Well, after much frustration with myself and a lot of thinking, I finally came to the conclusion that I cannot properly design an endoskeleton that demands highly engineering knowledge.
And therefore, I will try to make it the simplest way I can come up with, but I cannot garantee it will withstand the 1 ton threshold.
Of course, you can simply choose to use composite materials such as carbon fiber, fiber glass or wood+resin (or ultra high performance air-concrete). But, like I said, quality is also not a garantee when you make composite materials by yourself. Specially when you're building something to withstand 1 ton of weight.
You could also use solid steel (or aluminium 6061/7072) rods with 9cm in diameter and 30cm in length, but it will still weight around 2 tons (or 600 kg if you use aluminium).
Henceforth, with all this said, let's get this bread.
Off-topic:
Well, I guess off-topic topics are now a thing, since I can't just shut up myself.
I forgot to actually right what I had in mind, lol.
So... What I was trying to say:
Pulse jet engines are a simple but extremely powerful type of engine, however, these have some defects.
These aren't as fuel efficient as Turbine Jet engines of similar size/thrust, but they have superior thrust-to-weight ratio and are incredibly simple to make.
(this guy sells his PulseJet projects, by the way).
However, as you may not know (just like I did), pulse jets actually aren't detonation engines.
The difference between deflagration and detonation would be something like the difference between a flamethrower and a explosive.
Anyway, the thing is that there actually are detonation engines, that work by supersonic detonation.
And as you could see, there are rotating detonation engines, which, as you could see in the video above, use a rotating wave of detonation that pulses the air in a spiral just like the blades of a Turbine Jet Engine.
So, a turbine jet engine without moving parts.
My mind just blew away with such concept.
The thing is, that if you put obstacles in a tube in which a deflagration reaction is happening, it actually becomes a detonation wave.
Who would guess that obstructing a wave would make it go faster?
So... If you use a Pulse Jet engine that turns into a pulsed detonation engine and then stack a lot of those in a circle, and then ignite them in a rotating succession... You get a rotating detonation engine.
Maybe.
I couldn't find any examples like this.
Maybe you would need to reintroduce fuel in the pulsed detonation chamber in order to make it work better, but... Who knows?
Would you be able to rocket thrust around like in the games/animes/movies?
The Endoskeleton Bones:
Well, like I should have done since the beginning, I will use trusses made out of wood.
I mean, it was so simply and in front of me all this time, I could've just used them.
Here it is what I mean:
See these metal plates? These are called brackets, so you can literally "just' take a plate of metal and go using both as a holder for nuts and bolts and as a structural reinforcement.
Not to mention that Oak wood can have the density of 0.82 g cm-3, meaning that, even if you were to use solid Oak wood rods with 10cm in diameter and 30cm in length, the entire structure would still weight just 247kg.
... Wait...
Waaaait...
Wait, even if I use solid Oaks as an endoskeleton, then why should I waste time desinning the damn truss structure?
I mean...
I could have done this since the beginning...
Just using wood...
And I could even cut the wood in different shapes, so I could make a knee or a shoulder bone structure...
By the way, 2 meters of wood beams/columns range greatly in price, but normally it costs 10 reais (2 dollars) per meter, and since we need around 38,4 meters of this thing, you may need 400 Reais (77 dollars) for the entire damn body.
It was so simple.
The solution was in front of me all along.
bruh.
Anyway guys, it seems that the endoskeleton structure is more or less complete...
This means now that I will break my head over motion capture.
Now the real headache starts.
By the way, I received another answer saying that a 15cm in diameter and 3mm in thickness steel tube would be able to withstand these forces.
Which would be cheaper and lighter but... How to be sure?
I just give up on trying to figure out on my own... Wood it is.
By the way, you could make trusses with rope (made of metal or not) and other elements:
I just feel like this project log has become just a lump of frustration and uselessness.
It is just... I keep looking at the fricking wall of tutorials, and I keep looking at the clock, and the hours simply pass.
For some reason I just feel frozen, and the fact that I took 20 days to do absolutely nothing just fills me with anxiety.
When this "mind block" goes alway I will make a new project log.
I just want to forget this thing for now, I just feel frustrated with all my failed attempts by now.
So, I just found out that I could simulate this kind of stuff on a program called "FreeCad", which, if I figure out how to use, can help me a lot.
Also, New Year y'all, I hope I finish this DIY Mech project this year instead of coursing 5 years of engineering.
Also, sorry in advance, because my brain is not working and I don't feel like working on this migrane of a project right now.
Off-topic:
You know what time is this bois?! It is time to write 30 pages of useless knowledge that nobody cares.
Remember when I was talking about Ionocrafts on Project Log 17? So... I was wondering something.
