09/03/2024, Saturday, 11:58

This project Log was another failure, I ended up doing absolutely nothing and just yapping and yapping.

I copy-pasted all my project logs to a google drive, it didn't pass the videos, neither some images because their link expired, but it resulted in literally 999 pages.

999 pages of time wasting.

Maybe I never wanted to finish this project, I just wanted to distract myself, or something. Who knows...

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Literally no one reads these logs, but sorry, I'm procrastinating a lot for some reason.

Not just in this project, but everything in my life right now. I don't understand it either.

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I was thinking on keeping this as a draft until I actually made something, but... Right now I'm pissed and confused, so I will leave this here, I'm still adding new content whenever I actually make said content (like buying the goddang pump).

I hate this project...

Being honest, I feel like I hate myself more. I literally didn't even make a single scaled-down prototype of any of my ideas...

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You know what? Screw it all, let's just do it. DO IT.

Screw efficiency, screw precision, screw reliability, screw durability, screw it all! Let's JUST DO IT.

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In any manner, let's begin with the beginning:

• The energy source will be any kind of stationary generator that I can get my hands on, even if it means just plugging it directly to a plug in my house.

I could find a lot of combustion engines with a single cyinder, in fact, I found a few motorcycle ones that achieved 75 horsepower.

The problemo is that it costs 4000 reais (800 dollars).

• I don't think that I can make any kind of electric motor that can properly work, so I was thinking of using the REB-90 number of poles and energy consumption as a basis for an air core linear brushless motor:

I will make the coils out of casted aluminium, not the best, but cheap and easy do find and melt (easy enough, at least).

I kinda want to use normal electric motors instead of linear motors, but for now, the production of it seems easier than the conventional one.

The coils will be encased in silicon rubber or epoxy resin (the cheaper I can find) with the thermal paste for heat dissipation and maybe fibers for strength. 

This means that it will looking like a thick, long spaghetti.

The specific number of turns on each aluminium coil is still unknown to me, I still need to calculate that stuff.

On top of that, I need to find a way of making the ESC for a brushless motor that needs to get hundreds of amps and hundreds of volts...

One interesting fact is that I don't really know how many volts I should have since the voltage in a brushless motor defines its RPM, which would be dozens of times faster than mere centimeters per second of linear speed.

• The structure will be any crap that I come across, be it wood, steel, aluminium or even Polyethylene.
  I don't give a damn, I will just build it thick enough until it stops breaking.

That's it.

Now I "just" need to do it.

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Actuator:

The torque of the REB 90 is 300 Newton meters, and since the motor has 27cm of diameter, then a linear version would have 200kg of pulling/pushing force. But this is a spaghetti linear motor, so only pulling force.

The kilowattage is rounded up to 80kw, but in reality it uses 60-70kw continiously. In any case, since it uses 800 volts, it would use around 100 amps. Accordingly to the AWG of aluminium wire, I would need 1AWG of aluminium wire, which is 7.5mm of diameter, almost a centimeter.
Since it has maximum 4000 rpm with 800 volts, I would assume that its KV is 5. I don't need the speed of 4000 rpm in linear motion, but the actual number depends on the position of each linear motor.

I forgot the number of poles and slots that the REB-90 was supposed to have...
I did count 59 magnets and 44 slots in the 3D models that I've made. Dunno if it is correct, the number of poles and slots should be dividible by 2 and 3 (2 poles and 3 phases).
So it is probably 60 poles and 45 slots.
Also, I forgot: this is the widing calculator: https://www.bavaria-direct.co.za/scheme/calculator/

Now I don't think this winding scheme/calculator is a good example for a tubular linear electric motor, since the coils would be one above another in this case.

If I find the winding process too difficult I may just stick to the conventional square linear motor...
Maybe it will be easier to turn a induction motor into a tubular motor, they are already stacked in a diagonal, just need to straight it out:

I can't find for the love of me the number of turns required. It changes between 10 and 200 turns in each stator. :|

Plus, the Reb-90 is a long motor, with aorund 20cm of height/thickness, meaning that I would need to make the turns like it was in a 20cm long slot, and then keep it in a tubular shape for the linear electric motor actuator.Well, I will do the following: I will make a 3D model occupying the space around the stator teeth, by taking the volume and the density of aluminium, I can find more or less how many turns I would need.

It would occupy around 90 cubic centimeters of space, and since I'm assuming the original would use copper wire, it would weight around 800 grams. But since it has 45 slots, it would weight around 35kg, in total, but the original is said to weight around 23kg.
Assuming that the copper weights 15kg in total, then each coil weights around 300 grams instead.
Taking a volume, density and weight calculator, it would be 2.51 meters in length.

By the way, since the Reb90 has 27cm of diameter, it would have 84cm of length. So it would also actuate 84cm, totally 170cm of length in total. But it would be so long the electromagnets wouldn't be able to "catch" the moving part.

I'm buying the parts to make the furnace, but I don't think I will have enough aluminium scrap to use...
Also, I was thinking on 3D printing a coil and then use it as a mold for a paraffin/wax sacrificial mold.
But an AWG 1 aluminium wire has only 7.5mm of diameter, which wouldn't make it pretty solid. I was thinking on making a pretty solid coil as the mold, something like this:

I will try the two types and test it out which one is better.

It is embarassing how much time it took me for 3D model these square coils on Blender. All the tutorials that I found are crap.

I really need to learn how to use FreeCAD. I will try it tomorrow, I'm done with this crap for today.

Maybe I should just make a giant ass spiral on a bucket of sand mixed with sodium silicate and then cut it to size for the aluminium coils.
The problem is: a spiral made out of what?

I thought on maybe using one of those giant syringes with a hole the exact size and then extrude some partially molten paraffin.

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In any manner, just now I stopped to considerate the weight and price of everything.

Although I assumed each coil would weight around 300 grams, in actuality it would probably weight around 100 grams maximum.
So, since every spaghetti muscle has 45 coils and more 60 replacing the permanent magnets, I would have 10kg per muscle with the coils alone (not counting all the silicon rubber and so on), and since I would need around 30 of these per limb, I would have 1575kg of weight in total.
On top of that, the initial problem of not being able to find aluminium scrap and other metals in general doesn't help.
Asking around 100 sellers online, I could only find 2 that would sell aluminium scrap per kilogram, and they offered 60 reais (12 dollars) per kilogram, so this would already explode into 9000 reais (1800 dollars), which is a pain in the ass.
Yes, I can go around scrapyards and attempt on find more scrap, but like I said on previous project logs: it is hard as hell to find scrapyards that actually sell their scrap, they normally buy and resell to other companies/government.

I can only find aluminium scrap for 50 reais (10 dollars) per kg, a seller said they would sell for 20 reais per kg (4 dollars), but when I was looking the price that crushed soda cans are sold for, it was just 6 reais (1,20 dollars) per kg.
For the life of me I can't find anywhere that sells for that price.

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This means that I would be forced to use the idea of dielectric elastomers were fibers with the same polarity are close to each other, repelling each other, simulating a muscular contraction. You could use anything to mix the carbon/graphite with, silicone rubber, latex, plastic etc.
But unlike the previous idea, these don't have any kind of position control at all. Electric motors (rotary or linear) have a easy and practical way of making position control even without encoders, you "just" need to "freeze" the waves in one position and that's it.
The DEA's only turns on or off, so if you want the muscle to contract half-way, you would need to low the power input, sacrificing strength over position control. This way, I would need to be forced to make the actuators way stronger than they need to be in order to lift something half-way.
The other idea would be to turn on and off the muscles at high frequencies so they stay in one position only. This seems promising, but I'm concerned with the durability of the material, since the higher the frequency, the faster dielectric breakdown occurs.

Of course, unless I use the equivalent for an linear electric motor that uses electrostatic charge with 3 phases:

Source: https://www.sciencedirect.com/science/article/abs/pii/S0957415814000324

... Buuuut I don't know how to mass produce it with these materials...

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There is always hydraulics...

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... I could maybe use a mix of hydraulics and encoders to lock the limbs in certain positions... Maybe...?

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Maybe I could use encoders in the limbs and use antagonistic control like it is done with pneumatics...

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One thing about the Dielectric Elastomer Actuators is that the dielectric material has a dielectric breakdown limit, for example, Silicone Rubber has a resistance of 250,000 volts per cm of thickness. By adding other dielectric materials, such as titanium oxide, teflon and/or dielectric silicone grease, you can increase the resistance to 1.000.000 volts/cm or more.

This is relevant because every dielectric elastomer, as its name suggests, needs a dielectric layer. The thinner the layer, the stronger the electromagnetic force, but the thinner it is, the lower the voltages it can withstand.

Most dielectric elastomer actuators shown in articles have layers with micrometers, or even nanometers of thickness. And accordingly, they need very little voltage to work, but also very little work to do.
It would be wonderful to have a 1 nanometer thick layer with whatever dielectric breakdown you want, but that is not how things work...

Of course, one thing that is also relevant to note is that if you have parallel wires, the voltage is divided by the number of wires.
So, even if you have very high voltage, if you divide by the number of fibers, you don't need thick dielectric layers.
I was thinking on using something more akin to a rope going around the limbs, but it seems that I will need to find a way of connecting the fibers to the limbs, like ligments and tendons.

Well I didn't show many images in this document, so here is a shitty drawing I made explaining:

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The good news is that I could use burnt wood and grass for charcoal and turn charcoal into graphite, then mix it with any kind of plastic, rubber or whatever.

THis plastic, rubber or whatever that I could mix with graphite and/or graphene could allow for a cheap conductive material, while the dielectric layer, the more expensive part, could be applied later.

By the way, mixing white glue and talc in a 70:30 ratio will make a material that acts exactly like plastic (source).
Both are cheaper per kilogram than silicone rubber and plastic, because, like always, I can't fucking find plastic scrap to recycle anywhere.

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Well, I found some websites were people sell scrap of everything, the problem is that I need to own a company in order to even have an account and see the prices.
Luckily, I have family members that have companies and I can buy the scraps through them.

But now I'm divided between actually going through with the dielectric elastomer fibers or the aluminium linear motors...

Speaking of it... Why I can't find dielectric elastomer actuators that are fibers just the way I described? I do wonder if it is because it doesn't work or if it is because nobody thought of it yet...

Which makes me wonder if it would work the same way if conventional electromagnets, although I don't know how one would make fibers have the same electromagnetic polarity...

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By the way, I was complaining that the aluminium linear motors would weight 1575kg in total, but if you remember: dielectric elastomers with 20 grams of weight can lift 1000 grams (1kg) of weight, a difference of 50 times its own weight.

This means that if I wanted to lift 10.000kg, the muscle would weight 200kg (at least), the requirement of lifting 10 tons is due to the fact that this muscle would need a disadvantage of 10:1.

So, if there are 30 of these in total, then it would be 6000kg.

Well... That ratio is questionable in this scenario, those are meant for conventional DEA that are sandwiched by horizontally connected actuators, not parallel fibers.

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By the way, I think I found a method to make the dielectric fibers as thin as possible without the nano needle, it is called "electrospinning".

The only problem is that I can't create single continuous fibers, so I don't know if it would still be okay for dielectric fibers...

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Then, you have 5-3 ton rated hydraulic cylinders that only weight around 10kg each...

... But you would need a single motor or a motor for every cylinder...

Ugh... Back to square 1...

I don't know how to properly size the fricking pump...

Well, I would guess that I "just" need to make an electric motor and pumps with the total horsepower required.

If legs needs 100 horsepower for 1 ton of weight, then I would use x number of pumps that fit in that power input/output.
And then, the body sensors would automatically regulate the oil flow based on the sensors you pressed more during movement.

But even then, I don't know how well it would work. Every hydraulic cylinder needs a fluid flow of 200 liters per minute and around 30 bars of pressure (assuming just 3 cylinders are actuated).
But... If I take the information of hydraulic pumps with 100 liters per minute of fluid flow and stack them, I would need way more than 100 horsepower to compensate...

Or I simply misscalculated things, because I tried again with that hydraulic pump chart from aliexpress and I would end up using around 40 horsepower.... It is probably incorrect (again) because it would mean that I would be able to do the work of 100 horsepower with the energy of 40 horsepower, meaning I simply calculated a perpetual montion machine. lol
Actually, that isn't the case, I recalculated and it seems I actually misscalculated the initial 10 horsepower per 100kg of weight. Huh...

(I inserted too much rpm for the limb and ended up being 109 hp)

Also, the hydraulic cylinders are in diagonal because of the stewart platform configuration, so they would probably need to be even faster than the linear one, which could explain the horsepower.

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If I make a electric motor for every joint, the coils would be too heavy for the insane amperage. If I make linear electric motors, the issue continues. If I make dielectric elastomers, the insane voltages will fry everything and it will still weight a lot. If I make hydraulics, the central electric motor can be too heavy still and not as responsive.

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Screw it, we ball.

I just bought a hydraulic gear pump with a displacement of 28cm³, which would be around 50 liters per minute at 1750 rpm and 98 liters per minute at 3500 rpm.

And yes, I know that gear pumps are not that efficient (80% to 85% efficient) and that they only start pump properly once they reach around 1/3 of its rated nominal rpm.
There are way more efficient hydraulic pumps such as axial and radial piston pumps, but these are at least 10 times more expensive than my little gear pump.

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Now, when it arrives, I will have to make a copy out of plastic scrap or epoxy resin...

By the way, this is how you extend the hydraulic pump:

Also, for some fricking reason I'm feeling utterly stupid because of this project...

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By the way, I don't feel confident on the idea of using a super long hydraulic pump or a pump with multiple stages.

Not exactly because I'm afraid of the precision, but because the distribution of fluid flow through the pump.
For example, if I were to make the pump like the example above, then I would need the same amount of torque to drive a single actuator moving in the mech's body.
If I connect everything in a weird parallel system, the fluid flow may suffer from the distribution and turbulent flow through the system until it reaches the required actuator.

So, the idea is to take this hydraulic pump, 3D model it in Blender and then make a bigger version of said pump, 3D print in resin and then finally make a mold with a physical copy.
Yes, theorically I could "just" take the measurements of a hydraulic pump's blueprint that I could find on the internet and attempt on making a pump.
Actually, I did try that before on previous project logs, but it didn't go well because I didn't had any kind of reference or palpable scale on the pump. So I ended up with a 3D model full of mistakes that I couldn't tell for sure if it would actually work or not.

(I would have posted the screenshot of what I'm talking about, but the archive where I used to make 3D model sketches got corrupted and I lost a lot of things)

Being honest, I don't like this idea that much, because I feel it would be a waste of time and money to buy a perfectly useful pump just to throw it away. But hey, I will at least try it.

Oh yeah, I also have the option to literally 3D scan the thing.

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By the way, I did look for solenoid valves to use as solenoid pumps, but they aren't efficient, and on top of that, they never tell the pulling force that the solenoid has, only the holding force, which really doesn't matter in this specific use.

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Also, I forgor the dimensions of the hydraulic actuators:

85mm of bore diameter, 50mm of rod diameter, 30 bar of pressure, 311.7245 liters per minute to achieve linear velocity of 1.4m/s with 1000kg of force.

Pump needs around 10Nm for 30bar and 3500 rpm for 100 liters per minute of fluid flow, needs 14 horsepower (30Nm + 3500rpm) per hydraulic cylinder.

For a single  leg, this would be 44 horsepower (90Nm + 3500rpm). Assuming that every limb actuates (legs + arms + torso) = 220 horsepower, however, not all limbs will be activated at once, neither at full force and speed. Still, the electric motor/pump must be built to achieve that, even if for a few brief moments.

Now, I'm between adding chain-gears from motorcycles/bycicles to connect both pump and motor, but I would love to make a direct connection. Le problemo is that I don't know if I have enough precision for that.

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The hydraulic pump arrived today, I will disassemble this bitch tomorrow (newsflash, I don't have the the tools to open this now, I need to buy them, I've been using those jaw locking clamp pliers and hammering the living hell out of it and the screw didn't move a fricking milimeter).

By the way, this thing weights like, 10kg or so, and even though the insides are completely oiled, I couldn't even rotate the axis.

Note to myself: when you double the scale of a object, its volume increases 8 times.

I doubled the size of a cylinder with 1 liter of volume and it changed to 8 liters, square cube law guys.

This is relevant because of the 3D model of the hydraulic pump.

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Even though I'm first focusing on the pump, even if I'm able to make the electric motor to run all of this, I don't think I will be able to supply enough energy to it either through batteries or generators.

I'm afraid I would require to use copied combustion motors for it...

Actually, I don't even know if copying a conventional combustion engine would even work. You see, they are built with the strength of Steel in mind, no the strength of plastics and resins.

An HDPE piston rod would need to be around 3 times thicker than the aluminium one.

Also, I do remember that once I showed some scientific articles showing micro generators that I could DIY. The "trick" is to use a gearbox that converts the output shaft rpm and torque to a very high rpm and very low torque.

... I mean... Whatever, one thing at a time. Now hydraulic pump, next electric motor, next ESC, next combustion engine, next generator.

Now I need to make a hydraulic pump based on a real hydraulic pump.
Then I need to make the hydraulic valves.
Then I need to make the hydraulic hoses.
Then I need to make the hydraulic tank.
Then I need to make the electric motor.
Then I need to make the controller of the motor.
Then I need to make a combustion engine from scratch.
Then I need to make a generator.

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No matter what I do, this fucking screw doesn't move a single milimiter.

I literally crushed it using my vice and hammered the entire thing in an attempt on moving it.

My jaw locking clamp plier is all messed up.

And I don't know if I actually bent the hydraulic pump by accident or if it already came like this.

The gears are turning just fine, so it i probably just superficial level stuff.

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Just now I remembered that you could use a heat source to force the metal do expand, I just don't know if it would work or damage the hydraulic pump.

It is me from the future.

My heat-gun broke.

It literally spilled its heating wire in a molten metal mess.

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My aunt's husband is a mechanic, I asked him to try to take it off. I will receive it back in at least 2 days. I just hope I didn't actually bent the inside of the pump/screw, wasting three fricking hundred bucks...

In either way, I'm so f*cking pissed right now that I'm willing to actually buy another pump from the same seller, but paying more for him to disassemble it for me.

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FRICKING FINALLY!

By the way, my uncle unscrewed the pump, I still had to hammer this crap for the parts to separate.

The video tutorials always show the disassembly process like a walk in the park, but me? I just idented every single part of this accursed thing trying to take it apart.

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Dunno if you can see it, but basically, this is a shaft seal. I couldn't take it off for the life of me and now it is completely ruined.

There isn't a single goddang tutorial on how to replace this specific type of seal, I bet you literally need to burn it off and when replacing with a new one, use heat to fix it in place.

It seems to be this type of seal, unfortunately, it isn't like the one in the image, or else I could've actually removed it.

Needless to say, this seal is fucking awful, I will need to use a new one in the new hydraulic pump.

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I'm half procrastinating, half sick as hell. But hey, buying an actual hydraulic pump wasn't that bad of an idea after all...

You see, I checked all of those highly detailed 3D models on GrabCAD and I noticed that they never have things right when it comes to the gear teeth and sealing in general.

However, one thing that actually makes me kinda regret it was those functional water gear pumps on thingiverse and the like.
I could've actually skipped all this trouble by 3D printing and molded those things from the beginning. But a part of me says that they wouldn't perform as well as actual hydraulic pumps (not that I have the resources those youtubers have to test all these parameters).

In any way, I think I should start scanning the parts on a printer scanner so I can make vector shapes from those things.

And yes, I did try to find blueprints from which to make these vector shapes, but I couldn't find any.

If only I found an image like this with every part...

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For some reason right now I'm kinda interested on the possibility of linear screw actuators, they have an efficiency as good or better than the current hydraulic system that I'm planning, and they are supposedly easier to make.

(Like I said, I need to make these things quicker or else I end up changing my mind after I already bought all the materials.)

But... I don't know...

I really need someone's help with this project... :/

I know that I said "hydraulics are simpler than electrics", but now I'm in face of a electric motor that would need 300 amps and 900 volts to drive a hydraulic pump that I don't even know if it woud be efficient or even practical.
How I even begin to design the ESC for this beast?

I made the math, and I would need 2.5kw for each screw actuator, but 12.5kw for every pulley actuators.

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The only issue I have with this idea is that I always assumed stewart platforms to distribute its loads equally between all actuators at all times, which is not the case.

I was thinking of using something like this... But I don't know if this stewart platform is hyper flexible because it has extra actuators or because of its unique joints.

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Well, guess what?

I was right, unfortunately.

In a rough estimation, if a stewart platform is expected to handle X amount of weight/load/force, each actuator should be able to output and/or withstand at least Y amounts of that force/weight/load.

And the general rule that ChaGPT/BingGPT/PoeGPT comes with is that each actuator should at least be able to output 1.5 to 3 times the force you want to output and withstand a load of 7 times the output force.

Whenever I choose hydraulics, mechanical or electrostatic actuators, this is the "rule of thumb" for the stewart platform, and thus, the actuators would need to be built accordingly.
Even if I actually had the capability to properly calculate all the loads, I would still need a similar factor for safety factor.

Which kinda sucks because this means extra weight for extra strength.

"But Fulano, are you sure you want to trust the stupid ChatGPT?!"

Well, I always ask on forums and other websites specialized on the subject, and most of the time I don't receive answers at all, so this is really my last resort.

Besides, I did receive a single answer on reddit, and it was suggesting that every single actuator to be able to output at least 3 times the force you are expecting to apply.
So literally 9 ton actuators to lift a single ton.
Not exactly great...

Well, since I would need 2.5 kW to move 500 kg at 1.4 m/s, then I would need 22.5 kW for 4500kg at same speed, and around 45 kW for 9 tons.

A freerchobby 15kw motor weights around 2.88 kg, and since I would need 30 of these (at least), it would weight 86.4kg (at least).

There are in fact, 45kw motors out there and these often weight around 5 to 7kg, so 150kg to 210kg in total respectively. But I think that is overkill anyway.

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Now, unfortunately, I will have to figure out the number of poles, turns and teeth in this electric motor, just like the REB-90. I had all the time to do that with that motor, but now I have to do the same thing all over again...

Well, I couldn't find any information on the motor, but I found this one:

It is named a "30kw freerchooby", however, when looking at its wattage output, it actually peaks at 26kw.

It is said to have 

• MOTOR: MP 15470
• KV: 55
• MAX POWER: 30KW
• RATED POWER: 12kw
• MAX CURRENT:300A
• ESC:120V 500A ESC /22S 500A ESC
• MAX VOLT: 100V
• RPM: 5500
• SIZE: 154 x 69.5( without shaft )
• TORQUE: 50Nm 
• THRUST:60KG
• POLES: 20 (40 MAGANET)
• SLOT:36
• PWM:8-16KHZ
• TIMING DEGREE: 15 
• NET WEIGHT (kg):3.5

I don't know what "net weight" means, but I will guess that it is the weight of the motor. So, with 30 of these, it would weight around 105kg.

And dammit, it also has 300 amps, how the hell does this produces only 50 Nm of torque with 300 amps while the REB-90 can produce 300 Nm with only 100 amps?

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Well, f*ck.

I decided to make the screw actuators instead of hydraulic cylinders, but now that I actually calculated the weight, it would be a pain in the butt either way.

Basically, making the screw actuators with HDPE tubes with 50cm of length, 20cm of diameter and 3cm of thickness, it would weight around 8kg each (believe or not, when using beam loading calculators, the thinner I made the walls of the hdpe tube, the stronger the load it was able to withstand for some reason.

8kg x 6 actuators per limb x 5 limbs = 240kg in total.

Well, this is optmized to simply withstand 2000kg of weight in either compressive or bending loads, and since I need to make not only the screw, but also the outer tube to hold it in place. With 20cm of inner diameter and 5cm of thickness, it would increase the total weight to around 27kg each + 3.5kg of each electric motor.

30.5kg x 6 actuators x 5 limbs = 915kg

bruh...

Now I know how aerospace engineers feel.
Like a rocket, the heavier it is, the more thrust you need to move it, and more thrust requires more fuel, which makes everything heavier.
Obviously, rockets don't go infinitely in this loop, I "just" need to find a weight to force ratio that allows this mech to exist...

Each brushless motor is capable of lifting 2 tons and a little more, but goddang it, I will need to spend 50horsepower just to stand and walk?
And even if I didn't use an independent brushless motor for every limb, I would still need more and more powerful motors to pump hydraulic fluids.

Well, I asked ChatGPT for advice:

"Interpretation
A weight to force ratio of 0.4575 means that for every kilogram of the actuator system, it can handle approximately 2.18 kg of force. This ratio is a useful metric to assess the efficiency and effectiveness of the actuators in handling loads relative to their own weight.

Summary:
Total Actuator Weight: 915 kg
Total Force Capacity: 2000 kg
Weight to Force Ratio: 0.4575

This analysis shows that your actuator system is relatively efficient, given the substantial load it can handle compared to its weight. As you mentioned, this optimization challenge is similar to what aerospace engineers face, balancing strength and weight to achieve the best performance. If you need further optimization, consider materials with a higher strength-to-weight ratio or redesigning the actuator assembly to reduce weight without compromising structural integrity."

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Then I asked again:

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"Carbon fiber composite weight reduction:
Carbon fiber composites can be around 70% lighter than HDPE for the same strength.
If the HDPE actuator assembly weighs 30.5 kg, a carbon fiber version might weigh approximately 9.15 kg (30.5 kg * 0.30).

New Total Weight:
Weight per actuator with motor: 9.15 kg + 3.5 kg = 12.65 kg
Total weight for 6 actuators per limb and 5 limbs: 
12.65 kg × 6 × 5 = 379.5 kg
12.65 kg × 6 × 5= 379.5 kg

Force to Weight Ratio:
Given the force capacity remains 2000 kg:
Weight to Force Ratio = 379.5 kg
2000 kg = 0.18975

Weight to Force Ratio = 379.5kg/2000kg = 0.18975

This means the system can handle approximately 5.27 kg of force for every kilogram of the actuator system, achieving a force to weight ratio of over 5."

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And yes, I know ChatGPT is not the most trustworthy AI bot out there, but honestly, do I have any choice left?

In any manner, I do think I'm looking at this problem through the wrong perspective.
This is a Screw actuator, not a hydraulic one. I don't need 100% solid walls, I could make these with holes and protuding structures and even hollow beams for support.

On top of that, even if eventually switch back to hydraulics, I do think that 30 bar of pressure is just too low for the actuators.

HDPE can survive even 30MPa of tensile strength and compressive strength, I could elevate the hydraulic pressure to 150 bar (15Mpa) or even 200 bar (20 MPa) and stay with relatively smaller components.
For example, if I increased the pressure to 150 bar, the hydraulic cylinder would need to be only 6.5cm wide inside of it, and a wall thickness of 5cm, it would only weight 5kg, maybe 2 to 3kg with the rod and valves. And it would result in 8x6x5 = 240kg in total.
Of Course, this is counting in the pulling hydraulic actuators, I doubt they would be capable of pushing.

---

I used pressure vessel calculators and it seems like 5cm of wall thickness is ok enough, but 7cm is the ideal thickness.

Now I need to figure out what should be the ideal thickness for the rod of the hydraulic cylinder, and then recalculate the weight.

It seems like 10 to 15cm of diameter for the rod is enough.

By the way, in hydraulics, the pushing and pulling action are absurdely different in strength, accordingly to the hydraulic calculator, this 6.5cm wide hydraulic rod would push with a force of 5000kg while the pulling force would be 2000kg.
You can "solve" it by making the hydraulic cylinder a double rod, but then you will have a giant rod sticking out of the back of the actuator.

Both would weight around 10kg together, and since there are 30 actuators in total, it would weight around 300kg in total. By the way, this is with a safety factor of 7, even lighter than the screw actuator.

... But this is weird, it has more or less the same dimensions of a 3 ton steel hydraulic actuator, but it weights just as much...

Well, I reached those results (wall thickness, rod thickness etc) by using online calculators and inputing the yield strength of HDPE (25 MPa) and things like that, however, now that I directly asked all the GPTs around the internet, they actually calculated/said that the dimensions of the materials would need to be severely bigger in order to withstand its strengths.

For example: I did calculate the pressure vessel to have 5 to 8cm of wall thickness for safety factors, but being a pressure vessel is different than being a pressure actuator. So I presume it would need to be even thicker (and thus, heavier) for safety and strength related to sustaining both the pressure and the weight put on it.

In the screw actuator I actually took that into consideration and you could use virtual spring/impact dampening with the electric motor programming, a hydraulic cylinder would need something similar, which if I recall correctly, is named "snubber" for some reason.

---

As you have noticed, I'm kinda stupid, and I completely forgot to considerate the weight of HDPE composites and not only HDPE.

For example, I was planning on using flash graphene and/or milk graphene to incraese its strength, not to mention fiberglass and silicon carbide.

In either way, fiberglass and silicon carbide can double to triple the strength of polymer composites with around 30% per weight. Although I don't have the information about how much graphene increases the strength of a material per weight, we can make a conservative estimation that it would also double the strength.

However, adding all the three at same time may not result in an "adding" of strength nor in a "multiplication" of strength.

I don't know what should be the ideal mixture, but I would risk going 10% of each and 70% of HDPE.

I asked multiple times to all the ChatGPT's out there and all of them said that it could increase the tensile and compressive strength to around 2 to 2.5 times if all three are added individually, but not together.

Well, in any case, their sources normally observe that when making a non-uniform composite of HDPE, the benefits start disappearing when 30% of the additional material per weight of HDPE is reached. You could use either 30% of a single one or a mix of all three.

In either case, I'm adding the three because of by uga-buga brain says that the safety factor would surpass even though my conservative estimations are just 2 to 2.5 times.

Either way, it would only cut the weight to around half, from 900 kg to 450-500 kg in total, and taking out around 40% of the weight trough the honeycomb structures that I was planning, the total weight of the actuators could still reach around 180 to 200kg.

(the electric motors will also weight around 90-110kg on top of that)

Although considerably better, it is still a lot and I would need to check the final weight of other actuators.

Don't forget the fuel (200kg), the pilot (100kg) and skeleton (not known yet).

---

Just now I noticed that I've made a 2 ton actuator and not 4.5 ton, which is not the value I need to output.

It should be at least 1.5 times the value, so 4.5 tons, which would still make both electric and hydraulic weight even more.

In any manner, I remembered that structural solidity is not the way of optimally using polymers.
In short, a rope rated for 2 tons made out of polyethylene will always be the same size than a steel rope made for 2 tons, but lighter and cheaper.
So, the optimal way of using HDPE in the actuators is not structuraly, but in tensile applications, like artificial muscles.

