is cheap, simple and can output force proportionally to the energy you input without worrying too much about efficiency losses, weight and the like.
The problem is that I don't know very well which size of wire, voltage and amperage are the best for it to work.
As I explained in further detail on Project Log 84, I choose 14mm thick aluminium square wires that would be 1mm apart while receiving 500 volts and 400 amps of continuous electrical current in order to output 200,000 watts maximum without heating too much.
I used solenoid calculators, but those showed absurdely high force outputs that wouldn't be reflected in real life, but I'm using the approach anyway.
I'm working with the principle that energy is neither created nor destroyed, but transformed. So, if an electric motor needs X thousand watts to lift an Y amount of weight at a Z speed, then a solenoid actuator with the same amount of power being inserted would output a similar force and speed.
Unfortunately, in order for the coils to work, they need to be exposed for the sliding contact. This obviously means that the actuator will be extremely, extremely dangerous for direct contact with the human body.
In fact, all these options are dangerous in their own right specially because of the proportion in which I will be using them. They will need A LOT of energy to work and will output A LOT of force. at a high speeds.
Needless to say: anything here can easily kill you.
Hydraulic Mech:❓Taking into consideration the previous project log were I calculated how many liters per minute you would need to make an hydraulic mech to work, I can say with some certainty that hydraulics are out of the question for this specific task.
It doesn't matter if you are applying a few grams of force or a few tons, they will require thousands of liters of hydraulic fluids being pumped in order to actuate.
Being honest, I'm looking again at the calculations and I probably didn't make it right. I will post the result on Project Log 87 when I finish it.
There are artificial muscles that work hydraulically or pneumatically, the most common one are the McKibben artificial muscles.
But either working on liquid or pneumatic, the maximum efficiency these can achieve with a good selection of materials is around 65% with a maximum contraction of 25%. You can achieve 40% or a little more if you make hundreds of thin-braided McKibben muscles, but that would be too labour intensive.
Compared to the traditional hydraulic cylinders that achieve 95% of efficiency and contraction ratios up to 90%, this option may not sound as interesting.
But even though they need a lot of work to manualy make them, these are really light and cheaper to make.Besides, there are a lot of articles trying to increase their efficiency and performance. So maybe I didn't find the correct one, or maybe a new, better design will be published tomorrow.
For example, these two redesigns of a McKibben artificial muscle achieved 45% and 65% of efficiency while working with Pneumatics.
https://www.mdpi.com/2076-0825/10/5/100
https://www.science.org/doi/10.1126/sciadv.adi7133
Maybe if you work with hydraulics these could reach an even bigger efficiency. Maybe.
Taking that into consideration, the two most interesting actuators for this option (at least for me):
Flexible Pulling Hydraulic Cylinder Actuator:
Essentially, the idea is to have a flexible material to be a pulling hydraulic cylinder, this way you could make something light and easy to make. Something that works just like an artificial muscle, but has better efficiency (90% or more) but without the bulkness of a conventional hydraulic cylinder.
Of cours,e this is an illustration that I found, but you could replace the piston head with a membrane expanding chamber in order to reduce friction.
Radial Piston Hydraulic Motor:
This one is way more complex than the previous option, but if you are dead-set on using rotary actuators, I do think this is a good option.
Obviously, it would be easier to make this out of polymer, like the structure of the mech.
Hydrolysis Pneumatic Mech: ❓If you don't remember, the idea is to separate hydrogen and oxygen from water, you would need 1 liter of water to generate 1857 liters of hydrogen+oxygen gas.
(I forgot to link the article that gave the idea)
Based on the weight of the hydraulic fluid, I can take the volume of the liquid, more or less 400 to 500 liters and multiply by the pressure I intend on working with, which is 6 bar/atm, so, 500 x 6 = 3000 liters in total (since gases are compressible, unlike hydraulics).
So, 3000 liters for the mech to contract all muscles, 1500 if half is actuated, but I don't know how many liters will be used per minute, or even per hour.
We are talking about using 1500 liters of gases for a single contraction, after all, the amount required to keep the mech moving is just a guess, but it woul require a lot.This would still require thousands of liters of air being pumped, but since you can control the output force, then it is one less source of energy losses.
- However, hydrolysis is 60% to 70% efficient.
- And I can't find a specific number, but it is said that pneumatic systems are 2% to 20% efficient, this is due to leaks, poorly sized valves and pipes and so on.
Even without a pump, you would need those. - But if you count only the actuator, it can be as high as 80% to 90%.
- You would need compressed gas tanks, made from scratch with plastic (like everything else) or bought.
- You would need mechanical brakes for position control, also more weight and complexity.
- You can recycle the hydrogen and oxygen with a fuel cell after they are used by the pneumatic system, like a turbocompressor recycling the the exhaust gases of a combustion engine.
- Limited pressure (6 bars), so bigger muscles, so big they might start weighting significantly
- hydrogen is combustable and so light/small it can pass through solid material, but HDPE and/or UHMWPE are polymers used in liners for hydrogen storage to avoid that, so I can assume it would be somewhat safe.
This one has a lot of pros and cons, and overall.
I will try and search for a material that can be separated into more inert gases for safety.
... And I can't find one at all...
I know that there is hydrogen peroxide and you could decompose it into water vapour and oxygen, but the process isn't reversible like hydrolysis...
Maybe I'm overthinking this idea?
For example, water is only 10% hydrogen, I could just react the hydrogen with the outside air in a fuel cell, like I previously suggested, and only use the oxygen released during hydrolisys in order to make it work.
It would be dangerous if something was leaking close to fire sources, but it would be way safer than use hydrogen and oxygen to power up the pneumatic actuators.
Nope, there is a whole do's and don'ts of oxygen concentrators (which work with way less oxygen output than this idea), and they literally say to NOT use any kind of cigarettes, aerosols (sprays) or even petroleum based products close to it because the oxygen concentrator can make these combust.
Evaporative Pneumatic Mech: ❓
Esteban kidnly suggested me using a refrigerant called "Trichlorofluoromethane R-11" (what a mouthfull), it is non-flamable and it evaporates at 24ºC. You could just use any other refrigerant.
So it has all the pros of the hydrolysis pneumatic mech, but without the possibility of burning me alive.
But it still has some cons related to pneumatics:
- You would need an onboard refrigerator, and if it fails, you would really need safety valves, because all of it would turn into vapor.
- And since it is a evaporative refrigerant, it would need a really big heat exchanger and/or a electric heater, or else all the tubing would freeze and crack (leading to leaks).
- I'm still trying to find more information on how to handle this one specific refrigerant, but its liquid form depends on its pressure and temperature. Which for some reason, googles doesn't show me which is.
Accordingly to this graph, at 6 bar of pressure it should liquid, and it would evaporate at around 71ºC.
But wait, doesn't that mean that the gas in the muscles would be at liquid state since they are also at 6 bars of pressure? - I can't find a specific number, but it is said that pneumatic systems are 2% to 20% efficient, this is due to leaks, poorly sized valves and pipes and so on. Even without a pump, you would need those.
- But if you count only the actuator, it can be as high as 80% to 90%.
- You would still need compressed gas tanks, but it wouldn't be much of a problem.
- You would need mechanical brakes for position control, also more weight and complexity.
- This time, the pressure wouldn't really be a limiter, but working with lower pneumatic pressures is still more efficient and practical.
Being honest, now I'm divided between dielectric elastomers and evaporative pneumatics...
Actually I noticed a relevant characteristic of it that may turn it non-viable: the compressor.
Assuming that you let some of the refrigerant liquid evaporate and pressurize, what will happen when you take it out of the muscle?
It will continue to be in the gaseous form, forcing you to compress around 1500 liters of refrigerant gas as fast as possible before it saturates the gas tanks.BUT I don't know if it would be that simple, you could use the evaporation intake of the refrigerant to cryogenicaly cool the exhaust refrigerant gas.
On top of it, you could allow the exhaust gases to accumulate until they also reach 6 bars of pressure and let the compressor to work at somewhat minimum efort, but I'm unsure how all of that would really work.Compared to the hydrolysis and DEA mechs, this one sounds a little too complex.
BUT if I am unable to solve the problems of the dielectric elastomers, I will pick this one.I was calculating how much air flow you would need with this refrigerant in order to make the mech work, and as such, the amount of refrigerant gas you would need to compress back to liquid in order to do that:
- Since a human takes 3.24 steps per leg in a second while running, and since half of the mech needs 1500 liters for a single actuation, then it is safe to assume that the total number of liters in total per minute would be:
- 3.24 steps per second x 1500 liters x 60 seconds = 291,600 liters per minute.
So, 300,000 liters per minute of airflow, or 10,600 CFM is a really big amount.
This fan is capable of having such an airflow, and it has a diameter of 44 inches, or 110cm.I would need a compressor with this insane amount of airflow to work.
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Needless to say, this is not viable.
... But I will still go through the trouble of finding out how much energy it would consume and how big it should be if it was a compressor unit.
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This is a 10,000 CFM air compressor unit and it uses around 1800 kilowatts, or 1 megawatt of power.
This one below is a 1,000 CFM (cubic feet per minute)/33.6 CMM (cubic meter per minute) 8 bar air compressor and it uses 160 kilowatts (200 horsepower):
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It also weights 4 tons.
Unfortunately, this is not viable. :/
Maybe measuring the compressor I'm looking at it incorrectly?
For example, looking at this chart of refrigerant gases, you can see that some of these need to be at more or less -30 degree celsius to stay at room pressure (14 psi), and as such, you would need to have a sufficiently big enough mass/cooling system to turn the used gases into liquid again.
I asked chatgpt, and for a air flow of 10,000 CFM, I would need around:
- Q=1.08×CFM×ΔT
- Q = cooling capacity or BTU/hr
- CFM = is the volume flow
- ΔT = the difference in temperature in fahrenheit.
- From room temperature of 25ºC (77ºF) to -30ºC (-22ºF)
- 1.08x10000x(77-(-22)) = 1,069,200 BTU/hr
QkW=QBTU/hr×0.000293071071 BTU = 0.00029308323 kWh.
(I don't know why the text is weird like this lol)
Q_{kW} = Q_{BTU/hr} \times 0.00029307107
- Q kW = 1,069,200 x 0.00029307107
- kW = 313.3 kilowatts or 417.8 horsepower.
It is not really a small amount, BUT, at least it seems more viable than before.
I just don't know how big of an air compressor I would need for 1 million BTU/hr...
Commercial/house air conditioner units can have up to 60,000 BTU/hr, and most of them use around 6,000 Watts per hour.
1,000,000/60,000 = 16.6666 x 6,000 = 100,000 watts or 133.3 horsepower.