(content warning, if you have arachnophobia)
Spiders, somehow can fly using static electricity, like balloons in the wind.
I wonder if it would also happen to an aircraft using more or less the same principle...?
Also: the video I showed saying that ionocrafts are aboslutely not viable is kinda misleading, the own wikipedia page the guy shows tells that the low "1 watt per gram" ratio of ionoctafts were only found on early 60's prototypes.
I asked around and it seems that this method of flight is also a no-go. It is definitely not scaleable since the cratures that use this type of flight have less than 10 miligrams of weight.
Well, there it goes my dream of a creepy flying object full of electrically charged spikes and strings... 🥹
(yes, this is from Matrix)
Also, I totally forgot about a subject about ion propelled aircrafts: they are similar to the speed-size "ratio" that the conventional aircraft have.
Dunno if it is a real ratio, but... basically, the bigger the propeller blades of a turbine, rotor or other type of propulsion, the bigger the lifting generated, but its speed is severely affected.
That is why aircrafts with smaller propellers waste so much energy trying to fly vertically compared to convetional big rotor craft.
Well, the thing is: it is not so different about ion propelled aircraft, they need those big wings because the wings are the propellers.
So, you either make them ginormours, or make them smaller, but with greater speed.
In either way, just like in the conventional aircraft, you will have advantages and disadvantages for each type of propulsion system that you need to verify if these align with your required parameters.
And, of course, the same applies for wings, aircraft size and so on.
Oh yeah, I also remembered something:
Basically, you can kinda "cheat" the size of your wing span if you increase the number of wings. Of course, this comes at the cost of increased drag/friction on air.
That's why some old aircraft used double wings, and why some modern aircraft have some complicated wing dividing mechanism when it comes to landing and taking off:
I wonder if one would be able to make a flying ship with enough small wings... 🤔
Also, I just found out about Kite-surf and Paragliders.
Isn't it crazy that one could simply fly (with enough paragliders/kites) using these methods hundreds of years ago?
We could have flying sail ships, but real life is just too boring, ain't it?
(wallpaper from Treasure World)
Paragliders normally are meant for two people (because they are too risk to be used by an untrained/unlicensed person), so, assuming both people weights 200 kg (440 pounds), you would need more or less 5 kites for each 1ton.
You would need 5000 thousand paragliders/kites to lift the 1000 ton warship.
(Source: "Shen Comics"). Literally impractical... It would be an worse case than UP's house:
But hey, that is just a theory. A MOVIE THEORY!!
Also, I just now remembered that actually I was completely wrong about the paraglider:
The paraglider only works with the speed of the wind, you can't goo faster than the speed of the wind when what its moving you is the wind itself.
And you also can't make use of wings, because you are moving with the wind, not against it.
You would need something like the video bellow, where the rotating blades are actually providing more speed than the wind. But if you were to make it move a rotor in an aircraft flying ship, your rotation output would be as fast as the wind makes you go (I think). Even if you used gearboxes, I don't know if you would be able to make it work...
And no, it wouldn't be a perpetual motion machine, because the energy is coming from the wind itself, just like a wind turbine powering an electric engine.
Anyway, back to the real topic:
FreeCAD design:
Well, I received suggestions to, instead of using a solid rod or a tube, to use various smaller tubes, like a honeycomb.
We are back to step 1, where I suggested exactly the same thing on Project Log 18 with the semi-monocoque design.
😗
Well, well, well.
I did have a person on quora saying that maybe next week they will try to calculate a better semi-monocoque design for me.
If they will or not, I do not know, but I do know that I won't just wait for an answer falling from the heavens.
I didn't test anything on FreeCad yet, by the way, I'm still watching the fricking tutorials.
Not exatcly just the bones, but the shoulders.
I now noticed that, even though I have Stewart Platforms as the shoulders, it may be not enough for the full range of motion.
Remember: the McKibben Hydraulic muscle shorten in just 6cm, 20% of a 30cm long muscle.
This means that, even though the shoulder has a Stewart platform, it is still has not enough movement.
Again, maybe.
I didn't built the thing yet and I still need to test it out on FreeCAD or Blender.
However, if this in fact doesn't give enough freedom of movement to the shoulders (and other limbs), I will be forced to come with a more unothordox approach. Or even a more biomimetic apporach.
With the later not being that nice, since biomimetic = more actuators. More actuators = more energy consumption. More energy consumption = less autonomy.
And that not even entering the subject of complexity of control, an onboard computer still needs to translate all your motion capture to movement.
The video above shows cells being grown into flexible vitros, so the robot movements helps these grow into real muscles.