Well, well, well... How many times I will be sent to square 1 until I learn my lessons?

Now I need to figure out a way of calculating how much force the HDPE threads need to withstand with hydraulic McKibben muscles, and that was one of the reasons I discarded the idea: I couldn't figure out how to reliably calculate McKibben muscle sizing and output.

I found this article that shows stackeable and modular vacuum artificial muscles, I should take it as inspiration for the Mckibben muscles for ease of production and the like.

-

---

I don't know, but maybe I'm just trying every single alternative before making the next step.

For example, I would love to make and test the dielectric elastomer fibers that I described.

And on top of that, I was "researching" a little bit about plasma jet engines, some time ago a team of chinese researchers made a microwave plasma thruster that used a few kilowatts of power.

Although we already have combustion engines, this one is interesting because you don't need the complicated stuff surrounding the combustion ones (supposedly).
So, the idea would be to replace everything on a combustion engine by plastic or cheap metals and having a lighter and cheaper engine.
(I said the same thing about the hydraulic actuator and it endend with the same weight and size)

Maybe I could make an electric engine to rotate a pump with hundreds of horsepower without using copper, laminates or complex electronics.

The first big issue with this thruster is the heat it produces, they needed to use a metal base with the plasma going through a quartz channel.
Even modern cutting edge turbine engines that use super alloys to survive its absurd temperatures, they still use ceramic coatings and air/liquid cooling channels in the turbine blades.
The only thing that makes me thing that one could maybe make a conventional metal turbine is the possibility of using these cooling channels, after all, that is how plasma cutters survive.

(plasma torches have 95% efficiency on thermal transfer by the way)

The only thing that makes me think that this might actually be lighter is that HDPE is better at making ton lifting ropes than actual hard structures.

By the way, this one of the methods to 3D print metal:

-

---

---

Energy Source:

I don't really know what to use for energy source for this thing.

I mean, obviously I would need to plug it on something, even if it is the electricity of my house, but I don't know how to supply kilowatts of power with a cheap equipment that I can buy online.

Remember: I can only spend 300 reais (60 dollars) per month.

Which makes things... Hard.

-

---

Also, I just found out something interesting.

On half a hundred project logs ago I thought on using alkaline fuel cells instead of other sources of energy, but since the density of hydrogen is really small, it wouldn't be viable to go carrying a 500 liter high pressure hydrogen tank around.

And one of the interesting stuff I learned is that alkaline fuel cells could theoretically use any kind of fuel containing hydrogen, including hydrocarbons. However, the carbon content would poison the sodium hydroxide (responsible by the reaction and name of this type of cell) and make the fuel cell useless.

However², I just found out that there are molten alkaline direct carbon fuel cells, which uses a molten Sodium Hydroxide at around 650ºC to convert hydrocarbons (fossil fuels) and air directly into electricity.

Supposedly, it can reach 80% efficiency. However, as you can imagine, their useful life-span is not that great, and the paper I linked above uses Inconel alloy 600.

I searched online and I could find a sheet of inconel mesh with 30cmx30cm costing around 500 reais (100 dollars).
I don't know if that would be enough to completely supply a 200 horsepower fuel cell...

Also, it seems I was mistaken, the "direct carbon" part literally means that it uses solid carbon as the fuel, not hydrocarbons.

Somehow, coal and graphite have energy densities equal or higher than hydrocarbons. And yes, this includes charcoal.

Which makes me wonder: should I use the heat of the molten electrolyte to turn the bio-mass into charcoal?

Direct carbon fuel cells supposedly could also use solid hydrocarbons, the only solid hydrocarbon I found was paraffin wax/paraffin oil.
Dunno if they would work as well as coal and the likes on this type of fuel cell.

Unfortunately, it seems like this type of fuel cells is kinda of a single use type. It needs water to keep the molten hydroxide from carbon poisoning, so, if the water runs out, the cell will eventually stop working.

The article I linked above (which I should've read completely before posting) says that the material lasted around 40h in an average of 1 watts (that kept decreasing).

Which is an interesting time span for this system, but it also means I would need to increase the system by 100,000 times more to reach 100 horsepower.

Which is not possible.

So all of this section was a waste of time.

Well, actually, since I said earlier that this fuel cell has the same energy density than gasoline, then it would be safe to assume that I would need around 100kg of charcoal to power it for the same amount of time.
I just don't know how big the electrolyte chamber would need to be to convert all the carbon into electricity on demand tho. 

It is like having a firebox/boiler, how much charcoal I can pump into it without suffocating the flames?

One way I thought on doing that would be by calculating the heat in the mass of the electrolyte and calculating how much of its heat it would lose depending on the amount of kilograms of carbon mass and liters of air it would receive to realize its chemical reaction..

I forgor the exact numbers of joules and the like, but I would need 20 kilograms of molten sodium hydroxide electrolyte and inject 20 kilograms of charcoal with 200 liters of air per hour for 100 horsepower-hour of energy.
This would be like, 0.333 kilograms of charcoal per minute and 3.3 liters of air per minute, you could literally supply the air with a computer cooler fan. lol

My only concern is that I'm unsure on how much energy I will actually be able to collect, my insecure mind tells me that I really won't be extracting 75 kilowatts of power with a simple inconel and copper mesh like in the article I showed before.

Well, I asked again and again and again to every type of chatgpt that there is out there and reached a rough estimate of a metal mesh size required to output 100kw of power with this fuel cell.
It changes from 12 square meters and 10 square meters, so basically, metal meshes that are at least 10 meters wide and 10 meters long, which would weight around 20 to 30 kilograms.

And since inconel metal mesh is expensive as f*ck, I will be forced to use Stainless Steel 316L or 310 and use welding rods that come in that grade.

I'm back again, and accordingly to my calculations, I would need around 40kg worth of stainless steel 316L welding rods in order to reach 10m², which would cost around 5000 reais (1000 dollars). Which is not viable.
However, I calculated what would be the value with 1kg of steel 316L wire with 0.8mm of thickness and it would be around 19m² of surface area.
My only concern is that this could fricking melt the goddang wire...

... Even though I like the idea of using this supposedly simpler fuel cell, I don't feel confident on this idea, specially because I don't see how this would generate around 100 to 300 horsepower peak with this setup...
And this is still using MOLTEN SODIUM HYDROXIDE.

Every idea I try to explore (mentally) I feel like it is not going to be practical enough, I guess that is the biggest obstacle of every research on exoskeletons/mechs.

(being honest, I don't even know which one is best: molten carbonate or molten hydroxide fuel cells)
(definitely molten hydroxide, lithium carbonate is expensive as f*ck)

-

---

Oh crap, just now, after 2198398021389 project logs and going through article after article about fuel cells and fuel reforming, I finally found a compact equipment that can actually convert hydrocarbons into hydrogen.

It is called a "plasmatron fuel reformer" or "plasmatron fuel cell", however, it is a relatively new technology and I still didn't go through a lot of articles, but it seems it can be both used as a fuel converter and as a fuel cell.

Source: https://www.sciencedirect.com/science/article/abs/pii/S221298202030113X

There is a lot of different types, but it is said that the vortex design (the above image) is the most efficient until now.

I just read the article and it is about converting Co2 into other products, but maybe you could use to convert hydrocarbons into hydrogen?
The only problem is that... Well, at this point, I don't know if using hydrocarbons is efficient for hydrogen generation, you are basically waisting half of the fuel to take out the hydrogen.

In 1 liter of gasoline, you have around 34 megajoules (34 million joules) of energy, then, taking the hydrogen out of this one liter, you get around 14 megajoules of energy in the hydrogen content.

Well, I asked PoeGPT to take the values hydrocarbons alone (gasoline, kerosene, methane etc) and make a conversion of 30% (assuming it is the conversion in a combustion engine) and then take the hydrogen content in these fuels and making a 60% conversion (assuming it is the efficiency of fuel cells) and interestingly enough, the final energy in joules of each fuel is pretty close.

Which is interesting to say the least, that taking hydrogen out of gasoline and then passing through a fuel cell would generate as much energy as taking the gasoline and passing through a combustion engine.

Although, it does make me wonder how much energy you would be able to extract with a direct hydrocarbon fuel cell...

---

And by the way, Palladium can store hydrogen around 900 times its volume, which is insane.

If palladium wans't a super expensive and rare material, the fuel cell problem would be essentially over.

I do wonder if it would be possible to synthesize materials with a particle accelerator tho...

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Well, while I'm procrastinating to make the 3D model of the new hydraulic pump, I was searching for thermoelectric generators (again).

Although it is not very efficient (below 10% efficiency), it seems like the more you increase its temperature, the more efficient it becomes depending on the materials you use.

There are materials that aren't gold, germanium and the like and work wonders for thermoelectric materials. However, they are still super complex and super expensive to make/buy/find.

The best I can do for now is asking which materials have high "ZT" to chatgpt, and it goes explaining the material is mid at best.
For example, copper oxide, silicon carbide, silicon metal, graphite powder, iron, nickel and the like.
Supposedly I would need to make a good mix of materials to increase the efficiency of the thermoelectric generator.

It needs to have good electrical conductivity, but low thermal conductivity and good seebeck coefficient.

If I could precisely calculate what values I need, I could try and elaborate a good ratio of material for each characteristic I require...

-

---

I'm still procrastinating while "studying" about combustion engines, and one very interesting thing I came across whas porous recuperator combustion engines.

Basically, on the top inside of a piston engine cylinder they insert a porous mesh were the fuel is injected through and during combustion, instead of a conventional flame forming, all of the fuel is combusted in the recuperator, basically making a hot-air engine.

Source: https://www.researchgate.net/publication/50283981_Potential_of_Porous-Media_Combustion_Technology_as_Applied_to_Internal_Combustion_Engines

The same applies to turbine engines.

It is also increases the efficiency of thermoelectric generators if you pass the flames through this said porous material, since the heat will be transmitted more efficiently through this porous material.

Source: https://www.mdpi.com/1996-1073/15/15/5597

The best way I can think of how to explain this is that it is that the porous media acts like thousands of micro fuel injectors, burning the fuel and air as efficiently as possible.

However, you need to size it properly, or else the air bubbles will become traped in the material, producing a heat insulator (like the ones in the space shuttle) instead of a fuel burner.

---

---

Structure:

I don't know what to use as the structure, I was thinking on either buy HDPE or get more aluminium scrap, I still don't know what to do with it...

Also, an idea for the structure: rolling contact joints.

These seem quite interesting.

03/02/2024, 15:55, Saturday.

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So, remember when I said "You can't run from the laws of Physics"?

Good, because I should listen to myself more.

Basically, the human body doesn't use 300 watts, it uses the same amount of energy as any other equipment.

If the human muscles used less energy than it produces, this would mean it is a perpetual motion machine.

This means that all the equipment that I bought in the hopes that it would consume less energy than it produces is completely useless and stupid.

This means² that I wasted too much money. Again.

In any manner, I will be in my room and thinking on how to proceed with this project. :)

My room:

---

Well, at least I bought Silicon Carbide:

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You know what? I will just post this and let anyone willing to help, give me a hand, because gawd, do I need it...

---

Well, I feel like I'm being ahead of myself again and creating this project log too soon....

In either way, I spent another 300 reais (60 dollars) to buy other materials. But I will only be able to buy the rest of the materials next month (thus my concern to make this too soon).

Now I will have the adjustable power source, silicone rubber, dielectric silicone grease, silicon carbide, sodium silicate and sucrose.

---

An odd selection of materials, but let me explain them:

• The silicone rubber will be used to mix with graphite powder (which I already have) for the dielectric elastomer electrodes.
• The silicone grease will be used to make the dielectric layer on the dielectric elastomer.
  Yes, I did say that I would use Polyvinyl Alcohol and Polyvinyl Acetate to change the positive side and the negative side. But it would be cheaper to do the way I'm doing, after all, I will just test it out.
• The sodium silicate, silicon carbide and sucrose will be used to make the porous heater.
  I will mix the three with water and once it is solidified, I will heat it over until the sucrose turns into dust, leaving a porous structure behind.
  I will use it to test if I can turn 1 liter of water into steam in 1 minute without requiring 47 kilowatts.

---

However, I'm still missing a few things, like the high voltage low amperage transformer for the dielectric elastomer actuator and dielectric pump and the PVA for the hydrogel heater I talked about in Project Log 77.

I will take another month to buy these two and test it out.

---

After all of that, I still need to test my hypothesis on the eccentric electric motor that I also talked about in Project Log 77.

That one will require 3D modelling and 3D printing.

... Which I didn't even started yet... y-y

---

Well, the adjustable power source just arrived, but I can't use because it doesn't come with a fricking plug.
It is supposed to be fed by another power source, either from a bigger adjustable power source or one of those switched power supply.

And I don't have one of these, I mean, I have one, but it is not for this voltage.

Either way I will have to wait for another fricking month until I can actually test some things out.

And yes, I can only spend 300 brazilian bucks per month.

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Highly Porous Heater:

Since I already have all the materials to make this one, I'm still highly confused about the ratios I need for this thing.

I should've had thought this through (history of my life), because I'm pretty sure I would need to test various ratios for the perfect heater in this case.

And I just have a kilogram for each material.

I really should've paid someone to do this for me (like I had any money to do so)...

---

Although... I think it would be easier to make it porous if I used alcohol or the like...? Well, I will test it out on both cases, I bought more than enough anyway...

I also tried to search for electric steam generators that uses silicon carbide as porous heaters, but I had no sucess until now. If I could find a single article talking about it, I could've spared around 100 brazilian bucks...

By the way, Sucrose is just common sugar, I definitely didn't just waste 60 bucks on buying a chemical grade Sucrose without checking it first. Definitely not, this would be very stupid of me.

Just now, after asking for 298398392398th time, chatgpt suggested me using salt. and then dissolve it in water... And paraffin wax...

I mean, WHY DIDN'T I THINK OF THAT BEFORE?!

I could just have used carbon fiber as the heater...

---

In any way, here are some of the ratios I will be testing:

• In the first try I will go with the gut, I will measure the amount I have for each material first and then adding it to a small pot until it "looks right", then I will measure the materials again so I know how much I used for the mixture.
• Then I will try to use a ratio suggested by ChatGPT:
  26% of sodium silicate
  32% of silicon carbide
  21% of graphite
  19% of sugar.
• Next I will try using a ratio suggested by BingGPT:
  20% of sodium silicate
  40% of silicon carbide
  30% of graphite powder
  10% of sugar

---

Well, it seems my intentions of publishing the project log before testing things out actually worked out very well.

For example, Esteban pointed out that using a silicon carbide heater directly in contact with water is a no-go because it reacts with water at 500ºC.

When it reacts with water, it creates Methane gas and Silicon Dioxide, more known as Silica.

This means that if I were to actually use this thing on a steam generator, I would be talking with the angels, because this is literally a bomb.

This is fine.

In any manner, I will try to use only graphite on the porous heater instead of silicon carbide. Maybe I can make a furnace with the silicon carbide for melting other stuff, but for now...

By the way, I will have to wait another 2 months to be able to buy the carbon fiber to be used as the porous heater...

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---

About the dielectric elastomer:

So, it just came to my attention that I don't need two electrodes.

The idea of a dielectric elastomer is that both electrodes attract each other due to reverse polarities.

However, if you make the electrodes fibers, and all the fibers have the same polarity, they will repel each other. Simulating a contraction.

And since you can easily transmit very high voltages and very low amperages through hundreds of kilometers without much loss.

Plus, you don't need make complex stacks:

However, it also comes with many problems:
How to control contraction? How to predict contraction? How much force can the fibers take before failure and/or fatigue?

Electric motors continue to be the kings of reliability and pretictability.

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Off-topic:

Well, like I said before: I need to figure out a way of making the direct contact electric motor.

The problem is that this design is so utterly alien to traditional electric motor design that I don't even know how to start it, I gave the idea of using hypocycloidal drives whre the teeth were the electromagnets. I still think it would be the best option, but I'm simply not qualified enough to figure out how to do it.

For example the only way I was capable of thinking on how to make dual pole teeth would be like this:

Of course, assuming the north and south pole would interact with anything outside of the stator. And then, even if I made all the dozen of teeths on both stator and rotor like this, how I would organize them on the 3 phases of the motor?

So... I think I will be forced to do the conventional way (as shown below), but wobbly just like in the example above:

But I mean, what would stop the rotor from just rotating on the axis instead of wobblling as intended...?

While looking around I found this thing:

Source: https://visforvoltage.org/comment/77084

Way simpler to make and it still has direct contact, both rotor and stator have the same amount of poles...

Another problem on either idea is the phase quantity and sequence of activation. The best I could think of was individually activate and/or reverse each pole with a program and sensors... But the phase and wiring configurations have been used for decades (if not centuries).

Example:

What would be the ideal phase of this thing?

I really need help with this...

---

I THINK I can calculate somewhat how this direct contact motor could produce both as torque and RPM.

In resume, I will just pretend the electromagnets are piston heads rotating a crankshaft. The stroke of each electromagnet is 0.5mm, and as such, the crankshaft will have that same radius.

Only 2 are working, one attracting and other repelling. For such thing, I will try to use the force of the holding electromagnets for this estimate. As such, there will be 4 electromagnets activating at time.

So, a 50kg electromagnet consumes 10 watts, so 4 of these consumes 40watts. Since stacked electromagnets don't add force, then it would be 100 kg of force in total.

So, accordingly with the torque calculator, I would have 0.5 newton meter (I'm already not liking where this is going). And accordingly to the torque and rpm to horsepower calculator, if it had 3000 rpm, it would output 150 watts of power while only consuming 40 watts.

So I would consume around 3.9 times less power. Not the 100 times less power I was hoping...

For example, if I had an electric motor that outputed 100 horsepower or 75.000 watts, I would consume only 34.4 horsepower or 25.641 watts.
This seems to violate the laws of physics, but do keep in mind that the human body consumes at maximum 300 watts in activities while the Atlas from boston Dynamics consumes 3000 watts.

From all the other crazy ideas, I think this one is the most reliable, safe and understandeable to work with.

(it almost makes me wonder if I even should have attempted on testing the other alterntives and wasted my money...)

---

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---

On top of that I will still try to figure a way of using electrostatic current (high voltage low amperage) instead of the conventional ones, essentially making every pole a capacitor.

Not because of I want to make something special or anything like that, it is simply because electrostatic electricity goes pretty well in any kind of high resistance material, unlike conventional currents, which needs copper wires.
I'm broke and I can't be buying copper and custom laminations whenever I like it or not. Simple as that.

The only electrostatic motors I could find were these two:

As expected, there isn't much information o the subject, only claims by patent owners.

As far as I could understand, it works just like conventional motors in the sense that it has 3 phases and the rotor has positive and negative poles.

The problem is that I don't know how much torque and rpm it makes per watt of power, they simply don't care about showing these things...

Plus, it seems like a weird option to use copper as the conductive material, specially since it can suffer passivation during prolonged exposure to high voltages...
I guess that since these are PCB plates it is reeeeally cheap to make them.

---

I think I found them:

Source: https://www.sciencedirect.com/science/article/abs/pii/S0304388620301212

This one is awfully familiar with the first "electrostatic" motor that I've posted up there.

Of course, it is a "Corona Discharge Motor", not electrostatic, if the current is flowing it is not static anymore.

But, as shown in the graphs on the article itself, it has a really low efficiency and a really low power usage.
In fact, it only has a few miliwatts of power.

This guy made and tested his corona discharge electric motor, and the results really meet up.

Friday, 26/01/2024, 08:43

Well, since I bought my power source from Aliexpress, the goddang thing will take 75 days (and some times, more), so I have a plenty of time doing a whole of nothing involving this project.

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You know what? I'm getting a little bit pissed off with myself.

I keep repeating myself over and over with "let's make a turbine, no, let's make a stirling engine, no, let's make a fuel cell, no, let's make a plastic piston engine, no-"

For f-ck sake, I should just shut up and just do something instead of listing 12932893282389 options that I will never use.

... Well, it would help a whole lot if I had any money to begin with...

(this is my hobby, I do it for fun, I'm having a lot of fun)

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Let's talk about energy sources.

What I mean by "universal fuel engine" is that there are multifuel engines that can work with multiple types of fuel, but a lot of them have a small range of fuels.

Of course, you probably don't really need a universal fuel engine, but since I'm broke, the most probable fuel that I will find is grass and wood.

You can't put grass and wood in a turbine engine, neither a piston engine.

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Asking to ChatGPT and BingGPT, steam turbine engines can convert fuel into heat, and thus steam with an incredible efficiency, around 80% or even more.

Of course, this is not a surprise if you ever saw anything about stationary energy production, like one of those giant turbine geneartors.

The bigger the blades, the more efficient they are, not to mention that the whole facility is specially built in order to make the finest control possible on fuel, fuel burn and heat exchange.

Of course, the compromise is size.

Not an issue for a energy generation facility, an issue if you want something energy dense, portable and efficient.

---

These madlads are building a monstertruck motorcycle, and the engine they are using (as shown in the thumbnail) has 150 horsepower, fits in a backpack and could easily power an exoskeleton.

The issues are:

• It can only use a single type of fuel.
• The generators are many times heavier and bigger than the combustion engine.
• Low efficiency, around 30% (not low for combustion piston engines).

Of course, I did find some interesting articles about ultra high speed alternators that could possibly solve the issue of generator size and weight.

(this is a conventional 10 kilowatt AC dynamo generator and it "just" weights half a ton)

The articles in question are the following:

• https://www.sciencedirect.com/science/article/pii/S1876610219313967
• https://www.researchgate.net/publication/224713273_An_Ultra-High-Speed_500000_rpm_1_kW_Electrical_Drive_System
• https://www.pes-publications.ee.ethz.ch/uploads/tx_ethpublications/zwyssig_IAS05.pdf

Of course, these are really small energy outputs, but look at the size of said generators, one of them is as small as a match head.

This means that it would be easier to use a gear box that multiplies the rpm instead of torque.

Of course, there are very low rpm geneartors, but these are not really compact. Although, they are very easy to make... At the cost of size.

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Universal Fuel cells:

Basically, the first thought I had was to use a universal fuel cell, which was the idea of having a fuel cell that can directly use any kind of hydrocarbon fuel.

Of course, I'm not a company, and my Co2 footprint would be completely meaningless compared to the smallest airplane, lol.

In any manner, these supposedly "universal" fuel cells are called "direct carbon fuel cells", and apparently, the most promising ones (accordingly to the wikipedia article) are the solid oxide fuel cells and the molten carbonate fuel cells.

Both are equally complicated on their own, and both are extremely expensive on their own also. On top of that, information is limited I can barely find anything online.

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Another possibility is the use of hydrides.

There are multiple types of hydrides, but the most promising ones are Ammonia-borane and Sodium Borohydride.

When the right conditions are achieved (like heating up ammonia-borane to thousands of degrees), they release hydrogen gas and are further decomposed to boron-nitride and sodium borate respectively.

Like always, information on this fascinating type of technology is scarce and I doubt I would find a way of replicating the results in a DIY way.

Here are some articles that may be interesting to read:

• Effective hydrogen release from ammonia borane and sodium borohydride mixture through homopolar based dehydrocoupling driven by intermolecular interaction and restrained water supply - Journal of Materials Chemistry A (RSC Publishing)
• A comprehensive study of hydrogen production from ammonia borane via PdCoAg/AC nanoparticles and anodic current in alkaline medium: experimental design with response surface methodology | Frontiers in Energy (springer.com)
• Activation of sodium borohydride via carbonyl reduction for the synthesis of amine- and phosphine-boranes - Dalton Transactions (RSC Publishing)

Oh, by the way, "PdCoAg/AC nanoparticles" stands for "palladium-cobalt-silver alloy nanoparticles", I have absolutely no idea how to put my hands on such material.

I said in previous Project Logs, but there are "Catalytic Condensers", which are materials that imitates the actions of catalysts by passing a current through it.

Like always², information on the subject is scarce.
Probably everyone is trying to make a patent and earn a living, it would be nice if scientists didn't need to worry about earning a living with proper support, I'd suppose if I knew what I'm talking about...

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Room Temperature Turbine Engines:

Yes, adding to my list of insane ideas that will probably put me in an asylum are turbine engines that are specifically designed to operate at room temperature.

The turbine on turbine engines face temperatures from the combustion chamber up to 1700ºC, in which most common metals would be in liquid state. That is why turbines are made using superalloys such as inconel.

So, in order to make a turbine engine operate at temperatures closer to a turbocharger or even at room temperature, the idea is to cool the air exitting the combustion chambers as much as possible.

One way of achieving this would probably maybe using vacuum ejectors/jet pumps/steam injectors.

The hot air coming out of the thermally insulated combustion chamber would be at 1700ºC and a pressure around 20 MPa (common pressure inside turbine engines), such insane pressure would result in a very high amount of airflow and room temperature.

The ideal gas law tells that the air pressure is proportional to its temperature, so with such gas pressure expanding at high speeds while exchanging its temperature with the surrounding air, it would create a high airflow.

Of course, this would most probably not work.

If it was that easy to make a room temperature turbine engine, it would have already been done.

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Another idea was to instead use air flow generated by the combustion chamber to drive a turbine on the outside of the combustion chamber.

Basically, the idea would be to do more or less the same thing with the previous idea, but the entire vacuum ejector would be around the entire assembly and the airflow around the engine would drive a turbine.

Imagine it like a reverse turbofan.

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Just putting this here because I think it is interesting:

This is a 60kw microturbine engine with 40% of efficiency.

This one is a 25Kw with an bigger option for 500Kw, it is said to have 85% of efficiency.

Of course, I think it is bullcrap, but in both cases the efficiency must be higher because of the heat exchanger/recuperator.

In both cases it is a design that can fit in a backpack (I think).

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I was thinking of using an electromagnetic bearing on the tip with the generator/alternator unit.

Maybe I could make a DIY titanium aluminide turbine blade, BingGPT suggested Haynes alloy HR-120 (33 wt % Fe, 37 wt % Ni and 25 wt % Cr [and maybe a little bit of tungsten]), which seems... Viable to do at a DIY setup.

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Oh yeah, I completely forgot that I could "just" make a hero turbine engine. The only problem is injecting fuel on it.

(the one in the right)

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Stirling engines:

Stirling engines are the bane of my soul.

They always come up, when I'm trying to find alternative engines, but they usually suck ass.

Not in the sense of efficiency, they usually achieve efficiencies of around 40%, and have almost no moving parts. Of course, the properly made ones, like the ones made by NASA or something.

Most of the time they look like this:

This insane piece of metal can't produce a single horsepower.

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In any manner, let's talk about the properly made ones:

Recently, China has launched "the most powerful stirling engine yet that the world has never seen making a breakthrough that will SHOCK the industry", you know, that clickbait trash.

This chonky boy has 2 fricking meters of length and can produce 103 horsepower, it is meant for use in submarines, to turn waste heat into electricity.

And that is a common theme between stirling engine endeavors: they aren't meant to be the main power source, but a recycler of waste energy.

For the life of me, I couldn't find the diagrams, pdfs, articles or anything useful showing how this specific stirling engine works. Which I'm not very surprised, after all, it is a submarine stirling engine, who in their right mind would share this kind of top-secret machine?

However, trying to find how this ting works, I came across two types of stirling engines that I liked very much:

Free piston stirling engines

(I searched for 1 kilowatt stirling engines like the one in the pic, they are 45cm in height and 30cm in diameter, I need at least 30 of these, lol)

... And thermoacoustic stirling engines

Source: https://www.researchgate.net/publication/301791408_Stirling_cycle_engines_for_recovering_low_and_moderate_temperature_heat_A_review

Thermoacoustic stirling engines have absolutely no moving parts, and they can be used on a compound configuration, basically, mixing all kinds of energy generation systems.

For example, you can mix magnetohydrodynamic generators and free piston stirling engines on the same engine. Maybe even piezoelectric buzzers to convert the vibration into electricity.

Source: https://advanceseng.com/thermoacoustic-stirling-power-generation-lng-cold-energ-low-temperature-waste-heat/

Source: https://www.researchgate.net/publication/281593423_Analytical_study_of_thermoacoustic_MHD_generator

Source: https://www.sciencedirect.com/science/article/abs/pii/S0196890422002990

There is also the https://technology.nasa.gov/patent/LEW-TOPS-80 Stirling patent, but I can't find the schematics anywhere.

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In any manner, I decided that I will stick to the Compound Thermoacoustic Stirling engine for the Universal Fuel Engine.

The only issue is that I don't know how compact this would be.

I remember seeing a few kilowatt thermoacoustic stirling generator that had 0.3 meters of length (30cm), it was multistaged and stackeable, but I couldn't find the gooddang picture again.

I searched for the picture for 5 hours straight and I couldn't find it, I thought I saved it on the thermoacoustic paste...

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I just said this and I found it:

Source: https://www.researchgate.net/publication/276902981_Development_of_a_3kW_double-acting_thermoacoustic_Stirling_electric_generator

It is a 3 kilowatt generator, so I would need 10 of these stacked to a mere 40 horsepower generator. 

It is also stated in the article itself that it only has an efficiency of 16%...

-_-

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While searching for the subject I came across this two way-one way turbine, whenever direction the pulse from the burning element.

Source: https://journal.hep.com.cn/fie/EN/10.1007/s11708-020-0702-3

But I doubt I will be able to do it, my intention is exactly avoiding moving parts.

I didn't even read the articles about thermoacoustic stirling engines so I barely know those things work...

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However, this did gave me an idea. I think I already talked about something like it before.

The idea would be to make a toroidal tube and add cylinders to it, they would be piston heads and this turbine would be inside the toroidal tube.

half of the cylinders/pistons would detonate and the other half would compress the other pistons, just like a liquid piston engine or a pulsometer engine.

The only problem is that I don't know how well it would work or how well

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Thermoelectric Generators:

So, afterEsteban's comments in this project log, it made me realize that maybe thermoelectric generators are a more realistic option, even with its downsides.

Just like I said in Project Log 74, the thermoelectric generator could be 3D printed using Sodium Silicate, copper oxide and graphite.

You know the drill, mix this (thermoelectirc generator configuration:

And this (heat exchanger with a turbocharger):

With the air compressor feeding air like a blast furnace:

And finally, I do think it would be interesting to use the vacuum ejector idea from the "room temperature turbine" in order to use the exhaust for air flow generation, and thus, making a cooler with no moving parts. Increasing the heat difference between the cold part and the hot part.