The only problem is the size:
I found this marine air cooling unit with 360,000 BTU/hr:
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You would need 2 to 3 of these for this mech to work.
Peltier pellets could also work, but those have only 20% of efficiency when cooling.
... Which makes me wonder: if my approximation of the 10,000 CFM of air is even correct, wouldn't this means that I wouldn't need such big screw compressor just to compress/cooldown the refrigerant gas?
I genuinely think this idea would work if you had a cryogenic bath of liquid nitrogen, liquid CO2 (carbon dioxide) or similar.
... But in order to achieve a bucket worth of liquid gases, you would need a cryogenic cooler.
Unfortunately, the most efficient (and expensive) cryocooler out there is the pulse-tube cryocooler, and it only has a maximum 20% of efficiency.
Now that I thought about this a little more, the idea of using the evaporation of coolant to pressurize the actuators in the pneumatic mech should not dependent on the cooling rate and efficiency.
I kept worrying about removing heat as fast as possible in order to turn the coolant into liquid to avoid using compressors, inherently using compressors to keep everything cooled down.
Cooling is the inverse of heat engines (aka combustion engines), thus, it has an efficiency equal to them.
Thus², it can’t really be that efficient IF you use the cooling process to turn it into a liquid. With a smaller and thus, lighter pressurized tank.
However, if you use pressure alone to turn the coolant into liquid, it is not so dissimilar to an air pressure tank. The only difference is that the pneumatic working gas is stored in the liquid form.
In fact, it would be way lighter and compact, since 1 liter of water can be turned into 1500 liters of water.
The issue is: coolant gases can be very expensive in high quantities (and nobody sells R-11 anymore, which would be the ideal coolant for this, since it boils at 23ºC).
For some F*CKing reason, all of the online sales for gas coolants only shows the weight, not the pressure, nor liters.
Dielectric Elastomer Actuator Mech: ❓
Yes, it would be feasible IF the dielectric elastomer in question can lift at least 1000 times its own weight.
For now I'm still trying to find some place were the article with the high performance DEA is available, and IF I happen to find its, and IF happens to be simple enough to make, then it will my choice.
The article in question.
I forgot to write the pros and cons:
- Conventional DEA's materials are readly available and easy to find, most of the time.
- High performance DEA's materials really can't be sourced on stores and need to be specifically sourced through chemical companies.
- I have no idea how I will take liquid silicone rubber and turn it into 1mm thin thick square fibers for the actuators.
- Its actuation method is somewhat safe in small cases like the ones in the articles, but it is unknown how well it would work in thousands of fibers at same time, specially with such high wattages being required per actuator.
- It requires a really, really good insulation on the electronic equipment or else the electrons will just go though the insulation and toast everything in its path.
- Dealing with thousands of fibers will be a task on its own, not that the McKibben wouldn't have the same issue, but that is also a characteristic.
- It will be extra hard to figure out which fibers aren't working properly.
- Position control will need mechanical brakes.
Well, while I don't have access to the article in itself, I will at least try to find dielectric elastomers with a significant energy density and performance.
In the previous project log I used this one as a basis for calculating the weight, but I think I misscalculated something, since this one can clearly carry 1000 times its own weight (it can lift 200 grams while weighting 0.2 grams).
So, if I wanted to pull a weight of 3000kg, It would weight 3 kilograms, no?
- "Modeling and Characterizing a Fiber-Reinforced Dielectric Elastomer Tension Actuator":
Anyway, said actautor has a energy density of 10.7 Joules per kilogram. - "Printing Reconfigurable Bundles of Dielectric Elastomer Fibers":
This one has 134 W/kg, so I may assume that since this one has 134 J/kg of energy density, meaning it can lift 10,000 times its own weight? - "A Jumping Robot Driven by a Dielectric Elastomer Actuator":
This one has 28.71 J/kg. - "Triblock Copolymer Organogels as High-Performance Dielectric Elastomers":
This one (use sci-hub) has its energy density measured in MJ/m³, which accordingly to chatgpt it is around 1600 J/kg and an efficiency of 90% from electrical input to mecahnical ouput. - "A processable, high-performance dielectric elastomer and multilayering process":
This one has energy densities scales in watts and in joules, and it shows that it has a energy density of 2000 W/kg and around 90 J/kg... - "A large-strain and ultrahigh energy density dielectric elastomer for fast moving soft robot":
This one has 225 J/kg, and around 2400 W/kg so also 20,000 times its own weight?
In any manner, how each DEA is synthesized accordingly to each article:
1: Modeling and Characterizing a Fiber-Reinforced Dielectric Elastomer Tension Actuator
The soft composite layups were prepared using VHB F9473 PC elastomer tape. Within the elastomer layers, cottoncoated polyester fibers were arranged in meshes with fiber angles ranging from 15◦ to 85◦ with a constant element edge length between samples. Then for each layup, a layer of the elastomer tape was applied on either side of the fiber mesh. Once the layups were prepared, single-walled carbon nanotube (CNT) electrodes (Carbon Solutions, Inc. P3-SWNT) were applied on both sides to make the completed DEA composite. Once prepared, the maximum stress in each sample was measured with both ends fixed, such that λ2 = 1. The DEA composites were attached to a custom-built tension testing machine made with a Zaber T-LA60 A linear actuator, Zaber TSB60-I translational stage, and a PCB Piezotronics 1102-05 A load cell. The samples were stretched taut, and the actuator was exposed to a step input and held at voltage until the measured tensile force stabilized. Actuation voltages ranged up to 9 kV (UltraVolt 10A24-P15-I5) and the data was recorded by a National Instruments USB-6009 DAQ card.
A sheet of VHB 4910 elastomer tape was used for the dielectric of this experiment and was biaxially prestretched to λP S = 5 to improve its dielectric properties and discourage pull-in instabilities at low ramp rates [20]. The elastomer was left to relax for 24 hours to minimize viscoelastic effects. At this stage, CNT electrodes were applied to both sides, and aluminum foil leads were attached to the nanotubes to connect later with the power supply. Fiber meshes were prepared following the procedure outlined in Section III-A with VHB F9460 PC elastomer tape layers encapsulating fiber meshes ranging from 15◦ to 75◦ and were applied over one of the CNT electrodes. Finally, polyamid seeding particles (Dantec Dynamics PSP-50) were distributed across the surface of the elastomer. The samples were then connected to a high-voltage amplifier (Trek 20/20C-HS) and actuated up to 5 kV at a rate of 50 V/s. A further increase in voltage leads to wrinkling of the dielectric, which causes out-of-plane deformations not predicted by the modeling. Images of the actuator were taken using a Nikon D7000 at a variety of voltages. The images taken were then modified to black and white images and processed using PIV software (TSI Insight 4 G) to obtain the deformation fields in both the DEA and the surrounding elastomer. MATLAB was then used to determine the strain fields and calculate the boundary conditions applied by the surrounding elastomer on to the DEA region. Another strain test was performed to attempt to improve the strain results. [20] showed improved DEA performance was achievable using higher strain rates and lower prestrains, achieving five times higher linear strains resulting from the increased viscous impedance which prevents pull-in failure. Following this, we fabricated another actuator made from VHB 4910 biaxially prestretched to λP S = 3.5 without a relaxation period, applied an encapsulation layer, and actuated it with step inputs up to 7.5 kV. Images taken from the Nikon camera were then processed to determine the intersections of each fiber element which defined the size of a given element. After this, the dimensions of the elements in their initial and final positions were used to calculate the engineering strain. This process was repeated for all complete fiber elements and the average was reported.It seems that this "VHB F9473 PC elastomer tape" is just a transfer tape (61 dollars/300 reais for every 50 meters), the single-walled carbon nanotubes are just too expensive and the "VHB 4910 elastomer tape" is just a silicone rubber tape.
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The "VHB4910" is easy to find, it is a silicone tape. It costs 100 reais (20 dollars) for every 20 meter of this tape, it normally has 12mm of thickness. I don't even know how I would attach the electrodes to it...
Translation: "it supports 3.4 kg of weight for every meter"
2: "Printing Reconfigurable Bundles of Dielectric Elastomer Fibers"
Dielectric Ink: Fumed silica nanoparticles (CAB-O-SIL TS-720, from Cabot Corp.) were dispersed in Ecoflex 00-30 (Eco30) part A (Eco30A) and part B (Eco30B) separately by mixing in a SpeedMixer (Flack Tek, Inc) at 2000 rpm for 18 min. 12 g of the Eco30B/silica mixture was weighed into a separate container and 0.36 g (3 wt%) of SloJo cure retarder was added and mixed for another 2 min. 12 g of the Eco30A/ silica mixture was added to the container. Finally, 8 g of SE 1700 (Dow Corning Corp.) base and 0.266 g of SE1700 curing agent were added to create a final composition with a weight ratio of 3:1 Eco30:SE1700 and 30:1 SE1700 base:SE1700 curing agent. The composition was mixed at 2000 rpm for 12 min in a SpeedMixer. The resulting dielectric composition included 7.88 wt% TS-720 silica, 32.8 wt% Eco30A, 32.8 wt% Eco30B, 24.5 wt% SE1700 base, 0.82 wt% SE1700 curing agent, and 1.10 wt% SloJo. To improve the dispersion of the nanoparticles, the dielectric ink was roll milled (Torrey Hill, T50) three times. The ink was loaded into 20 cc syringes and centrifuged at 4000 RPM for 20 min to remove any trapped air. Rheology measurements were performed on an AR-2000EX shear rheometer at 25 °C using stainless steel parallel plates with a diameter of 40 mm and a gap of 0.3 mm. After lowering the top plate to the target gap, the sample was allowed to settle for 300 s before starting the measurement. Oscillatory measurements were carried out at a frequency of 1 Hz over a range of shear stress from 1 to 10 000 Pa. Cured dielectric matrices were characterized by shear dynamic mechanical analysis (DMA) using an AR-2000EX rheometer. Samples of uncured dielectric matrix were loaded into the rheometer equipped with a 20 mm steel plate with a gap of 0.3 mm. The samples were heated to 100 °C while collecting oscillation measurements at 1 Hz to monitor the curing. After fully curing, samples were cooled to 25 °C and shear DMA was carried out at a strain of 1% over a frequency range from 0.1 to 100 Hz. Parallel plate capacitors were prepared by blade coating the dielectric ink onto ITO-coated PET. The dielectric ink was cured at 80 °C for 12 h. Gold particles were used to define top electrodes with a diameter of 1 cm. Capacitance measurements were collected using an Agilent E 4980A using controlled using a Labview program. Electrode Ink: Carbon black nanoparticles (AB100, from Soltex, Inc.) were weighed into Eco30A and Eco30B separately at a content of 13.8 wt%. The compositions were mixed at 2000 rpm for 18 min using a SpeedMixer (Flack Tek, Inc). 12 g of Eco30B/AB100 mixture was combined with 0.12 g (1 wt%) of SloJo curing retarder and mixed for another 2 min. 12 g of Eco30A/AB100 was added and mixed at 2000 rpm for 12 min in a SpeedMixer, followed by roll milling three times. The dielectric ink was loaded into 20 cc syringes and centrifuged at 4000 RPM for 20 min to remove any trapped air. Rheology measurements were performed on an AR-2000EX shear rheometer at 25 °C using stainless steel parallel plates with a diameter of 40 mm and a gap of 0.3 mm. After lowering the top plate to the target gap, the sample was allowed to settle for 300 s before starting the measurement. Oscillatory measurements were carried out at a frequency of 1 Hz over a range of shear stress from 1 to 10 000 Pa. Mechanical Testing: Samples of the dielectric and electrode elastomer for tensile testing were printed into rectangular planar sheets with dimensions of 0.8 mm × 60 mm × 60 mm. After curing, the sheets were cut into dog-bone shapes following the ASTM D412a standard scaled down by 2.5 times. Specimens were stretched until rupture on a homemade stretcher (Mint, Baldor) with a load cell (FUTEK LSB200, 2 lb, JR S-Beam Load Cell) at a strain rate of 0.1 s–1. Data was acquired using a LabVIEW program. For electrode inks, the resistance was measured by a Keithley 2636A connected to the two metal clamps of the stretcher. The measuring voltage was 1 V. Device Fabrication: A multicore-shell nozzle (Figure S3a,b, Supporting Information) was prepared by an Aureus Plus 3D printer with a layer height of 25 µm and an X-Y resolution of 43 µm, as described in the previous work.[41] The nozzle, dielectric, and electrode inks were mounted to an Aerotech 3-axis stage (Aerotech, Inc.). The pressure of each channel in the nozzle could be controlled by an Ultimus V pressure pump (Nordson EFD) and switched on and off by a solenoid valve while printing (Figure S3c, Supporting Information). The relative dimensions of the DEF samples were printed onto glass plates covered with a Teflon adhesive film (Bytac, Saint-Gobain). Because the ink rheology was temperature-dependent, quickly increasing the curing temperature leads to a viscosity reduction that causes the printed structures to sag under their own weight. Hence, printed samples were first cured at a low temperature of 60 °C for 24 h to drive solidification, followed by curing for 24 h at 80 °C, and finally for 24 h at 110 °C to achieve a fully cured state.