All this project would be so much simpler if I could simply put my blood (or from an animal) on a vitro and simply grow them. I also wouldn't need expensive batteries or electric generators, just injecting food down the robot's throat, lol.
I think I will try to make a rope/line to represent the McKibben Artificial Muscles on FreeCad and then test the body movements. *If* the FreeCad allows for such programming.
It will be a little off-topic at the beginning, but please, just let me elaborate, lol.
Just now I found out that there were (and there are) ships/boats made out of concrete.
It may not be a great deal for you, but it certainly was for me.
My mind was just blown alway, because I always thought concrete was way way denser than steel (7.85 g/cm³), but it is actually almost 1/4 of its density (2,4 g/cm³). Aluminium is 2,7 g/cm³, by the way).
In fact, it is so light, and so resistant, that people are actually thinking of making air planes out of it.
And a nice thing is that you could use the same techniques applied to Ultra-high-perfomance concreteto make a cheap endoskeleton out of concrete.
The video below may be really useful, although it is talking about bunkers, it could be used for building the endoskeleton.
I would have never thought that I would say such things as boats, air planes and robots made out of concrete... O.o
Well, as you can see, you can add steel fibers, carbon fibers, glass fibers and a lot of other types of fibers, not to mention that you can even use actual textiles/meshes into the concrete in order to make it stronger.
You could also add other kinds of things, like Sodium Silicate (water glass), plastics, and even bacteria to make self-healing concrete.
But of course, I still need to check out other alternatives, simply because I still didn't made any progress or test on the fricking FreeCad yet.
After all, if I made this thing like this, using the basis of 30cm of length and 9cm of diameter, all the bones would still weight around 600 kg (1320 pounds), since it has moe or less the same density of aluminium.
I was messing with a program called "Interactive Physics" just to see what I could do with mechanical advantage in simple terms.
I forgor something:
The mechanical advantage necessary to lift 1 ton with a 10 cm long effort arm and a 30 cm long load arm isn't 5 tons, but (around) 3 tons.
I completly forgot that I don't need 5 tons, and that I just added the value for redundancy.
Which reshapes my perspective about the other issues that I talked about, such as the distance of contraction at the shoulders. After all, one of the downsides of McKibben muscle is its low contraction under certain loads.
Which means that it is probably good enough the way I've already planned it.
I totally forgot about this, but the geared hydraulic pumps can either be used as a pump or as a rotary hydraulic actuator.
But I don't know what is the maximum load/torque these can withstand, and are kinda expensive, so I don't know if these are worth the trouble.
(not to mention that the current McKibben muscles only need 0.05-0.07 liters at 4 bar, while these may need more fluid and more pressure)
But these are cool nevertheless.
I too totally forgot to think about motive flow.
Also known as vacuum pump/aspirators, basically, when you pass a high pressure fluid (gas or liquid) through a convergent nozzle, it creates a vacuum pressure, moving more liquid at a more or less medium pressure.
This could be used on the high pressure fluid that is released when the McKibben muscles are uncontracted, so you can lessen the effort of the hydraulic pump, since some part of the flow is being recycled.
Or even on the hydraulic accumulators in order to make even more fluid to flow.
Unfortunately, I think I will just post the final result when I'm done, the document is already lagging and I didn't even start doing anything.
I feel disappointed with myself now...
Guys! Someone actually answered me, and it is an engineer (student)! :DDDD
3 to 6 stainless steel tubes?!
Just that?!
Thank god!
... Too soon, I guess.
7 feet thick?! That's like, 2 meters!!!
Maybe I could fill the tubes with concrete or something... Or more smaller tubes...
I still didn't do anything yet on FreeCAD.
I feel so dumb right now...
Well, taking into consideration all these times somone just said it isn't feasible (goddamn is about time!), I believe I will have to try the truss design:
Not necessarily making it out of carbon fibers, as shown in the picture above, but making it out of trusses.
Something that I totally forgot when calculating the weight of the skeleton: Density.
You know drag cars? Those cars that literally work on speeds so fricking intense that they can only work one race and breakdown?
So, they use aluminium, because aluminium is just 1/4 of the density of steel, so if you make an aluminium bar bigger than a steel bar in order to withstand the same weight as a smaller steel bar, it would weight more or less half (or even a third) of the weight of the steel bar.
This guy explains it better than me:
So... Calculation time:
Well, I forgot to write the calculation, but basically, a 9 cm diameter 30 cm length aluminium rod would weight just 5 kg, which in total woud weight around 600 kg (1322 pounds).
However, just like I said, I would need to make it bigger, so I tried something around 15cm of diameter and I got 15kg per rod, which would give the same results in the projec log 18.