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Another point I was thinking on making:

I think that I could use a mold for making the DIY thermoelectric generator instead of building a paste 3D printer, like one of those silk screen printing plates.

Basically, 3D printing or paying someone to 3D print a mold for each layer, since these tecnically are two "E"s of each material type connected to each other in someway.

Plus, if I want to make a blast furnace-style thermoelectric generator, I would need to mix not just sodium silicate, but also refractory cement. Because blast furnaces can reach temperatures up to 1800 ºC.

The only problem is that I don't know how to make the hot air to reach all the thermoelectric cells, since the temperature lowers the further it goes away from the source.

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I swear to god, I may be talking big about all these exotic energy generators, but I bet I will just switch to a simple combustion engine and shut up myself on the future.

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Off-topic:

I was looking in the internet and there is a type of propulsion system called Arcjet Rocket, which has an exhaust velocity of 16 kilometers per second, accordingly to the rocket calculator, if the mass was 100kg and the final mass of 99.882kg ( 10 liters of compressed air at 10 bar weights 0.118, which would be ejected into an arcjet for extra thrust), it would accelerate the mass to 60km/h.

However, it is not that simple. Some arcjet rockets use hydrazine (super cancerous chemical) and I can't find an specific value of how many watts it consumes per thrust, but it seems to be highly dependent on the gas used.

I remember seeing one source affirming it consumed 1 kilowatt per 0.1 newtons of thrust, this would be around 100 kilowatts per kilogram of thrust. lol

Well, this paper had some graphs that would say that it more or less consumed around 90 volts and 10 amps and generated almost 180 newtons of thrust, this would be around more or less 50 watts per kilogram of thrust, which is more than electric motors.

21/01/2024, 08:22, Sunday.

I'm quite stoopid, I already said I gave up on the project, but I can't, for the life of me, just give up.

And besides, like I said on previous logs: looking for artificial muscles/soft actuators is my hobby now.

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What I need to look for?

In any manner, using electric motors and combustion engines is a no-go for robotics, since a human speed exosuit/mech/robot would need megawatts of power to lift tons of weight, the only way I can make these viable is to reduce the consumption for at least 100 times.

And for that, I need to find a good actuator option that has a power-consumption below 1 watt in order to make this thing viable, more precisely, around Miliwatts of power. Which is 0.001 watts.

Electric motors are complex machines, but are very reliable and precise, I would love to "simply" make an electric motor that uses 0.3 watts (or less) per kilogram of force at 40m/s of speed... But it is not that simple.

One way I could think of was to reduce the air gap between the stator and the rotor to micrometer or nanometer distances. After all, the smaller the distance between electromagnets, the stronger the electromagnetic field.

The issue is: the stronger the electromagnetic field, the stronger the eddy current, the reluctance and a myriad of different things.

Every type of electric motor is an ecosystem on its own, and in order to figure it out, I would need to understand the fundamentals of electric motors.

---

With that in mind, I found myself looking at a concept called "zero air gap permanent magnetic machines" with this paper: https://digital.wpi.edu/pdfviewer/9p2909417

One of the suggestions is using ferrofluids to "close" the gap, but as far as I could see it, it actually had some substantial effects, like almost doubling the torque of the electric motor.

But still nothing close to miliwatts...

It makes me question if the micro/nanometer gap would even make any difference at all...

Ah, by the way, the article talks about a company specialized in super tight tolerances and super dense brushless motors called "Thin Gap", which uses a slotless winding that I couldn't quite grasp how it is done.

This one is said to have 100 kilowatts of power.

The paper I linked above kinda explained how these are done, but I don't think I quite grasped it yet.

In any manner, I can't find anything on the subject as much as I like, so I don't think I will have any luck trying to DIY my way into this type of exotic BLDC motor (and unfortunately, I would love to)...

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I also searched for other articles:

• https://www.researchgate.net/publication/322650195_Airgap-less_Electric_Motors_with_External_Rotor
• https://www.mdpi.com/1996-1073/13/17/4286
• https://www.researchgate.net/publication/319035525_Airgap-less_electric_motor_A_solution_for_high-torque_low-speed_applications

If I didn't read it incorrectly, you can achieve up to 4 times more torque with the same amount of energy, which would reduce the power consumption from 3 megawatts to "just" 750 kilowatts, which is like, 1000 horsepower to lift 1 ton of weight.

Very interesting results, but nothing close to miliwatts...

They achieved that (if I'm not mistaken) by making the electric motor's rotor enccentric, so it physically touches the stator's teeth, like a radial piston engine, except with electromagnets instead.

So, if they literally physically touch and can only multiply the torque by 4 to 5 times, then this is probably a dead end.

The only reason the rotor strength doesn't increase even more is due to the fact that it is eccentric, only a small part of the rotor is touching. Only 2 teeths out of 17 teeths are in direct contact with the stator, so I could imagine a maximum increase of 8.5 in torque if full contact was possible. And it would probably be possible by stacking the eccentric just like radial engines did:

Assuming a gross approximation of simply taking 3000 Nm (to lift 1 ton at 30cm distance) and divide it by 4 and then further by 8.5 it would reduce the power consumption to 2300 watts from 78,000. Resulting in a total of 92,400 watts, or 123 horsepower for a full mech/exosuit.

This is a reduction of 32 times, not 100, but it seems viable to me.

Well, I do wonder how long these eccentric direct contact electirc motors would last, even with proper lubrication...

One could shape them like gears... Which would be interesting...

Hum... This makes me remember of this type of pump:

Maybe an hybrid of both could be made for a hydraulic pump?

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Oh yeah, I think this is relevant, but I don't know how to explain in a quick way. But basically:

The directly-tounching electromagnetic teeth of the electric motor work more or less the same way the holding electromagnets.

These use very low energy, around 14 watts to hold 100 kilograms (0.14 watts per kg), and the direct-contact electric motor would do the same. But like I said: it uses this energy to hold such weight, not to move it.

An electric motor with such design would need to take into consideration the distance between the teeth of the gear I showed before, since some teeth would need to be electromagnetically attracted to rotate.
A mere distance of 1mm distance is enough to reduce the electromagnetic field for for more than half of its power, so the teeth's clearance must be very tight and require a very well thought design and control in order to diminish the waste of energy in other distances. Which could make this very expensive to make this custom motor from scratch...

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Yes, I did say that electric motors are expensive, copper is also expensive and so on. But honestly, electric motors are way more understood and widely used than other options. It is way more practical to tell someone to make an electric motor with better precision than to go into uncharted territory and face thousands of different issues that no one has an answer for.

But an electric motor? Ask a professional why the machine is acting in a certain way and they will have an answer.

In either way, I will """just""" need 1 electric motor per mech/suit in order to drive a hydraulic pump.

I will try to study and test every option before I finally come to a conclusion.

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Steam-driven Actuators:

The first thing that comes to mind (besides electric motors) is the steam powered actuators.

There are a couple of ways of achieving this, but first things first:

• 1 liter of water can be turned in 1600 liters of steam.
• Since steam is compressible, these 1600 liters must divided by the amount of pressure that will be used.
• The faster you need to heat the water the more energy you need.
  In 1 Hour takes around 750 watts.
  In 1 Minute takes around 43,000 watts.
• The bigger the pressure, the higher the temperature to turn water into steam. Around 5 bars, the amount is negligeable.
• Electric to thermal conversion is 99%, the thermic energy used to transform water into steam is also 99% efficient.
• Using steam alone to actuate things has maximum efficiency of 30% to 40%.
• Steam powered actuators can lift at least 1000 times its own weight.

With this alone, steam doesn't seem much attractive, but you need to remember that water isn't the only thing that can be turned into steam, neither that using a simple resistor is the only way of heating it up.

Liquids like ethanol, ether and chloroform have boiling points around 30ºC and 60ºC. Which can be used, chloroform is the only one not flammable, buuuuut... It is toxic to humans.

The only liquid that the fricking half-useless BingGPT suggested that isn't flammable nor toxic is Novec 649, a fire extinguisher and coolant that has a boiling point of 49ºC. So it would consume half of the wattage's water.

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In any manner, I found this article:

"Preparation of Linear Actuators Based on Polyvinyl Alcohol Hydrogels Activated by AC Voltage"

Source: https://www.mdpi.com/2073-4360/15/12/2739#

It uses PVA hydrogel with borax (slightly conductive) and distilled water, however, the current used to heat it isn't DC, it is AC at 220V and 500 Hz with an efficiency in the 0.8%'s.

The interesting part though, is that it uses only 0.04 watts of power, around 40 miliwatts and it takes around 1 to 2 seconds for full contraction.

And besides, I don't even know if it would be better to have a central "steam converter" using hydrogel fibers (as in the article) or resistive sponges to make steam and use a Steam Injector or use the artificial muscles to rotate a water pump.

Let me explain:

Steam injectors are water pumps (or steam pumps/jet pumps) with 95% of efficiency in pumping, while the artificial muscle driven pump (imagine a piston engine, but replace the pistons with muscles) would have around 40% of efficiency (and yes, it would still use miliwatts of power even while using more than twice the power).

The steam injector pump rubs me the wrong way because it is fricking steam, it is basically a bomb. Yes, I could limit it to 5 bars (around two times a pressure cooker takes), but even so, it would still be dangerous in some level, specially with the amount of steam required.

... Maybe I'm being too overly cautious with this, fire extinguisher tanks are meant for 2 MPa, around four times more pressure than I intend on using.
I could use discarded ones for the boiler.

BingGPT said I would need around 10 bar of pressure in order to pump a fluid to 5 bar of pressure in a Steam Injector/Jet Pump system.

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I know that it sounds strange to use an artificial muscle to drive a pump, but hydraulics have a lot of advantages, for example:

I don't know how to make a compliant hydraulic actuator, but hot dang, is this fast (and strong, in the description it says it has a force of 10,000 Newtons, or 1 ton).

Accordingly to certain articles, they use a miniature hydraulic accumulator for passive compliance. The only issue I have with it is that they change the stiffness of the compliance by changing the pressure in the accumulator's bag/bladder. Not a big problem of anything like that, I just don't like the extra amount of complexity.

One could simply add a spring accumulator and adjust the stiffness by compressing it more or less, you know, by just rotating a nut or something among the lines.

This paper suggests using magnetic shape memory alloy, but one could also use magnetorheological/electrorheological fluids that changes viscosity with magnetic/electrical forces being applied to it.

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This could mean that:

• Water could be turned into steam with the same wattage using the same hydrogel borax method.
• The use of a highly porous heating element could highly improve the water to steam conversion.

But again, the only way to be certain is to test things out.
But again², I'm broke.

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Dielectric Elastomer Actuators:

Well, if you read the previous project log, you know the drill.

• Dielectric Elastomer Actuators have efficiencies above 90%.
• They can be 3D printed and/or 2D printed.
• They have multiple types of stacks that highly impact its contraction.
• They need really high voltage and high low amperages, around 5000 Volts and 0.00025 amps.
• They work best with really thin layers and really thin electrodes, which can be hard to make.
• Most dielectric elastomers actuators can lift around 50 to 100 times its own weight, which is a problem, but it can be a result of its implementation. The use of fibers can solve such issue.
• Bubbles and material quality can heavily influence the efficiency and performance of the actuator.
• Not many examples out there, this can mean lower endurance.

Source: https://www.pnas.org/doi/full/10.1073/pnas.1815053116

I thought on using a 3D printer with a syringe needle as the extruder in order to make a continuous 3D printed Dielectric Elastomer Actuator stacked in the same manner as in the image.

However, like I said, the thickness of the layers is imperative, and I really don't think I can achieve such insane precision with a DIY 3D printer.

One of the possible methods is using Airbrushers and mixing silicone rubber with alcohol (or acrylic with acetone), which makes the silicone rubber less viscous and allowing for an even thinner layer.
Heating the bed would also allow for faster curing time.

But I would need, like, one of those belt 3D printers.

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One of my ideas for this actuator was to use microfibers by extruding conductive polymer through syringes and making micro-wires or even nanowires. The wires would be the electrodes and the dielectric layer would be over them, the positive side would be covered in Polyvinyl Alcohol and the negative side covered in Polyvinyl Acetate.

This way one could use water to dissolve the dielectric layer of the positive electrodes for power connection while using acetone to dissolve the Polyvinyl Acetate covered negative electrodes.

Well, the idea is that both fibers would attract each other and twist in someway, but I have absolutely no idea if it would happen.

(something like this)

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In any case, I'm at a loss on how I should use the dielectric elastomers.

Should I use them directly into the suit? Should I use them in an piston engine configuration where the pistons are pulled by the artificial muscles?

I feel like the motor thingie would be easier to produce, no? I would need to make the same exact actuator and glue them together in a radial configuration.
It would spin at a predictable speed, with a known force and a known stroke. Either to drive a hydraulic pump or an electric motor (I like the electric transmission idea, but you know, it is very expensive).

While the direct attachment would need to be considered, the fibers need to be glued to the bones (that could unglue at any moment) and so on.
I do like the idea of direct connection, but the constant exposure to outside elements (even with fabric layers of protection) could damage the already fragile fibers.
The hydraulic pulling actuators would be made of recycled, more resistant materials like PVC, Polyethylene and the likes of it. 

Another argument that could be used for the use of artificial muscle driven pump (and valves) is the fact that you can't make precise movements with the Dielectric Elastomer Actuators (DEA), like the Pneumatic Artificial Muscles, it is either on or off precisely because of the way it works. If you apply less voltage in order to parcially contract the DEA muscles, you would also use the parcial strength.
The strength applied by the DEA is equal to its electrical force, so you can't position it precisely, unlikely electric motors and hydraulic actuators which can tweak with its rpm and torque at will.

The only I could think of circumventing this (besides individually activating fibers, which is too labour intensive) is by rapidly turning it on and off before it can actually fully contract.

But this would need an unknown amount of hertz and a encoder on the axis of the artificial skeleton (either of an exoskeleton or mech) for full position control.

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But again, the only way to be certain is to test things out.
But again², I'm broke.

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Dielectric Pump:

Speaking of dielectrics, let's talk about dielectric pumps.

• They also use high voltage low amperage just like dielectric elastomers, requiring milia
• They can also be 3D printed without the precise requirements of Dielectric Elastomers Actuators.
• I couldn't find the efficiency of such pump, but it doesn't matter.
• Its performance depends on the number of electrodes, length of the fiber pump and dielectric properties of the material.
• The fiber pump in the article uses an specific chemical liquid that forces passivation of the copper wires after 3-5 days of continuous use. Passivation occurs when a high voltage low amperage current passes through a metal material, which forces an oxide layer on its surface in the presence of certain materials.

Source: https://www.science.org/stoken/author-tokens/ST-1105/full

The paper of this fiber pump uses an specific dielectric liquid that costs thousands of dollars per liter, however, one could replace it with other liquids, such as oils and deionized water.

It is meant for microfluidics, meaning that using it for hydraulics that needs dozens of liters per minute and several atmospheres of pressure will require way more voltage.

Another concern I have is Passivation.
Although the paper uses a very specific liquid, the passivation of copper (or metals in general) can occur at myriad of different conditions, even by exposing it to air.

Passivation generates a oxide layer on the material, in other applications it is good for corrosion protection, but in this case, it can literally make a insulation layer between the metal connections of the conductive materials.

What a pain would be if every X amount of time the thing simply stops working because an oxide layer was created in every possible connection, essentially killing the electronics?

The only solution I can think of is using conductive polymers (like silicone rubber mixed with carbon powder) in the place of copper on the system that converts the current to very high voltage very low current.
And the only system that I can think of is a transformer, and I'm not very sure about it either.

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I was thinking of making a fiber pump for every individual actuator, which seemed like a good idea, but I'm wondering if it really is.

Each fiber pump has to be at least 5 meters long and have multiple tubes, I thought on wrapping them around each actuator, but taking into consideration the absurd amount of actuators required and the small space they will be fitted in, the pumps would probably be rubbing on each other during activities, and thus, slowly being degraded.

A central fiber pump would be a better option, I suppose, but I find hard to imagine would I would fit a 5 meter long fiber pump with a thickness of a human body inside a mech.

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But again, the only way to be certain is to test things out.

But again², I'm broke.

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Testing things out:

I'm going to try and buy the equipment for this endeavor during next months, but I wish I could already test everything.

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I bought the adjustable power source for around 40 dollars, which is around 200 reais + import taxes.

Here is the pic:

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The first annoyance is that the high voltage converter only works with 400 kilovolts and above, I just need 3 kilovolts, specifically because of dielectric breakdown. The materials that I have available aren't the best, neither the most expensive, unlike the ones used on the dielectric elastomer actuators papers.

There are adjustable kilovolt power sources, but they cost thousands of brazilian bucks.

I will, unfortunately, be forced to make my own.

On top of that, I will be forced to use a faraday cage, because once I saw a guy make a homemade ionocraft while using these High Voltage generators and all of the electronics on his house simply fried because it was liek a continuous EMP.

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I'm 2 minutes in and I already want to give up.

Can someone do it for me, please? y-y

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16/01/2024, Tuesday, 20:47

Converting the 40cm/s of linear speed with the 1/10 mechanical disadvantage of the human body in a forearm with 30cm of length, the rpm of the arm would reach 250 RPM, or 4 meters per second of linear speed (I heard that a punch can reach 45 km per hour of linear speed).

Now, if we input these numbers in an mech arm with 60 cm of length (since the entire mech is twice the size of an average human), and we maintain the linear speed of 4 meters per second, which would give 130 rpm, we would need 6000 newton-meters to lift 1000kg.
By the way, it doesn't matter if the load is put in a difference distance, if it is going to lift 1000kg on the tip of 60cm, the lever arm length won't change the final wattage, no matter how you tweak the rpm and torque, you can't scape the laws of physics.

And, if you input the numbers in a torque to horsepower calculator, it gives you 81,686 watts, or 109 horsepower.

If we take the more "whatever" approach and simply say that the arm and shoulder are the same, the torso uses the same amount of energy and the legs use 3 times more, it would still give 545 horsepower, or 408,750 watts.

This is basically half a megawatt.

If we take a somewhat precise approach and simply multiply the other limbs force requirement by 3, the numbers go bonkers.

109 hp to the forearm + (109x3) to the shoulder, ((109x3)x3) to the torso, (((109x3)x3)x3) to the legs, which would give: 

4360 horsepower or 3,270,000 watts of power.

You would need 3 megawatts of power to a simple mech that moves at same speed as a human being.

It is not "super speed", just "super strength", you would still run miserable 10 km/h with the mech (average human running speed), maybe 20km/h due to the double size of the limbs (a mech even slower than this could be viable, but what would be the point?)

And a exosuit with 100kg of lifting capacity would use 145 horsepower/109,000 watts, not much lower than the mech (a exosuit even slower than this could be viable, but what would be the point?²).

Plus, I'm calculating only a 100% efficient machine, which is not possible. With inneficiencies, the energy consumption would increase even more.

In any manner:

In the end, it is indeed it is 81.6 watts per kilogram of weight at 4 meters per second of speed. A simply legged exosuit would consume around 8 kilowatts/10 horsepower for every 100kg of weight being lifted at 8 meters per second, half at 4 meters per second.. Not great, not bad, I'd rather say.

(by the way, the lightest mech in Armored Core's weight around 35 tons)

But, as a consolation prize, maybe walkers will be viable, since they don't need to carry the extra weight the arms and torso would need to carry. xD

Maybe some day I actually try to make a walker-forklift hybrid, but who knows...

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Oh, by the way², you would spend 35 to 40 horsepower for every 100 kilograms if you were using drone motors to lift your body weight, so you could jump around like you are in zero gravity (or with super human strength, lol).

This would make 260 watts per kilogram, but you would need 4 times more power to to make things move 4 meters a second. Dunno if it would make sense to insert a lot of propellers in a humanoid mech.

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Well, one thing I noticed: the Boston Dynamics robot Atlas consumes around 3000 watts-hour during exercises.

Since the robot carries a 3000 watt-hour battery and can only do it for 1 hour, then I'm assuming it uses around 3000 watts per hour. It can move at around 2.5 meters per second and carry maximum 14 kg of load while the robot itself can weight around 90kg to 195kg.

It is hard to find a definitive answer, I can only find scattered information through news articles about the subject. The website from boston dynamics also doesn't give clear information on the subject either.

https://bostondynamics.com/atlas/

On top of that, there are other versions of Atlas, some weight almost 200kg, the shorty white one weights around 90kg.

In either case, I do think it to be strange for this robot to be able to only consume 3000 watts while carrying weight and it might indicate that in fact I'm calculating something wrong.

But taking the 81.686 watts I calculated before and take the force and speed out of it, it makes a little more sense. The robot carries 10 times less weight and at 1.6 less speed, so in total it would be 5105 watts or 6.8 horsepower.

However, the robot is said to only consume 3000 watts or 4 horsepower without the stewart platform skeleton where the load is proportionally divided by all joints.

Of course, there can be a lot of information that is not specified, including the way the robot moves, the way it distribute its loads and so on.
Not to mention that the marketing department simply took approximated values and putted them into the website.
After all, a stepper motor may have a rated speed and torque, but its actual capabilities can only be shown into a graph.

But... I think it is realistic to assume that the estimate I've made is correct.

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It happens that I wrote so much on the first Project Log 74: Tech Tree for Mechs¹. that the hackaday Website started deleting older text. :|

I contacted the Hackaday email asking if it was possible to check older edits so I can copy the part that was deleted (I received an automatic email response saying they would take like a week to answer).

... And no, I don't write my project logs in a other documents. Yes, I'm that stupid.

... And that is why I completely lost whatever it was deleted. Forever. :|

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I literally cannot write a single new phrase on the previous project log, but basically, I think it would be worth it making the electromagnetic artificial muscle I suggested making with the nanometer 3D printer with actually the airbrush 3D printer.

I know that it would take ages 3D printing and calibrating properly, but it would still be possible. I just don't know if it would be viable or practical, still, you would face the same problems relating to 3D printing electronics with resin and metal powder.

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Well, I'm still not actually giving up on the mech idea, but I'm simply have a lot of difficulty find solutions (cheap and simple solutions) for the actuator problem.

Like I said in the previous project log: I settled on at least trying to find a way of making a solenoid pump or something that can be used as a pump and doesn't need electric motors, combustion engines nor piezoelectrics.

Electric motors are expensive and need really big batteries, combustion engines are low efficiency, expensive, heavy and need solenoid valves, piezoelectrics can't be homemade, aren't efficient and neither can pump massive volumes.

I mentioned the possibility of using Nitinol Shape Memory Alloys, but those have efficiencies below 20% and cost 500 dollars per kilogram.

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By the way, while asking my trillion of random questions over and over again, ChatGPT said that the conversion of electricity into heat (using a heater like Nichrome or other types) is almost 99% efficient, and that the conversion of heat into steam using this method is almost 99% also (I searched online and it seems to check out). 
So, there is also the option of using steam to pump the fluid or something else. You could use steam instead of pneumatics or hydraulics, you could use it to make a steam engines ( that are around 40% efficient) and so on (turbine engines sit around 65% to 90%). I also believe that steam powered artificial muscles would be as efficient as pneumatic ones (30% of efficiency or less) because they are essentially the same thing, but using different fluids.

Source: https://www.science.org/doi/10.1126/scirobotics.aaz4239
It is a unthetered artificial muscle in which induction heaters are used to heat iron oxide nano-particles in order to turn water into steam, making the muscle actuate. It is less efficient than what I'm suggesting.

But I don't know which is the best method, and to be honest, I don't feel comfortable carrying an electric steam boiler on something that can simply fall on the ground and break what is basically a bomb.

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The few positives that I can think of would be the speed of actuation, compared to hydraulics and electric motors, it is hard something as fast as a pneumatic actuator consuming the same amount of energy.

Not to mention that you wouldn't need the power of a turbine engine to compress thousands of liters of air.

... But it is also not that simple.

I would need to calculate how many liters of water you would need for a given pressure and flow of steam, which, as far as I could calculate in the past, it ins't that hard, but it isn't that easy either. It would entirely depend on the full system.

1 liter of water produces 1600 liters of steam.

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Maybe it could be useful for an ornithopter...

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But going back to the real subject:

Steam powered artificial muscles:

The same problem of pneumatic and thermal artificial muscles arise: which is how to control its actuation properly.

I found a few suggestions that have its own pros and cons:

• Completely activate single strands based on how much weight you want to lift and how far you want to lift.
  This one I accidentaly found out about when looking for Battlemech, ironically.
  The description is that these are high voltage activated electric artificial muscles that activate independent strands.

However, as you can guess, I can't possibly do that because each individual capillary-thin strand would need its own independent valve, and each independent valve would need to be controlled.

Buuut this idea could really be useful for thermally activated artificial muscles, like the Shape Memory Alloys and that carbon-fiber-silicon rubber one I showed on the previous project log.

Another idea for thermal actuators is divide the actuators in sections, so you could progressively contract certain parts of the artificial muscle fiber. But it would be a pain in the ass to wire everything.

I also gave the idea of simply spraying cold water at the rate parallel to the thermal muscle contraction in order to make it contract in a certain distance.
But how to control the force?

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• Another option would be to "simply" turn the appropriated amount of water into steam required for a given action.
  ... Which is really not that simple. And just like I calculated in other previous project logs, the faster you want to turn water into steam, the more power you would need. To the point a single small muscle would require 2000 watts of power to contract in half a second.
  
  However, a possible way of combating this would be to have multiple independent and interconnected steam generators throughout the body of the mechsuit/exosuit.
  This way if one steam generator is not enough to supply a given action, others will open their own valves and help with the extra boost.
  But, as you can guess, this option still requires a lot of solenoid valves and careful control, which means proper programming, which is not my forte.
  And yet, I like the idea of multiple small steam generators instead of a single big one. If one of these were to blow up, the detonation would be smaller and less dangerous.

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• Another obvious option would be to copy the already existing pneumatic controls, but use it for steam.
  Normally, if an actuator (like an arm with pneumatic artificial muscles) wants to make a precise movement, opposing actuators would be opening and closing in order to reach that position. A biceps can't move if the triceps is already pulling it back, which would lock the arm in the desired place.
  This need a fine, precise and very expensive kind of sensors, progressive valves and it is really inefficient since half the effort of the arm will be spent counter acting the arm.
  This option is not very good in my opinion.

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• There is still the simpler option of simply making steam with the electric method and rotating a steam turbine that would rotate an hydraulic pump.
  But, as you can guess, this method wouldn't be so simple. And steam turbines are heavy and expensive.
  However, they seem to be very versatile, since this one here (accordingly to the random website I found) could output a power between 100 to 3000 kilowatts of power (which is absolutely insane).

By the way, the bigger the steam turbine, the more efficient it is and the slower it needs to spin (just like helicopter/turbofan blades), so, depending on the amount of horsepower/watts I would require for the Mechsuit/Exosuit, I would need a custombuilt steam turbine engine.

But even then, if such an insane idea of using a steam turbine engine on the backpack of a Mechsuit/Exosuit works out somehow, you would still find the issues regarding common hydraulic systems: solenoid valves, control feedback and so on.

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• The ideal manner of pumping water using steam would be using steam itself without any mechanical means.
  The best two results I got were Vacuum Ejectors, buuut I don't know how to make it to pump water and refill the steam boiler at same time using a Steam Injector.
  In normal occasions you would either use one or the another. 

The vacuum ejector uses a higher pressure fluid to create a vacuum and mix with another fluid in order to create a very efficient mixer or a high airflow thingie.

I couldn't find anywhere the efficiency of steam ejector/vacuum pumps.

I found a source that claims it to be 90%, but ChatGPT/BingGPT says it has around 10-40%.
I asked an engineer in a discord group and he said that the efficiency depends on the type of fluid being worked. air on air = 90%, air on liquid = 60%, liquid on liquid = 30%, but in the source I talked, the pressure being ejected is at 1.1 bar since this is a mixer, not a pump, meaning that proper pumping has to be properly tested.

A steam injector on another hand, uses the higher pressure steam from the boiler to pump water back into the boiler.

Since this would be a new type of pump, I can't tell how efficient such pump would be...

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• I did found out about pistonless pumps, which operate in a different principle and are quite interesting as far as I could see.
  Of course, just like any other steam mechanism, it is way more complex when you want it to do something you want...

Savery Pistonless pumps are simple: fill in a tank with steam directly connected to water, the steam will expand and push the water, then you let the steam get cold and create a vacuum, pulling the water. Rinse and repeat.

They even used a similar approach for a rocket engine in order to save weight and money instead of using turbopumps.

Source: https://arc.aiaa.org/doi/10.2514/6.2014-3784

For last, there is the Pulsometer pump that also works with the same principle as the others, but with a different structure.

If I'm not understanding this incorrectly: it works the same way as the others, but it has extra chambers, allowing for a continuous operation unlike the Savery's one, which needs to wait the steam to cool down.

Well, if these are the equivalent to a piston pump, I wonder what would be the equivalent to a centrifugal pump...

... But the problem comes back to the efficiency problem: expanding steam is just like pneumatics... And pneumatics aren't efficient.

A piston steam engine has 40% efficiency, and this is basically a piston steam engine, but without the pistons... So... It is safe to assume comparable efficiencies.

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Well, I forgot to talk about Dielectric Elastomer Actuators.

The video explains it very well, but basically, the non-conductive elastic medium is sandwiched between two conductive layers/electrodes, once static electricity is passed through it, the two layers attract each other, simulating a contraction.

The funny thing is that this is actually a shape-changing capacitor.

Capacitors have three layers: two electrodes and a dielectric (non-conductive) layer.
A bunch of electrons are concentrated on the electrodes and since they have a dielectric (non-conductive) space between then, it keeps them in place by the electromagnetic attraction, once the two sides are connected, the electrons instantly jump all at once to the other side.

(By the way, for the little I think I know, there aren't positively charged electrons? The only thing that can be called "positively charged" is something lacking electrons, no? I'm confuser)

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In anyway, I just didn't give much credit to this type of actuator simply because I don't know what is their efficiency and how precisely are these made.

Some articles say Dielectric Elastomers have more than 80% of efficiency, in others it is said they have less than 20% of efficiency.
They normally have a really, really small stroke, less than 10%.

On top of that, there are numerous and numerous types of Dielectric Elastomers.

Some are based on acrylates, some are based on silicon rubber or are fluid assisted, some use carbon nanotube electrodes, others simply uses graphite powder on its place.