Fumed silica is cheap and easy to find, ecoflex is just sculpiting silicone rubber that already comes with its uring agent, carbon black is expensive but replaceable, teflon is easy and the last one is "cure retarder", I don't know where to find this exactly type, but there are ones you can buy online, you can even mix acetone or alcohol to silicone to make it more liquid and retard the curing process for some time.
3: "A Jumping Robot Driven by a Dielectric Elastomer Actuator"
"The fabrication process of multilayer DE includes two processes: the fabrication of single-layer DE and the stacking of multilayer DE, as shown in Figure 8. The DE material is VHB4910 produced by the company 3M, and the main material is acrylate. In the single-layer process, a DE film with a thickness of 2 mm was stretched to 12.25 times (3.5∗3.5) its original area by a biaxial stretching machine to obtain a pre-stretched DE film with a thickness of 100 μm. The pre-stretched DE film was taken out with a large retaining ring and a small retaining ring with inner diameters of 160 mm and 140 mm (PMMA, cut with a laser cutter), respectively. The upper and lower surfaces of the pre-stretched DE film were covered with a mask (Release film, cut with a laser cutter) which had been vacated for an electrode. The flexible electrode was applied by spin coating, and the electrode pad was attached. In the multilayer DE stacking process, the prepared DE with a small retaining ring was sleeved inside another DE with a large retaining ring, and the air bubbles between the two layers of DE were removed by rolling. The large retaining ring was cut off along the edge to obtain two-layer DE with a small retaining ring. The two-layer DE was then nested into a new DE layer with a large retaining ring. We repeated the above operation and ensured that the electrode pads were aligned in the alternating layers. Variety in the multiple-layer DE could be obtained according to the requirements of different actuators by this way."
Again, the "VHB4910" is easy to find, it is a silicone tape. It costs 100 reais (20 dollars) for every 20 meter of this tape, it normally has 12mm of thickness, which is more or less the thickness that I was thinking on working with... I don't even know how I would attach the electrodes to it...
Translation: "it supports 3.4 kg of weight for every meter"
4: "Triblock Copolymer Organogels as High-Performance Dielectric Elastomers"
We developed systematic synthetic strategies to tune the bimodal system’s stress-strain responses and viscoelasticity. First, short-chain cross-linkers with softer and more-extended chains were used to replace previously explored short and stiff molecules, such as hexanediol diacrylate (HDDA), thus achieving more tunable stretchability and tensile strength (Fig. 1C and figs. S2 and S3) (8). The cross-link density/gel fraction (fig. S4) as well as the stress-strain responses were further controlled by changing the concentrations of the short-chain cross-linker, PNPDA (Fig. 1C) (8). Without PNPDA, the DE shows a similar long stress-strain plateau to that of non-prestretched VHB (fig. S5) (5, 6). With the bimodal network structure, our DE stiffens after a critical stretch ratio in its non-Gaussian region (20), which can suppress EMI. This critical stretch ratio shifts to a smaller value as the cross-link density increases. Second, the concentration of hydrogen bonds was optimized in the DE network to modify the viscoelasticity while maintaining its stress-strain relationship. A small amount of acrylic acid (AA) comonomer (2.5 parts of weight) was added, which provides side groups to form hydrogen bonds with themselves, as well as with the –NH– groups on the CN9021 and PNPDA cross-linkers (fig. S6) (21). The mechanical loss factor of DE, a measurement of the viscoelasticity, was then decreased from ~0.22 to ~0.11 at room temperature and low frequencies (fig. S7) without changing the strain stiffening behavior (table S2) and high elasticity (fig. S8). After AA is added, hydrogen bonds partially replace covalent cross-links in the network. Hydrogen bonds act as weak, physical cross-links and can dynamically dissociate, leading to a lower glass transition temperature (Tg) (fig. S9) and higher chain mobility in the network (22). As more AA is added, hydrogen bonds become highly concentrated, and the density of covalent bonds decreases (fig. S7), which results in inhibited actuation performance (fig. S10). At frequencies above 20 Hz, the storage modulus and loss factor of DE also increase rapidly (fig. S11).
Asked web search GPT, all of these costs around 400 reais (75 dollars) per 100 ML/100g. Some don't even have a price tag for them, you need to ask a quote from the supplier.
5: "A processable, high-performance dielectric elastomer and multilayering process"
"We built a bimodal-networked elastomer using two cross-linkers with different chain lengths and tailored its electromechanical properties for high actuation performance. DE films were fabricated through solution processing and cured under ultraviolet (UV) light. The long chain segment in the bimodal network ensures large elongation, and the second relatively short chain segment raises the modulus at modest strains to resist the rapidly increased Maxwell stress during actuation and suppress EMI (Fig. 1A) (8, 17). Figure 1B shows the molecular structures of reactants. Detailed formulations and nomenclature of samples can be found in table S1. Butyl acrylate (BA) and isobornyl acrylate (IBOA) were selected as comonomers to lower the modulus and improve the toughness of copolymers, respectively (18). They were also important to reduce the viscosity of prepolymer solutions (19). CN9021, a urethane diacrylate (UDA) with a high molecular weight, was selected as the flexible long-chain cross-linker, and propoxylated neopentyl glycol diacrylate (PNPDA) was used as the short-chain cross-linker (fig. S1). 2,2-dimethoxy-2-phenylacetophenone (DMPA) and benzophenone (BP) were used as cophotoinitiators to ensure complete curing through the bulk and surface of the film.
"We developed systematic synthetic strategies to tune the bimodal system’s stress-strain responses and viscoelasticity. First, short-chain cross-linkers with softer and more-extended chains were used to replace previously explored short and stiff molecules, such as hexanediol diacrylate (HDDA), thus achieving more tunable stretchability and tensile strength (Fig. 1C and figs. S2 and S3) (8). The cross-link density/gel fraction (fig. S4) as well as the stress-strain responses were further controlled by changing the concentrations of the short-chain cross-linker, PNPDA (Fig. 1C) (8). Without PNPDA, the DE shows a similar long stress-strain plateau to that of non-prestretched VHB (fig. S5) (5, 6). With the bimodal network structure, our DE stiffens after a critical stretch ratio in its non-Gaussian region (20), which can suppress EMI. This critical stretch ratio shifts to a smaller value as the cross-link density increases. Second, the concentration of hydrogen bonds was optimized in the DE network to modify the viscoelasticity while maintaining its stress-strain relationship. A small amount of acrylic acid (AA) comonomer (2.5 parts of weight) was added, which provides side groups to form hydrogen bonds with themselves, as well as with the –NH– groups on the CN9021 and PNPDA cross-linkers (fig. S6) (21). The mechanical loss factor of DE, a measurement of the viscoelasticity, was then decreased from ~0.22 to ~0.11 at room temperature and low frequencies (fig. S7) without changing the strain stiffening behavior (table S2) and high elasticity (fig. S8). After AA is added, hydrogen bonds partially replace covalent cross-links in the network. Hydrogen bonds act as weak, physical cross-links and can dynamically dissociate, leading to a lower glass transition temperature (Tg) (fig. S9) and higher chain mobility in the network (22). As more AA is added, hydrogen bonds become highly concentrated, and the density of covalent bonds decreases (fig. S7), which results in inhibited actuation performance (fig. S10). At frequencies above 20 Hz, the storage modulus and loss factor of DE also increase rapidly (fig. S11)."
Asked web search GPT, all of these costs around 400 reais (75 dollars) per 100 ML/100g. Some don't even have a price tag for them, you need to ask a quote from the supplier.
6: "A large-strain and ultrahigh energy density dielectric elastomer for fast moving soft robot"
"Polymer design:
To develop a high-performance DE under low electric fields, we design a random copolymer of 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA), 2-ethylhexyl acrylate (EA) and dodecyl acrylate (DA) (Fig. 1a). The transparent dielectric elastomer was synthesized by mixing the three comonomers in one-step UV photopolymerization (Supplementary Fig. 1). In this strategy, the rich and highly polar CF3 groups in HFBA segments provide high dielectric constant.I just asked web search GPT to find these chemicals, all of these costs around 400 reais (75 dollars) per 100 ML.
I know that this can sound disappointing after I copy pasted so much crap from these papers, but I was considering switching from Silicone Rubber to Polyurethane Rubber, at least for the electrodes.