Like I said on Project Log 10, the joints of wrists, torso and all that stuff will all be universal joints.
But the only universal joint that I think would be able to withstand fricking 5 tons would be universal joints for trucks/tractors, and of them costs 200 Reais (37 dollars) each, and I need around 16 of those.
So... 3200 Reais (605,30 dollars) just for the joints.
Yes, I know that the muscles need to lift 5 tons, but the overhaul weight will still be just 1 ton.
But, as you know: all the weight of walking, running and jumping will be going down on the legs and feet, and these will absolutely need to be extra resistant.
I'm also guessing, of course. These things are meant to rotate, not to withstand impacts.
Another big problem is that carbon fiber is terrible when it comes to screws, and joints.
Those metal connections on carbon fiber tubes need to be inserted before the resin is applied to the fibers.
How to I apply this to the writs, to the shoulders, to the elbows, the knees, the feet?
Worse of all, carbon fiber is terrible against impacts.
But I was thinking on possible solutions for these problems, I just don't know how to calculate if they would actually work or not.
The idea was to either:
Make a Matryoshka of tubes of carbon fiber and tubes of steel one inside another. So the impact would be dispersed on the maleable steel/aluminium, and the weight be sustained by the carbon fiber.
Insidert a carbon fiber tube inside a steel tube. The steel would protect the carbon fiber from impacts and the carbon fiber would sustain the weights.
Probably none of the above would work, nor be light or cheap.
And I don't know how to make the universal joint rotate on its axis like those Stewart Platforms do.
I'm also not being able to find heavy duty ball joints for vehicle sor anything like that.
Bruh, I just need the wrist to rotate, why is this so hard? y-y
I also found this company called "Dragon Plate", which specializes on carbon fiber modular structures.
They showed this (impressive) picture of a 500 lbs (200 kg) at a distance that I don't know which.
Just to remind you of mechanical levers: the greater the distance from the basis of the structure, the greater the weight it is applied to it.
So, even though it is "just" 200 kg on the tip, it is actually an even bigger weight on the bars in the other tip.
I took a random online torque calculator and assuming this contraption has 3 meters of length and the 500 lbs is completely applied to the extreme outer tip, this would be applying 63 thousand kg force per centimeter (of torque).
But this isn't a rotating mechanism, this isn't a torque matter, but even then...
Maybe I should use the work distance equation?
Work = Force x Distance.
So:
1961.33 newtons x 3 = 5883 n . m or 5883 joules.
5883 newtons = 599 kg
hmmm
This puts into perspective that maybe this thing doesn't need to be made out of solid metal rods...
Maybe I could make a really dense structure like this one with these modular carbon tube fittings.
Bruh, we really need an engineer...
Well, I guess I will need to improvise something.
I was thinking on making an outer tube of carbon fiber, insert a thin inner metal tube with low friction, then take a solid carbon fiber rod, cover it with a thin outer metal tube and insert it inside the bigger carbon fiber tube. This way it would be able to rotate and distribute the loads throughout all the structure.
Now I "just" need to find a way to avoid the tubes from slipping out of each other like a telescopic tube. lol
And the complexity just increases...
The best result I could find was heavy duty hinges or 1 ton hinges.
these sure do look heavy...
I guess I don't have any choice but to make everything out of the thickest carbon fiber composite and metal-carbon tube contraptions and gambiarras.
Which is not my preferred option, simply because I would need to make everything by hand.
And making everything by hand means making everything half-assed by hand, but taking longer.
I will publish this right now, but I don't feel any bit complete.
I just feel like the discussion I opened here can attract people.
I didn't had an idea for a Project Log 18 yet, but since I added so many off-topics on Project Log 17, my Hackaday website started to lag and I was afraid of resulting in the same problem/bug that happened in the Project Log 16.
Now that I think about it...
I feel like the Project Logs are taking more and more time to be made and its subjects are getting harder and harder to calculate.
The fact that I procrastinate 80% of the time doesn't help...
But I do feel that I deeply underestimated the difficulty to actually complete this project log in specific.
And guess what? I was right.
I barely scratched the surface of the 2º topic, and the Project Log is already lagging and bugging.
So, unfortunately, I will be forced to postpone the 3º topic to other project log, because I feel like I will beat my head a lot trying to figure out the structure.
Okay, first, let's list what I need to talk about in this project log:
Materials:
Let's talk about possible materials that I could use. Such as Aluminium, Steel, Carbon Fiber, Wood etc.
Fuselage and structure:
Then let's find the best shapes these materials could withstand force and how to calculate these things.
3D modelling.