And I can't find enough information properly comparing each type's performance and efficiency, the information is all over the place, scarce and imprecise.
I would need to build every single type and personaly test every single one, but some need such complex polymers that I would need to directly contact some chemical factories for custom orders on the materials.

Example:

Source: https://www.mse.ncsu.edu/2016/11/new-bottlebrush-electroactive-polymers-make-dielectric-elastomers-increasingly-viable-for-use-in-devices/

This dielectric elastomer is a modified silicon rubber to be used specifically for this porpuse, it can have a stroke of 300%.

I couldn't find what the hell is a "bottlebrush polymer", but after searching a little bit on google, I think I found something that is probably the same thing, which is a normal silicon rubber being modified by at least 3 compounds:

• PDMS Monomer: Monomethacryloxypropyl terminated polydimethylsiloxane.
• Crosslinker: Methacryloxypropyl terminated polydimethylsiloxane.
• Initiator: hermal-initiator: 2,2′-Azobis(2-methylpropionitrile).

To me, these three sound like old eldritch god forbidden names.

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Not to mention the myriad ways you could stack these dielectric elastomers for different porpuses.

Also, as you can see, the dielectric elastomers are a reversedely actuated artificial muscles, meaning that they relax when activated and contract when disactivated.
After all, the two electrodes are attracted when charged, not the opposite.

Of course, it depends on the type of stack.

In any manner, I am divided between the vertically stacked and the spiralled/cylindrically stacked, simply because I could add milk-graphene to the flexible electrodes and absurdly increase the strength of the silicone rubber, while that is not an option for the vertically stacked...

(I think this is a good way of making the cylindrically stacked dielectric elastomer:you restrain one of the parts and it curves, it would curve in one direction, this one shows a different set of fibers that work like Mckibben which would coil on itself [supposedly]).

The spirally stacked would have its electrodes connected end to end while the vertically stacked would be divided with soft silicone in between...

Assuming that I wouldn't do the same thing as the electromagnet idea where the conductive connecting parts would be on the outside.

On another note, I could see the Spiralled stacked being easily mass produced, you would only need a conveyor belt and three airbrushers making three continuous layers of dieletric elastomer that would be solid by the end of the belt, which would be automatically spiralled and twisted, just like a rope.

But I don't know how the vertically stacked could be mass produced, I can imagine it being 3D printed with specialized conveyor 3D printers, but not as fast as in the gif.

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However, I do think that this has the same problem as the stacked electromagnetic artificial muscles that I suggested previously: stacking the dielectric elastomers won't stack their strength, forcing you to make multiple parallel strands to increase strength.

Which is impossible to do by hand, forcing you to use a 3D printer specific for this job.

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On top of that, using airbrushers would severly add air bubbles to actuators, forcing you to use a vacuum chamber to get rid of them.

... Which wouldn't be possible with a mass produced process of airbrushers, requiring conventional 3D printers:

(this is me from the future, you could mix silicone rubber with alcohol or put it on a warm surface to get rid of the bubbles, but syringe 3D printing is also nice)

... But this also brings up other problems: like in the thumbnail, the actuators would be too thick.

The thinner the layers are, the better the DEA works. Some papers used electro spun layers of silicon and electrodes, the same method used for microchips and other things.

Of course, one would need to check how much the air bubbles would interfere with the performance of the DEAs and how much the thickness would also interfere in order to find a middle-ground or a better option of the two.

... Which would need to be tested...

(ChatGPT and BingGPT said that thickness messes up with the response and softness, air bubbles with the capacitance and life cycle)

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By the way, you could use any kind of conductive material as long it has the two flexible electrodes and a flexible dielectric filler.

This means that you could even use polymers, normal rubbers and so on.

And as such, maybe you could get rid of the air bubbles using plastics like PVA and/or PVP...

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By the way, dielectric elastomers use electrostatic current, meaning that the voltage is on the 5 kilovolts, but with an absurdely small amperage.
So, 5000 volts x 0,0001 amps = 5 watts, Just like 5 volts x 1 amp = 5 watts.
The conversion of normal current into electrostatic has also its own inneficiencies.

Even so, it has its own limits (as shown in the first video on the subject), you would need to find the ideal thickness and the ideal way of carry the electric charges through the actuators.

The same problems I talked about the electromagnetic artificial muscles, which the same (possible) benefits of being simple and as fast as electricity can be.

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I looked in a random wire diameter calculator and for a 5000 volt and 0.001 amperage, I would only need a AWG 25 copper cable, which has 0.4 mm of diameter, even if you had 100,000 meters of cable.

And as thus, it is probably not a big deal to calculate which should be the thickness of each part. An advantage over the conventional electromagnetic artificial muscle.
After all, I still couldn't find a way of calculate what should be the thickness of each wire based on is resistivity.

I tried asking to ChatGPT and BingGPT multiple times, and accordingly to them, I would need a cable with 1 cm to 10 cm of diameter to transmit a 1 volt 8 amp current through a material with 5.56e-7 ohms per meter of resistivity (the resistivity of electrolytic copper powder). While electrostatic current in the other hand, would still need the same diameter of the previous calculation (0.4mm to 0.2mm) to transmit the same amount of watts.

Guess Dielectric Elastomers seem to be the winner... 🤔

... If it wasn't for the fact that I can't possibly figure out its efficiency, stroke length and strength.

(Doesn't that mean that I could simply change the actuator for an electrostatic electromagnet instead of a dielectric elastomer?)

Source: https://www.science.org/doi/10.1126/sciadv.abc0251

Source: https://www.researchgate.net/publication/369858087_Versatile_Ultrasoft_Electromagnetic_Actuators_with_Integrated_Strain-Sensing_Cellulose_Nanofibril_Foams

By the way, comb drives use a system similar to biological muscles, but they use electrostatics in order to work.

However, these are used for sensing. One could make them this same way, and these aren't insulated, one could maybe add something dielectric or non-conductive layer to avoid short-circuiting between the teeth.

Although I don't know which would be best...

ChatGPT said that an insulator layer wouldn't work.

"In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field." Wikipedia.

(why did I've made an habit of checking wikipedia as the last resource? Bruh

I'm suggesting this other type of dielectric/electrostatic actuator because to me, it seems easier to 3D print and mass produce, since it wouldn't have the same issues as the other types I talked about before;
The dielectric layer don't need to be soft, in fact, almost no part on it needs to be soft...

But it would still benefit a whole lot if it was as thin as possible, however, since the elastomer is so dense, I think it would compensate for the lack of thinness?

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I found this document: https://escholarship.org/content/qt7kf261zf/qt7kf261zf_noSplash_e480d01e957c9dd7a9e06b13b7356899.pdf

In page 38 it has a chart with different types of dielectric elastomers, and their efficiencies vary between 80% to 90% and a strain/stroke of around 30% to 60% (with the exception of pre-strained acrylic, which achieves 300%).

If it is so simple, then why companies aren't employing dielectric elastomer actuators in their bipedal robots and whatsoever?

What I'm missing...?

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I asked on Quora and other websites including ChatGPT and BingGPT about this and it seems like the "catch" is the durability of this type of actuator. 

Some sources say these only survive 1000 cycles, others say 1 million cycles.

I searched the amount of cycles that humans take for every hour, and it goes around 4800 to 13000 cycles per hour, which would mean each dielectric elastomer actuator would survive for only 3 to 8 days of non-stop walking (if its durability is around 1 million cycles).

On the dielectric elastomer wikipedia section itself is said that using hydrogels is a possible way of increasing its durability.

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ChatGPT suggested me making an hydrogel using PVA, borax, glycerol and a conductive powder like salt, with the exception of the later two, this is basically the recipe for shear thickening fluid, lol.

By the way, I was thinking of using hydrogels for the electrodes and silicone rubber for the dielectric part that is to be sandwiched.

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Not to mention the low strength, but that could be solved by simply twisting the filaments just like they did with fishing line artificial muscles, which have even lower stroke lengths and even lower force values.

... One thing makes me wondering, though... If thee actuators work like capacitors, wouldn't that mean that the actuators themselves are capable of storing energy somehow? And that energy could be reused for other actuations? Increasing its overall efficiency...?

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By the way, dielectric elastomers are both sensors and actuators, so you could also make them into a sensor/haptic feedback system.

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If you figure out a way of making a dielectric elastomer actuator that can withstand the strengths in a mechsui/exosuit, maybe you could make ornithopters...

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Oh yeah, I almost forgot: you can still choose to use the dielectric elastomers as hydraulic pumps instead of use them as the primary actuator.

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By god I hope this is the last time that I edit this project log (today is 31/12/2023, I've created the first tech tree log 2 months ago)

Well, let's just remember that I'm going through all this trouble of studying every single type of artificial muscle because I don't know how to make Carbon Nanotube artificial muscles.

I heard they are extremely efficient (I couldn't find any kind of precise information for that), but as far as I could find, the electrical way they activate is through Lorentz Force, which is not that strong, neither that efficient. But the carbon nanotubes have advantages over other mediums (such as copper wires) because they are on the nano-meter scale, and thus, the closer the electromagnetic field, the stronger it is.

This is the video in which he explains how the muscle works, which sounds extremely similar to how lorentz force works. One could still use extremely thin copper wires or other materials for that.
The thinnest copper cable is AWG 50, which has 0.02 mm of diameter, which is 20,000 times bigger than a medium-sized carbon nanotube (just now I found out about copper nanowires and zinc-oxide nanowires, but I couldn't find any source explaining how to make them in a way as useful as carbon nanotubes, they are normally used as conductive powder/catalyst).

On top of it, the last big breakthrough on the production of carbon nanotubes was 3 years ago and it was growing 12cm of it uninterrupted for days, and to me, it seems like it would need some post-processing.

You literally need to pump acetylene gas (explosive, flamable and unstable) in a chamber with a metal plate at hundreds of degree celsius.

How you do that in a homemade setup? You don't.

 And there really isn't any other way I know of, because if it was, carbon nanotube muscles would be common.

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You know what I said about metal oxide nanowires? There are also polymer based nanowires.

There is a crapton of ways of making these polymer based nanowires out of conductive polymers like Polyacetylene, Polyaniline, Polypyrrole and Polythiophene (I can't find them to buy online, only through polymer factories).

But while searching I think I got an idea:

There are syringes which have needles with an inner-diameter in the 2-5 nanometers of opening, these are called nanoneedles and are super cheap to find. From tattoo pens, to syringes to insulin pens.

This means that I could simply mix conductive polymers and conductive materials (like graphite or copper nanopowder) and extrude them through these nanoneedles, making little spagethi streams of conductive nanowires that are the same size as caron nanotubes and would act just like them (maybe). :|

I don't know how well it would work, but you could dissolve conductive polymers on acetone/glycol/ethanol and extrude it on warm (warm, not boiling) oil, so the polymer can dry out and not be on risk of simply breaking due to its absurd thinness.

(But since I can't find conductive polymers for the life of me, I would either make super fine graphite/graphene powder or try to make a graphite mold out of the needles and extrude molten copper)

... I kinda feel stupid since I didn't had this obvious idea before.

But to be honest, it is hard to tell if adding conductive powder will work, after all it is a needle with around 2-5 nanometer of diameter.

What garantee I have that the powder won't clog and probably damage (or even pop) the syringe needles?

I would be forced to either make a super ultra mega DIY thin powder or I would need to use only conductive liquids/polymers in order to make it to work.

maybe I could also use the same techniques used on carbon nanotubes in order to increase its strength, stroke and efficiency.

... Actually, the more I think about this, the less it feels like it wold work. The carbon nanotube artificial muscles uses voltage charges, meaning it is dielectric.

I could simply make graphene infused silicone rubber nanofibers with PVA/teflon as an "enamel" layer, but even then, I don't think it would work...

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By the way, this nanoneedle also means that I could make super ultra thin dielectric elastomers (if the nanowires doesn't work out) with PVA on the electrodes and pure silicone rubber as the dielectric material (or the reverse).

I wish I could add the extra thingies that I talked about (graphite/graphene powder), but it wouldn't pass through the nanoneedles.

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Speaking of which, would a fibrous electrode dielectric elastomer work?

What I mean is: nano-wires A is the entire positive electrode and it is covered in dielectric material (like enameled copper), nano-wires B are the negative electrode and they are exposed (or also covered), would these two fibers attractand coil on each other? Like a muscle?

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However, if you change what you want from the muscles, the picture changes a lot.
Specially if you want a high lifting to weight ratio.

I were only looking at the speed, strength and easiness of production, but if you look at the lifting ratio, all of them are quite bad.

The dielectric elastomer silicone rubber can only achieve a lifting ratio of 10 times its own weight (10:1), meaning that if I wanted to lift 3000 kilograms, I would need 300 kilograms worth of dielectric elastomers. Even the elastomer muscle video can only lift 50:1. The steam muscle is a really good option, but I'm really afraid of the consequences of using high pressure steam. The nylon/polyethylene only achieve 100:1, the hydraulic and pneumatic ones 1000:1.

(By the way, just now I remembered that the dielectric elastomer has a limited lift-to-weight ratio because it isn't various fibers, the same problem with the electromagnets stacked one above another)

But the winner of them all (in force to weight ratio) is the thermal carbon-fiber/silicone rubber artificial muscle, which can lift 12,000 times its own weight.

This muscle and this muscle works by the expansion of material, pully the fibers apart, just like any  mckibben muscle, the difference is that the material is solid and the fibers are inside of it.

Yes, I would need to add a whole amount of sections to heat it up progressively like I talked above, plus the water spray for instant cooling, but it would still be more practical than the others.

However, I was wondering if adding polyethylene/nylon would make the muscle work better, since it depends on the swelling of the silicone rubber heated by the carbon fiber.

Accodingly to ChatGPT and BingGPT, silicone rubber has a high coefficient of thermal expansion, unlike polyethylene and nylon, which have half to less of it.

Well, if that is so, I wish I knew more about the properties of materials in order to seek out the best ones for artificial muscles. If thermal expansion coefficient is better at certain materials, then the thermal coefficient of others won't be as attractive. I can only imagine if I knew what were the best properties of every material in order to make the perfect artificial muscle...

I thinkit would be like searching for a good orange for a bitter plate and knowing that a lemon is a better source of bitterness.

By the way, silicone rubber has a coefficient of thermal expansion (CTE) of 200 to 400 ppm/ºC.

• Ethylene-vinyl-acetate (EVA) with 950 - 960 ppm/ºC
• Natural rubber with 920 - 930 ppm/ºC
• Polychloroprene (Neoprene) with 1,200 - 1,300 ppm/ºC
• Polyisoprene rubber with 930 - 940 ppm/ºC
• Polyurethane with 1,000 - 1,300 ppm/ºC
• Silicone elastomers with 1,300 - 1,800 ppm/ºC

These are the materials that BingGPT sent me.

By the way, I saw this thermal artificial muscle made out of HDPE and COCe (Cyclic Olefin Copolymer Elastomer). I can't find COCe to buy online for the life of me, but maybe with the use of EVA, Polyurethane and meltable rubber, one could replace it with a more common material.

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Being honest, after all this useless talk, I really don't know which option is best... I just feel stupid and useless to be honest...

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Third: Structure.

The actuators need an skeleton to be attached to.

This one is not an actual impossibility at the moment, any kind of aluminium, steel or even plastic can support the force of the muscles and the weight of the mech.

The problem is that you would need to design the damn structure and go through the problem of actually building it, which would be both labor intensive and require a professional engineer to check/project such structure.

I thought on maybe trying to make a 3D model on my own using FreeCAD or Blender, but sincerily, I don't think I have any will power left in myself after 1 year of hitting roadblock after roadblock with this project.

What would even be the point of giving my all on making an articial skeleton since all other problems weren't solved?

I don't even have the money to test each part of the project, imagine actually building it.

---

Relevant to remember Hacksmith industries, they've made actual mechs (including the one above), and in all videos they show how difficult such task actually is.

I mean, they are sponsored professionals, so they have all the resources and all the resources that they needed.

... And yet, they had a crapton of difficulties, almost gave up on the project and still, on the end, the robot simply broke up, ending their years of effort.

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Now, imagine me, a dumbass without any kind of degree on anything useful (I have on graphic design coff coff). Trying to do a mech. Alone.

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In either way, one would need to plan how many tons of weight each limb would support, and on top of that, figure out if the structure will handle falling into the ground, running, jumping and whatever other actions one would need to peform.

Let's just remember that each part of the body is technically a lever, and each subsequent part of the body needs to be more powerful than the previous one. The shoulders would need to be X times stronger than the arms, the torso be X times stronger than the previous two and finally the legs that would need to be X times stronger than all others.

The "best" rule of thumb is to make everything somewhat stronger than it needs to be and make the legs 3 times stronger (it is said that the lower part of the human body is 3 times stronger than the upper part, and that is why you can carry weight and still be able to run and jump, besides your own weight).

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I thought on using High Density Polyethylene (HDPE) reinforced with fibers (of whatever type, glass fibers, carbon fibers, even wood fibers etc) at first because I could simply recycle it, but I couldn't figure out how thicker the structure would need to be. And assuming that the tensile strength of HDPE (around 20 to 30 MPa or 300 bars) is 1:1 to kilograms, then it would be able to sustain 300kg... But I don't know at which thickness, which structural shape would be the best and so on.

The same applies to Aluminium, which I thought on turning it into heat treated aluminium 6061 or aluminium 7075 and on top of that, reinforce it with iron or steel cables, like a metal composite.
But aluminium is terrible with fatigue, in the sense of being not that good with dealing with repeated tension/compression cycles very fast, like in a mechanical component.
Drag cars use aluminium piston rods on its construction because of the light weight, but these same piston rods wouldn't last more than a month in a conventional car.

However, I don't fully understand metallurgy and how much material properly acts under certain circumstances. Which a professional would be able to tell.

I also thought on DIYing Titanium Aluminate, which is a 60% Titanium 40% aluminium alloy that uses the benefits of both alloys.
I would be doing that by taking titanium dioxide (which is both a food and agriculture product that is really cheap) and use the hydrogen reduction reaction to take off the oxygen from the titanium.
But even then, I would need a furnace that reaches the temperature of titanium to melt (2500 ºC) which is not easy even with industrial standards.

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Steel is the final option, and I thought on mixing silicon and tungsten with it in order to create a good steel alloy like AR 500 or other types.

But Steel is hard to deal aswell, and the tools required to weld, forge, hammer and cut are expensive and equally as heavy.

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One would need to actually figure out how much material and in which shape, size and weight each type of material would require to be in order to make something appropriate for a mech or/and an exoskeleton.

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Fourth: Control.

Well, what is the need for a mech/exoskeleton if you can't control it?

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Like I said in the beginning of this tech tree thingie: you could "easily" overcome the problem of control and precision with proper encoders and programming, but you would exponentially increase the cost and complexity of the system. Just like an industrial robot, and those robots are as expensive (or more) than a house.

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The best I could think/find was something similar to what James Bruton first did do his DIY Iron Man exosuit:

In resume, he put hall sensors (cheap proximity sensors that only know the distance it is from a magnet) in a rubber box, so the more he approached one of the points, the more the suit moved in said direction.

The idea would do the same thing to the Exoskeleton or Mechanoid suit, but putting the hall sensors in the body of the pilot on the same points the artificial muscles would be in the artificial skeleton.

So, if you lifted a biceps in a certain way, both hall sensors (under and over your forearm) would notice a difference in distance over time and try to keep the suit from overpulling and underpushing the arm as fast as it could; In the case of the exoskeleton it would be "easier" to do this, since the body would be moving with the suit at the same time.

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The Mechanoid suit wouldn't be so easy, as far as I could think.

For example, if you made a solid shell around the pilot's body using this technique for motion control, the system would be more or less "blind", because you wouldn't be receiving the sensation feedback.
You would need some haptic system (a system that simulates the touch of the mech into your own body), it would be easier to do if you connected servos in some kind of motion suit like in the Avatar movie.

But I think it would be a little complicated to do that with an artificial muscle system.

Another option that I was able to think was to make a "second skin" both for the mech and for the pilot while connecting these.

Let's say, like a large blanket full of sensors (like piezoelectric sensors).

Piezoeletric buzzers/actuators/sensors generate a small eletric current when exposed to vibration and/or impacts, and when receiving electric currents can produce sound and/or vibrate in a certain way.

The problem is that this option would be pretty labour intensive and could be full of defects and problems, you could make a different "sleeve-skin" for every part of the body, but still, it would be a lot of piezoelectric buzzers.

Plus, how you would define the vibration?

For example, how do you know where is your mouth is when eating? You know that because your sense of touch is "on" all the time, this way you know where each part of your body is at all times.

How the vibration of the second skin would transmit the sense of touch all the time? What about scratches? Bumps? Impacts? Changes in temperature? How you would convey the information you want to transmit into the haptic suit?

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By the way, there is a myriad of different ways of making haptic sensors, this one uses fluids connected to sensors (I forgot which type) and can be made with silicon, rubber or whatever other flexible material.

Source: https://www.semanticscholar.org/paper/Skinflow%3A-A-soft-robotic-skin-based-on-fluidic-Soter-Garrad/2d76201c5700dc899ab18d419119d82be113f0fc

The problem is still the same: even if the "skin" itself is relatively easy to make and on the cheap, it is labour intensive.

Even if you could simply connect a flexible silicon skin from the mech to the person inside without any kind of electronics, how the heck you would fill and connect all the thousands of tubes? What if some of them rip apart or simply pops?

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I also found this interesting article:

Source: https://www.nature.com/articles/ncomms6747

Well, I didn't read this article yet to see how they were able to make the sensors, but I would make a guess that one would be able to make printable skin sensors with conductive inks.

In each video below it shous varios methods for printing circuits and other types of sensors, including thermal sensors and even antennas.

(by the way, these printed circuits and sensors can be applied to any medium: paper, cloths, plastics, rubber sheets etc)

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Well, I don't know what would be the best method of DIYing these printable sensors (using conventional printers or relief prints, like old journals were made), but one would need to figure out what sensor to put where and how to connect each one.

For example, what is the sequence of sensor layers you would need to use? Touch, thermal and humidity one above another? Maybe put each one on the same layer? How you would connect and transfer these sensations to the haptic suit of the pilot?

Would the printed sensors be able to be used as printed actuators?

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While searching for a little bit, I found this electromagnetic ink printed actuator:

Source: https://www.mdpi.com/2076-0825/5/3/21

Well, it is not that useful for an artificial muscle, but maybe if you made a coil on both ends, it could be used as a vibration actuator for haptic sensing...

Although I don't know how I would make it through a large blanket/sheet, maybe you would need to align two sets of blankets that would attract and repel each other in order to make a vibration.

... But I don't know how perceptible it would be, a lot of things that I suggest would need to be throughly tested in order to be considered viable for its function.

... Which further increases the cost and complexity of the project.

I also found out this video this guy made, again, you could replace the magnet with an opposite magnetic coil.

The problem is that you would need to find a way of making a flexure stand.

Well, this madlad here made a speaker with conductive ink and paper:

Source: https://www.zachrotholz.com/paper-speakers.html

As far as I understand, sound is vibration, so if you can make a speaker with conductive ink and a mirroed coil (assume that the paper in the picture is folded in the middle), you've made a vibration actuator.

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Maybe a good way of making a inkjet printed haptic actuator would be to not use any actuator at all, but electricity itself.

The idea would be to directly electroctute the skin with a small voltage in a sequence simulating vibration.

Source: https://www.nature.com/articles/s42256-022-00543-y

I found this article that uses hydrogel.

The only problem is that the haptic material needs to be in direct contact with the user's skin, which is not convenient if you want to wear clothes. >.>

Maybe this could be reserved for the feet, lower legs, forearms and hands. Which are exactly the parts of the body that you would be using the most, and you can easily lift you clothes for these parts.

I also saw other options that suggested using printed heaters for the haptic feedback, but I don't know how fast it would be to generate enough heat to simulate touch.

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Also, I found this option here that I thought it was interesting:

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01/01/2024 and I'm still editing this blasted project log.

Well, even though I said I gave up on the project, I still actively search on all my free-time simply because it is some kind of hobby, I suppose.

And one of those times while I was researching, I accidentaly found out about brain-computer interface.

The thing is that one could make a radar array around the human brain and interpret the sinapses/signals of the brain, spine or local nerves in the body in order to control prosthestics.

I couldn't find much information on the subject, and the little that I found, I didn't even gave a chance on trying reading them.

But let's imagine it like this: imagine the brain activity detection array of said radar is made of thousands of voxels with 1x1 mm of diameter.

One could "brute-force" the interface by detecting the position of every part of the body, every part of the brain and making a Deep Learning AI to interpret the signals in order to command the prosthetics in a certain way.

This way you could control the mech/exosuit with your brain instinctively, maybe you could even help prosthetic users with such thing.

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... The problem is: how to make said radar array? Can radars even be used to see human brains?

Magnetic Ressonance Imaging? This thing uses superconductors cooled by liquid helium and costs million of dollars.

Electroencephalography (EEG) Sensors? These only work with a general activity of your brain.

The closest thing I could find was TMS (transcranial magnetic stimulation), which works with induction coils (I think), which could be used both to detect and to induct responses on the brain.

Buuuut... As you can imagine, there isn't any kind of machine like that.

In fact, I don't even know if the MRI machines have such insane resolution as 1mm voxels, imagine doing it in real time while you think on a myriad of different things?

Imagine the amount of gigabytes you would produce per second.

With radars? What kind of radar can see the human brain? I just found this one picture, but it doesn't look like it would have 1x1 mm definition...

Source: https://www.researchgate.net/publication/320360706_Radar_based_technology_for_non-contact_monitoring_of_accumulation_of_blood_in_the_head_A_numerical_study

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(The induction coils make me wonder: could one use them to make a blind person see again by inducing currents on the eye nerves and/or on the brain?)

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Accordingly to this link there are 684,000 neurons in a 1x1mm voxel.

... Which puts into question if this is enough.

Also, I don't have any idea of how to make a Voxel Scanner, but it seems like it is conventional practice on MRIs and the like.

The best idea I could come up with was simply imagining the electromagnetic waves as light, just imagine that each radar is a magnifying glass, focusing light in a single point in the air, and there are thousands other radars focusing on other 1mm focused light balls through your brain.

The obvious problem is how to do that.

The human brain typically has motherfricking 1,100,000 cubic milimeters, how the hell I am to make a homemade Voxel Radar that will have 1.1 million focusing points?

If one where to reduce each voxel to 1 (on) and 0 (off) state, you would still consume 0,0011 gigabytes for every time you scan, so, let's say, a 24 FPS (or 24 scans per second) would give 0.02 gigabytes per second of information.

A single second. :|

On top of that, as you can see in the picture above, there is no such thing as a simple "on and off" neuron (I think).

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In any manner, I'm checking DIY electromagnetic 3D scanners, maybe these can be useful for something.

(it wasn't)

Also, this guy made a DIY MRI machine

15/10/2023, 09:49, Sunday.

Well, good morning.

I was planning on making this project log on 26 of november, which would be the 1 year anniversary of this waste of time of a project.

But I will make this now because I need to take this out of my mind.

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But yes, I'm giving up on the project (for now, I think), and I will list all the problems that need to be overcome in order to make this project viable.

Which could be easily overcome by an actual engineer, but since I'm not one....

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So, Mech, or Mechanoids (humanoid + mechanical) are not practical, nor viable, without some problems being solved.

One could definitely make a mech, but it would be unholy expensive and unnecessarily complex for something that can be easily replaced by a goddang forklift.

Thus I would like to list all the problems one would need to solve in order to actually make something viable.

(tech tree from mechwarrior)

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First: Power Source.

One would need to find a power source that is light, somewhat efficient, compact and cheap enough to be used in a humanoid mech.

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Out of the batch, batteries won't cut it.

These have low energy density, 10 to 20 times less energy density than fuel. Which is normally measure in either by weigth or by volume (which doesn't make sense to me, since density is volume divided by mass) in the watt-hour per kg.

Lithium-ion batteries have 100 to 200 wh/kg of energy, meaning that if you want 15,000 watts in 1 hour, you would need at least a 150kg battery (with various smaller batteries stacked or not), and since you would need any kind of machine work for several hours, you would need to add 150kg for every hour of operation.

Which is not really practical.

In the other hand, gasoline has 12,000 watt-hours per kg, but due to the innefficiencies of combustion engines, you would actually have 5400 wh/kg.

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Edit⁴:

So, now I'm completely confused.

Well, long story-short, I was looking at how much energy a laser weapon would consume, and it said it would consume 10,000 joules per shot, which would consume 20,000 watts in total, around 26 horsepower.

However, an AA battery has a total 10,000 joules of energy, but can only output 5 watts.

Meaning that a single AA battery would be able to energize a fricking laser weapon in a total of 30 min.

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The thing is: I understand batteries as a "life bar", if the battery has 5 watts, and you connect it to a 5 watt consuming source, it would consume 5 watts and deplete. Simple as that.

... But... There is a relation between Watt (the maximum output) and Joules (the total energy in the battery), which relates to watt-hour (it is the total energy consumed over a 1 hour at a constant rate of one watt).

... This means... That I can extract... The equivalent of 26 horsepower out of a single AA battery?

... Then... Why there is all that fuss about "batteries not being energetically dense enough for cars"?

I... I don't understand...

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Conventional combustion engine generators are efficient, but they aren't cheap and definitely not light. Commercial diesel engine generators with some as "little" as 2000 watts to 4000 watts weights 100kg.

More potent generators are way heavier and way more expensive, the price of cars even.

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I even thought on using a micro turbine engine with a high speed alternator, which would be way lighter, but these aren't cheap, easy to make, nor efficient.

This one is a 8 kilowatt microturbine generator, I literally cannot find anything like that online, but taking into consideration that turbine engines uses titanium alloys and/or inconel alloys, it definitely ain't cheap.

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Edit¹:

Just now I remembered about free-piston turbines, basically, it is a piston engine that uses its exhaust to rotate a turbine, not so dissimilar from turbochargers.

However, I don't know how intense would be the conditions of such machine, like I said, conventional turbine engines need very expensive and absurdly strong alloys.

It is known for being too heavy for airplanes, but the idea is being revisited for its higher efficiency and simplicity.

There is also the free piston generators, where the pistons have magnets passing through coils. But I don't know how efficient and power dense these are.

I found this video saying that toyota is making this free piston generator, which would supposedly be capable of producing 20,000 watts of energy.

However, the video is like, 9 years old. Where is this darn super compact generator?

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Also, another type of generator that is kinda of interesting are thermoelectric generators and stirling engine generators.