Accordingly to web search GPT, higher tensile strengths for dielectric elastomers can POTENTIALLY increase its contraction ratios, its energy density, durability, dielectric breakdown limit and efficiency.
Polyurethane rubber can have a tensile strength as high as 44 MPa while Silicone rubber can have a range of around 10 MPa. Silicone rubber has an elongation of around 700% and polyurethane can have around 300% to 400% maximum. Polyurethane rubber would be more durable than Silicone rubber, and it would also be better at tear resistance.
And yes, I do intend on adding fillers for both materials both at the electrodes and at the dielectric layer, like silica powder, flash graphene, dielectric grease, titanium dioxide and fiberglass. So the current properties of either material can end up significantly changing.
It is a consideration, I don't know which one is the best for this job, and I can always mix a little bit of both.
I would need around 42 kilograms of polyurethane/silicone rubber.
I found out that there are more rigid and stronger silicone rubbers (like the ones used in tires) which rigid called "shore" raging from 00-05 to 45A. The polyurethane rigidity is from 60 going up to 75.
Well, I said all that, but it seems like it is bullcrap generated by GPT, since I found some Polyurethane/Silicone rubber suppliers that actually have a data sheet, and their tensile strength is around 3.5 to 2 MPa.
Some variantions can have up to 5 MPa and an elongation at break that ranges from 200% to 400%, but it doesn't seems like these values have any kind of relationship with tensile strength and shore hardness.However, with that in mind, Polyvinyl Alcohol has a tensile strength of 40-90MPa, 200% elongation at break and a shore hardness of 70A. It also has 10 times better dielectric constant than silicone rubber and 2 times better than polyurethane rubber.
It is also cheaper than both.However, it doesn't mean I will only choose PVA, I'm actually looking at several options, when I'm decided I will try to make an update.
By the way, I found dielectric elastomers that use liquid metals as soft electrodes. Hum...
Source: https://www.researchgate.net/publication/369887430_Liquid_Metal_Smart_Materials_toward_Soft_Robotics
Source: https://www.mdpi.com/2073-4360/14/4/710
After all of that, I think that maybe the best option may be HASEL actuators, since they don't need to stretch themselves, they have less losses to friction.
Since dielectric elastomers (even HASEL ones) are essentially bending capacitors, you can recycle the electrical current and increase the efficiency to 60%.
You can also make a few modifications in order to increase its contraction ratios:
https://par.nsf.gov/servlets/purl/10191286
Thermoactive Actuators Mech: ❓
Esteban also suggested thermoactive artificial muscles, such as Nylon/Polyethyelene (fishing line) or shape memory alloys like Nitinol.
Nitinol is an alloy of nickel titanium, needless to say, this is quite expensive Shape Memory Alloy to work with, costing 500 to 700 dollars per kilogram.
There are other shape memory alloys that use cheaper materials, but Nitinol is still the best option both in performance and efficiency.
Of course, there are other options besides these, such as the silicone rubber carbon fiber composite artificial muscle that can lift 12,000 times its own weight (here).
This one works because the silicone rubber expands when heated, pulling the fibers apart, simulating a contraction.These are interesting alternatives, but:
- They are too slow to contract.
- Even slower to relax.
- You would need a robust refrigerant system and turn the materials into composites with thermal paste for fast thermal dissipation.
- They reach even less than 10% to 20% thermal efficiency.
- You would need to separate the muscles in sections for a somewhat precise position control, if you are not interested on using mechanical brakes.
- They are cheap (the thermalpolymer ones) to find and make.
- They are the somewhat safe to work with, however, if the heater exceeds the polymer's temperatures, they will irreversibly melt and even catch fire. Ruining most of the muscle.
- You could "just" let the muscles in pressure bags with refrigerant liquid/gases that would evaporate at the maximum temperature the materials are allowed to heat up.
Or maybe just flow oil/water all the time so the muscles always can easily cooldown.
But both of these potions seem sketchy to me.
This video is about nitinol wires as artificial muscles, contracting and relaxing them by pumping water with different temperatures into the bundle.
If you need to pump hot and cold water this fast, wouldn't that be the same as having an hydraulic actuator tho?
I even thought on maybe attempting to make peltier plates on the fibers themselves, but these would be too small and complex to mass-produce at home.
And to be honest, even thought it has all of these cons, if Nitinol wire wasn't 700 dollars per kilogram, I would've used these a long time ago to make the mech.
By the way, there are a lot of variations on Nitinol wire, the cheapest ones are called "superelastic" and the "shape memory alloy" type is the most expensive.
There are other shape memory alloys, shape memory polymers and thermoactive polymers, but I never found one type that is easy to make at home and it is super strong.
Maybe google didn't show me all the alternatives or I simply didn't mind to look closely enough.This one article is about a high energy density shape memory polymer and it explains how the polymer is synthesized:
"Synthesis and Film Preparation:
This synthesis is a modification of a previously described synthesis for PDMS-based, amine-terminated macromonomers. (32) A solution of H2N-PPG-NH2 (Mn ≈ 400 g/mol, Jeffamine D400) and anhydrous dichloromethane (8.0 g in 150 mL, 0.13 mM) was prepared under a N2 atmosphere. Methylenebis(phenyl isocyanate) (MPU) was added in a 1:1 molar ratio of amine/isocyanate functional groups (5.0 g, 0.13 mM). The resulting mixture was stirred for 72 h at room temperature, until the solution gelled and partially precipitated. The synthesized polymer was quenched in methanol and then fully precipitated by adding an excess of hexane. The recovered polymer was subjected to vacuum evaporation for 2 h at 90 °C. Molecular weight according to GPC: Mw = 12.0 kDa, Mn = 10.6 kDa, ĐM = 1.1 (Figure S10). 1H NMR (400 MHz, d2-C2D2Cl4, δ/ppm): 7.75 (br, 4H), 7.30 (br, 4H), 7.03 (br, 4H), 3.93 (br, 2H), 3.81 (br, 1.5H), 3.45 (br, 17H), 1.09 (br, 17–18H) (assignments given in Figure S11). Elemental analysis data: Analytical calculations for (C39H62N4O8)n: C, 65.5; H, 8.7; N, 7.8; O, 17.9. Found: C, 64.3; H, 8.5; N, 8.3; O, 18.9 (remaining).
Film samples were prepared by drop casting 100 mg/mL solutions in CHCl3 onto SiO2 wafers treated with a monolayer of octadecyltrichlorosilane (OTS) to allow for easy removal of the film and dried for over 12 h at room temperature and then again at 70 °C for at least 24 h. Higher quality films were obtained using lower concentrations (e.g., 50 mg/mL compared to 100 mg/mL), though the resulting drop-casted films were much thinner for lower concentrations, due to the decreased solution viscosity."
I was curious, and it seems like there are liquid/gel based thermoelectric materials, which maybe it could make a fibrous thermoelectric/peltier unit possible. This way you could heat and cool it on command without a super complex refrigeration system.
Source: Liquid-like Materials May Pave Way for New Thermoelectric Devices - www.caltech.edu
Source: Popular strategies for constructing polymer gel thermoelectric materials (wiley.com)
I was searching for polyvinyl alcohol based ionic polymer actuators, which is basically like a mix of a fuel cell membrane and a dielectric elastomer. However, I did found this article about a PVA shape memory polymer artificial muscle able to lift 1,100 times its own weight.
Basically, it is treated with sodium hydroxide and... That's it.
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7610272/
Increasing efficiency:
I'm still writing the Project Log 87 at this moment, but I did find some information about increasing the efficiency of Shape Memory Alloy actuators:
This article claims “energy savings of up to 80%" (80% of 90% is 72% +10% to 15% = 82% to 87% efficiency):
Nickel/Titanium free SMAs:
https://www.intechopen.com/chapters/67075
https://link.springer.com/article/10.1557/s43578-021-00444-7
https://www.sciencedirect.com/science/article/abs/pii/S0141029618305030
https://www.mdpi.com/1996-1944/15/22/8089
I don’t know if this one is a rare-metal free shape memory alloy, but it showed a method to make it actuate 35 per second (35 hz): https://www.nature.com/articles/srep21118
(maybe I just missed it, but they didn’t write which alloy was used)
Other options: ❌
You may notice that the list is actually very small compared to the insane amount of different actuators out there, and that is simply because of a couple reasons:
- I only listed the ones that seems more viable and easier to DIY. Every actuator/artificial muscle sounds ✨amazing✨ when you read a news article about them, until you check its speed of contraction and relaxation, force-to-weightratio, efficiency, cost, practicality and manufacturing process.
- Not all actuator types have their performance carefully explained and listed.
- Google simply didn't show me others.
For example, there is
-
Project Log 81: Screw it, let's freaking do it.²
05/28/2024 at 14:59 • 5 commentsTuesday, 28/05/2024, 11:41
Well, well, well...
I didn't, in fact, "do it" and finally start building things.
And the previous project log was so long it started deleting new text, so I'm forced to make this one.
Uuuuuuugh, this is me from the future, and even though I call ChatGPT stupid for not making math correctly, guess what? Neither does I, I keep forgeting certain parts on the equations and I need to make everything again and again.
This is me from the further future, you know what? I'm gonna redo all the calculations!
(obviously, you won't notice after the log is edited)
Not related, but look, I just found this cool scene featuring a mech:
(and yes, I go around youtube watching all kinds of mechs in media, I just think the scenes are cool)
-
In any manner, I'm trying to figure out how to make the McKibben hydraulic artificial muscles. And before I actually build those, I need to figure out how much force the materials will need to withstand and how much force the actuator will be able to output.
As you may not remember, since it was many project logs ago, the best way of making the most efficient hydraulic McKibben muscles is to make a non-elastic (but flexible) bladder and make it more filament like.
Not to mention that the easiest way to mass-produce filament-like McKibben artificial muscles is by using a small sock knitting machine.Sources:
- https://www.researchgate.net/publication/309272509_Modeling_and_testing_of_a_knitted-sleeve_fluidic_artificial_muscle
- https://www.researchgate.net/profile/Jordan-Chipka/publication/289579804_Variable_recruitment_inelastic_bladder_hydraulic_artificial_muscles_for_high_efficiency_robotics/links/6113ce070c2bfa282a391aec/Variable-recruitment-inelastic-bladder-hydraulic-artificial-muscles-for-high-efficiency-robotics.pdf
- https://www.researchgate.net/publication/308043606_Musculoskeletal_lower-limb_robot_driven_by_multifilament_muscles
- https://www.researchgate.net/publication/337094820_Recurrent_Braiding_of_Thin_McKibben_Muscles_to_Overcome_Their_Limitation_of_Contraction
- https://www.sciencedirect.com/science/article/abs/pii/S0924424723002303
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Anyway, I do need to figure out how to mass-produce the inner bladder, although I can buy kilograms of plastic tube, it would still be preferable to handmake those instead of buying, it will be expensive enough to buy the required equipment for the pump and electric motor.