Let's design a basic 3D sketch model based on these new shapes.
and it gave me an idea. Basically, Wax Motors are linear actuators that are used as solenoid valves in some applications. It uses a wax-copper/heating element mix, which helps melting it.
Obviously, I won't use paraffin wax actuated McKibben muscles, simply because they are slower than a snail.
However, as you people may remember from Project Log 1, "polyethylene/nylon artificial muscles are not viable for control and actuation, because they are slow and need a lot of surface area".
HOWEVER, if I mix copper powder, heating element powder (like carbon fiber powder) just like the wax motor, I will (maybe, perhaps, I think, probably) exponentially increase the contact area between the nylon and MAYBE allow it to contract like a muscle without the need for kilometers and kilometers of nylon fiber.
I will just buy a 5 dollar nylon rod from aliexpress or something like that and then test it out (with aluminium foil and graphite powdered in a blender), I will need to make a lot of holes so the nylon can easily contract and cool down with circulating oil.
(yes, this was an impulsive purchase that I will regret for the next 99838923 years, even though it is just a couple of bucks)
Or, maybe, I think I will try to pass air flow through the molten nylon in order to make it porous, or just mix it with alcohol and wait the thing to scape (and not burn my house down).
One could make a personalized 3D printing filament in order to do that, but I don't have the money, nor the will to get all that trouble.
I could use polyethylene (a strong type of plastic, used even in bulletproof vests and milk jugs) as a matrix/binder and wood fiber composites.
A few types of composites.
2. Fuselage and Structure:
I don't think I talked about this clearly enough on Project Log 16, but basically, the idea of using aerospace engineering techniques was to make the fuselage/endoskeleton of the mech as light as possible and able to withstand the most loads as possible. Which is a way of circumvent the safety issue of smashing everything in your way by accident.
You can use CNC laser cutting wood for that, and still getting incredible amounts of strength while being lightweight.
I just need to figure out how to calculate all this crap... >.>
Well, I tried to ask around, and I got no answers, and the answer I received were "why not just make it like *machine that already exists*? It is easier than reinvent the wheel".
Anyway, someone actually suggested me a motherfricking Forklift design, for my "lever".
Well, I don't have a forklift certificate, maybe that's why I'm maindenless, lol.
Also, yes, I'm still asking around.
Asking things like "I need a mechanical lever that can lift 5 tons, but I need to save wait, so I'm trying to find a way to calculate and design a monocoque/semi-monocoque design, could you help me out?".
Maybe not the best written text/question to ask around, but hey, I'm trying dude...
And guess what? Everyone tells me that I should just make a tube, that I should just pay an engineer and so on.
Bruh, I'm broke and I'm trying to save some lives here, saving lives by not smashing them under this stupid mech.
Well, I guess that I will run into the same problem as the chatbot: you can only get a good, detailed answer if you ask a good, detailed question.
The output is as good as your input.
So, let's try to ask a good question here:
"Would this mechanical lever with semi-monocoque structure withstand 5 tons of weight?
In resume, I'm interested on making a semi-monocoque structure that need to be lightweight and strong enough to withstand 5 tons of weight in a small point of the structure (around 5-10 cm of area). Until now, I thought on the following:
The entire structure would be a cylinder with 30 cm of length, and 15 cm of diameter. The primary material would be aluminium.
The inner disks would be 1mm thick aluminium plates separated by nuts with 2cm of height used as spacers.
The aluminium shafts/rods with 8mm in diameter would pass through these nuts, totalling 10 shafts in a ring. You know, just like a semi-monocoque structure.
Finally, there would be a "i" linear plate with 30cm of length, 15 cm of width and 1mm of thickness passing through the structure, which would be more like a "spine".
Would such structure be able to withstand 5 tons?
This is meant to be a mechanical lever with an axis of rotation, but for simplicity sake, just imagine this as an static cylinder that will have 1 point where 5 tons of weight will be applied.".
Well... Bad news.
I couldn't find anyone that can actually reply me, simply put, it is too damn complex.
The reasons I wanted a semi-monocoque design:
It is lightweight, so in case of colision iwth humans, it would be innofensive.
Since it is lightweight, the muscles would nees to apply less pressure.
Depending on how one designs the structure, it would be easier to build.
I don't know about you, but it certainly is easier, cheaper and safer to put a lot of plates together with nuts and bolts instead of heavy welding everything with a torch or a high voltage welding machine.
Also... This made me remember something about our bones:
The video shows the inner structure of the bones.
It is basically like what we do in 3D printing fills:
And since we are in the topic of 3D printing here, let me confess something:
I'm a little hater of 3D printing... For some engineering applications.
It is just so fricking overhyped when they can't even compare to cast pieces (in certain applications)...