Basically, these two types of generators can turn the difference in temperature of two parts (heat and cold) into electricity, allowing the use of any kind of fuel.

The problem is that their efficiency is below 10%, meaning I would need more fuel and bigger generators, increasing the overall size and weight, decreasing the efficiency even more.

In the case for stirling engines it is said that some models achieved an efficiency of 40% to 30%, which is the same as conventional combustion engines. However, I couldn't find any kind of commercial stirling engine that I could easily copy. Only those small demonstrators for educational porpuses.
There is this model, it weights around 40 pounds (20kg) and only produces 300 watts of power, less than half of a horsepower. I can only imagine how a 20,000 watt model would look like...

Stirling engines:

There are types where which uses the free-piston type for generating electricity:

Now, for thermoelectric generators, you can use a ton of different materials, but some use those peltier coolers for computers.

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Well, just now I found this video:

Basically, he made a thermoelectric generator using graphite paint and aluminium paint, basically, epoxy mixed with graphite and aluminium powder.

He also shows older videos of his where he made a thermoelectric generator using copper oxide wires  (in said older video he made a TEG using copper wires with an oxide layer, the copper oxide could replace the aluminium since the later would absolutely melt under higher temperatures) .

In summary, I thought that this could be interesting, since you could actually use Sodium Silicate, which can sustain thousands of degrees of heat.

So, as said in the video above, you could "just" print thousands of these generators using sodium silicate, graphite and aluminium in a fairly cheap way.

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Also, I would add two things to a DIY Thermoelectric generator:

1:

This is the image of a thermoelectric generator added to a car exhaust, the hot part and the cold part are added in a sandwich-like manner where the channels for the cold part and the channels for the hot part are crossed.

(however, this only produces 1,000 watts of power, so you can imagine how big should a thermoelectric generator, specially a DIY one, need to be in order to generate enough energy)

2:

This is the image of a blast furnace, used to melt iron out of impurities.

The intake air exchanges energy with the exhaust air, heating up. Finally, it is pumped into the flames so it increases the temperature exponentially.

You could add this to the Thermoelectric generator, after all, the bigger the difference in temperature, the bigger the energy generated.

However, this is still has an efficiency of 20% to 5% (which is the range normally shown by thermoelectric generators, but I don't think a DIY one would achieve these numbers).

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There are thermoelectric generators that achieve 40% efficiency or higher, but these are made out of gold, germanium, silicon, gallium antimonide, Indium gallium arsenide, indium gallium arsenic antimony and Gallium arsenide, not to mention it only works at hearts of 1900ºC to 2400ºC.

At such temperatures and materials, if I'm not wrong, this isn't even a thermoelectric generator anymore, but a infrared photovoltaic cell (aka solar panel that only works with infrared, infrared radiation = heat).

Source: https://www.nature.com/articles/s41586-022-04473-y

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Well, just now I found about this: Magnetohydrodynamic Generators.

In grossely simple explanation: when you pass a heat source through a magnetic field, you turn kinect energy and thermal energy directly into electricity.

The best way I could explain is that a ionized gas (aka plasma) generated by a "seed" of ions generates electricity through the electromagnetic coils the same way an alternator works: you apply electricity to make an electromagnet and the movement of the material changes the electromagnetic field, generating electricity.
The difference is that in magnetohydrodynamic generators you're using plasma instead of rotational motion.

I saw a lot of different amounts of efficiency that this tech can supposedly produce, something between 22% to 65% of efficiency.

However, I don't fully understand how this works, and the first paper that I saw saying about a design of a supposedly 50%+ efficiency needed cesium or potassium to be compressed to hundreds of atmospheres of pressure while being directed through a special nozzle that would make the gas accelerate to thousands of meters per second (while using superconducting magnets).

Source: https://www.britannica.com/technology/magnetohydrodynamic-power-generator/Major-types-of-MHD-systems

From Wikipedia article about the subject:

The efficiency of the direct energy conversion in MHD power generation increases with the magnetic field strength and the plasma conductivity, which depends directly on the plasma temperature, and more precisely on the electron temperature.

As very hot plasmas can only be used in pulsed MHD generators (for example using shock tubes) due to the fast thermal material erosion, it was envisaged to use nonthermal plasmas as working fluids in steady MHD generators, where only free electrons are heated a lot (10,000–20,000 kelvins) while the main gas (neutral atoms and ions) remains at a much lower temperature, typically 2500 kelvins.

The goal was to preserve the materials of the generator (walls and electrodes) while improving the limited conductivity of such poor conductors to the same level as a plasma in thermodynamic equilibrium; i.e. completely heated to more than 10,000 kelvins, a temperature that no material could stand.

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Well, with all of this in perspective (plus, I couldn't find any information on portable versions of such generator), I think it is safe to say that it would be incredibly hard to make a DIY version of this.

If is worth anything:

Turbine engines, more specifically, the turbine blade of the engine uses Inconel, a superalloy, in order to survive the high temperatures, but the combustion chamber faces the highest temperatures and only uses conventional steel materials.
The material is still able to survive due to an air layer that it produces, after all, air is a terrible heat conductor.

You could use this to make a magnetohydrodynamic furnace reach incredible high temperatures without destroying the whole thing, after all, the plasma gas don't necessarily needs to touch the walls to generate energy, only to pass through the electric fields.

But the problem of miniaturization still persists.

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Ps: I still have no idea how this works and how to improve it. lol

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The best option I thought was using fuel cells.

A combustion engine takes air and fuel, reacts both and generate a combustion, which pushes the pistons in an engine or rotate a turbine.

In the case of fuel cells, the fuel reacts with air and directly generates electricity.

It doesn't have any moving parts besides the air and the fuel, it is light and efficient.

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The fuels that normally are used is hydrogen, ethanol, methane and methanol.

Hydrogen needs to be stored inside expensive carbon fiber hydrogen tanks that can be dangerous if something goes wrong, like a mech falling in the ground.
Methane suffers a similar problem, but it also needs very specific types of materials for a fuel cell, such as very specific (and expensive) types of ceramics.

In fact, you need a different set of materials depending on the type of fuel your fuel cell works with (as far as I know), so I don't know if an hydrogen fuel cell would work with ethanol or vice-versa.

There is a process called "steam reforming", which converts hyudrocarbon fuels (like methane, ethanol, methanol etc) into hydrogen gas on demand.
However, I couldn't find anywhere how to make a miniaturized version of such process (probably because it isn't possible) and on top of that, it also needs energy to convert the hydrocarbons into pure hydrogen, it uses steam, after all.
Which would diminish the efficiency of the entire system in the end. By how much, I don't know.

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Another problem is that fuel cells need expensive materials to function, such as its membrane and its catalysts, that normally is Platinum.

Recently I found about Catalytic Condensers, which basically allows for common metals such as aluminium and copper to work as catalysts by applying a certain voltage to them.

However, it seems this class of material is very recent and I couldn't find any information about it, specially relating to fuel cells.

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Second: Actuators.

Well, if a machine doesn't have any moving parts, it wouldn't work well as a mech.

Actuators is basically the moving part of a machine that acts for a certain function, like electric motors, hydraulic cylinders in a excavator or even artificial muscles.

There is a myriad of different actuators with a myriad of different functions, working principles etc.

However, after almost a year searching on the subject, artificial muscles are generally not that efficient and some times, not even that practical, nor cheap.

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By the way, I was thinking of using Stewart Platforms (or parallel manipulator) in the limbs.

This way the loads would be equally distributed between all the actuators, allowing for a high efficiency machine.

This walking chair is can be used as an example, it uses stewart platforms for the legs.

The idea would be to use the same thing to the mech, but instead of directly touchting the ground, the platforms would be attached to limbs.

It would be a total of 5 stewart platform, one platform for each leg, 1 for each shoulder-arms and 1 for the torso.]

Of course, you don't actually need to use linear actuators, one could use hoist/pulleys for example.

---

As far as I could calculate:

With the Stewart platform in mind, taking the 1000kg weight range that the 3 meter mech would carry, we have to estimate how much energy such a system would require once more.

If such a mech had a forearm with X centimeters of length and the actuators are placed laterally in ⅓ of its length, then the group of actuators should output 3 times more force, and thus, 3000kg of force in total to lift 1000kg.

However, since the load is equally distributed between the 6 actuators, then each actuator would require to apply 500kg of force, which can easily be done by hydraulic cylinders. In fact, most commercial hydraulic jack cylinders are normally meant for 2 to 5 tons of weight.

Taking a commercially available hydraulic cylinder meant for 3 tons with 50mm of bore diameter, then, according to online hydraulic cylinder actuator calculators, it would need 25 bars of pressure and 35 liters per minute of fluid flow.

The fluid flow is the speed the fluid is being pumped through the system, and not necessarily the amount of fluid required to run it. If the pump was connected to an infinite reservoir, it would pump 35 liters per minute.

Taking into consideration the value for hydraulic gear pumps, in order to pump 36 liters per minute with 2000 rpm and 200 bar (20MPa, or 20 Newtons per m²) of pressure, we would need 12.8 kilowatts, or 17.1 horsepower.

Since we are using 8 times less pressure, and thus, 8 times less torque, then the full energy required to pump enough fluid at the required pressure would be 1600 watts, or 2.1 horsepower at 2000 RPM. Accordingly to online horsepower/wattage calculators, of course.

Since the arm is attached to a torso, then the load would also need to be lifted by it, also using 1600 watts of power. Since in a biped configuration the legs need to exert 3 times the force  of weight X in order to lift a load X, then the legs of this mech would need 3 times more power, thus 4800 watts could be distributed by both legs using stewart platform mechanisms.

So, in order to lift 1000kg, this mech needs 8000 watts, or 10.6 horsepower in order to work. Since this is a hydraulic mech, then the mechanisms don’t need power to stand still.

Also, if you make an exoskeleton with 10 times less lifting capacity, then you would need 10 times less power, needing only 800 watts to lift 100 kg.

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Obviously, this calculation assumes ideal distribution of loads and ideal efficiency, in reality things would be different.

For example, this assumes the use of electro-hydraulic actuators, meaning that every hydraulic cylinder has an electric motor rotating an hydraulic pump.

But if you are going to use electric motors to begin with, then why not just use electric motors directly?

Plus, the pumps are expensive, the pistons are expensive and the electric motors are expensive.

The hydraulic actuator shown in the image has a 8000 Newton (800kg) lifting capacity, with a speed of 2 cm per second, and costs around 400 dollars. You would need at least 30 of these throughout the body.

In addition to that, the speed of the actuator for the mech would need to be at least 15 times faster than that, at around 30 centimeters per second of linear speed (and more).

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After this, the idea I had was to use gardening hoses (that can withstand 20 atmospheres of pressure) and insert a piston with a cable, the fluid would be pumped with an electroosmotic pump, making an action similar to an artificial muscle.

Something like this.

An electroosmotic pump is an electric pump with no moving parts, however, one would need around 2 to 10 liters per minute of fluid flow (or more, depending on the inner diameter of your actuator) and 5 to 20 bars of pressure.

I couldn't find any electroosmotic pump designs that were able to reach anything close to such amount of fluid flow and pressure.

These kinds of pumps are meant for microfluidics and really small pressures.

For example:

This electroosmotic pumping membrane can achieve woping 5 liters per minute per square meter.

A 1x1 meter blanket just to pump 5 liters in a minute, think about that for a moment.

I heard that you can basically use any non-conductive material, such as plastics. But how many kilovolts you would need? For how long it would work? How efficient it would be? How I could test it in a DIY setup?

(by the way, the electrostatic pump from this log looks promising)

---

Yes, I could use conventional hydraulic pumps, but I would either need dozens or hundreds of them in total, which would need dozens or hundreds of electric motors rotating them.

If I were to actually make something like this, it would be simpler and better to use dozens or hundreds of electric pulley motors acting as artificial muscles.

And even though the idea seems interesting, since its efficiency and somewhat simplicity, the idea falls short because of its price.

Electric motors that are potent enough to act as pulleys-muscles are somewhat cheap if bought individually, but when you stack hundreds of them, the price gets absurd.

Not to mention all the circuit boards and controllers you would need to buy for them.

If your robot doesn't need to lift hundreds or thousands of kilograms, them you can buy really cheap motors, but what is the function of a mech that can't lift anything?

---

I also thought on a central pump with a solenoid valve system, but solenoids face the same problem of costing a lot in high quantities and on top of that, they lack the continuous manipulation of the fluid flow.

Progressive valves/servo valves are harder to control and more expensive, way more expensive.

Not to mention that the pump would need to peform the work of dozens or hundreds of pumps at same time, which would need an absurd amount of power.

These guys make a robot hand with hydraulic articifial muscles (which has maximum 60% of efficiency) and they needed so many solenoid valves that you could cover the entire table with them (and in some older videos, they actually cover).

This is just for a single hand, imagine for an entire body?

---

There are a myriad of different types of artificial muscles, and again, all of them have low efficiency and often, very expensive.

For example, nitinol shape memory alloys convert heat into contraction, however, the efficiency is bellow 10%.

I wouldn't mind such drawback if the material was cheap, after all, all you need is a electrical heat source and a spring-like nitinol wires.

However, nitinol shape memory alloys cost thousands of dollars per kg, more or less 900 dollars per kilogram. I would need at least a dozen or even a hundred of kilograms of this thing in order to make a mech.
Also, this is the price for Shape Memory Alloy Nitinol wire type, there are other types of nitinol wire that may not work like an artificial muscle, for example, superelastic nitinol wire for dental appliances.

One could try to DIY this thing at home, but you would need to make a high vacuum furnace in order to melt nickel and titanium together and on top of that, a cryogenic cooler in order to give the metal its specific properties of acting like a muscle.

There are other types of shape memory alloys, including polymer shape memory alloys. All of them have terrible efficiency and are insanely expensive.

---

By the way, even though I kinda gave up on this project I still look up for new actuator articles and stuff of the genre.

Just now I found out about this interesting actuator that is "just" twisted carbon fiber inside silicon rubber:

As shown in the thumbnail, the video is speed up 4 times so I slowed it on youtube option 0.25. Which ends up on the long, long list of "super duper ultra new actuators that is totally revolutionize the world... If the video wasn't speed up 40 times and the materials didn't cost 32923909329 dollars per gram".
Still, even though Carbon Fiber is expensive, I still think it is maybe worth the trouble of looking it up, since it could be a good replacement for Shape Memory Alloys like Nitinol Wire.

I had to use Sci-hub to read the article, and well, I'm not in the mood to read right now (because I'm just so done) and as far as I could read, basically, using a voltage of mere 6v, the carbon fiber heats up to 130ºC and the silicon rubber expands.

I still don't get why does it happen, neither I know for how long can the silicon rubber withstand such temperatures and so many cycles of actuation.

Which would have all the benefits of using the nitinol wire muscles without the cost drawback, but still with the thermal transfer drawback.

---

Another option that I forgot to add was artificial muscles made out of Nylon or Polyethylene wire, I didn't want to talk about these at first because it has basically the same problems as the Nitinol and silicon-carbon-fiber muscles.

However, accordingly to Wikipedia, these muscles can lift 100 times its own weight, unlike the nitinol and silicon that can lift more than 1000 times.

Meaning that if I were to lift 1000 kg of weight, I would need 10kg of nylon no.6 or polyethylene.

A lot of articles and DIY attempts on replicating these muscles fall under the problem of electrically heating it with a resistor wire such as nichrome, steel or even copper. Some articles actually used silver plated nylon wires (which is expensive as heck).
But, as you can imagine, these options aren't ideal, specially if you were to make a mech/exoskeleton using 10kg worth of manually twisted muscles.

The "best" solution I could come up with was buying pellets or solid chunks of nylon/polyethylene, melting them and mixing with some kind of conducting resistor powder, such as graphite, milk graphene and/or silicon carbide.
The wire could be extruded by a machine that already makes it twist, like a spaghetti machine or something more DIY, it doesn't need to be super precise either, it just need to be twisted.

Nylon costs around 200 bucks per kilogram if you're buying solid pieces of it, there are Nylon bobins for fishing that are way cheaper than that, but you need to remember that the nylon these use may not be as ideal, or even worse: it probably will be polycarbonate.

Polyethylene is way cheaper than nylon by a huge margin, but I don't know about its endurance.
I tested a random polyethylene/Dyneema fishing wire by twisting it and heating it with an heat-gun, it definitely twisted, but for some reason the more times I did it, the more... Rigid it felt to the touch, and if I kept heating too much, the filament would either stop moving or simply melt in a thousand plastic crumbs.

---

The best option I could think of was making DIY electric motors.

But guess what? It still is too expensive and complex.

You would need to melt iron or silicon steel into paper-thin laminations for the stator and use a crapton of copper windings.

The iron is quite alright with DIY furnaces, but the copper windings? It costs 100 to 200 bucks per kilogram of copper wire.

Not to mention the magnets necessary for the rotor and the precision required for each part.

By the way, you could make a composite with iron powder and resin, which would be called a soft magnetic composite core.
But these don't produce stators as efficient as the ones made with laminations.

---

Just now I remembered that one could use insulated iron/silicon steel/nickel wires as stators if you bend then in the same direction.

... But if it was that efficient or that simple, we would be seen more examples like this in day-to-day applications. Which is not the case.

(I couldn't find any visual examples)

---

Another thing I forgot was EDM machining.

This technique allows for parts with an absurd amount of precision, making those viral invisibly cut parts.

One could make customized stator laminations with this with quite ease, however, I couldn't find any DIY option.

The best one I could find was this one, and in the end, they couldn't make it work properly. And even if it worked, it wouldn't have the same amount of precision like in the example I showed.

---

The "best" idea I had was using fully 3D printed electric motors for the electric pulley-muscles, but... This is a can of worms on its own.

Not a 3D printed motor with copper windings (because it would still be expensive and labor intensive), fully 3D printed motors.

This one uses a paste with conductive material for the winding and a insulating ceramic paste material for making a winding. One could also use a metal powder for the stator.

By the way, there are other alternatives to use as the medium for the conductive metal powder, such as acrylic+acetone+powder, in which acetone dissolves acrylic and when it evaporates, leaves solid acrylic behind.

---

Edit²:

Just now I remembered that you could also use conductive ink with a mix of sodium silicate, epoxy resin (like the previous video) or a metal/ceramic paste that can be sintered in a post-process. Some desktop 3D metal printers in the market uses the metal/ceramic paste method, which is easier and safer to handle in a DIY way.

You have a lot of options on how to 3D print an electric motor, but the problems persist.

Just imagine making a STL model of an entire printable electric motor with coils and everything...

Still, the other problems persist, even with conductive or insulating ink. But maybe it would be easier to make a DIY liquid printer rather than a paste printer, you could even use a laser engraver to dry out the sodium silicate ink...

Just saw this video and no, liquid printing is not easier than paste printing.

---

And on top of that, there aren't many machines nor methods out there that can reliably make a fully 3D printed electric motor.

I could only find the video above on the subject and almost the same amount of news articles exploring the subject.

The only other video I saw on the subject was this video below where the author simply mentions the possibility of 3D printing electronics on future videos.

(at 9:10 mark)

And even then, I don't know how efficient, how powerful or practical would these 3d printed electronics be.

You would need conductive 3D filament and a multiextrusion 3D printed, and both are really expensive not that great at its job.

---

But, like I said before: you need laminations for an efficient electric motor (and also neodymium mangets).

So a fully 3D printed electric motor would fall short on the matter of efficiency, meaning you would need even more energy to compensate for the lost energy. But it would still be cheap and simple to produce in big numbers.

---

Edit³:

So, Even though I gave up on this project, I'm still trying to research and find solutions for the problems here presented.

For example, I think a good type of electric motor to make a fully 3D printed version would be induction motors, more specifically the 3 phase "squirrel cage" induction motor.

These don't need brushes neither magnets on its rotor, but brushed motors would still be a little more efficient.

PS: When I say "Brushed motors", I refer to those that have electromagnets both on the stator and on the rotor, these don't need permanent magnets, but do need brushes/commutators/slip-rings, which is a point where efficiency is lost due to friction, heat and other caveats involving rotating electric connections.

In simple terms, the laws of physics (I forgor which one) dictates that where there is an electric current, there is an electromagnetic field, and where there is an electromagnetic field, there is a electric current.

And as such, the idea of a induction motor is that the electromagnetic field generated by the coils will induce an electric current on the rotor, which in turn will become a mirrored electromagnetic field.

Also, copying this kind of motor in a fully 3D printed version would mean that I would need to supply 3 phased electricity to all motors with 220V AC current.

Which I think it would be very dangerous if some accident were to happen...

Also, I don't even know how I would make or find copper powder.

Metal powder that is good enough for this kind of stuff is expensive to come by, specially copper powder. Like, two to four times more expensive than just regular copper.

It is kinda easy to make iron powder throught hydrogen reduction of iron oxide and all that, but copper...

---

So, I researched a little, so you could turn copper into copper carbonate by mixing copper with sodium carbonate (aka soda ash/washing soda, you can make it by heating up baking soda) with water and heating it up.
You can also turn copper into copper sulfate by mixing it with epsom salt in an electrolysis reaction (you can also use sulfuric acid instead, but it sounds kinda dangerous to me, so I think it is better to use copper carbonate), this mixture can then be turned into copper carbonate by mixing sodium carbonate with water and heating the mixture.

PS: copper carbonate and copper sulfate are toxic, but for some reason you can by kilograms of it online.

Then you heat up copper carbonate and it will release carbon dioxide and leave copper oxide, then you can do the hydrogen reduction by exposing copper oxide to hydrogen gas at high temperature, it will react with hydrogen, making water vapour and leaving pure copper behind.

However, it is relevant to remember that very fine metal powder is very chemically reactive, if you let it by itself it will just react with oxygen again, and it can also combust (not to mention that it is toxic to breath it).

---

Lastly, let's just remember that this is just a DIY way of possibly making metal powder of certain materials.

I simply don't know how fine the powder would be, the methos that make nano-sized metal powder are expensive for a good reason.

Maybe if you grind everything for minutes or hours on a mortar... Maybe the metal dust particles will reach a fine enough size.

---

Also, just one last thing: What should be the optimal rato of resin and metal powder?
95% metal powder and 5% of resin?

... This wouldn't also mean that the entire thing would just become 5% lighter and still weight too much?

---

Well, there was a bigger text here trying to calculate how many 30 watt induction motors I would need for each limb, and the answer is 1800, lol.

Obviously, it is best to simply use a single bigger motor, such as a 9000 watt (12 horsepower) motor for every motor-pulley "muscle" in the legs. Each one only weights 5 to 10kg, and besides, you would need around twice as that because of the inneficiencies of the 3D printed version... But the exact size and power can only be determined by actually building and testing them.

---

By the way, it is relevant to remember that 9000 watts will be the total of consumed power by one or two legs at one given time, so the motors don't actually need to have 12 horsepower.

Assuming only 3 of the 6 pulley-motors were working in each given leg, they would be able to lift 18,000 kg if they were to actuate at maximum power and in conjunction, but you wouldn't need that normally.

If the actuators were linear actuators (like hydraulic cylinders or screw lifters) then in total it would be able to lift 36,000 kg.

In both cases, I have no idea what kind of monstrous skeleton one would need in order to sustain such obscene amount of weight...

---

Also, a 12 horsepower induction motor with a reduction gear of 10:1 will be enormous and cumbersome, but a 80kw (106 horsepower) brushless motor with 300 Nm of torque only weights 23kg.

Maybe a 3D printed brushed motor with the same size of this 80kw brushless motor could work... But hey, I don't know how well it would perform, neither how to build it.

The motor in question is called "REB-90", I've made an attempt of a 3D model copy of said motor, but for a brushed or induction version of such thing would need to be incredibly different..

One would need to make a version from scratch, which is completly outside my knowledge.

By the way, I googled it just to check it out, but a 100 horsepower induction motor with 300 Nm of torque is the size of a person and weights around 500 to 1000 kg (and I couldn't find any exception to the rule).

There is also that megawatt induction motor made by MIT, but heh, I doubt I could even come close to such performance and efficiency...

Well, some news websites call it an induction motor, others, like this one, says it has a hallbach array arranged magnets on the rotor...

---

By the way, just now I found out that there are other methods of transmitting power in a rotary electrical connection, such as rotary transformers, inductive coupling and capacitive coupling, both methods transmit electricity without physical contact, unlike brushes, slip rings or commutators.

Again, this is out of my limited scope of knowledge. And as such, I wouldn't be able to design something like this on my own.

---

By the way, just now I found out about direct drive servos, hollow shaft motors and/or torque motors.

They are motors specialized on high torque low rpm without the need of gearboxes.

In any way, thinking a little about the induction motors driving pulleys would maybe not be that great. Simply because it would have too much inertia during rotation, not that relevant for continuous rotations, quite annoying to robotics that need to make repetitive motions on opposite directions.

---

It also makes me wonder another things about fully 3D printed motors: how to make them survive the absurd loads that it would suffer?

Maybe the shaft and bearings could be made out of steel, but even so, it makes me wonder if the electromagnetic field would be so strong that it would literally crush the 3D printed parts...

Innitially, in my head it could be totally okay, since the loads would be directed towards the shaft, but the connection of the rotor to the shaft could easily be broken.

So you would need to make various small fully 3D printed motors that would only apply the amount of force the materials used to build them could withstand.

... Which goes back to initial problem, since you would need to find the proper size of motors that could fit in a mech/robot without being too bulky. I tried to check 30 watt induction motors, but these are the size of a coffe bottle.
So a mech with 1800 of these per limb wouldn't be feasible.

---

By the way, just now I found out about limited anlge torque motors, or rotary voice coil actuators.

Some are like linear electromagnetic actuators, others are more like conventional electric motors.

There is also the tubular version, just like a piston.

Obviously, I was thinking on inserting electromagnets both on the part that moves and the stator, but again, I don't know what would be the final efficiency of such system, specially for high torque applications. Also, you wouldn't need to use commutators/slip-rings or anything like that, since the motor would only rotate a limited amount. It would need to be like a weird stepper motor.

Not to mention the fact that I literally have no idea how to make any of these types of motors...

---

One could make a flexible version of these linear electromagnetic actuators:

Source: https://www.semanticscholar.org/paper/Bidirectional%2C-Thin-Film-Repulsive-Attractive-Force-Schaler-Jiang/cd083cd842340162c220d93086dbd1e91a552810

Well, these ones basically took the printing of circuit boards and applied it to a flexible part. One could make a tubular version of these and even print it in a DIY way.

But, again, I don't know how it would work, how efficient would be and how to make it in massive quantities; so one could use these as artificial muscle fibers (I think).

Being honest, I don't even know why I didn't went for this idea to begin with. I think this could be a possible solution for the actuator problem.

---

The problem is that linear electromagnetic actuators need to be activated in a certain pattern and in a specific sequence, you can do that in a really big one, but how would one make it with hundreds or even thousands of these? Specially if the actuators were to be as small as the one shown above (these are coin-sized).

---

Also, just now I remembered something:

Solenoid artificial muscles, or using electromagnets instead of coils.

Basically, it is just a bunch of solenoids attached to each other. However, a really big problem is that it is just like a chain: the whole chain is only as strong as its weakest link.

Meaning that if you stack 10 solenoid motors like in the image, and each solenoid having maximum 2kg of force, the force won't be added.

You would need to make hundreds of thousands of parallel coils in order to add strength, just like metal cables.

However, as you can imagine, this is absolutely not practical in any sense.

The idea I had was to make extremely thin coils, as thin as wires in order to add their strength. But as you can imagine, this is simply not practical to do in a DIY manner. Maybe it would be viable with a specifically built machine.

However, just like I suggested using 3D printed electric motors, you could use the 3D printer in order to make fully 3D printed electromagnets/coils.

But you would need to check its efficiency, its resilience and built a super specific 3D printer to print something as insane as a wire-thin chain of electromagnets.

The fully 3D printed electromagnet in question.

I just found this one too.

---

But assuming that I am actually able to mass 3D print hundreds of even thousands of these electromagnetic filament artificial muscles:

How the hell I'm going to wire everything up?

---

The "best" idea I had was to cover the outside of the electromagnet-stacked "wire" with two conductive sides, one for the negative and other for the positive. This way you could simply find the two opposite sides of every wire.

You could also cover these plates with the flexible rubber and only take off the parts you will open for connecting electricity. Just like trying to wiring enameled copper wires.

However, I'm still not really sure how I would connect every single super thin wire on an entire muscle piece.

What if I need hundred of these muscle fibers? Or thousands? How I would connect to the limbs? How I would fix them if they were damaged or overly stretched?

I thought on maybe printing entire muscles with their respective connections already in place.

But how I would 3D model such an insanely complex piece of equipment? With micrometer precision no less!

How I would make sure everything is working properly? How I would 3D print the coils in these non-optimal positions?

---

I'm probably talking crap, but I had an idea for a nanometer scale resin 3D printer.

The spin coater (obviously) spins a plate with a liquid on it until its thickness reaches nanometers of scale.

This is used on the production of MicroChips/MicroProcessors. First they apply a liquid coating, then use a laser to blaze-off the coat in an specific pattern, then they apply another liquid that will be spon out, filling the spaces left out by the laser.

The idea would be to spin resin, apply the UV light, then use the laser to take out the undesired parts and then repeat the process.

However, this idea sounds kinda wasteful, and the only different manner I could think of would be using a coating and laser cutting on every layer, leaving behind space for the resin.
This would avoid the waste of resin, but it would still need for a proper planning for optimal coating removal (if you want to remove it at all).

But the other idea would be to use transparent plates with the coating removed with a laser and then use then as molds for each type of resin required for use.
Spray resin of an specific type on a transparent plate-mold, press on the fiber/wire, apply UV light, change for another mold, rinse and repeat.

In either way, I don't think I have the knowledge to do something this complex.

Of course, all of this was with resin in mind, but you could use other materials, such as the acrylic dissolved in acetone as shown in the video above.

---

---

In any manner, I think that a good option would be to use the hydraulic "artificial muscles" with gardening hoses with a pump actuated by some inexpensive and easily "DIYable" actuator, maybe one of the ones mentioned in this Log.

It could be a fully 3D printed solenoid pump, it could be a Nitinol muscle pump...

I just don't know what should be...

---

... In fact, I had the idea of using solenoid pumps for the hydraulic artificial muscles, for some reason I didn't follow up with the idea.

I think my head was just so full of crap that I simply forgot....

Aaaanyway, I guess this should be settled then: when I actually find some money to expend, I would try to make a fully 3D printed Solenoid Pump connected to the gardening hose actuator idea.