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This one costs 57 dollars or 250 reais (without the taxes).
Actually, I think I'm just overthinking the inner bladder thingie, I could "just" extrude it just like the filaments for the braided sleeve.
In any manner, it is only left for me to find out the optimal dimensions for the materials since I intend on applying 150 bars of pressure.
And after all of that, I need to figure out a way of making/testing/calculating the dielectric elastomer fibers, because I have a gut feeling that these braided sleeves won't be that great in the end.
Well, I think the first approach I will attempt on how to calculate the knitted braided sleeve is to assume each hole between the braided sleeve is a ring, just like in a chainmail.
This way I will probably find a rough estimation on how much force the fibers need to withstand in order to survive. Then I will add a safety factor of 7.
Funnily enough, the answers I got from ChatGPT are actually almost the same, but there is something I'm finding weird. Basically, they all agred that 900kg of force would be applied to the ring area and then divide the force bewteen the six links.
But since the tension on the links is being concentrated on 6 points, it doesn't make much sense that it would equally divide the force between linking points...Maybe I should've asked it to pretend it is a chain link...
I got the answer and it keeps saying it is around 300kg or 2000kg, maybe the idea of a safety factor of 7 was asking for too much...
In either way, I will have to use those 2 ton sized HDPE ropes...
Well, I was looking at charts about Rope Strength based on material and thickness of the rope so I can figure out how thick should be the DIY HDPE rope for 2 tons in these artificial muscles, and lo and behold: any kind of polyethylene that doesn't use UHMWPE is not shown.
Source: https://denverrope.com/rope-strength-guide/
It seems like Nylon, Polyester and even Polypropylene have higher tensile strength than HDPE. :|
Well, Prolypropylene has an yield tensile strength (tensile strength before permanently deform) of 20 to 45 MPa, so this means that I still can use the composite of HDPE and graphene/silicon carbide to double the strength of the fibers of HDPE.
In any manner our rope of 40 MPa made out of HDPE+graphene+silicon carbide (I'm thinking on giving up on fiberglass it is kinda messy to work with) would need the following dimensions:
- 38mm of diameter and 3 twisted strands.
Well, I don't even know how I will fit this thing in a filament muscle with 28mm of diameter, lol.
Well, I asked chatGPT to use that old equation for McKibben muscles that I asked in this post
on worldbuilding stackexchange, but it gave me results around 900kg and 1600kg.
I tried to make the equation as follows:
- 15000*pi*28^2(3(cot(20)^2)(1-1.30*0.2)^2-csc(20)^2)
And it resulted in:
- 3142595105.5096786503920999.
(even if you take out the three zeros behind 15 KPa, it still gives around 300 tons of force, which is absolutely not possible)
I feel like I will never make this equation correctly...
Well, I found an article about a 21mm in diameter McKibben muscle that uses 7MPa of pressure and 8 kilonewtons (800 kg) of force.
I couldn't check it with sci-hub either, but at least this is a good indicator.
If we simply take the pressure and output and doubles, the result of 1600kg is also right.kelvinA kindly shared the source for a free access article.
Source: https://www.fujipress.jp/ijat/au/ijate000600040482/
However, the article only uses 7 MPa as the maximum pressure input and 2 MPa as the nominal pressure input.
But in one of the graphs it is shown that in fact, it would output 800 kg of force with a diameter of 21mm.
At 2 MPa it outputs 300kg of force.
By the way, I was calculating the weight of the hydraulic fluid if I were to fill the hydraulic muscles.For example: let's assume that the muscles have 30cm (24cm when contracted) of length and a diameter of 28mm when fully actuated. So, this single muscle would weight 0.12kg.
- 0.12kg x 90 (9000kg of output) x 30 muscles in total = 324kg in total for the hydrauic liquid alone.
Just remember that in reality the artificial muscles would be way longer since I intend on braiding them to increase contraction ratios, so it would weight way more than that.
Sure, not all muscles would be contracted at all times, but letting things as simple as that wouldn't change much either.
Now I need to figure out where the hell I'm going to find 300+ kg of hydraulic oil (400 Liters). :|
If it was water, it would be easy to collect, now hydraulic oil...?
I think I could reduce the liquid volume required by using sponges or other materials, although the sponges aren't rigid, they still occupy space, but since they are solid and not compressible, they wouldn't allow for more fluid to get into the muscles.
Reducing the weight based on the amount of volume they are occupying.
I suggested sponges because it was the first thing in my mind, solid rods/chains of plastic/metal would still help to reduce the hydraulic oil required, but not saving in weight. HDPE has a density similar to hydraulic oil, it would still weight the same, but I wouldn't need to expend money on hydraulic oil.
Yes, I could "just" use water and a water pump.
But even then, I don't know anymore.
a 30kg brushless motor with a 80kw output converted to 300kw or even 400kw would weight around 120kg to 150kg.
How much would the pump weight?
So, 300kg to 400kg of working fluid + 120kg of motor + Xkg of pump + 200kg of fuel + 100kg of pilot + Ykg of skeleton (that would weight just as much as the rest of it) = 720kg + X + Y.
All of this crap just to lift 1 ton of weight...
I don't even know how to strike a balance of "weight required to be lifted" and "weight of the system".
Maybe someone smarter than me would've figured it out by now. Maybe a professional would.
... Or maybe a professional would rapidly understand that this whole endeavor is a waste of time.
Re-calculating:
I need to remember something:
- The artificial muscles that I'm calculating have a length, force and speed proportional to a human sized humanoid. I did it at the start for simplification's sake, like a template I can easily edit later. Depending on the final size of the mech skeleton or even an exoskeleton, the input wattage/horsepower would considerably change, maybe triple or even octuple (8x).
- On top of that, I do need a safety factor, which would increase the weight even more.
- Last, I need to add more muscles to compensate for the weight of the strucutre of the mech itself, like the weight of fuel, pilot, endoskeleton and equipment (containing the hydraulic fluid if it is to be used).
I don't know which value to use for the weight of the skeleton, and it will heavily change based on the size and shape, which will also require the increase in actuator's weight.
It may be a waste of time to calculate the weight of the muscles and horsepower output even before designing the rest of the structure, but I kinda prefer to just take this part out of my mind first.
When I finally start designing the skeleton, I will need to come back here and use the weights as reference.
But it got me wondering, is making the next limb x times stronger than the previous one even a good idea?
This is literally an exponential equation that would only get out of control
Multifilament Hydraulic McKibben Muscles:
So, 2 MPa is already good enough, me thinks. The paper does say it would output around 300kg of force, and I think this is already good enough. The author literally had to use PBO fibers (expensive) and a 3 layer inner bladder for this one.
3 times extra strength for every consecutive muscle 21mm:
- Biceps/Arm: 3 tons = 10x 2 MPa fiber muscles = 1.2kg x 2 sides = 2.4kg
- Shoulders: 3 ton x 3 Extra force = 9 tons = 30 muscles x 6 stewart platform actuators = 180 x 0.12kg = 21.6kg x 2 sides = 64.8kg
- Torso: 9 tons x 3 extra force = 27 tons = 90 muscles x 6 stewart platform actuators = 540 x 0.12kg = 64.8kg
- Legs: 27 tons x 3 extra force = 81 tons = 270 muscles x 6 stewart platforma actuators = 1620 x 0.12kg = 194.4kg x 2 sides = 388.8kg
- 2.4 + 64.8 + 64.8 + 388.8 = 518.64kg in total.
- Safety factor of 2: 1,037.28kg
- Safety factor of 4: 2,074.56kg
2 times extra strength for every consecutive muscle 21mm:
- Biceps/Arm: 3 tons = 10x 2 MPa fiber muscles = 1.2kg x 2 sides = 2.4kg
- Shoulders: 3 ton x 2 Extra force = 6 tons = 20 muscles x 6 stewart platform actuators = 120 x 0.12kg = 14.4kg x 2 sides = 28.8kg
- Torso: 6 tons x 2 extra force = 12 tons = 40 muscles x 6 stewart platform actuators = 240 x 0.12kg = 28.8kg
- Legs: 12 tons x 2 extra force = 24 tons = 80 muscles x 6 stewart platforma actuators = 480 x 0.12kg = 57.6kg x 2 sides = 115.2kg
- 2.4 + 28.8 + 28.8 + 115.2 = 173.04kg
- Safety factor of 2: 346.08kg
- Safety factor of 4: 692.16kg
- Safety factor of 7: 1,211.28kg
1.5 times extra strength for every consecutive muscle 21mm:
- Biceps/Arm: 3 tons = 10x 2 MPa fiber muscles = 1.2kg x 2 sides = 2.4kg
- Shoulders: 3 ton x 1.5 Extra force = 4.5 tons = 15 muscles x 6 stewart platform actuators = 90 x 0.12kg = 10.8kg x 2 sides = 21.6kg
- Torso: 4.5 tons x 1.5 extra force = 6.75 tons = 22.5 muscles x 6 stewart platform actuators = 135 x 012kg = 16.2kg
- Legs: 6.75 tons x 1.5 extra force = 10.125 tons = 33.75 muscles x 6 stewart platforma actuators = 202.5 x 0.12kg = 24.3kg x 2 sides = 48.6kg
- 2.4 + 21.6 + 16.2 + 48.6 = 86.64kg
- Safety factor of 2: 173.28kg
- Safety factor of 4: 346.56kg
- Safety factor of 7: 606.48kg
1.2 times extra strength for every consecutive muscle 21mm:
- Biceps/Arm: 3 tons = 10x 2 MPa fiber muscles = 1.2kg x 2 sides = 2.4kg
- Shoulders: 3 ton x 1.2 Extra force = 3.6 tons = 12 muscles x 6 stewart platform actuators = 72 x 0.12kg = 8.64kg x 2 sides = 17.28kg
- Torso: 3.6 tons x 1.2 extra force = 4.32 tons = 14.4 muscles x 6 stewart platform actuators = 86.4 x 0.12kg = 10.36kg
- Legs: 4.32 tons x 1.2 extra force = 5.18 tons = 17.28 muscles x 6 stewart platforma actuators = 103.68 x 0.12kg = 24.3kg x 2 sides = 12.44kg
- 2.4 + 172.8 + 103.68 + 124.4 = 403.28kg
- Safety factor of 2: 80.65kg
- Safety factor of 4: 161.31kg
Conventional Hydraulic McKibben Artificial Muscles:Now I need to take that equation in the paper and see if I can actually find calculate something.