For those who don't know what casting is:
And both of these methods are (in a really general way) not as good as subtraction manufaction (in some applications).
But subtractive (aka "machining"), can be more expensive.
Each method has its advantages and its disadvantages and each application may require different types of manufacturing.
One cannot simply say one method is better than another, you need to play with its advantages and limitations in order to squeeze the best each method can produce. A great casted part may not be viable through the machining method, a great machined part may not be viable through the casting method, and a great 3D printed part may not be possible in both these methods.
You cannot produce certain things with machining, you can't make certain things with casting and you can't just 3D print the fricking world.
And that is why I'm kinda of a hater of 3D printing, except I don't make talking about it my entire personality, like normal haters, lol.
Also, I bought a plastic FDM Ender 3 3d printer, and my god, I f*cking hate that thing. It is as frustrating to use as conventional ink printers.
By the way, there are other methods of manufacturing. Maaaany more methods.
And that is one of the reasons why I got so interested on continuum robots, you could (hyphotecically) make something as complex as a laser 3D printer; using the cirurgically precise continuum robots to cave a path through the structure.
But it would also have its limitations, and it wouldn't be able to make things super precise without trade-offs.
For example, while machining, depending on the method, a more rigid structure is preferable, because it is easier to calculate and thus, make it more precise.
And precision is expensive as heck.
But how to make it at home? And in a budget?
You would need fiber lasers, maybe a water jet cutter, or a plasma cutter.
I don't have any of those.
I thought on using the technique this video bellow shows though, but at a lower pressure; because his power washer breaks down and he buys a stronger one.
I would "just" need to figure out the rate the material is subtracted from the part, and then figure out how to make a continuum robot hoose that doesn't fly all around like those firefighter hoses.
Anyway, back to the topic:
I just remembered about the backhoe loader structure, for some reason, its arm is in a wide "v" shape:
I don't know why they are like this, but I think it is worth looking into it and maybe adopt that to the structural design.
Oh yeah, I also completly forgot about this cellular lattice strucutre made by NASA and MIT inteded for air planes:
These kinds of lattice structures makes a knot on my brain... I have no idea how to calculate the ideal size for my application.
And yet, it is quite an interesting structure. It is absurdly light, it can be easily mass produced, even at low budget levels and are inifinitely modular and constumizeable.
However, I don't know how to model them, how to calculate them, and all the informations I can find about them are like "here is the prototype, I can do this, this and this" and never "here how to do it at your backyard".
And for obvious reasons, it is a study article, not a video-tutorial. And that is the biggest limitation of this project and mine: knowledge. And knowledge needs time.
Of course there is always the good old aluminium extrusions, but I don't know if these could withstand 5 to 6 tons...
Also, I just found out these slotted steel bars, also known as "industrial shelfs" or "Drive-in pallet racking":
This looks interesting, but I do remember messing with those when I as smaller and... These are not nice to manipulate with your barehands, specially if these are rusted.
I also don't think I would feel safe with a super thin metal plate almost like a sword hitting me at any speed...
There is also metal pipe/tube connectors, but I don't know which one can withstand 5 tons or more.
Now that I stopped to think about it, aren't my requirements for the artificial endoskeleton just too proposterous?!
Like, think about it: a car, a fricking car weights around 1 ton (or 3000 pounds).
And I want five of them in the middle of a 30 cm long tube??!!!!!/1?!?!//??
Well... All of this crap would be sooooo easy if I simply wanted to make a normal exoskeleton or robot, but nooooo...
And on top of that, I would need to make the actual thing to withstand even more weight for redundancy sake...
Basically, I would need either a 9cm diameter solid metal rod, or a 11cm diameter tube, where the inner hole would have 2cm of diameter.
And that would be for temporary loads. TEMPORARY LOADS, if I where to make an static load tube, I would something even more monstrous.
Accordingly to this steel rod weight calculator that almost got me a heart attack, this thing would weight 0,0153 tons, or 13,8 kg (30,5 pounds).
Which isn't as heavy as I though it would be...
But taking into consideration that we have... How many bones again?
...
...This many.
Of course, taking out the smaller mones, axis, and not considering that some bones are bigger than 30cm and smaller than 30cm and so on.
We would have 128 bones.
128 x 13.8 = 1766.4 kg (3894,2 pounds)
1766.4
1766.4
1766.4
1766.4
I think I've made a mistake.
We have no option, let's see how carbon fiber and glassfiber goes.
Edit¹:
Well, nobody answered me, and the ones that answered me are kinda useful, but really demeaning.