---

By the way, the resistivity of copper metal is: 

• 1.77 × 10^-8 ohm-metre

(of course the value can change significanly based on the gauge, but I don't think it will be significantly enough compared to the values of the 3D printed)

Now the resistivity of electrolytic copper powder with a purity of 99.9% (accordingly to bingGPT):

• 5.56 x 10^-7 ohm-metre

Copper nano powder:

• 2.86 x 10^-7 ohm-metre.

So... In the case of a fully 3D printed electric motor and/or solenoid, you would have less than half of the conductivity and more than twice the resistivity.

Meaning that you would use almost twice more energy (or more) for the same actuator.

... Now I remember why I gave up on this idea...

I thought on using silver ink to increase the conductivity, but... Well... Conductive silver ink has a lower conductivity than copper metal, contrary to what I thought, silver ink has a lower conductivity than copper metal and I couldn't find anything with a value closer (still searching tho).

Well, it seems like no powder has a resistivity closer to copper (even carbon nanotubes and graphene), so the solution could be simply using electroless copper plating.

Basically, you mix Formic Acid (very dangerous) with copper oxide and distilled water an all you have to do is cover something with it.

ChatGPT and BingGPT said that i could replace Formic Acid/Sulfuric acid with acetic acid, citric acid and tartatric acid, which are all organic and harmless, but I'm not so sure...

---

But to be honest... I don't think this is an actual solution.

Just imagine the amount of acid required to dissolve kilograms of copper? And how you would get it off once you applied to the printed part? It would simply dissolve everything.

Not practical in any way.

---

In any case, I asked to ChatGPT and BingGPT for how many extra watts I would need to pass through the electrolytic copper powder in order to compensate for the higher resistivity, and it said I would need to increase the amount of watts 3 times.

... But I don't like this answer, my question is simply too dubious, I would assume that I would actually increase the AWG of the printed copper wires by 3 times in order to compensate for the higher resistivity. After all, different AWG wires have different resistivities, not to mention that if one were to use aluminium wires in the place of copper wires, they would need to use twice the amount to compensate.

... However, I simply don't know how this "compensation" would occur. By increasing the length of the wires? Their diameter? The amount of turns? Changing the voltage and amperage appropriate for the material?

---

Well, since I wrote so fricking much, the Hackaday website simply started deleting the project log for any extra text I added, so I had to split it in two project logs:

Project Log 75: Tech Tree for Mechs².

Wednesday, 13/09/2023, 12:13

I'm feeling like whatever the hell I wrote in these "serious" project logs are complete nonsense, not only because I'm talking things with almost no basis in fact, but also because it looks like writings of a mad man.

I was simply trying to read previous project logs and I mix texts were I wrote it in the past and parts that I wrote in the present, so I may be referring to something like I'm talking about "the previous subject matter" but there are multiple paragraphs referring to something completly different.

... Which makes me wanna make more project logs that are more organized...

... But I'm holding myself to not do such bullshitery simply because I didn't finish the goddang 3D models yet.

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Well... Hi, good day, good afternoon and good night.

I'm still in an awful mood, but I would guess that it would be useful to simply do something (anything) rather than do nothing.

And well...  I'm just going to post here everything I need to watch so I stop procrastinating...

---

... It is kinda funny how I plainly said that this project is dead on Project Details, but I keep going with the project.

---

Being honest, if I had the money, I would've pay someone actually skilled to make this project a reality instead of cracking my head against the wall...

---

To be honest², even though I'm watching video per video, I'm not understanding half of the stuff that I'm looking at.

... I really need help with this project...

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Also, one thing that I forgot to talk about in all these project logs: remelting of 3D printed parts.

Basically, you could 3D print parts with 100% infill, put them in a medium such as plaster/gypsum and then put the thing inside an oven with more or less the melting point of the plastic being used and take it out.

Basically, 3D prints have a problem of layer adhesion, meaning that all 3D printed parts are basically a pile of sheets of paper-thin plastic layers held together by the adhesion of its surface.

By remelting the parts, you are turning the entire thing in one solid piece of plastic.

I saw other methods that use salt instead of plaster.

---

In anyway, you could commission 3D printed parts on a plastic of your choosing (such as HDPE) on one of those 3D print online stores and use this method to make the parts stronger.

Plus, you could drill the parts and infuse them with fillers such as steel wire and such.

Or just embed the wire on the 3D print during printing. lol

---

I just saw this video from the same channel, it is another interesting option.

Although carbon fiber is expensive, glass fiber isn't that much.

---

You could use either method to make the 3d printed parts stronger:

• Drill holes and inserting the steel wires and remelting.
• Drill holes and inserting carbon fiber/glass fiber and remelting.
• Injecting epoxy with glass/carbon fiber in the 3D print.

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Well, I was looking into buying slew bearings and make copies of them, and while I was doing that I stumbled upon this video.

I don't know what material it uses for the flat bearing plates that it has, but I thought it was an interesting concept.

Plus, I did like the idea of inserting limiters on the ring in order to, well, limit its rotation.

---

This means that the bearings that I've made aren't suitable as the way they are now, I need to remake them with a better concept in mind.

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Here the videos that I need to remember to watch and re-watch until I learn what I need to learn:

Okay, now for actual Finite Element Method I will put the concept ones first... Because reasons...

There was like one tutorial here, but it was incomplete because the full explanation was in the guy's course, which cost 90 dollars.

This one is actually very old (which certain tools are a little different) and the video stops before explaining how to see the loads.

This one explains it a little better, but I still don't know if the red parts are too difficult

---

Still watching and not understanding a hint, my mind simply drifts away while watching the videos.

I'm tempted in simply making everything as rugged as possible with steel instead of giving a dang about efficiency or weight savings...

... As if I had the money to do such thing, thus the reason why I need to learn.

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By the way, I asked ChatGPT how much pressure would be being applied to the bearing with 4cm of height and 20cm of diameter (just like the bearing I've made) in a 1,20 meter long lever attached to it and a weight of 300kg at its tip, it would be suffering a force around 3000 Newton meter.

Converting this to MPa, this would be around 0.1 to 0.3 Megapascals, and since HDPE has 30 MPa of tensile strength, this is way below its capacity.

Of course, it is ChatGPT we are talking about.

But nevertheless, I checked a beam calculator with said length and a load of 300kg (3kn) at 1 meter (1000mm) to 1,2 meters (1200mm) with a support at 0cm and another at 20cm (200mm), the weight on both parts was more or less around 15 to 30 kilonewtons, which would be more or less 0.03 MPa.

I also did the same thing for lever calculators and the loads were also equivalent.

---

Well, I hope I'm right, but this seems like I'm really working way below the breaking point of either HDPE and Aluminium.

Even if I were to increase the weight to 3000kg, 10 times more, I would still be under its breaking point.

I think.

Don't go using these results on your own or you may be seriously hurt or even dying, you take these values on your own risk.

---

I asked around and it seems like neither aluminium nor HDPE are suitable for the 300kg load, in either way, I can't know for sure until I actually learn the simulations and/or test it personally.

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I'm still procrastinating and screaming in despair, but hey, I think I had an interesting idea.

The bearings that I've made/found are quite complex to get it right in a simple 3D printer, even harder to calculate how much load these pieces would sustain.

However, I was thinking on actually using a mix of biomimicry and tensegrities.

In broad terms, the idea would be to make ligaments using a lot of metal wires attached to simpler versions of bones. This way I could keep the costs lower and still be able to calculate the overall forces the structures would be under without any kind of simulation.

Think of it more like a woven wood structure, but with other materials, such as steel wire or fishing line.

Now mix in with a bit of biomimetics:

Source: https://www.researchgate.net/publication/261479910_Design_of_an_anthropomorphic_robotic_finger_system_with_biomimetic_artificial_joints

Source: https://www.researchgate.net/publication/338912205_Material_and_mechanical_emulation_of_the_human_hand

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Of course, maybe.

Maybe it can work out, maybe not.

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... Maybe I'm just being lazy so I don't have to actually mess with these simulations...

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Now, one week later, now that I'm finally making something, I find out that Blender is a terrible program for exporting valid 3D models for Finite Element Analysis.

As such, I think I will just make a simple cylinder with the general dimensions of the bearing and check if it would be able to withstand the loads.

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Well, I tried my best but I could only make this ugly ass thing you are looking at:

Plus, you have to input the pressure as KPa instead of newtons or MPa, which confuses me because I need a value to translate to KPa, and the only value I had was kilonewtons.

30,000 Newton meters = 30 KPa

And in the simulation above, I used a 100 KPa load, which I don't know if it will suffice.

Well, I used the data of PLA instead of HDPE because there isn't data for HDPE on FreeCAD, but apparently, PET and PLA have better tensile strength than HDPE.

Which puts into question why the actual crap would I use HDPE?

---

I mean... HDPE ropes are rated on the range of 6 tons... Why we don't see these kinds of ropes made out of PLA, PET and others...?

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Well, I tried to convert Kilonewtons to kilogram force per cm², but it assumes that is kilonewtons per square meter.

Which would be around 300kgfcm² = 29419 KPa

I added the new value and everything was alright.

(There is an "nm" there, is Newton Meter or other measurement unit?)

---

Maybe this means that if I want to know how well this thing will survive under bigger loads, I would need to make everything again from scratch but on FreeCAD...

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... Right now I'm really not in the mood...

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I was thinking here... I think it would be for the best if I simply abandoned the rollers in the slew bearings and used a similar approach to the slew bearing video in the begnning of this project log.

Basically two disks with flat connections instead of rollers/bearings and a layer of low-friction material such as PTFE.

Something like this, I think.

This way would be easier to 3D model and simulate on FEM and on top of that, it would be relatively stronger.

The only problem would be post-processing.

I would need to make the pieces a little bigger than they actually need to be in the friction areas and then sand it down until it has an ideal surface.

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Or just make something like this:

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Returning to the subject of biomimetic artifcial exoskeletons, while imagining how it would work out, I keep running into the problem that I would need to make an entirely new anatomy for an exoskeleton.

The human skeleton wasn't thought to have something inside of it, so I can't take it on 1:1, but I was thinking on certain parallels.

For example, the problem of misaligment between the human joints and the joints of the exoskeleton.

Let's say, if you add an artificial femur to the side of your thighs, it would perform the rotation in the front direction pretty well, but it wouldn't be able to rotate on its own axis, that is why you wouldn't be as mobile as simply using slew bearings and such.

However, I was thinking that maybe one could use the same principle of rotation of the forearm/wrist.

The idea would be to add two or more parallel artificial bones that could rotate just like this, allowing the user full range of movement without the need for bearings.

... Hyphotetically.

---

But the positive of this is that I could test it out with cheaper materials and easier manufacturing than bearings...

... If I stop procrastinating...

---

But I still think that I could use that idea of linear guides in a stewart platform configuration for the thighs and shoulders, but I don't know how well those would peform.

---

Right now I'm divided between the idea of an angled bearing exoskeleton, a conventional bearing exoskeleton, a biomimetic exoskeleton and a linear guide exoskeleton...

All options have their own pros and cons, but I think I should at least rule out the biomimetic (exoskeleton, endoskeleton can use it) and the angled bearing exoskeleton.
These are the most complicated to do, even though the biomimetic would be the cheapest to make.

I say this because how the hell you would be sure every joint is properly attached? How you would be sure every load was properly distributed? You would be on the blind in the case of the biomimetic.
Now the bearing one you can know for sure what is wrong, what is right, and can still make it adjustable for every user.

I could also use a mix of the linear limiters and conventional bearings exoskeleton...

---

... I'm starting to think that maybe that I should try making the mech suit first... I wouldn't need to worry about not killing whoever is inside of it... But both are equally hard on their own right...

To be honest, neither option is the best, because I still didn't solve the actuator's problem.

I either need an absurd amount of small electric motors to act like "pulley-muscles" or waste an equally absurd amount of efficiency in a central pump driven by a single engine/motor.

I need to find a way of using the elecstrostatic/dielectric/electroosmotic pump...

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Just digging myself in this stupid rabbit hole...

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How I will even make it adjustable for everyone...? Ugh...

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I swear, I will try start these new bearings tomorrow.

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Off-topic:

I don't know if I already talked about this in previous project logs, but...

Basically, some metals such as aluminium and titanium weld with itself under vacuum, their atoms simply chemically bond with each other.

So I was wondering if it could be possible to use this in a manufacturing process, basically, taking titanium powder or aluminium powder and mixing with graphene (or other materials, such as carbon/glass fiber), putting everything under vacuum and hot pressing everything with an hydraulic press.

I wonder if it would be capable of actually coming closer to "cold"-weld everything together...

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By the way, I was checking the numbers and it seems like I would need 3 times more energy to make the artificial muscles to go into the same velocity as the real muscles.

For example, the biceps brachii muscle has a lever arm that is approximately one tenth that of the center of mass of the forearm and, thus, the muscle needs to generate a force over 10 times the weight of the forearm in order to produce elbow flexion. It has subsequently been proposed that muscle-derived forces are the primary source of mechanical loading that generates bone strain [8, 9].

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4306629

Basically, the mechanical disadvantage that I was planning was one-third, in other words, if I apply a  force at a speed, I would receive 1/3 of the force and 3 times the speed at the end of the limb.

However, since the disadvantage of human muscles is 1/10, this means that it applies a speed and a force that is divided and multiplied 10 times.

Human muscles reach a speed of 40cm/s, just like my artificial muscle, but it receives a boost of 10 times its original speed.
But mine only receives 1/3 of the speed, meaning that in order to compensate, I would need 3.33 times more speed to compensate.

Force x Velocity = Energy.

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I can replace hydraulic artificial muscles with thermal artificial muscles, which are the best in force per weight (around 10,000 times its own weight), but supper slow and inneficient, just like the real deal. Plus, the one that I intend on using has a linear speed of around 40cm/s also.

03/09/2023, 13:20, Sunday.

Well, I'm writing this² after finishing this project log because I feel like I failed this project log.

Even though I reached a few conclusions on how much energy I would require depending on the type of pump I used, I didn't reach any satisfactory conclusion.

Neither did I make any useful 3D model.

I will try again later and maybe this little message will be deleted, but still.

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So, I'm writting this here because I had some ideas for making a cheap DIY pump, my stupid brain simply insists that I'm simply not trying hard enough when there is simply no easy way of doing these kinds of things.

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Well, where do I start?

I was checking some other solenoid valves that aren't 5kg of force, and decided to at least give a try with the 25 newton solenoids.

This one weights 100 grams, but I would bet it is more likely because of the steel part rather than the copper coil.
In either way, you could use aluminium wire instead of copper, but it is a little bit cheaper per kg than copper.

Anyway, this one uses 4.8 watts of power, but in some sites it says it uses 30 watts.

So I thought on making a free piston/plunger with 7mm to 8mm of diameter (needing a force of 19 Newtons to 25 Newtons respectively) moving 50 times a second, it will be able to achieve 1.5 liters per minute in each side of the pump, so 3 liters per minute in total.
This would be able to more or less actuate two filament artificial muscles, however, if you braid those like intended, you would use longer muscles that in turn would need more fluid flow.

Now, for the working principle you have two options:

1. Using a soft iron core with two coils that will alternatively pull the free piston torwards in alternating turns.
   
2. Using a Neodymium magnet as the free piston with a single coil that will change the electromagnetic poles, making the magnet move up or down.

Both have advantages and disadvantages, but let's remember that this thing will be moving 50 times a second, I'm confident the iron core can handle it, but I don't know about the neodymium magnet.

In both cases you will need a way of knowing where the free piston is, using some kind of sensor.

First I thought on using a hall sensor or a mechanical switch, but the hall sensor has to take into consideration the electromagnetic field and the mechanical switch has to take into consideration the pressure inside the chamber, so it doesn't activate with the pressure.

I'm pretty sure there is a easier way of doing that, but I couldn't think of anything.

---

With a 1kg of copper and 100gram coil per solenoid pump consuming around 30 watts of power, you would be able to power 20 muscles, or in the worst case, 10 muscles.

Since 1kg of copper wire is 100 reais (20 dollars), you would use 1500 to 3000 reais (300 to 600 dollars) in total. Not so dissimilar than the 10 dollar brushless motor.

But the downside of the brushless motor is that it needs a reduction gear and a very bulky hydraulic gear pump.

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Now, about the hydraulic gear pump and/or the axial piston pump.

One thing I was very clear on talking about was the precision between the parts, which I don't really think it would be easier (or possible) to do in a DIY way.

The idea would be to simply do two things:

1. Using a glass plate with abrasive material on it.
2. And/or using a DIY lathe.

The glass is the flatest surface that one could have at home, so by using it like a "sand paper", you could achieve incredibly flat surfaces.

In this video the guy does something similar, at the 6 minute mark.

This will be useful both for the axial piston pump and gear pump.

However, as you can see, both pumps have round surfaces, either with the gear teeth and/or with the piston heads.

In such cases, you will need to use a DIY lathe with a drill or something like that, there are plenty of 3D printable lathes on thingiverse and other similar websites.

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However, the idea here is to 3D print either pump with a overhang in both cases and sand it down using both methods, and after that, use the sanded 3D printed parts to make a mold, and finally, make a copy using resin or molten plastic.

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In the case of the gear pump, I think it would be harder to sand down the gear teeth, whily the axial piston pump would probably be the easiest to DIY.

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By the way, you can easily find a lot of gear pump and axial pump 3D models on thingiverse and grabcad.

Although you have to pay attention to their description in order to know if it is a mockup or a super detailed and/or functional 3D model/3D print.

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I don't even know why I'm doing this Project Log, like I said in the project details. I really can't keep up with this project, but my mind simply says that I'm not trying hard enough even though I gave my best...

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One would need one of these DC power supplies in order to test it out, but I don't have money for them.

One would need to buy 1kg of copper wire or enamelled aluminium wire, but I don't have money for that either.

In resume, I'm broke as hell, and the only way I would be able to continue this project is if I had any.

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In either way, I'm trying to find an equivalent for the tiny brushless motor's hydraulic pump.

The Samguk Series brushless motors have a maximum RPM of 30,000, but hydraulic pumps normally operate at maximum 2500 to 3000 RPM with a minimum of 0.8 Nm to 2 Nm.

The idea would be to have a hydraulic pump that can directly be mounted to such small motor with such rpm.

The best I first thought was to make a solenoid pump, but these aren't as efficient and are heavier than the aforementioned brushless motor. Such motor only weights around 50 grams and outputs 750 to 900 watts of power, while the solenoid itself can weight around 100 to 200 grams and only output a maximum 30 watts.

The motor would be able to supply 10 muscle filaments at same time (if connected to a gear pump and a reduction stage) while the solenoid pump can only fulfill only 1 to 2 muscles.

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Obviously, one should take care of cavitations at such high rpm. But if the pump is as small as the motor, I don't think it would be much trouble.

Again, I THINK, this is not a good indication to begin with.

Anyway, I tried to calculate:

Basically, I know I want to make a 5 to 6 piston axial pump, and that it would rotate 500 times a second, giving 30k RPM.

So:

500 * 5 * 60 * x = 20,000 mL per minute.

x = (20,000/150,000)

x = 0.13333333333

So, each piston will need to have a 0.13333333 milliliter displacement.

And accordingly to the pipe volume calculator, I would need a 5mm diameter bore/piston with a travel of 6.79mm.

And in turn, the entire axial piston pump would need to be something with around 48.62794mm of diameter or less in order to achieve 5 bar of pressure with the Samguk torque of 0.2387 Nm.

But since there will be 5 piston heads, and 2 to 3 will be travelling downards, does this mean that it will need 2 to 3 times the force? If so, it would need to be 26.5222mm to 17.68148mm in diameter.

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Oh yeah, I forgot, the 0.2 Nm is the torque when the electric motor will be at maximum wattage (750 watts), but since it needs to work at +/- 300 watts, it would need half of that diameter, so 13.2611 mm.

But this value is so small that I don't think the piston heads would even fit inside of it, I think it would be better to actually cut by half the diameter of the pistons to 2.5mm and simply double its travel to 13.58mm.

The diameter of a piston pump is more or less the distance of travel, so the radius and the stroke are pretty close, which is a positive sign.

Now I have to stop procrastinating from making the exoskeleton and the hydraulic pump at same time...

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Well, I tried to make the axial piston pump on blender with these parameters, but it seems this specific pump is way too complicated for my limited knowledge in 3D modelling...

You can still take the first piston pump I made earlier and just scale it down, but heh, we are talking about a piston with 2.5mm of diameter, it wouldn't be worth the trouble even if it was possible to 3D print such thing.

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Accordingly to this piston speed calculator, the piston would be travelling more or less 6.79m/s when pulling the fluid.

But I don't know if this will be enough to create cavitations tho.

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I would assume that it wouldn't, simply because cavitations are caused by vacuum, and the bigger the surface area, the stronger the vacuum, since this is so small, even if cavitations occurred, they wouldn't be as destructive as in conventional pumps.

This is a rough guess made by a person that doesn't know anything about hydraulics.

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Also, I was wondering, even with a pump proportional to the brushless motor, there is still the problem of actually reaching the appropriate speeds.

For example, I found this old video about preloaded artificial muscles here on hackaday and it takes an awful lot to fill each opposite muscles:

Obviously, I'm not trying to insult or demean anyone, but a lot of DIY attempts focuses on doing the stuff rather than trying to think on how well the stuff does certain job.

The person uses a RC hydraulic pump, which can achieve 100 bar (10 Mpa) of pressure, but only has 1 to 2 liters per minute of fluid flow, which can be responsible of such slow actuation.

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Also², I was searching for articles about untethered artificial muscles (again), just because I know a thing or two more than I did before.

For example, I remember seeing one which used a heating element to heat up paraffin and expand the muscle, but it took literal minutes to do so. If I were to accelerate such process, I would need to make hundreds or even thousands of super thin paraffin muscle filaments

Source: https://www.researchgate.net/publication/296619826_Thermally_activated_paraffin-filled_McKibben_muscles

Source: https://www.researchgate.net/publication/340673235_Actuation_of_untethered_pneumatic_artificial_muscles_and_soft_robots_using_magnetically_induced_liquid-to-gas_phase_transitions

This one uses one of those electromagnetic heaters, which takes 3000 watts to work.

In both cases it would be better to simply use silicon carbide powder in both cases and a microwave source, just like I talked on previous project log.

But in either case I don't think the materials would survive very longer under such extreme heat, it will be maximum 100ºC in the case of water, but still, we are talking about a thin layer of plastic.

Maybe one could use ethanol, perhaps? "Just" heat-muscles with flamable fluids, what could go wrong?

Also, something that I didn't talk about in the previous project log was the idea of adding a water spray system to Shape Memory Alloy/Polymer muscles in order to achieve rapid cooling, which would also be useful in this specific case.

Although I don't know how well this system would work with a high frequency actuation, like when you are running, for example.
In such case, how do you get rid of the fluid?

"Simply" spraying cold air would be interesting, but air has a terrible heat conducting, unlike fluids.

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I don't know why I would want a mech/exosuit to run very fast, but I can see a slower one being used for heavier loads.

Maybe I should give up on a fast moving mech/exosuit and stick with something simpler.

A thermal McKibben filament artificial muscle would be way easier to mass produce and assemble than a hydraulic one with hundreds of filaments and even more hydraulic pumps and brushless motors.

... But it would create another problem, the problem of efficiency...

... And I also don't know how well I could calculate and predict their actuation before even making them myself...

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I asked to ChatGPT and it said that the energy conversion of silicon carbide powder in turning electricity to heat is around 90%, although I don't know its efficiency of microwave to heat conversion (I'm waiting for answers in other websites).

I can in turn take the energy required to heat up an "X" grams of silicon carbide to a "Y" degrees and then see how much energy one needs to heat up an "Z" grams/ml of a certain liquid to "W" degrees, and finally, how many "V" ml/liters of gas these "Z" ml of liquid would produce, and thus, how much pressure it would apply inside the McKibben muscles.
Not so dissimilar from calculating how much energy one needs to input in order to boil water (aka Calories).

Then I would need to approximate how many liters of water I would need to spray on the muscle bundle in order to absorb this X amount of heat.

Even if the efficiency of the Silicon Carbide powder to heat is 90% and the efficiency of liquid to gas is also 90%, the water pump and the heat exchanger will diminish the overrall efficiency of the system.

In either way, I'm starting to wonder how in tarnation I would make the silicon carbide heating element for this muscle.

I doubt I could simply add silicon carbide powder to a liquid, pass an electrical current through it and everything will heat as expected.

I think one would need to make DIY heating elements by either making a DIY conductive ink but with silicon carbide or making a semiconductive filament with silicon carbide powder.

During the video (+/- 1:40 min mark) the guy explains how to calculate how much electricity would be required to generate an X amount of heat.

Which makes me wonder how I'm going to deal with the heat conduction of each material, since the cooling system (and thus, the diactivation system) is on the outside. I would need to either make reeeally thin McKibben muscles and/or use highly thermally conductive materials, like copper and/or aluminium.
Which² would also increase the chances of ending up having short-circuits all over the place, since said materials are also electrically conductive.
Which³ would also increase the difficulty of production and weight, plastics are easier enough to melt together in a tubular shape (or you can already buy something with a tubular shape), but metal foils on the other hand...

Maybe I could put a liquid spray inside the muscle so it condenses the vapour back to its liquid form, but I would be dealing either with water or ethanol, and both are not so ideal options.
Water needs to much energy to boil/vaporize, but ethanol is flamable...

... The more I think of it, the more I think it is not a good idea overrall...

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Well, I was kinda lazy, but I think I have all the necessary information for calculating these new muscles.

So, 1 calorie is a unit of energy required to heat 1 gram of water to 1ºC at room pressure.

Is useful to remember that the boiling temperature of water increases with the pressure, so the bigger the pressure inside of the artificial muscle, the more energy I would require to vaporize water.

So, inside a 1 inch diameter muscle with 30cm of length, there are 0.152 liters, or 152 grams of water at room temperature.

Assuming that room temperature is 27 ºC, I would need to add 73ºC of heat to the water to 100ºC, so 152x73 = 11096 calories.

This is more or less 12,8 watt-hours.

However, at 5 atm (or 5 bar), the boiling pressure of water is around 151ºC.

152x124 = 18848 calories = 21.9 watt-hours.

Of course, this is a calculation with perfect heat transfer and perfect conversion to water vapour. Which is not possible.

(By the way, I would need to use silicone rubber or polyurethane as the inner bladder since now the temperature is so high)

Now, I need to find how much ml of water I would need to boil from that 152 ml of water in order to achieve 5 bar of pressuree inside the muscle.

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"Steam is a specific kind of vapor that is only produced through boiling. And when steam is created, it also expands. Each liter of water that is boiled will expand to 1600 liters of steam!"

Source: https://tuttnauer.com/blog/autoclave-sterilization/basic-concepts-of-steam#:~:text=Steam%20is%20a%20specific%20kind,to%201600%20liters%20of%20steam!

Well, since 1 liter = 1600 liters of steam, in order to make 0.152 liters 5 times to achieve 5 bar/atm of pressure, I would need 0.76 liters of steam...

So I would need to divide 0.152 liters by 1600 liters of steam? I'm a little bit confused.

0.152/1600 = 0.000095 x 5 bar = 0.000475 liters

I asked ChatGPT, I think he got it right:

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"To determine how many liters of water you would need to produce 0.76 liters of steam, you can use the given ratio:

1 liter of water produces 1600 liters of steam.

You want to find out how much water is needed to produce 0.76 liters of steam. You can set up a proportion to solve for it:

(1 liter of water) / (1600 liters of steam) = (x liters of water) / (0.76 liters of steam)

Now, you can cross-multiply and solve for x:

1 * 0.76 = 1600 * x

0.76 = 1600x

Now, divide both sides by 1600 to isolate x:

x = 0.76 / 1600

x ≈ 0.000475 liters of water

So, you would need approximately 0.000475 liters (or about 0.475 milliliters) of water to produce 0.76 liters of steam at room pressure according to the given ratio."

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So, since to heat 1 gram of water in 1ºC I would need 1 calorie, this means that in order to heat 0.475 milliliters (or 0.475 grams) of water, I woudl need...

0.475x124 = 58.9 calories = 0,06845489 watt-hour of energy.

Well, I don't know how incorrect I am, but this... Looks too much too little. lol

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You telling me in order to make an 100kg rated artificial muscle to achieve 5 bar of pressure, I would just need 0.06 watts?!

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I asked this around and someone said to me I should give a look at "the latent heat of vaporization" of water.

"For example, the latent heat of vaporization of water is 540 cal/g and the latent heat of freezing of water is 80 cal/g. Therefore, changing a given quantity of water to steam requires 5.4 times as much heat as warming it from 0°C (+32°F) to 100°C (212°F), and melting ice requires as much heat as warming water from 20°C (68°F) to 100°C."

Source: https://byjus.com/physics/latent-heat-of-water/#:~:text=For%20example%2C%20the%20latent%20heat,water%20is%2080%20cal%2Fg.

So, I don't know which value to take from this, 5.4 or 540.

In either way:

0.475x124 = 58.9 x 5.4 = 318.06 calories = 0,369587 watt-hour.

0.475x124x540 = 31806 calories = 36,9 watt-hour.

If I use both values:

0.475x124x540x5.4 = 171752.4 calories = 1996,1 watts.

Well, now this sounds more right, I guess...

When water converts from a liquid to a gas, a quantity of heat energy known as the latent heat of vaporization is required to break the hydrogen bonds. At 100 °C, 540 calories per gram of water are needed to convert one gram of liquid water to one gram of water vapour under normal pressure.

Water can evaporate at temperatures below the boiling point, and ice can evaporate into a gas without first melting, in a process called sublimation. Evaporation below 100 °C and sublimation require more energy per gram than 540 calories. At 20 °C (68 °F) about 585 calories are required to vaporize one gram of water. When water vapour condenses back to liquid water, the latent heat of vaporization is liberated. The evaporation of water from Earth’s surface and its condensation in the atmosphere constitute the single most important way that heat from Earth’s surface is transferred to the atmosphere. This process is the source of the power that drives hurricanes and a principal mechanism for cooling the surface of the oceans. The latent heat of vaporization of water is the highest of all common substances.

Source: https://www.britannica.com/science/seawater/Thermal-properties

So, if I understood this right (which I may probably be wrong), since 540 is 5.4 times more energy per gram of water, this means that I need 100 calories, then after that, I would need to multiply by 5.4 for every degree?