- F = (pi/4*(D0^2*P))*(1/sin(O0))^2*{3(1-e)^2*cos(O0)^2-1}
Well, I tried in MPa, in KPa and it still didn't give any result that made sense.
- (pi/4*(21^2*2000000))*(1/sin(20))^2*{3(1-0.20)^2*cos(20)^2-1}
- -565384994.5986882470453348857008804125900264872223170612834861024
But somehow ChatGPT was able to make the equation correctly for some reason. :|
The output force depending on the diameter at 2MPa would be:
- For a 50 mm diameter muscle: approximately 13634 N / 1390 kg
- For a 100 mm diameter muscle: approximately 54536 N / 5561 kg
Weight of one 50mm diameter muscle with 30cm length: 0.79kg
Weight of one 100mm diameter muscle with 30cm length: 4.77kg
3 times extra strength for every consecutive muscle 50mm:
- Biceps/Arm: 3 tons = 3x 2 MPa muscles = 0.79 x 2 sides = 1.58kg
- Shoulders: 3 ton x 3 Extra force = 9 tons = 7 muscles x 6 stewart platform actuators = 42 x 0.79kg = 35.55kg x 2 sides = 71.1kg
- Torso: 9 tons x 3 extra force = 27 tons = 20 muscles x 6 stewart platform actuators = 120 x 0.79kg = 94.8kg
- Legs: 27 tons x 3 extra force = 81 tons = 59 muscles x 6 stewart platforma actuators = 354 x 0.79kg = 279.66kg x 2 sides = 559.32kg
- 1.58 + 71.1 + 94.8 + 559.32 = 726.8kg.
2 times extra strength for every consecutive muscle 50mm:
- Biceps/Arm: 3 tons = 3x 2 MPa muscles = 0.79 x 2 sides = 1.58kg
- Shoulders: 3 ton x 2 Extra force = 6 tons = 5 muscles x 6 stewart platform actuators = 30 x 0.79kg = 23.7kg x 2 sides = 47.4kg
- Torso: 6 tons x 2 extra force = 18 tons = 13 muscles x 6 stewart platform actuators = 78 x 0.79kg = 61.62kg
- Legs: 18 tons x 2 extra force = 36 tons = 26 muscles x 6 stewart platforma actuators = 156 x 0.79kg = 123.24kg x 2 sides = 246.48kg
- 1.58 + 47.4 + 61.62 + 246.48 = 357.9kg
- Safety factor of 2: 715.8kg
1.5 times extra strength for every consecutive muscle 50mm:
- Biceps/Arm: 3 tons = 3x 2 MPa muscles = 0.79 x 2 sides = 1.58kg
- Shoulders: 3 ton x 1.5 Extra force = 4.5 tons = 4 muscles x 6 stewart platform actuators = 24 x 0.79kg = 18.96kg x 2 sides = 37.92kg
- Torso: 4.5 tons x 1.5 extra force = 6.75 tons = 5 muscles x 6 stewart platform actuators = 30 x 0.79kg = 23.7kg
- Legs: 6.75 tons x 1.5 extra force = 10.125 tons = 8 muscles x 6 stewart platforma actuators = 48 x 0.79kg = 37.92kg x 2 sides = 75.84kg
- 1.58 + 37.92 + 23.7 + 75.48 = 248.8kg
- Safety factor of 2: 497.6kg
- Safety factor of 4: 995.3kg
1.2 times extra strength for every consecutive muscle 50mm:
- Biceps/Arm: 3 tons = 3x 2 MPa muscles = 0.79 x 2 sides = 1.58kg
- Shoulders: 3 ton x 1.2 Extra force = 3.6 tons = 3 muscles x 6 stewart platform actuators = 18 x 0.79kg = 14.22kg x 2 sides = 28.44kg
- Torso: 3.6 tons x 1.2 extra force = 4.32 tons = 4 muscles x 6 stewart platform actuators = 24 x 0.79kg = 18.96kg
- Legs: 4.32 tons x 1.2 extra force = 5.18 tons = 4 muscles x 6 stewart platforma actuators = 24 x 0.79kg = 18.96 x 2 sides = 37.92kg
- 2.4 + 28.44 + 18.96 + 37.92= 87.72kg
- Safety factor of 2: 175.44
- Safety factor of 4: 350.88kg
- Safety factor of 7: 614.04kg
3 times extra strength for every consecutive muscle 100mm:
- Biceps/Arm: 3 tons = 1x 2 MPa muscle = 4.77kg x 2 sides = 9.54kg
- Shoulders: 3 ton x 3 Extra force = 9 tons = 2 muscles x 6 stewart platform actuators = 12 x 4.77kg = 57.24 x 2 sides = 114.48kg
- Torso: 9 tons x 3 extra force = 27 tons = 5 muscles x 6 stewart platform actuators = 30 x 4.77kg = 143.1kg
- Legs: 27 tons x 3 extra force = 81 tons = 15 muscles x 6 stewart platforma actuators = 90 x 4.77 = 429.3 x 2 sides = 858.6kg
- 9.54 + 114.48 + 143.1 + 858.6 = 1125.72kg
- Safety factor of 2: 2251.44kg
2 times extra strength for every consecutive muscle 100mm:
- Biceps/Arm: 3 tons = 1x 2 MPa muscle = 4.77kg x 2 sides = 9.54kg
- Shoulders: 3 ton x 2 Extra force = 6 tons = muscles x 6 stewart platform actuators = 12 x 4.77kg = 57.24 x 2 sides = 114.48kg
- Torso: 6 tons x 2 extra force = 18 tons = 4 muscles x 6 stewart platform actuators = 24 x 4.77kg = 114.48kg
- Legs: 18 tons x 2 extra force = 36 tons = 7 muscles x 6 stewart platforma actuators = 42 x 4.77kg = 200.34kg x 2 sides = 400.68kg
- 9.54 + 114.48 + 114.48 + 400.68 = 639.18kg
- Safety factor of 2: 1278.36kg
1.2 times extra strength for every consecutive muscle 100mm:
- Biceps/Arm: 3 tons = 1x 2 MPa muscle = 4.77kg x 2 sides = 9.54kg
- Shoulders: 3 ton x 1.2 Extra force = 3.6 tons = 1 muscles x 6 stewart platform actuators = 6 x 4.77kg = 28.62kg x 2 sides = 57.24kg
- Torso: 3.6 tons x 1.2 extra force = 4.32 tons = 1 muscles x 6 stewart platform actuators = 6 x 4.77kg = 28.62kg
- Legs: 4.32 tons x 1.2 extra force = 5.18 tons = 2 muscles x 6 stewart platforma actuators = 12 x 4.77kg = 57.24kg x 2 sides = 114.48kg
- 9.54 + 57.24 + 28.62 + 114.48 = 209.88kg
- Safety factor of 2: 419.76kg
- Safety factor of 4: 839.52kg
- Safety factor of 7: 1469.16kg
Fluid Flow:
Well, all options seem interesting...
However, all of these muscles still needs a fluid flow to supply them, and that needs to be taken into consideration for the hydraulic pump that is going to supply them.
Of course, let's take into consideration that:
- The muscles will already be partially full, meaning I will need half of the fluid flow.
- The plastic filler will also keep half of the muscle full.
- The lower density of the hydraulic fluid would make the total weight slightly lower, but the amount of liters would stay the same.
The 21mm muscle - 2 times stronger than the previous muscle - Safety Factor of 2: 346.08kg
- Actuated weight: 0.12kg if water, 0.1 kg if hydraulic oil
- Unactuated weight: 0.08
- 0.12-0.08 = 0.04 kg of liquid need to be pumped for every fiber.
- Amount of fibers: 346.08kg/0.12kg = 2884
- 2884 x 0.04 = 115.36 liters need to be pumped.
- Since it needs to be delivered in a speed to make the muscle contract with a speed of 1.33 meters per second: I will admit, I have no idea on how much fluid flow this would require, but I used the Hydraulic Cylinder calculator, added a bore of 20mm and a stroke of 130mm at 20 bar, and it said that the total volume would be 0.04 liters, and in order to achieve 1.33 m/s, it said it would need 25.0699 liters per minute.
- I also tried to take a Speed Calculator, inputing the speed and the distance, it gave me 0.015038 seconds, so I would need to supply 0.04 liters at 0.015038 seconds, which in one minute would be:
- 60 seconds / 0.015038 = 3989.89227291 x 0.04 = 159.595690916 liters per minute?
- 25.0699 LPM x 2884 fibers = 72,301.5916 LPM
- 36,150.7958 LPM if half of the muscles filled by the filler
- 18,075.3979 LPM if half of all muscles are actuated.
- If we assume that the 160 LPM is true, then it should be: 115,360 LPM (divided 2 times)
The 50mm muscle - 2 times stronger than the previous muscle - Safety factor of 2: 715.8kg
- Actuated weight: 0.79kg
- Unactuated weight: 0.53kg
- 0.79 - 0.53 = 0.26kg or liters if water
- Amount of fibers: 912 fibers
- 912 x 0.26 = 237.12kg or liters
- Hydraulic Cylinder calculator said it is: 156.6869 liters per minute for a volume of 26 liters.
- 60 seconds / 0.015038 = 3989.89227291 x 0.26 = 1037.37199096 LPM.
- 912 x 156.6869 = 142,898.4528 LPM
- 71,449.2264 LPM if half of the muscles are filled by the filler
- 35,724.6132 LPM if half of all muscles are actuated.
- If we assumed that the 1037 is true, then it should be 236,436 LPM (divided 2 times)
The 100mm muscle - 1.2 times stronger than the previous muscle - Safety factor of 2: 419.76kg
- Actuated weight: 4.77kg
- Unactuated weight:
- 4.77 - 2.35 = 2.42kg
- Amount of fibers: 44 fibers
- 44 x 2.42 = 106.48kg or liters
- Hydraulic Cylinder calculator said it is: 156.6869 LPM for a volume of 2.42 liters.
- 60 seconds / 0.015038 = 3989.89227291 x 2.42 = 9655 LPM
- 44 x 156.6869 = 6,894.2236 LPM
- 3,447.1118 LPM if half of the muscles are filled by the filler
- 1,723.5559 LPM if half of all muscles are actuated.
- If we assumed that the 96554 is true, then it should be 106,210 LPM (divided 2 times).
Well, well, well... Isn't physics a pain in the butt some times?
If I take a hydraulic pump that produces around 7 LPM with 1750 RPM and 5 Nm of torque at 1.25 horsepower, I would need:
- 115360 LPM / 7 LPM = 16480
- 1.25 x 16480 = 20,600 horsepower.