The problem CANNOT be answered - to any degree of real answers between 0.1 (units long, units being undefined at present) to a parsec. YOU have not told us (who are trying to answer your question by asking for data so we can make a free estimate worth reading) the length between the two/three/four/five/six (or more supports) YOU have not told us what the method of failure could be: Excess sagging? Minimal sagging? Too expensive to purchase? Shear force? Imprint force of the 5 tons into the surface? Fracture? Plastic yield after long periods of time? 2% bending failure? 10% bending failure? Failure after 3,000,000 cycles? Failure at -40 deg C? Failure above 200 deg C? Failure by tension - if the 5 tons were pulled from below? What kind of suspension(s) at each point of suspension? Common or linked suspension or independent? What minimum safety factor for the product? What maximum safety factor?
Yes, all of this information is useful, which I could take into consideration in future calculations.
But bruh, I asked this thing on quora, with a smaller word count per question than twitter.
It is a generic-question-asking website, and I asked a generic question.
Anyway, if a 9cm in diameter solid steel rod can withstand 5 tons, I'm damn sure a 9cm diameter solid carbon rod would out-perform it.
Friday, 13:32, 23/12/2022 I will try to finish this now, I swear.
Again, not mfixing grammar mistakes.
Well, the Project Log 16 bug definitely deleted all the things I wrote at topics 2 and 3, it is not like I just wrote the title and didn't work on anything at all. hehe. >.>
The project logs that I wrote are basically this meme, lolololol.
Hydraulic accumulators.
Basically, one could simply use a cheap 12V tire inflator/air compressor to fill up a bladder hydraulic accumulator. But these are expensive, and I don't know how long a 300 PSI air compressor for tires will take to fill up homemade sketchy bladders. Also, pneumatics are kinda dangerous, they can explode.
Also, one doesn't really neeed bladders, I could simply use a car spring that is pulled by a electric motor. Like a electric jack/linear actuator. When the spring is pulled, the hydraulic oil will be forced in by vacuum action, then I just need to release the spring and the compression of the spring will compress the hydraulic fluid and that's it.
Kinda of, I need to find a way of calculating that. I remember once reading an scientific paper of a "novel design of hydraulic accumulator" or something among these lines, I need to find it again. Maybe they have a model/equation that I can use to guess how much pressure it will generate, if there isn't already an option that I can buy online. For some reason, the electric jack/lineart actuator is more expensive than the hydraulic jack... Bruh.
Or I could simply use a electric jack directly compressing the hydraulic fluid... I could also make a homemade pulley that pulls the hydraulic accumulator spring. Homemade because the fricking electric pulleys use the same 1hp electric motors the high pressure hydraulic pumps use, so... bruh.
Dunno what is the best option, I will need to calculate every single one of these. I hope the people I invited to this project could be able to give me a hand, we probably know as much as each other, but 4 heads think more than 1.
Costs.
I was thinking a little bit here about the overhaul cost of this mech. A single car in Brazil can cost 100,000 Reais, but in the US it costs around 30,000 Dollars (as foretold by google). If we can make this thing under 10,000 Reais (or just 2000 Dollars), doesn't that mean it is actually very cheap to make one in comparisson to cars?
hum 🤔 For example, if I used 72 5 ton hydraulic jacks that normally cost 100 Reais (19 Dollars) each, I would be expending 7200 bucks on the actuators alone, more 2000-3000 on the electronic parts including the hydraulic pump. This means this thing would cost kinda okay...? 🤔 (Not okay to me, I'm broke).
Off-topic:
Anyway, my brain is ADHD, and I will elaborate, and I won't make things clearer.
So, with this said, let's get back to continuum robots:
And it is cable-driven by electric motors, not artificial muscles...
Would it stumble the same problem I talked on Project Log 16? Where you need it to be so resistant to bending motion that it would simply become solid?
I don't know, it is morning right now, my brain isn't working properly (when it does, tho?)...
There must be a way of making this crap safe to be around that doesn't require the mech to look like a Michelin Man...
You know, it is not because it will look stoopid or anything like that, it is because it is not a definitive measure, it is merely an after-thought on the mech's core design.
It is merely an attempt to fix an unsafe design, instead of inserting the safety on its core design and mechanisms of operation.
Also, when I don't get an answer, my brain gets itchy.
It is like math: there is a solution, I just can't find the right equation for it.
Well, I just found this weird looking prothesis:
Not entering the merit of "if someone seriously gave me this thing after amputating my arm, I would beat them with it until they talk directly to jesus", but the structural design seems interesting.
Yes, I did say in Project Log 16 that "making something that bends at axis of rotation wouldn't change the fact that the limb should need to be stiff enough to not bend at 1 ton, and if it is stiff enough to not bend at 1 ton, it is surely hard as a rock".