So, let's say that I need to heat up the water to 200 degrees, since 150ºC is already the limit due to the 5 bar of pressure parameter.

I would need 50 calories x 5.4 = 270 calories + 58.9 calories = 328.9 calories = 0,38 watt-hour.

I don't understand, I'm on the right track?

---

I asked ChatGPT because nobody is being able to answer me:

"Your calculations are on the right track, but there are some nuances in your understanding of the thermodynamics involved in heating water and converting it into steam that need to be clarified.

First, the latent heat of vaporization for water is indeed about 540 calories per gram (or 540 cal/g). This means that to convert 1 gram of liquid water at 100°C to 1 gram of steam, you need 540 calories of energy. This value is constant, regardless of the initial temperature of the water.

However, when you're dealing with changing the temperature of water from a lower temperature to a higher temperature, you need to consider the specific heat capacity of water. The specific heat capacity of water is about 1 calorie per gram per degree Celsius (1 cal/g°C). This means that to raise the temperature of 1 gram of water by 1 degree Celsius, you need 1 calorie of energy.

Now, let's break down your calculation for heating water to 200 degrees Celsius:

1. To heat 0.475 grams of water from 27°C to 100°C:
   • ΔT (temperature change) = 100°C - 27°C = 73°C
   • Energy required = mass (0.475 g) x specific heat capacity (1 cal/g°C) x ΔT (73°C) = 34.675 calories
2. To convert 0.475 grams of water at 100°C to steam:
   • Energy required = mass (0.475 g) x latent heat of vaporization (540 cal/g) = 256.5 calories
3. To heat 0.475 grams of steam from 100°C to 150°C (assuming the 5-bar pressure limit):
   • ΔT (temperature change) = 150°C - 100°C = 50°C
   • Energy required = mass (0.475 g) x specific heat capacity (1 cal/g°C) x ΔT (50°C) = 23.75 calories

So, the total energy required to achieve your desired conditions is approximately 315.925 calories, which is approximately 0.367 watt-hours. This calculation takes into account both heating the water and converting it into steam.

You can see that this value is relatively close to your last calculation, which is a good sign that your approach is reasonable. The key is to correctly account for the energy needed to heat the water to the desired temperature and the energy needed for the phase change from liquid to steam.

Keep in mind that these calculations are idealized and do not account for losses due to inefficiencies, so in practice, you may need to provide slightly more energy to achieve the desired result."

---

To calculate the energy required to transform 1 gram of water into steam, you need to consider the specific heat of water and the heat of vaporization of water.

1. Specific Heat of Water (C_w): The specific heat of water is the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius. It is approximately 4.184 joules per gram per degree Celsius (J/g°C).
2. Heat of Vaporization of Water (H_vap): The heat of vaporization is the amount of energy required to transform 1 gram of water at its boiling point into steam without changing its temperature. It is approximately 2260 joules per gram (J/g).

Now, to calculate the energy required to transform 1 gram of water into steam at its boiling point:

Energy (in joules) = Mass (in grams) x Specific Heat (J/g°C) x Temperature Change (in °C) + Heat of Vaporization (J/g)

In this case, the temperature change is from the boiling point of water (100°C) to the boiling point of steam (100°C). So, the temperature change is 0°C because the temperature remains constant during phase change.

Energy (in joules) = 1 gram x 4.184 J/g°C x 0°C + 2260 J/g Energy (in joules) = 0 + 2260 J

Now, to convert joules to watt-hours (Wh), you can use the following conversion:

1 joule = 0.000277777778 watt-hours (Wh)

So, to convert the energy from joules to watt-hours:

Energy (in Wh) = 2260 J x 0.000277777778 Wh/J Energy (in Wh) ≈ 0.627 Wh

So, it takes approximately 0.627 watt-hours to transform 1 gram of water into steam at its boiling point.

Since I'm dealing with 3 grams of water, then I would need 0.29 watt-hour.

I mean, 0.1 gram = 0.0627 watt hour, since I'm going to need 4.75 times more.
So 0.0627x4.75 = 0.297825 watt-hour.

---

Unfortunately, I can't find an answer anywhere, so this value that ChatGPT found is the "best" answer we have for now.

And even then, it gives totally different results whenever I ask it the same queston.

One time is 11 kilowatts, other time is 0.6 watt-hours, another 2 kilowatts...

---

I received an answer:

You need to specify the initial temperature of the water. Although the vaporization phase requires most of the energy, so you won’t make a big error if you don’t specify it.

First, find the energy needed. There are two steps in the process: raise the temperature of the water to the boiling point, then vaporize the water.

To find the energy needed to raise the temperature, use the specific heat of water. c = 4.184 J/g•K. Then Q1 = m•c•delta-T. Assuming the water starts at room temperature, 20˚C, and must be raised to the boiling point, 100˚C, this gives Q1 = (1 g)(4.184 J/g•K)(100˚C - 20˚C) = 335 J. Note that the size of the K and the ˚C are the same, so they cancel.

To find the energy needed to vaporize the water, use the heat of vaporization. L = 2260 J/g. Then Q2 = mL = (1 g)•(2260 J/g) = 2260 J.

The total energy needed to heat and vaporize the water is Q = Q1 + Q2 = 2595 J.

The Watt-hour is a unit of energy. 1 Watt = 1 J/s, so 1 Watt-hour is 3600 J. So Q is already a quantity you can express in Watt-hours: Q = (2595 J)/(3600 J/Watt•hour) =0.72 Watt•hour.

If you want to deliver this energy in 1/5 = 0.20 s, the power you’d need is P = Q/t = (2595 J)/(0.2 s) = 12,975 J/s = 12,975 Watt.

Well, this is not efficient, I suppose...

---

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---

Also³ I just found this video of a soft pump:

Here is how the pump is made:

It makes me wonder why they didn't simply took a polyurethane/TPU tube and skiped half the work...

Source: https://www.science.org/doi/abs/10.1126/science.ade8654

It is pay per view and I can't find anywhere else, so I don't know its efficiency, the voltage required and so on.

In the video it shows a graphic with it achieving 8 kilovolts maximum, but still, I don't know the exact amperage and the efficiency of the system.

---

In the video there is the amperage and the voltage in a graphic.

So it has 5 microamps and 5 kilovolts, so it uses 0.25 watts in total.

0.000050x5000 = 0.25

---

I'm not very smort, the description of the video has a website and in that website there is a link to a free version of the manuscript:

https://www.science.org/stoken/author-tokens/ST-1105/full

Incorporating pressurized fluidic circuits into textiles can enable muscular support, thermoregulation, and haptic feedback in a convenient wearable form factor. However, conventional rigid pumps, with their associated noise and vibration, are unsuitable for most wearables. We report fluidic pumps in the form of stretchable fibers. This allows pressure sources to be integrated directly into textiles, enabling untethered wearable fluidics. Our pumps consist of continuous helical electrodes embedded within the walls of thin elastomer tubing and generate pressure silently through charge-injection electrohydrodynamics.

Each meter of fiber generates 100 kilopascals of pressure, and flow rates approaching 55 milliliters per minute are possible, which is equivalent to a power density of 15 watts per kilogram. The benefits in design freedom are considerable, which we illustrate with demonstrations of wearable haptics, mechanically active fabrics, and thermoregulatory textiles.

100 kilopascals = 1 bar of pressure.

55 ml per minute = 0.055 liters per minute.

If the artificial muscle is a 12,5mm inner diameter and 30cm of length, then it will need more or less 1.8 liters per minute, if it is a 1 inch inner diameter with 30cm of length, it will need 8.1 liters per minute.

I would need 5 times more pressure and 32.7 times more fluid flow in the filament case and 147.2 times in the 1 inch case.

I don't really know how to increase the pressure, but I would suppose that in order to increase the fluid flow I would need to increase the number of flexible pumps... By 32.7 times...

---

If I were to increase the pressure by 5 times and fluid flow by 32.7 times, I would need:

0.25x5x32.7 = 40.875 watts

Well, a little less efficient than the hydraulic pump with the brushless motor, which would consume 300 watts for 10 muscles, so 30 watts for every muscle.

Now, I "just" need to figure out how to increase the pressure and fluid flow...

It says "each meter", does this means that I need to increase the meter of the pump to increase the pressure? Or that I need to increase the amperage?

---

I just woke up, I will try to read the rest of the paper later...

---

Anyway, I'm trying to get a grasp on the subject, but I'm failing miserably.

In the "B(i)" graph, it shows how the max pressure lowers based on the increase in diameter of the tube, but increases the flow rate.
On the "C" and "D" graph, it shows how the pressure and flow rate increases with the length of the pump.

Which makes me wonder if in order to increase both pressure and flow rate I only need to increase the length...

I'm sending an email to the authors, I doubt I will receive any answer...

But I would bet that in order to achieve the desired flow rate I would need to put various parallel pumps, now, for the pressure...

---

I received an answer, and the authors said that they never tested the pump with these parameters, but said that I'm probably right that increasing the number of pumps in parallel and the length would increase the fluid flow and the pressure.

-------------

---

Also, in other images it shows that the copper electrodes are in direct contact with the fluid, which explains why they didn't simply glued the copper wires to the outside of a TPU (thermoplastic polyurethane) tube.

However, one could still buy a TPU tube, open it up, insert the rod with the copper electrodes inside it, remelt it in order to close the tube again and "glue" the electrodes to the inner walls.

---

The fiber pumps can pump continuously for up to 6 days before chemical deposits passivate the electrodes (fig. S7H). This is considerably longer than any other reported EHD pump, soft or otherwise (9), and can likely be improved further through careful selection of liquid and electrode material.

ffffffff- ok, how do I increase this value?

---

Edit¹: (12/01/2024)

This is me from the future.

One thing that I didn't learn until later on is that electrostatic currents can pass through anything, even thin wires with a lot of resistance.

In fact, you could replace the copper wires by conductive ink just fine (which puts into question on why go the trouble the guy went to use TPU and copper wires).

In fact², you could easily 3D print the entire pump in a compact manner for somewhat cheap.

I also made the calculation, you would need 5 meters for 5 bars of pressure and 219 parallel tubes for a fluid flow of 12 liters per minute.

If you have a 10 cm long reverse piston with 25mm of diameter (1 inch), you would be able to lift 25 kilograms, which would mean 2.2 watts per kilogram.

This is assuming 5,000 volts and the only 4 electrodes per tube, by increasing the length and the quantity of electrodes, maybe the amount of wattage will change. But again, I can't test that. I'm broke.

---

Of course, the bigger the flow rate, the bigger the energy required. So if you increase the velocity of actuation, it will consume more energy momentarily.

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---

To extend the operational lifespan of the fiber pumps and delay the passivation of the copper electrodes, you can consider alternative materials for both the electrodes and the working fluid. Here are some material options to consider:

1. Electrode Materials:

• Platinum or Gold: These noble metals are highly resistant to corrosion and can withstand prolonged exposure to the working fluid. However, they are more expensive than copper.
• Carbon Nanotubes: Conductive materials like carbon nanotubes can be used as electrodes. They have excellent chemical stability and durability.
• Graphene: Similar to carbon nanotubes, graphene is chemically stable and can be used as an alternative electrode material.
• Titanium: Titanium and its alloys are known for their corrosion resistance. They may be suitable for long-term exposure to certain fluids.

2. Working Fluids:

• Ionic Liquids: Ionic liquids have low volatility and are known for their chemical stability. They can serve as a suitable dielectric fluid in EHD systems.
• Fluorinated Fluids: Fluorinated fluids, like perfluorinated compounds, are often used as dielectric fluids due to their high breakdown voltage and chemical inertness.
• Silicone Oils: Certain silicone oils have good dielectric properties and are chemically stable, making them a potential choice for the working fluid.
• Custom Formulations: Depending on the specific application, you might consider formulating a custom dielectric fluid with additives to improve stability and reduce the likelihood of passivation.

It's essential to assess the compatibility of the chosen materials with the specific requirements of your wearable fluidic system. Factors such as electrical conductivity, dielectric properties, chemical compatibility, and cost should all be taken into account when selecting alternative materials. Additionally, long-term testing and monitoring can help evaluate the performance and stability of the chosen materials over extended periods to ensure they meet your desired lifespan requirements.

---

"Throughout this work, we used the dielectric liquid Novec 7100 (3M). This is a nontoxic, nonflammable methoxy-fluorocarbon with low global warming potential (20). It is commonly used as a solvent and for heat management but also performs well as an EHD fluid because of readily ionizable fluorine groups and a high electrical breakdown field of 10 kV/mm (20). Other liquids (including nonfluorinated compounds) may be pumped, provided that they have low conductivity and viscosity and are electrochemically stable (21, 22)."

I tried to look around and see if I could find this liquid, and boi, oh boi.

I kid you not, 3 liters of this fluid costs 16,000 reais (3,200 dollars).

Also, I just found this other link were it "only" costs 11,000 reais (2,200 dollars) and weights around 15kg:

This is more or less 1000 reais (200 dollars) per kg of fluid.

Of course, the paragraph says that other dieletric fluids may be used, but oh boi, what are the other dielectric fluids?

When it comes to dieletric stuff I don't know a hint.

---

Well, anyway, unless I can actually test the goddamn filament pump by myself, I can't know for sure how many of those I would need.

And in order to test that, I need money, which in matter of money, I don't have any.

---

In any matter, if I can simply increase the fluid flow and pressure of the pump by increasing the length of the pump, then it will probably not be worth the trouble.

We are talking about a 1 meter long (1000mm long) pump that can output only a few ml per minute and 1 bar of pressure.

If I were to increase its length 1 time per bar of pressure, I would need more or less 5 meters of tubing with copper or titanium electrodes for every 30cm long muscle.

I would already need kilometers for the bladders of the artificial muscles, just imagine how much TPU I would need...

---

If I can increase the pressure and fluid flow by simply increasing the voltage and amperage, I would still need 1 meter of tubing per 30cm of muscle.

---

I just found this video about electroosmotic pumps.

It uses 200 volts and 0.0022 amps, which translates to 0.44 watts.

The guy gives a way better and precise explanation, but basically, if you put two steel electrodes through a filter made out of glass in non-conductive water and pass a current through them, the water will flow to the negative electrode.

This is more or less the same principle the fiber pump I talked about before uses, but I don't know how much fluid flow I would get out of this system.

In fact, I don't even know how much fluid flow and pressure this system can output.

I couldn't even find a filter similar to the one used in the video.

I just found it, it is a fritter glass filter, and it costs around 130 reais (26 dollars) for every 10 units.

---

If this pump is capable of 5 bar of pressure and a fluid flow of 2 to 6 liters per minute, it would be really great for this project.

Even if it is not as efficient as a proper hydraulic pump, it is a system with no moving parts without expensive materials.

Until now, the problem is always the fact that I need an electric motor driving a pump, and both are expensive as heck.

A dielectric pump would be the ideal pump for this project, but alas, I don't know crap about these. And I can't find any accessible information on the subject...

---

I did found this graph for the electroosmotic pump:

Source: https://www.researchgate.net/publication/3425635_Closed-loop_electroosmotic_microchannel_cooling_system_for_VLSI_circuits

This is a micropump, and assuming that the graph scales linearly (which doesn't), I would need... 3.3 times more voltage (around 660 V) to achieve 500 kpa and 23 ml of fluid flow.

Assuming that this uses the same amount of amperage, I would consume 1.46 watts of power.

If I need to increase the amperage, maybe I could increase the fluid flow or pressure...

But I don't know, I need to test it...

... But again, I don't have the money to buy the equipment...

---

I'm writing this just for the record, if I were to reach 6 to 10 liters per minute, I would need more or less 260 times more fluid flow, which I don't know if is affected by the voltage or amperage.

Either way, assuming that 1.46 watts is just to achieve the pressure and the 260x is to achieve the fluid flow, I would need 379.6 watts of power to achieve 7 liters per minute and 5 bars of pressure that would allow 10kg of force.

This means that I'm expending 37 watts per kg of force.

25 times less efficient than using a brushless motor with a hydraulic pump, but since both of these are extremely expensive and bulky, the best option is still the electroosmotic pump.

---

Actually, if it is an actuator with 25mm of inner diameter and a shaft of 5mm of diameter, I would need 10 liters per minute and just 2 bars of pressure to reach 10kg of force.

Now that I'm under the pressure thresshold, I don't know how well it would increase in fluid flow...

Since I need 10,000 ml per minute, I would need 1250 times more fluid flow (10,000/8 ml = 1250), so... Assuming that the amperage is the same, I would need 550 watts in total. For 10kg.

... I really don't know how well the pressure and fluid flow would scale up based on the voltage and amperage, but I would still prefer this method over using pumps and electric motors.

---

For the record² I thought on something interesting for this pump.

Basically, the idea would be to use the glass filter itself as the piston head for the hydraulic actuator, so the actuator could be self-contained.

(I could also use a brushless motor with propellers so it pushes the water down, moving up, but I think this method is kinda stupid, lol)

However, the question is how the heck you would keep everything together and how strong are these fritted glass filters.

Not to mention that no fritted glass will be in the exact size/shape you want...

Dunno if you would be able to simply cut them into shape tho...

Of course, assuming that I need to use fritted glass filters.

The dielectric fiber pump didn't need no filters, and maybe non-conductive membranes such as polyethylene separators for car-batteries could be used (the guy in the video about electro-osmosis said that "it can use most materials, even plastic" in its pump).

... But I don't know if either fritted glass or polyethylene separators are ideal for such task simply because it is too much of fluid flow to pass through microscopic channels, maybe I would need to make holes on polyethylene or glass in order to reach such fluid flows.

... But the pressure would be lowered a lot...

I know that bigger fluid flow equals lower pressures and that the relation between pressure and fluid flow is the same as torque and rpm, however, in this case, the lower the pressure, the more fluid I need in the system, and thus, more weight.

---

Again, I need to test it myself (or find a video of such test), and for that, I need, well, money.

---

I was thinking here, maybe I could use dielectric elastomers as the pump...

I didn't want to use dielectric elastomers artificial muscles because they seem too complex to mass produce in a DIY setup, but maybe I could make dielectric elastomer pumps.

These pumps would have no mechanical parts and be relatively simple to build...

... But it runs in the problem that I need to find a way of calculating them and the problem of efficiency...

---

I keep forgeting that this "little conundrum" isn't just a little conundrum, this is a literal barrier that much more knowledgeable professionals around the world are trying night and day to overcome.

I doubt a feeble minded fool such as myself to literally go against all odds and find a solution first.

---

This will be me, 40 years in the future and still wasting my time with this stupid project...

---

I still think the simplest hydraulic pump (besides the dielectric ones) would be the linear pump: an actuator pushing a syringe.

The muscle only need 0.006 liters in a 1/5 of a second after all.

I could literally stack 10 artificial muscles (which can lift 100 kg) and only use a 60ml syringe and a small linear actuator.

(However, assuming that the muscle contracts 20% of its length and increases diameter 40%, it would need 20ml per muscle instead of 6, however, since the muscles would be bundled and braided together, the value would change significantly. On Project Log 26 I explain how I reached these percentages)

... Or I could simply glue a servo-motor on the syringe and pull its piston with a line and by releasing the force, the syringe will fill itself up...

Well, this sounds like the simplest hydraulic pump one could make...

... But I would need to figure out how much torque and how much RPM would the hoist mechanism need in order to pull the syringe. The torque would be dependant on the pressure and the piston diameter, by the way.

I think it would be best if one were to use a glass syringe as a mold, since those are incredibly precise and have minimal friction, unlike the plastic ones with the rubber piston.

https://www.thingiverse.com/thing:6002707

You could replace the rack & pinion of this STL file and simply attach a line to the servo motor's shaft.
But again, I don't know if a micro-servo will have enough rpm and torque for a 5 bar pressure at 1/5 of a second.

---

It is consistenly annoying and relieving it is to search for a myriad of different complex systems just to go back to the simplest idea one could have...

I went from a 1 ton lifting hoist mechanism back to artificial muscles just to go back to a hoist mechanism to pull a syringe...

---

I don't know how to feel about this...

---

Well, putting aside my feelings, I completly forgot to calculate the energy required to pump the fluid.

Although I said that the torque would depend on the piston diameter, it don't really matter when it comes to wattage.

If the syringe piston's head has 3 or 30cm of diameter and moves Xcm, it will need the same wattage to move 60ml of liquid, although the torque and speed of rotation would be different.

So, accordingly to the pipe volume calculator, if the inner diameter, and thus, the bore diameter was 2cm, I would need 19.1cm of length in order to fit 60ml.

And thus, I would need to move 19.1cm in 1/5 of a second with a force of 16kg (accordingly to hydraulic cylinder calculator, 5 bar of pressure would apply more or less this force to the piston head).

Assuming that the diameter of the electric motor's shaft is 1cm, accordingly to the rpm to linear speed calculator, I would need 1800 RPM, and accordingly to the torque calculator, I would need 0.8 Nm of torque.

And finally, accordingly to the Torque to Horsepower Calculator, I would need 150 watts of power in order to pump 60 ml of fluid in 1/5 of a second with 16kg of force.

---

Assuming that I'm using the 25mm inner diameter pulling hydraulic cylinder with 2 bar of pressure, then I would need half of that wattage because it would need more or less 70ml. Needing 1.5 watts per kg of force.

Actually, no. I actually made the math and I would need 30 watts of power. 600 rpm to reach 30 cm/s and 0.4 newtons to apply 10kg of force with a shaft with 1cm of diameter. Resulting in 3 watts per kg.

---

However, like I said before: the muscles may need 20ml per filament instead of 6ml, so this value may increase 3.33 times.

And thus, it may use 4995 watts of power in order to fully actuate 10 muscles with 10kg of force each, totalling 49 watt per kg of force.

---

If I'm going to apply such wattage with dozens or hundreds of tiny electric motors to convert electricity to hydraulic force, better off just using electric motors by themselves.

... Which is good on paper, but not in reality.

I can DIY my way into making a single big electric motor, not hundreds of tiny electric motors.

---

By the way, I took a few minutes to calculate how much energy a system with a central pump would need.

Basically, assuming that each 25mm inner diameter hydraulic pulling cylinder uses 20 bar of pressure having a stroke of 15cm and are only 30 in total, I would need around 300-400 liters per minute of fluid flow, totalling at least 15-20 horsepower at 2500-3000 rpm, rotating 3 to 4 pumps in order to supply everything fast enough with enough force.

This would be around 100 watts per kilogram of force.

(this is me from the future, this math seems faulty, since each limb/muscle bundle would equally distribute the loads)

I really don't want to use a central pump/motor because of this, even the low efficiency of the electroosmotic pump would be better.

And again, I can't fit a single pump with a single motor for every actuator, it would simply be just too bulky and heavy (and costly).

I really need a way of circumventing such problem... But I don't have the money to try it...

Thursday, 08:31, 24/08/2023

Well, morning.

By the time that I actually start making the exo/endo-skeleton, it will be buried under 3983932382 project logs.

... But I think this is relevant, because I need to talk about Dielectric Elastomers and I already wrote so much crap on the previous project logs about linear actuators that hackaday simply starts deleting new text on them.

---

Just to recaptulate:

The hydraulic artificial muscle system, although being lighter and allowing a higher efficiency, since it is lighter than metal hydraulic cylinders, its oil still weights a lot.
More or less 180kg to 225kg.

So I thought "hey, since I'm already facing such inneficiencies with such system, then why not try something else?"

Then I calculated pneumatics, but those are inneficient as heck and quite dangerous to work with.

Then I thought on Dielectric Elastomer Actuators, those wouldn't need an electric to mechanical to hydraulic conversion and make a somewhat efficient system, even if these aren't that efficient in the first place.

---

In any way, I was absolutely sure about the efficiency of dielectric elastomers to be really low, but after looking into some review papers of dieletric elastomers, I'm not so sure.

You see, for some reason, when I look at dielectric elastomers review papers (such as the one bellow), they always say that the efficiency of DEA's are around 80% to 90%.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/aisy.202000282

... But when I "ask around" and/or search for specific articles with new DEA's, it is always something bellow 40% efficiency.

And the problem is: when I try to look into the bibliographic sources these review articles use, instead of leading me to specific studies, they send me to older review papers with the same efficiency reference and I can't find the actual production method.

Bro, I'm reading articles from the early 2000's and I still didn't find a single fricking method of production (or I simply didn't pay enough attention, I have ADHD after all).

The article in question: 

https://link.springer.com/article/10.1557/PROC-600-119

You will need sci-hub to see it, but basically, it says it uses something related to acrylic.

---

In either way, there are 2 options here:

• Either I'm simply not reading the full information (since I'm literally fast scrolling though everything, that's my fault).
• Either some articles simply take references without double-checking their sources (which is doubtful).
• Either they are talking about dielectrict elastomer generators (that convert mechanical energy into electrical) instead of actuators.

A 4th option would be that the movement that the dielectric elastomer makes is highly efficient, but the elasticity of the material reduces the efficiency.

Most of the dielectric elastomers have a really low actuation, in the milimeters of actuation, so they need to make a reversebly actuated artificial muscle, just like the hydraulic ones I was thinking on making.

And thus, the necessity of making the muscle relax when voltage is on and contract when the voltage is off means a low efficiency of energy transmission.

---

Also, I thought on two ways of making dielectric elastomer artificial muscles systems.

Basically, I either do the reversebly actuated or the membrane actuated.

At more or less 2:11 time in the video, you can see how big it is the actuation of the membrane, if you were to pass a shaft/rope through the membrane and stacked a lof of these membranes, you could make an artificial muscle pull it up.

Something akin to this, but with a rope instead of a rigid shaft.

Now, the reversibly actuated you already know: you make a strand, when voltage is on, the strand relaxes, increasing length, and once the voltage is off, the strand contracts.

---

Or maybe neither of these, but continuum design (aka tentacles):

---

I posted it at the end of the previous Project Log about linear actuators, but here is the online article about the Acrylic Elastomer:

https://samueli.ucla.edu/wp-content/uploads/samueli/Compiled-PHDE-SI-Videos.mp4?_=1

(well, this was supposed to be a video, but it doesn't appear on hackaday)

https://www.science.org/doi/epdf/10.1126/science.abn0099

I'm just interested on this one in specific at the moment because ChatGPT suggested this one.

There are thousands of different Dielectric Elastomer articles around the internet and I need to find one that best suits my needs.

---

I don't know which method (membrane or strand) would be the best.

Plus, I need to actually read the goddang articles in order to find the easiest to make and the most efficient to use.

---

I tried to read a lot of articles and now I remember why I gave up with this idea before... It involves really complicated stuff (for my smooth brain) and chemicals that I simply can't directly buy on the internet.

One section of the previous article (that by the way, was the most clear and higher performance article that I found) says the following:

"A PHDE film was demonstrated to toss an aluminum ball, which is 20 times as heavy as itself, to 12.1 cm high (Fig. 2E and movie S3), reaching an energy transfer efficiency of ~10%(fig. S20)."

Well, I don't know if this is the energy transfer from the electric system to the elastic motion of the system that turns into knetic/mechanical energy on the throwing of the ball or if is the efficiency of electrical current being transformed into mechanical energy by the elastomer.

---

I asked ChaGPT to tell me the summary because I legitimaly couldn't find the answer:

"The processable, high-performance dielectric elastomer (PHDE) film discussed in the research paper is primarily composed of acrylate-based materials. The authors of the paper used a combination of specific acrylate monomers and cross-linkers to create the tailored elastomer network structure. The main components used in the PHDE film are butyl acrylate (BA), isobornyl acrylate (IBOA), urethane diacrylate (UDA), and propoxylated neopentyl glycol diacrylate (PNPDA), along with cophotoinitiators to enable curing under UV light.

In summary, the PHDE film is based on acrylate chemistry, and the specific combination of acrylate monomers and cross-linkers allows for the creation of the desired bimodal network structure with enhanced mechanical and electromechanical properties."

So they used a bunch of acrylic based polymers that I don't fricking know how to find on top of using "cophotoinitiators" or whatever lovecraftian name this sounds.

---

I can only find acrylic-poliurethane thinners, nothing closer to what I actually need.

I could make tests using conventional silicon rubber, latex rubber and/or polyurethane rubber, but I'm not very confident on the results.

In fact, I don't want to buy and test these things because I simply do not even understand the subject.

I guess I will have to work with either polyurethane (which is expensive) or liquid silicone rubber for this specific task.

Well, at least my time searching for copious amounts of silicone rubber weren't in vain I guess...

---

Welp, after looking for it for a while, I gave up on dielectric elastomers. It is really is something that I could only have a proper understanding of how much force and power each actuator applies if I were to build it and test it personally.

Which is beyond my technical (and brain) capabilities.

If you want to pursue this specific subject anyway, I will just let this chat with ChatGPT here:

---

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To increase the compatibility of silicone rubber for use as a dielectric elastomer actuator, various modifications and techniques can be employed to enhance its dielectric and mechanical properties. Dielectric elastomer actuators require materials with high dielectric constants, good electrical insulation, and mechanical flexibility. Here are some strategies to improve silicone rubber's suitability as a dielectric elastomer:

1. Fillers and Nanocomposites: Incorporating high-permittivity fillers, such as ceramic nanoparticles (e.g., barium titanate), can increase the dielectric constant of silicone rubber. These fillers can enhance its electromechanical responsiveness to an external electric field.
2. Cross-Linking and Curing: Proper cross-linking of the silicone polymer chains is crucial to achieve the desired mechanical strength and durability. Adjusting the curing process, temperature, and duration can optimize the cross-linking density and resulting properties.
3. Silicone Blends: Blending silicone rubber with other polymers or elastomers can help achieve a balance between mechanical strength and dielectric performance. For instance, combining silicone with a high-strength elastomer can improve overall mechanical stability.
4. Electrode Compatibility: Enhancing the compatibility between silicone rubber and compliant electrodes is vital to ensure good adhesion and electrical performance. Surface treatments or primers can be applied to improve electrode adhesion.
5. Plasticizers: Introducing compatible plasticizers into the silicone rubber matrix can enhance its flexibility and stretchability, which are crucial for actuation. However, careful selection is required to prevent plasticizer leaching and maintain stability.
6. Surface Modification: Treating the surface of the silicone rubber with plasma or chemical processes can alter its surface energy and enhance its adhesion to other materials, such as compliant electrodes or additional layers.
7. Layered Structures: Designing multilayer structures with different materials can provide enhanced performance. For example, incorporating a high-strength layer alongside the silicone dielectric layer can improve mechanical stability.
8. Temperature Stability: Silicone rubber's performance can be affected by temperature variations. Formulating the material to have improved thermal stability and reduced temperature-dependent changes in mechanical and dielectric properties can be beneficial.
9. Processing Techniques: Utilizing advanced processing techniques, such as melt blending, solution casting, or extrusion, can help achieve better dispersion of additives and fillers, leading to improved overall properties.
10. Thinning Strategies: Thinning the silicone rubber material while maintaining its dielectric properties can increase its responsiveness to electric fields, enabling higher actuation strains.