- 236436 LPM / 7 LPM = 33776.5714286
- 1.25 x 33776.5714286 = 42,221 horsepower.
- 106210 LPM / 7 LPM = 18966.0714286
- 1.25 x 18966.0714286 = 18,966 horsepower.
Of course, this is using the exponential growth and a random value that I took, but if you divide it by the number of safety factors, since it would mean the number of times the pressure inside the muscles are divided, it would get a little better, but not great...
I would really love to know how I could reduce the amount of horsepower... I mean, did I really do the calculations correctly?
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Dielectric Elastomers:
Although I already calculated the hydraulic McKibben artificial muscles, screw actuators, hydraulic cylinders, linear motors and all of that stuff, I'm actually very interested on Dielectric Elastomer Actuators.
Not because they are "cool" or anything like that, but because they would eliminate the need for a Hydraulic Pump and an Electric Motor to drive the pump. Both have their own complications to deal with and I'm really concerned on how in the hell I would make a BLDC motor capable of outputing 300 kilowatts and the ESC required to move it.
Not to mention that in the case of dielectric elastomers, I wouldn't need to worry about the weight of the hydraulic fluid, neither about tubing, solenoid valves and all of that stuff.
Yes, I would still need to figure out some problems, like motion control, electrical insulation and converting the electrical output of the fuel cells to 5 kilovolts and the like.
With that in mind, the electrostatic actuators would clearly be better suited for that, but I do wonder if it is possible to simplify its construction...
I also doubt my idea of reppeling fibers would work, so I do think I should just compromise and use a dielectric elastomer like this:
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As you can guess, this is a reversely actuated dielectric elastomer, sinze the inner electrode out get attracted to the outer electrode, increasing its length.
Although, I do wonder if it would be possible to mix this one with the below dielectric elastomer:
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This one has a braided sleeve just like a McKibben muscle, and it contracts just like one, but I doubt I would be able to print a continuous fiber like the previous example.
In either way, I need to figure out how much force dielectric elastomer fibers would output, and then I would need to figure out how much force they would also be able to output if they were braided like a rope.
From the GPT chats capable of search the web for actual sources, it seems that braiding/twisting ropes can increase the strength of said rope from 3 to maximum 7 times.
Obviously I will take the conservative approach of 3 times. and add a safety factor.
Anyway, actually trying to figure out how much force they would output and how much they would weight.
Accordingly to the article of the braided dielectric elastomer above, it weights 0.219 grams and was able to lift 200 grams.
Unfortunately I'm kinda confused about the contraction ratio, it keeps changing the number on "tensile strain", one time it says it is 14.7%, other says it is 2% depending on the testing conditions. Unfortunately, it doesn't tell the exact dimensions of the samples.So, taking into consideration the probable size of milimeters of the Dielectric Elastomer in the images, I would assuming it is a few millimeter squares.
By the way, the article says it uses VHB 4910 elastomer tape and 5 to 7 Kilovolts, such as in the image below:![]()
So, let's say it is 10 by 10mm and that its length is 300mm (30cm) or even larger since it will be braided/twisted, but let's take this length and then multiply a few times just to be sure.
- 0.200 grams x 30 = 6 grams = 200 grams of pulling force, I doubt it increases with length.
- 9000kg of pulling force / 1 fiber with 200 grams of pulling force = 45000 fibers x 6 grams = 270 kilograms.
- 270 x 30 actuators in total = 8100kg
- Even if you use only 3000kg/200 grams it gets 90kg per actuator.
My face thinking the dielectric elastomer would be lightest actuator of them all:
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I did find this acrylate based dielectric elastomer that was capable of lifting 8kg while only weighting 0.15 grams, this would be more than 50,000 times its own weight.
Unfortunately, like all good things in life, I don't have access to it, not even through Sci-hub.
And I don't know if this performance is intrensically related to the Acrylic itself or the use of SWCNT (single walled carbon nanotubes) in the electrodes.
And yes, I keep asking ChatGPT and searching google scholar myself for high performance dieletric elastomers, but for some god-forsaken-reason they never show me what I'm looking for.
Well, I literally looked around all day and I doubt I would be able to replicate the materials, since these high performance dielectric elastomers are normally made of super mega specific chemicals that would probably summon a demon if you spoke their names out loud.
I really don't know how to proceed with this project.
Did I take the weight of the actuators incorrectly? I didn't research enough for alternatives? Maybe the strength I'm requiring for the actuators is just too much?
What should I do...?
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Pneumatic McKibben
And yes, I'm still trying to find ways of increasing efficiency of pneumatic actuators.
One example is this one, it is said to be 31.2% stronger and 25.6% faster than conventional pneumatic muscles.
Accordingly to chat GPT, if we take the percentages, it would be something around:
- 30% = 0.30
- 22% = 0.22
- 31.2% increase = 1.312
- 25.6% increase = 1.256
- 0.30*1.312*1.256 = 0.4943616 = 49.4>#/li###
- 0.22*1.312*1.256 = 0.36253184 = 36.2>#/li###
Since the article doesn't talk about initial efficiency, we can only extrapolate like this.
This other article says it was capable of reducing the losses in 70%, but I'm unsure of what kind of losses...
By the way, one interesting thing I think about Pneumatic actuators is that it doesn't matter much the pressure you work with, it is still the same amount of liters, because gases are compressible.
So, it would be a waste of energy to attempt compressing the gases to 15 MPa, the lower the pressure, the more efficient the whole system would be.
Supposedly...
But this still makes me wonder: if the majority of the losses in pneumatic systems is due to the work being converted into heat, then why not just heat the gas?
Gases increase in pressure inside a chamber proportionally to its temperature after all...
Like adiabatic-pneumatics or isothermal-pneumatics, where heat is either not exchanged or at least constant.
I found this article that uses a reversible fuel cell membrane to convert water into hydrogen and oxygen, making a unthetered pneumatic muscle.
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It is not hard to make a reversible proton exchange membrane, but it would be hard to make in this such high amounts...
... Or I could "just" use a central reversible fuel cell in one point like a pump and suplement the muscles in the mech...
One interesting thing is that I could re-use the oxygen and hydrogen in the fuel cell to recycle some of the wasted energy. Like a turbocompressor of some sorts.
Well, guess what? It would need a really small amount of water:
1 liter of water produces 1235 liters of hydrogen and 622 liters of oxygen.
Maybe in the end this is the solution for the mech?
Well, a reversible fuel cell/regenerative fuel cell is kinda hard to make, a simple hydrogen generator is easy, you can always just burn both for water again.
Although, I kinda wanted a regenerative fuel cell so I could react the hydrogen and oxygen after they're used so I could recycle some of the energy...
Wait, I could just build a hydrogen generator and a conventional fuel cell separately...
No, really, I'm serious, should I even attempt this one? This REALLY looks promising, simple, light and cheap to do.
My concerns are:
- Hydrogen is known to be so light it can actually pass through solid materials, although many carbon fiber tanks for hydrogen have a polyethylene layer separating the fibers from the hydrogen.
- If there is any leak at all (which will have, it is a pneumatic system), the lesser the gases to compress.
- Hydrogen is combustable, and even worse than that: it has an invisible flame to the human eye. Should I only work with the oxygen instead?
- There is also the issue of position control, pneumatics need precise control of antagonistic actautors, and on top of that, I don't know how much is difficult to make reliable progressive pneumatic valves.
- Would the low efficiency of pneumatic muscles still be a problem?
I normally use the festo air arm as a reference, but that is already 13 years old.
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While nowadays, James Bruton's video showed that you can, in fact make simple precision control of pneumatic actuators using arduino.
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I also found this video, and its tittle made me know that there are in fact, mechanical breaks that could allow for reliable position control for pneumatics.
(unfortunately, for the life of me, I couldn't find a single image or video showing a pneumatic actuator with a mechanical brake)
There are also articles about position control using simple solenoid valves and mechanical brakes.
Screw actuator:
Before we start, I will need to calculate not only the size and weight of the thing (again), but also because I misunderstood something about volume and tensile strength.
You see, I saw once that Aluminium piston rods are 2 times bigger than steel ones, but they have the same tensilse strength, but 20% to 30% lighter.
So, my monkey brain went "this means that making it out of plastic would be even lighter!11!", which is absolutely stupid.
You just take the tensile strength of steel (200,000 PSI) and divide by the tensile strength of the material you want to use, then you multiply the result by the volume of said material and insert the density to find the weight.
For example:
- 1 m³ of steel = 7,850 kg
- Tensile strength of steel = 200,000 PSI or 1378 MPa
- Tensile strength of Aluminium = 95,000 PSI or 655 MPa
- 200,000/95,000 = 2.10526315789
- 1 m³ of aluminium x 2.10526315789
- 2.1052631578 m³ of aluminium = 5,705 kg
Now let's see HDPE graphene composite:
- Tensile strength of steel = 200,000 PSI
- Tensilte strength of Composite HDPE with graphene = 5801.51 PSI or 40 MPa
- 200,000/5801.51 = 34.4737835495
- 1 m³ of HDPE x 34.4737835495
- 34.4737835495 m³ of HDPE = 33,440 kg
As you can see, for every part made out of HDPE would literally weight 4.25 times more than any piece made out of steel (and yes, I know that a composite of HDPE graphene would have a different density, but that would probably make it maximum 20% to 10% lighter).
So I need to take a material that has a really good tensile/compressive strength, the first thing that comes to mind is carbon fiber, but that is just too expensive.
I also thought on aluminium matrix with iron or steel cables and silicon carbide for extra strength, or even using HDPE matrix in the place of aluminium.
Also, just now I remembered about an all PE based composite that could achieve around 1 GPa of strength. Maybe I could reach the same amount of strength by using HDPE.
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7435843/
I found another which uses HDPE too:
Source: https://www.sciencedirect.com/science/article/abs/pii/S0032386118301514
The problem is that both UHMWPE and PE wax are expensive and harder to find.
(I said that and I immediately found a link for PE wax in my country costing 169 reais or 32 dollars the kilogram)
I also remembered about that DIY plastic that uses talc powder and PVA glue, I always assumed it to be weak or just acceptable, but I just saw some papers and they were capable of reaching tensile strengths close to 50 MPa of tensile strength.
Source: https://www.researchgate.net/publication/304572845_Structure_and_properties_of_highly_filled_poly_vinyl_alcoholtalc_composites_prepared_through_thermal_processing_effects_of_talc_size
(it is available on Sci-hub)But this does makes me wonder:
PVA + Talc composite are obscenely cheap to buy and simple to make, but it is also has the problem of being soluable on water.
It would be like making a mech made out of paperboard, even if it was able to lift tons of weight, what is the point if it is going to melt in the rain?This one uses polyvinyl alcohol with polyacrylic acid reached 50 MPa of tensile strength, maybe it would be less soluable in water.