Remember that the modification process should be guided by a comprehensive understanding of the material's properties, the specific requirements of the application, and the trade-offs between dielectric performance and mechanical stability. Testing and optimization are crucial to achieve the desired combination of properties for silicone rubber-based dielectric elastomer actuators.

---

Certainly, here's a list of materials in each category that I mentioned earlier:

High-Permittivity Fillers:

1. Barium titanate
2. Titanium dioxide
3. Zirconium oxide
4. Strontium titanate
5. Lead zirconate titanate (PZT)

Cross-Linking and Curing Agents:

1. Platinum-catalyzed silicone curing agents
2. Peroxide curing agents (for addition-cure silicone)

Silicone Blends:

1. Silicone/Thermoplastic elastomer blends
2. Silicone/Polycarbonate blends
3. Silicone/Acrylonitrile Butadiene Rubber (NBR) blends

Surface Treatments:

1. Plasma treatment
2. Silane coupling agents (e.g., silane primers)
3. Corona discharge treatment

Plasticizers:

1. Dioctyl phthalate (DOP)
2. Dioctyl adipate (DOA)
3. Dimethylsiloxane-based plasticizers

Layered Structures:

1. Silicone layer combined with thermoplastic layer
2. Silicone layer on top of fabric reinforcement

Temperature Stability Enhancers:

1. Heat-resistant additives
2. Inorganic fillers for improved thermal stability

Processing Techniques:

1. Melt blending
2. Solution casting
3. Extrusion

Please note that the selection of specific materials from these categories will depend on the desired properties and application requirements. Additionally, the use of some materials may vary based on factors such as regional regulations and advancements in material science. Always ensure to refer to the most up-to-date literature and resources when making material choices.

---

I searched for (a lot of) silicone dielectric elastomer articles and all of the suggestions ChatGPT gave kinda checks out.

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While stumbling my way through unnecessarily exotic actuators to fulfill my endless curiosity, I found something called "MagnetoRheological elastomers" (or Magnetoactive elastomers), which, if you readed all my project logs may be familiar with.

Basically, it is just a rubber material with magnetic powder (like iron) on it, and it is used in a similar way as dieletric elastomers.

Le problem is that it needs magnetic coils to work.

Source: https://www.researchgate.net/publication/349147971_Magnetorheological_elastomers_-_An_underestimated_class_of_soft_actuator_materials?_tp=eyJjb250ZXh0Ijp7InBhZ2UiOiJfZGlyZWN0In19

Maybe you could make a coiled/braided magnetorheological fiber and put it inside of a long copper coil, forcing the braided magnetic polymer to follow the coiled path.

But again, maybe.

I don't know the efficiency of such system or how practical it would be to make it myself.

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By the way, while I was searching for the subject of dielectric elastomers, I also stumbled upon shape memory alloys, and one thing that I saw that I thought it was quite interesting was microwave activated shape memory alloys.

Well, unfortunately, microwave magnetrons (the part responsible to convert electricty into microwaves) are quite bulky, heavy and dangerous.

A possible solution I would suggest would use micro magnetrons and/or microwave antenna emissors. Although I doubt it would be as cheap or smaller.

---

I just found this instructables teaching about microwaves, and it says:

"Lower power microwaves can me produced by some solid state devices such as the FET (field effect transistor), the tunnel diode, the gunn diode, and the IMPATT diode."

Although the parts that he mentioned aren't that cheap either, it is a little bit cheaper and lighter than a fricking magnetron.

I found some fet mosfet like the ones in the image on google shopping, but I don't know if this little thing would produce enough microwaves to heat artificial muscles.

(But after asking to ChatGPT, it seems like you wouldn't need microwaves at all, silicon carbide is good conversor of electricity to heat)

---

Another possibility is using DIY conductive ink but instead, adding silicon carbide, since it transforms microwaves into heat more efficiently.

Silicon carbide is so good in converting microwaves into heat that it is used into microwave furnaces/kilns.

This method would also work with nylon/polyethylene artificial muscles instead of using nichrome or kanthal heating wire.

You can also electroplate it, although I don't know why you would go over such trouble if graphite and/or silicon carbide are already very resistive, meaning it would turn electricity into heat more efficiently than highly conductive nickel/copper/zinc.

---

Speaking of Shape Memory Alloys, here are other SMA's that aren't nickel-titanium (nitinol):

(by the way, nitinol is made by melting nickel and titanium in a vacuum either by electromagnetism or ark furnace over a water cooled copper table, thus the price)

"There are several other alloys besides Nitinol (Nickel Titanium) that exhibit shape memory alloy (SMA) behavior. These alloys are known for their ability to "remember" a specific shape and return to that shape when subjected to certain temperature changes or mechanical stress. Here are a few examples:

1. Copper-Aluminum-Nickel Alloys (Cu-Al-Ni): These alloys are often referred to as "Copper-Based Shape Memory Alloys." They exhibit shape memory behavior due to a reversible martensitic transformation. They are used in various applications, including medical devices and actuators.
2. Copper-Zinc-Aluminum Alloys (Cu-Zn-Al): Another type of copper-based SMA, these alloys have a similar transformation mechanism to Cu-Al-Ni alloys. They are utilized in applications such as eyeglass frames and thermal actuators.
3. Iron-Manganese-Silicon Alloys (Fe-Mn-Si): These alloys are known for their high-temperature shape memory behavior. They can recover their original shape after being deformed even at elevated temperatures. Applications include high-temperature actuators and sensors.
4. Copper-Zinc-X Alloys (Cu-Zn-X, where X can be Aluminum, Tin, or other elements): These alloys are part of the copper-zinc family and exhibit shape memory behavior due to a reversible transformation between austenite and martensite phases. They are used in various engineering applications.
5. Iron-Platinum Alloys (Fe-Pt): These alloys exhibit shape memory behavior at very low temperatures. They are being studied for applications in areas like cryogenic engineering and aerospace.
6. Nickel-Gallium (Ni-Ga) Alloys: These alloys show shape memory behavior in response to magnetic fields rather than temperature changes. They are used in sensors, actuators, and various magnetically controlled devices.
7. Copper-Gold-Aluminum Alloys (Cu-Au-Al): These alloys have a two-way shape memory effect, which means they can recover two different shapes upon heating and cooling. They find applications in microactuators and medical devices.
8. Titanium-Niobium Alloys (Ti-Nb): These alloys exhibit shape memory behavior in response to stress-induced martensitic transformation. They are utilized in applications where high mechanical damping and superelasticity are required.

These are just a few examples of shape memory alloys with various compositions and properties. The field of shape memory alloys is continuously evolving, and researchers are exploring new compositions and applications for these unique materials."

---

4.2. Cu-based SMAs
Cu based SMAs though not having supreme shape memory properties like Ni–Ti alloys, are exploited for their modest shape memory properties (superior to Fe based systems), cheaper production cost and ease of fabrication [46]. They are considered as cost effective because they are easily produced using conventional liquid metallurgy and powder metallurgy routes utilized for processing traditional Cu based alloys [8]. Also, they do not have high reactivity levels which necessitates special furnace environmental conditions during melting as in the case with processing of NiTi [8]. In addition the Cu based alloys have a wide transformation temperature range, a large superelastic effect, small hysteresis and high damping coefficient. All of these desirable properties have widened the potentials of Cu based in shape memory applications where the NiTi alloy is currently explored.

Source: https://www.sciencedirect.com/science/article/pii/S2215098616301070#f0010

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"Sure, here's a list of some shape memory polymers (SMPs) along with their efficiency, stroke length, and material content:

1. Polyurethane-based SMPs:
   • Efficiency: High
   • Stroke Length: Medium
   • Material Content: Polyurethane-based polymers
2. Polyethylene-based SMPs:
   • Efficiency: Low
   • Stroke Length: Short
   • Material Content: Polyethylene-based polymers
3. Polycaprolactone (PCL) SMPs:
   • Efficiency: Medium
   • Stroke Length: Long
   • Material Content: Polycaprolactone polymers
4. Polyethylene terephthalate (PET) SMPs:
   • Efficiency: Medium
   • Stroke Length: Medium
   • Material Content: PET-based polymers
5. Polylactic acid (PLA) SMPs:
   • Efficiency: High
   • Stroke Length: Short
   • Material Content: Polylactic acid polymers
6. Polyvinyl alcohol (PVA) SMPs:
   • Efficiency: Medium
   • Stroke Length: Long
   • Material Content: Polyvinyl alcohol polymers
7. Polyacrylamide-based SMPs:
   • Efficiency: Low
   • Stroke Length: Short
   • Material Content: Polyacrylamide-based polymers
8. Poly(ε-caprolactone-co-trimethylene carbonate) SMPs:
   • Efficiency: High
   • Stroke Length: Long
   • Material Content: Copolymer of ε-caprolactone and trimethylene carbonate
9. Poly(propylene fumarate) SMPs:
   • Efficiency: Medium
   • Stroke Length: Medium
   • Material Content: Poly(propylene fumarate) polymers
10. Poly(n-isopropylacrylamide) SMPs:
    • Efficiency: High
    • Stroke Length: Short
    • Material Content: Poly(n-isopropylacrylamide) polymers

Please note that the efficiency, stroke length, and material content can vary depending on the specific formulation, processing methods, and application requirements. The terms "efficiency" and "stroke length" might also have different interpretations based on the context of the shape memory application. This list provides a general overview of some commonly used shape memory polymers and their properties."

---

Well, this looks interesting.

The ones that I was able to find besides its lovecraftian names and interesting properties were: Polyurethane, Polyethylene, Polycaprolactone (PCL) and Polyvinyl alcohol (PVA).

---

"Certainly, here's a list of materials and methods commonly used in the production of Polyurethane, Polyethylene, Polycaprolactone (PCL), and Polyvinyl Alcohol (PVA) based shape memory polymers:

Polyurethane-based SMPs: Materials:

• Diisocyanates (e.g., MDI, TDI)
• Polyols (e.g., polyester polyols, polyether polyols)
• Chain extenders (e.g., butanediol)
• Catalysts
• Crosslinking agents
• Chain regulators
• Fillers (optional)
• Solvents (for processing)

Methods:

1. Solution Casting:
   • Diisocyanate, polyol, and other additives are dissolved in a solvent.
   • The solution is cast into a mold or on a substrate.
   • Solvent is evaporated to form the polymer.
2. Thermoplastic Processing:
   • Diisocyanate, polyol, and other additives are melted and mixed.
   • The melt is shaped using techniques like extrusion, injection molding, or compression molding.
   • Cooling solidifies the polymer into the desired shape.

Polyethylene-based SMPs: Materials:

• Polyethylene resins (various densities)
• Crosslinking agents (e.g., peroxides)
• Fillers (e.g., nanoparticles, fibers)
• Additives (e.g., stabilizers, pigments)

Methods:

1. Crosslinking through Irradiation:
   • Polyethylene is exposed to ionizing radiation (gamma, electron beam).
   • Crosslinking agents promote crosslinks between polymer chains.
2. Thermal Crosslinking:
   • Polyethylene is mixed with crosslinking agents.
   • Elevated temperatures initiate crosslinking reactions.

Polycaprolactone (PCL) SMPs: Materials:

• Polycaprolactone (PCL) polymer
• Crosslinking agents (e.g., diisocyanates)
• Initiators or catalysts
• Fillers (optional)
• Solvents (for processing, if needed)

Methods:

1. Chemical Crosslinking:
   • PCL is mixed with crosslinking agents and initiators.
   • Crosslinking reaction is triggered by heat or other stimuli.
2. Thermoplastic Processing:
   • PCL is melted and shaped through methods like extrusion or compression molding.
   • Shape fixation can be achieved by cooling or through crosslinking.

Polyvinyl Alcohol (PVA) based SMPs: Materials:

• Polyvinyl Alcohol (PVA)
• Crosslinking agents (e.g., glutaraldehyde)
• Plasticizers (e.g., glycerol)
• Initiators (for photo-crosslinking)
• Fillers (optional)
• Solvents (for processing)

Methods:

1. Chemical Crosslinking:
   • PVA is mixed with crosslinking agents and initiators.
   • Crosslinking is induced through chemical reactions (e.g., crosslinking agents or heat).
2. Physical Crosslinking (Physical Hydrogels):
   • PVA chains are physically crosslinked through methods like freeze-thaw cycles or crystallization.
3. Photo-Crosslinking:
   • PVA is mixed with photo-initiators.
   • Crosslinking is initiated by exposure to UV or visible light.

Please note that the specific methods and materials used can vary based on the desired properties of the shape memory polymers and the intended applications.

---

The only one that I was able to find materials to buy was PVA based Shape Memory Polymers...

Well, PVA by itself is already shape memory polymer, but I don't quite like the speed in which it moves.

Although you could just add silicon carbide and/or graphite to the mix in order to make it heat faster, you still is limited by the heat limit of the material, which is not a concern with Nitinol wires.

Besides, I didn't yet finish studying about the subject, maybe these are faster.

---

Well, I actually tried to read a ton of articles on the subject, and just like silonce rubber based dieletric elastomers, each article focuses on an specific function, method and characterization of the polymer instead of a general function of being used as an actuator.

And thus, I can't find enough information in order to understand and/or predict the properties of the shape memory polymer in order to be used as an actuator.

And thus, this project log was just a waste of time...

---

At this point I was even considering magnetic coils actuators.

Not voice coils or anything like that, magnetic coils.

When there is a big enough electric current passing through copper coils, they "contract" simply because the magnetic field becomes so strong it makes the coils compress.

I can't fing the goddamn video again, but a guy did that.

However, I don't know at which voltage and current he did that and neither I know how efficient it is or would be.

Found it.

It is at such high amperage the coil literally burns.

Dunno if it would work with the magnetorheological rubber inside the coils on concentric tubes with everything submerged in insulating oil for cooling.

But to me it seems an interesting actuator, but I don't really want to deal with 100+ amps just for a funny copper coil.

I don't even know how many grams of force this little thing can even output.

Also, this video is linked at the end of the previous video, kinda relevant since Lorentz Force is strong enough to move heavy wires.

---

Actually, I was even considering flexible voice coil actuators, but even then, I don't think I have enough knowledge on the subject even to attempt something like this...

In fact, I'm still not fully aware of how voice coils work, but I do know those are expensive and meant for really low force ultra high precision actuations.

(I mean, technically the previous idea would be a flexible voice coil actuator)

---

In either case, I just asked around on multiple websites, but I doubt anyone would give a serious look a this.

Also, I was thinking of making this like a "reverse electrostatic" actuator, in the sense that electrostatic comes in kilovolts (thousands of volts) but with an incredible low amperage (aka current) in the microamps (0.000001 amps), so a reverse electrostatic would have kiloamps and microvolts instead.

---

I asked around and dude, asking help on the internet is kinda tough.
People either know as little as myself and wish they could help more, or simply tell me to f8ck myself and stop waisting their time (which unfortunately is the one that happens the most).

In either way, I receive two interesting suggestions. These two websites show a lorentz force calculation, which I can't make heads out of. But I tried a little bit.:

https://danielteodesigntechnology.wordpress.com/theoretical/supplement-lorentz-force-actuation/

"An Electromagnetic (EM) scheme realized through a Lorentz-force principle requires an air-core coil where presence of current is only used to generate force. If the coil is wound around a ferrous material core and generates a magnetic field to propel a permanent magnet, it will be another form of EM scheme, termed Attraction/Repulsion, commonly found in solenoid actuator."

https://www.ld-didactic.de/software/524221en/Content/ExperimentExamples/Physics/Electricity/ForceAirCoil.htm

Field coil, d = 120 mm

---

In the second I don't know if the "field coil" is the electromagnetic field generated by the coil, the coil diameter or the coil length.

If it is the coil diameter, a 12cm diameter coil will give" F/I = 0.138 mN/A" accordingly to the link, which is milinewtons per amp (1 milinewton = 0.001 newtons)...

I wonder if its force would increase proportionally accordingly if you were to decrease the coil diameter by 10 to 25 times, with a coil with 12mm of diameter and 5mm of diameter.

Would the force be 1.38 mN/a and 3.45 milinewton per amp respectively?

---

This means that I would need 1000x more amps to convert 0,00138 newtons to 1 newton or 300 times more amps to convert the 0.00345 newtons into 1 newton.

So, it would be either 5000 amps or 1500 amps.

I asked ChatGPT what force would the lorentz force apply in newtons to a coil with 5mm of diameter and 18 AWG (+/- 1mm of diameter), 1500 amps and 0.06 volts (90 watts), it said it would be applying 40 to 70 newtons of force (in some other answers, it says I would have 200 newtons of force).

And as you guessed it, it changes answer everytime I hit the "regenerate answer" button. So this value may be completly incorrect.

Plus, it didn't calculate the heat generation.

But in any way, you can see that the system is incredibly inneficient, after all, it took 90 watts (1500x0.06=90) to lift only 7kg.

---

It will definitely be tough to make a 5mm diameter copper coil and continiously cool it.

Maybe one could make a more resilient insulating layer by using sodium silicate instead?

Maybe² the heating issue could be solved if you activated and disactivated the current very fast?

Maybe³ by increasing the number of coils receiving the current, the area will increase, the heat inneficiency will decrease and the efficiency with the magnetic field will increase.

It also makes me wonder if it would be possible to make a soft magnetic composite core and "contract" the length of both the coil and the core using both the lorentz force and the magnetic field. But like it was said in the first link: if you add a core it won't be a lorentz force actuator anymore, it will act like a solenoid.

So many questions... And I'm too dumb to answer any of them.

---

The closest I could find was this article: https://www.semanticscholar.org/paper/Prototyping-the-flexible-solenoid-coil-artificial-Takai-Alanizi/e2ce146b51b584ce50410afb4ef1590269fe0908

It uses a rigid articulated solenoid coil in order to act like a muscle.

It produces 0.08 newtons at 15 volts, hum...

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I don't know if I'm not trying enough, or if I'm genuinely facing a problem so big even professionals would struggle.

---

In either way:

I'm writting this here since I don't have space on the previous project log, but I think I got an idea to solve the weight problem of the hydraulic artificial muscles.

One would be to instert a filler and occupy at least half of its length, reducing the weight from 225kg or 180kg (depending on the density of hydraulic oil you use) to 112.5kg to 90kg.

Then you could reduce by half even more if you filled opposite muscles only to 56.25kg to 45kg

Example: you actuate only half of the muscles at one moment, but once this half is relaxed, it will actuate the other half automatically.

Well, I don't quite like this idea simply because you would have all muscles under some tension and may result on muscles not receiving enough fluid if I'm not careful with the design...

---

Now I feel stupid.

Couldn't I do the same towards air?

I mean, it is clear from the start that pneumatic systems need careful opposition control since they simply expand.

Couldn't I "just" keep the entire system pressurized at 5 to 6 bar and simply pump the air towards the opposite muscles?

... But you would need to be very careful with leakages, which is a hell of a time to deal with in the case of pneumatic muscles...

I don't really think that there is a way out of the hydraulic weight problem...

---

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Since I can't add text to the previous project logs about linear actuators, I would like to list some ideas:

Basically, there are tubular plastic coils/bobbins that don't have divisions inside of it. Basically, a super long tube.

These come in meters and/or in kg and are somewhat cheap and can be found in a myriad of different shapes and types of materials.

This is a Polyethylene transparent plastic.

And this one is a PVC transparent tubular plastic with 3cm of flat length and diameter of 1.9cm and I found in a brazilian website costing 100 reais (20 dollars) for 2kg or 117 meters of length.

There are other websites that sell more kg for the same price using different plastics (PVC is heavier), but you got the idea.

Maybe you could use it for the filament McKIbben hydraulic muscle and/or the reversibly actuated hydraulic muscle with steel springs.

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Well, even though I talk so much about efficiency, I didn't check the efficiency of the entire system (maybe because I didn't even plan the system in the first place).

So, let's say we have that 60kg solid state hydrogen fuel cell I talked about in the previous project log + 10kg of latex rubber actuators + 45kg hydraulic oil + maybe a 100kg exo/endoskeleton = 214kg.

Assuming the efficiency of the 60kg battery is 60%, the efficiency of the electric motor is 90%, the efficiency of the pump is 88% and the efficiency of the hydraulic actuator is 60% and I want the equivalent of 300watts to go pass through all of this, I would have... 85.5 watts at the end of the thing, meaning that I would need 3.5 times more power in order to compensate for the energy loss.

I thought that maybe the battery is not worth the trouble of extracting the percentage of power because it will provide the required power indepently of its efficiency of extracting power from its materials.
Basically, it is the "origin" of the power, not the passage, so to speak (although it is a passage of power from the baterry charging [you get the drift]).

The new value would be 142.56 watts at the end, meaning that I would need more or less 2.1 times more power to compensate.

So, assuming that I use 600 watts of power for the 30 muscle groups, I would need around 18,000 watts (of course, assuming every muscle uses the same amount of energy, which is not the case), so, a maximum of 24 horsepower (if all muscles contract at same time, again, not the case).

---

... But, if you include the weight of the mech/exosuit, in the meaning that it is wasting energy carrying its own weight instead of doing useful work, then it would be wasting 1/5 of its 1000kg rating, in order words, wasting 20% of its efficiency.

So, the final result would be 114.048 watts, more or less 1/3 of the initial energy value. So you would need to insert 3 times the initial energy.

So the final result would be 900 watts maximum for every 30 muscle groups, giving 27,000 watts or 36 horsepower.
Again, not every bundle will be using 900 watts, and not all 900 watts muscles will be contracting at same time. A generic value would be around 8100 watts in total or 10.8 horsepower.

---

If someone were to make a system with 90% of efficiency in every step with as few steps as possible, you could reduce the energy cost by half.

But there is the problem of cost, manufacturing etc, so you can't just put 30 electric motors everywere.

---

Which makes me wonder if I'm not forgetting something.

For example, I was needing 9000 watts with the full electric motors, this means that I'm severely misscalculating something or creating energy out of thin air.

I don't know the actual reason, but basically, I reached the conclusion of 9000 watts by insterting the distance of actuation and speed on online calculators:

https://www.omnicalculator.com/physics/torque

Assuming the distance is 5cm and a weight with 3000kg (or 30 kilonewtons), accordingly to the calculator, I would need 1500Nm of torque.

https://www.omnicalculator.com/conversion/torque-to-horsepower

If I insert the torque of 1500Nm and the speed of 60 RPM, then I achieve a maximum power of 9500 watts (12 horsepower).

But since it has 3 of these on the legs, then I would require 36 horsepower in total.

Since the torso and arms are using 1/3 of that, then it would be 60 horsepower in total, or 45,000 watts.

---

But the hydraulic pump needs around 300 watts to move it in a pressure of 5 bar and a fluid flow of around 50 to 70 liters per minute, and it is enough to supply 375 muscles with 80 newton of force each, which gives around 30,000 newtons of force (3,000 kg).

---

The math checks out in both cases, but I don't know what is the deal tho...

---

I misscalculated the artificial muscles.

How did I... Calculated that the muscles would need 0.021 liters per minute...?

I was checking the Project Log 67 and there is a part where I say this:

"Assuming that the initial length is 15cm and the elongated state is 30cm, I would need to move around 0.001 liters, or 0.737 ml"

This should be a red flag from the start.

How did I get 0.001 liters from a tube with 12.5mm of diameter and 15cm of length which resulted in an elogation of 30cm?

I think I know how, I simply made the mistake of changing the Centimeter to Milimiter without noticing.

In the case of the RAHAM (reversibly actuacted hydraulic artificial muscle), if I were to have a 15cm long muscle with 12.5mm of inner diameter, I would have 0.018 liters, since I were to double this value with the elongation to 30cm, I would need to pump 0.018 liters. I mean, duh.

So, 0.018 x 5 x 60 = 5.4 liters per minute of fluid flow.

The 5 there is that the muscle will need to contract in 1/5 of a second in order to make the limb move in a speed of  30 RPM.

If I wanted to elongate 300 muscles for the 3 ton value, I would need 1620 liters per minute of fluid flow.

If I had hydraulic pumps using 900 watts of power to pump 50 to 70 liters per minute, I would need 23 pumps using 20,828 watts of power in total. Or 27 horsepower.

---

If you read the description of the project, I wrote:

"I will try to list in this project here all the ideas I had/have because I'm noticing that I'm repeating the same cycle of ideas"

How I can make the same mistake again and again throghout 70+ project logs?!

Just how?

Can I not make a math mistake for 5 MINUTES?!

---

At best, you could use the artificial muscles for the 100kg rated exoskeleton and use the values previously noted here.

Basically:

A muscle with 1 inch in inner diameter + 30cm of length has 0.152 liters of volume and contracts to 40mm of inner diameter and 18cm of length, having 0.226 liters.

The actuation needed 0.074 liters.

0.074 liters x 5 x 60 seconds x 3 actuators to pull 300kg in total = 66 liters per minute, or more or less 900 watts.

The legs would need 3 times that value either in pressure or in fluid flow, so in total:

900 for the arms + 900 for the torso + 2700 of the legs = 4500 watts or 6 horsepower.

Plus, you would need the other half of the body that would also use more or less half of the energy, totalizing 9 horsepower or 6750 watts per hour.

Although these numbers look decent, if you were to increase the force 10 times to achieve the 1 ton force, you would be using 90 horsepower.

---

Being honest, I don't even know if the value of 900 watts is correct anymore.

See, the electric motor will be inputing 360 watts (to compensate for the 88% efficiency) and the pump will be inputing 300 watts, but the muscle will actuate with 5 bar of pressure and 22 liters per minute, outputing 100kg of strength.

So... I will actually need around 1/3 of what I previously thought? 2 to 20 horsepower?

So this means it is viable?

... And that the electric version still consumes more power?

---

I seriously need the help of an engineer...

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Just checking on other hydraulic pumps, I would need around 10.3kilowatt (13.8hp) for 200 bar of pressure and 3000 rpm (I'm talking about the one with 14 ml/r on the thing below).

Since I need 3000 rpm and 5 bar instead of 200 bar (20 MPa), this would be more or less 40 times less torque, so 34.376 Newton Meter/40 = 0.8594, 3000 RPM + 0.8594 Nm = 270 watts. :|

Even less power than before...

This would also mean that I would need 2700 watts (3.6 horsepower) for each 1000kg muscle.

By the way, here is the link for the mentioned hydraulic pump: 
https://aliexpress.com/item/32993498984.html

(You buy it on your own risk, I'm just linking it here for reference)

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Although it would be nice to only consume 2 horsepower for a single exoskeleton, It would be a pain in the butt to make 30+ pumps and buy 30+ electric motors to power them.

I think it would be the best if I were to take a single 100L/min rated pump, make it 6 times longer and fulfill the 600 liters per minute of fluid flow that all muscles would required to be activated at same time (or just half of it).

A single pump would need around 1 horsepower to pump 100 liters at 2500 rpm and 3 Nm of torque, so in total it would consume 6 horsepower in total (or 3 if you only take half).

Of course, if it would be to a 100kg rated exosuit, for a 1000kg rated it would take 10 times more energy to pump enough fluid.

The pump will activate a big hydraulic accumulator that in turn could be mechanically or electronically controlled to liberate fluid to the desired muscle through the preferred activation system (mechanical, using pinch valves or electronic by solenoid/servo valves).

Or you could make a single pump for every limb and and have 5 hydraulic accumulators in total.

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Yes I will try to make a project log for the hydraulic accumulator and valves, but I think I will put it under the Hydraulic Pump section.

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One thing that I forgot to talk: you need to put more energy on the hydraulic accumulator in order for it to work.

So in order to have a hydraulic accumulator that outputs 5 bar of pressure, I need to input 9 to 10 bar of pressure in order to charge it, already losing 50% of the input energy.

It may not be the best option, after all.

I think I already talked about this detail before...

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Well, there is so much text on this project log that this part is probably going to be deleted, but whatever.

I was thinking here that the best linear actuator is not the artificial muscles, but that flexible hydraulic cylinder.

Although I don't know how one would turn that hydraulic cylinder flexible, you can just use a conventional cylinder with a cable attached to the cylinder head.

Source: https://www.researchgate.net/publication/349986785_Simulation_Investigation_of_a_Soft_Hydraulic_Artificial_Muscle

Source: https://www.semanticscholar.org/paper/Micro-hydraulic-bending-actuator-for-minimally-Matsuo-Abe/23ed7b17c12ed49bb4d9d08cab2d17b4f2f1a635

I say this because hydraulic cylinders are 95% efficient, while McKibben muscles are 60% efficient, but since this "pulling hydraulic cylinder" could be made out of plastic with the same 5 bars of pressure, you would be using the best of both worlds.

Again, it wouldn't be flexible and to be honest, I don't know how you could make it flexible and being able to withstand the pressure inside of it without expanding the entire actuator.

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The second article show that the bending hydraulic actuator was able to withstand up to 1000 KPa (10 bar) of pressure, while I only plan on applying 500 KPa (5 bar) of pressure.

The thing is: would that be appliable to an actuator meant to lift 10 to 100kg?

Plus, the actuator is meant do coil like a tentacle.

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By the way, you would need a inner diameter/piston diameter of 15mm to reach 10kg of force at 5 bar of pressure or 50mm to reach 100kg at 5 bar of pressure.
However, depending on the cable, which occupies space, the final force may be lower.

PVC tubes can withstand pressures up to 7 bar of pressure, but I don't know if this would be enough to lift 100kg...

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By the way, I found that normal reinforced garden irrigation hoses can withstand pressures up to 20 bar and are still flexible.

One could use these hoses as this flexible pulling hydraulic actuator.

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By the way, just now this guy posted this interesting linear actuator:

It is just like those rotary to linear motion actuators, but instead of a crankshaft, it is a chain drive that allows for longer actuations.

Although the only problem I have with it is that sliding square thingie, even though I don't know what could be used to replace it...

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As far as I can remember, motorcycle chains can withstand up to 200kg of force, so you would need at least 5 of these for a 1 ton load or 15 of these in parallel for a 3 ton load.

Assuming that there aren't conventional sprockets/chain-drives that can withstand these kinds of loads...