This one is on PLA (also on Sci-hub), but they "only" got to around 50-60 MPa.
Well, first I will try to calculate the weight/volume of the all PE composites if they were to replace Steel:
- 1 m³ of steel = 7,850 kg
- Tensile strength of steel = 200,000 PSI or 1378 MPa
- Tensile sterngth of UHMWPE+PE wax composite = 1320 MPa or 191,449.8 PSI
- 200,000/191,449.8 = 1.04466027126
- 1 m³ of UHMWPE x 1.04466027126 = 1,013.3 kg
Almost 8 times less heavy than Steel while having the same volume, sweet.
However, there is always something, and this is that:
- The articles don't specify if it is yield or ultimate tensile strength.
- The articles also say it has increased elasticity/elongation of around 7.35%.
Both of these things may considerably change how much this thing would weight and how it should be shaped.
Accordingly to ChatGPT:
"However, for many engineering materials, the ultimate tensile strength is often found to be about 1.5 to 2.0 times higher than the yield strength12. This means that the yield strength is about 50% to 67% of the ultimate tensile strength."
Well, then it is actually 2,026.6 kg.
Although this is the equation that I was thinking of using, I'm kinda concerned when it comes to the screw actuator. The articial muscles would be "easier" to fix, because they are cylindrical pieces of cloth, not solid pieces of material.
It could mean that in the end I would need to make 6 different types of screw actuators with widly different sizes of motors.
I could simply use the final screw and just add it to everything, but... The motors would still be a problem.
Well, first, I need to find a 3 ton rated screw actuator/lifter and then take its dimensions.
(I'm having no success)
I also tried to ask ChatGPT and other gpts with access to internet to take the general value that screw actuators normally use for the dimensions and outputs in order to make a conservative approach based on the generalistic data.
Then they reach the conclusion of 2+2=22 around 40 times.
Me: "I need you to figure out the pitch of the screw based on the torque, which is 45 Nm"
GPT: "Why, yes, thank you, the diameter is 12mm and the torque is 2389 kilonewtons per meter"
Me: "That wasn't what I asked, please, redo the calculation."
GPT: "Why, yes, thank you, the diameter is 12mm and the torque is 2389 kilonewtons per meter"
Me: "That wasn't what I asked, please, redo the calculation."
GPT: "you reached your limit of allowable questions for the day, pay for the premium for more."
It is kinda pathetic how people wasted billions of dollars just to make an AI that can't even make f*cking math, how is that even possible since the AI are literally made out of MATH!?
Well, at least let me check about the hydraulic cylinders, right?
They have more of less the same structure (without the threads and the like), so I could at least use it as a starting point...?
In any manner:
3 times extra strength for every consecutive actuator:
- Biceps/Arm = 3 tons
- Shoulders: 3 ton x 3 Extra force = 9 tons
- Torso: 9 tons x 3 extra force = 27 tons
- Legs: 27 tons x 3 extra force = 81 tons
Now that I separated every consecutive actuator, I think I see the issue... I did say that this leads to exponentional growth, which is absolutely insane...
2 times extra strength for every consecutive actuator:
- Biceps/Arm = 3 tons
- Shoulders: 3 ton x 2 Extra force = 6 tons
- Torso: 6 tons x 2 extra force = 18 tons
- Legs: 18 tons x 2 extra force = 36 tons
Well, I could only find a 30 ton hydraulic cylinder, and it is CHONKY.
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I don't understand Mandarin (or Cantonese), so I don't know exactly which is the diameter of the rod and the diameter of the bore.
(Forget it, I found another link were it is in english)It has 80mm of rod diameter and 140mm of bore (inner diameter) and a outer diameter of 168mm.
It is meant to work maximum 300 meters per second (somehow) and maximum 30 MPa of pressure, which reaches the 40 ton mark, at 30 MPa its pulling side reached 30 tons.
And since the rod will be sticking out in both sides, then it would be 30 tons for both sides.It would need 827.3070 Liters per minute of fluid flow, and I'm supposed to ad 6 of these for each leg.
I won't even waste my time calculating this one, lol.
At least I now know how THICCC the screw actuator would need to be.
1.5 times extra strength for every consecutive actuator:
Now this one, the 10 ton hydraullic cylinder has 63mm of rod diameter, 100mm of bore diameter and 110mm of outer diameter.
![]()
It has maximum 7 ton of pulling force, so you know the drill, I will make the inner diameter a little bigger for the sake of reaching 10 ton. 110mm of inner diameter in this case.
It would also need 509.6085 liters per minute of fluid flow, or 3000 liters of fluid flow in total counting the stewart platform.
I can't go around making 4 different cylinders for each output force, so let's see how much fluid flow each would need:
- Biceps/Arm: 3 tons = 500 LPM but with a pressure limiter for 5 MPa
- Shoulders: 3 ton x 1.5 Extra force = 4.5 tons = 500 LPM pressure limiter at 7 MPa x 6 = 3000 LPM
- Torso: 4.5 tons x 1.5 extra force = 6.75 tons = 500 LPM pressure limiter at 10 MPa x 6 = 3000 LPM
- Legs: 6.75 tons x 1.5 extra force = 10.125 tons 500 LPM with no pressure limiter also 3000 LPM
- To supply one side of the mech at full speed: 9500 LPM.
- I would "only" need 90 hydraulic pumps with 100 LPM of output flow.
- Which would need around 585 horsepower in total.
- Not great, not terrible.
The 10 ton hydraulic cylinder weights around 15kg by the way, so 1+6+6+6 = 19 x 2 sidez = 38x15 = 570kg in total for the hydraulic cylinders alone.
1.5 times extra strength for every consecutive actuator:
Now calculating with the proper hydraulic cylinder sizing:
3 ton hydraulic cylinder: 50mm of inner diameter, 28mm of rod, 300mm of stroke, 16 MPa = 107 LPM.
5 ton hydraulic cylinder: 63mm, 35mm, 300mm, 16 MPa = 170 LPM.
6 ton hydraulic cylinder: (I couldn't find one, so I will use the force of a 8 ton) 80mm bore, 50mm rod, 300mm stroke, 16 MPa = 245 LPM.
10 ton hydraulic cylinder: 100mm of bore diameter, 63mm of rod diameter, 300mm of stroke 16 MPa = 500 LPM.
- Biceps/Arm: 3 tons = 107 LPM
- Shoulders: 3 ton x 1.5 Extra force = 4.5 tons = 170 LPM x 6 = 1020 LPM.
- Torso: 4.5 tons x 1.5 extra force = 6.75 tons = 245 LPM x 6 = 1470 LPM
- Legs: 6.75 tons x 1.5 extra force = 10.125 tons 500 LPM x 6 = 3000 LPM
- To supply one side at full speed: 5597 LPM
- I would "only" need 55 hydraulic pumps.
- Which would need around 357.5 horsepower in total.
1.2 times extra strength for every consecutive actuator:
- Biceps/Arm: 3 tons = 107 LPM
- Shoulders: 3 ton x 1.2 Extra force = 3.6 tons = 107 LPM x 6 = 1020 LPM.
- Torso: 3.6 tons x 1.2 extra force = 4.32 tons = 245 LPM x 6 = 1470 LPM
- Legs: 4.32 tons x 1.2 extra force = 5.18 tons = 245 LPM x 6 = 1470 LPM
- To supply one side at full speed = 4067 LPM
- Which would need around 260 Horsepower in total.
In any manner, this would show how much the screw actuator would also weight and how much energy it would need.
Although, it would be 7 times lighter if made with the all PE composite + graphene.
Tomorrow I will try to make a 3D model of the screw actuator with the dimensions into consideration.
Well, guess what? The scroll in my mouse stopped working, now I need to wait until the new one arrives at my house.
Dang it, the project log is already reaching maximum limit of characters.
But before I create a new one to post the screw actuator design: to calculate the linear speed and force into horsepower, and it seems like in order to lift 3000kg at a linear speed of 1.33 meters per second, I would need around 1000 watts (1.33 horsepower) accordingly to chatGPT, which is probably wrong...
So maybe I misscalculated some things on the previous actuators?
Nope, it is 81 kilowatts for 1000kg of force, ChatGPT was indeed incorret.
Also, this would make it simpler for the screw actuators or even for hoist actuators.
Out of curiosity, energy consumption with the extra force:
- 81 + ((81x3)x6) + ((81x3x3)x6) + ((81x3x3x3)x6) = 19,035 kilowatts = 25,380 horsepower.
- 81 + ((81x2)x6) + ((81x2x2)x6) + ((81x2x2x2)x6) = 6,885 kilowatts = 9180 horsepower.
- 81 + ((81x1.5)x6) + ((81x1.5x1.5)x6) + ((81x1.5x1.5x1.5)x6) = 3,543.75 kilowatts = 4725 horsepower.
- 81 + (81x1.2)x6) + ((81x1.2x1.2)x6) + ((81x1.2x1.2x1.2)x6) = 2203.848 kilowatts = 2938.464 horsepower.
Well, I definitely misscalculated something in the hydraulic cylinders, because it should be way above the values I got.
Off-topic:
One thing I forgot to talk about more in depth was the plasma jet engines.
Although I talked about them more like a conventional turbine engine, with compressor, combustor and turbine parts, you could also use them as a Tip-jet rotor.
Basically, it is a type of propulsion system in which the rotor/propeller/blades are hollow and air is injected into them, the centrifugal forces compresses the air further and at the tips of the rotor there is the combustion chamber that generates thrust.
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The thing is: since it is a type of propulsion system that doesn't need a combustion chamber and a turbine to work the same way as a conventional turbine engine, you could, maybe, use it in a plastic plasma jet engine, only using the ceramic/metal parts at the tips.
Like this one.
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Source: https://www.sciencedirect.com/science/article/pii/S1000936119302213
Maybe this could be useful to replace the 300+ kilowatt electric brushless motor, or it could even be used for a pneumatic McKibben muscle.
Adiabatic Combustion Engine:
SPEAKING of adiabatics...
There are a type of engine called "adiabatic engine", it is said to have around 50% to 60% of fuel efficiency.
Source: https://www.sae.org/publications/technical-papers/content/830314/
You "just" need to make all of the components out of insulating ceramics and then run it super mega hot so the energy loss to heat is minimal.
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It can also be done by doing a very high compression very fast, when I was searching for the most efficient combustion engines in the planet, ship engines were always the first to appear, and those had meter long compression. But I don't know how I would avoid fuel detonation with an engine at 1200ºC
DIY Mech or Exoskeleton suit.
Mechs are not viable, nor cheap, so I will try to design and build one alone anyway.