However, I was wondering here that it would be possible to make these solid sections out of silicon rubber (or anything like that), and make it stiff by pulling the inner cable, and thus, creating tension that would create structural stiffness.
Doesn't even need to be actuated by artificial muscle/electric motor or anything like that, just a bunch of sections of a 30cm long "donuts" of rubber a inner cable of steel, aramid or carbon fiber would be pulled until tension and hold in place by a nut and bolt.
Like those packaging/cable tensioners:
Now, imagine this, but a cable/wire/rope going through the the limb "tube" and hold everything in place.
The cable/wire/rope can actually even be a spring.
But again, this still won't be enough (I think), because, as I said myself, it would be required to be stupidly resistant to bending action (aka "stiff") of 1 ton that it would probably be as dangerous as a fucking metal bar.
I know that is annoying for you, reader, to read me rambling again and again with the same result again and again, but it is also annoying for me as well.
I'm no scientist, but the scientific method is trying to prove your own thesis is wrong more than it is about proving to others that your thesis is "righter" than everyone's else.
And I try to follow this method, because if I deny that I'm wrong or anything that I do/did is incorrect, eventually I will make the machine in real life and I will eventually face the consequences of that.
I'm trying the best I can to make this thing work, but it is more likely that I will fail. But I'm going through it anyway :)
I just remembered one thing:
If you put each page of a phone book one above the other, they will have so much friction between theen that not even two tanks can separate the books.
With steel cables is the same thing.
So, maybe, if you put the "rubber donuts" and the inner steel cables under tension to keep everything under tension and under friction, maybe you will be able to make it safe.
Nah, it will run in the same problem...
Everything would be so fricking easier if this was just a domestic robot or something like that...
But nooo, I need because I need a mech that can lift 1 ton...
Hey, looking at the bright side, this now seems very, very safe to use as an Exoskeleton. But forget about super human strength and feats, neither this nor your body will be able to withstand the forces involved.
Another off-topic even more off-topically:
I was wondering, if I use an oxygen concentrator and an air compressor to fill an air tank...
... And burned it in a rocket nozzle...
How much would that compressed oxygen gas fuel tank last? hehe
(I know, quite the stretch, let's just focus on making this thing work before thinking on how to make this thing rocket-dash)
Well, great, now my stupid ADHD brain is telling me to make a Hackaday project with flying ships...
A mech can be built in my garage, all the technologies already exist (hydraulics, electronics, actuators etc), but a flying ship?!
I would need to use a mix of hot air balloons (that have more bouyance than helium or hydrogen) and helicopter blades. I doubt I would be able to make such thing in my backyard...
70,000 liters of helium/hydrogen/hot air to lift 1 person weighting around 80-100kg, a bus sized balloon for every 100 kg.
I bet I won't be able to make a floating house any time soon. y-y
Even though I kinda wanted to use the way cooler ionic thrusters... And I feel like I actually can make ionocrafts at home, since they don't need complex manufacturing and expensive materials... hehe 😏
I just found out something incredible interesting (at least for me).
AS YOU CAN SEE ON THE MINUTE MARK 7:28, when you mix galinstan (gallium alloy), aluminium and water, you get pure hydrogen and aluminium oxide, and you can reuse galinstan as many times as you want.
Which this means, that you can make an hydrogen engine generator (or catalyzer) merely using aluminium and water.
And galinstan is pretty easy and cheap to make:
This is really really cool for power generation!
Enough of tangets! Let's get back to the real topics before I put too much stuff on this project log and end up with the same problem as Project Log 16!
Oh... Oh no...
The site is already lagging.
Me running to tell everyone 30 pages worth of random useless facts that nobody cares:
1. Hydraulic Accumulators:
I know that I said that pneumatics are dangerous, but as shown on the video below, the bigger the area the pneumatic actuator applies, the lesser the pressure required to do the said work.
At time 3:51, they show almost a ton being lifted with just 1-2 PSI of air pressure in the air cushion.
Meaning that I don't really need super strong, big and havy hydraulic accumulators in order to supply this thing.
I just need a bunch of "pancake" like hydraulic accumulators stacked or around the pilot's cockpit in order to supply the mech's body.
My only concern is finding out if the hydraulic pump is capable of supplying enough pressure/liquid to the thing.
Since the area will be so big, I intend on making it like an actual pancake with 1 meter in diameter.
5 to 10 cm of height.
All of this would have a capacity of 10 gallons or 40 liters.
The pressure inside the balloon will be 1-2 PSI.
The pressure we can produce is 0,4 MPa, or 58 PSI, or 4 bar.
We can achieve only 8-15 Liters per minute of fluid flow per pump (if I don't buy an actual hydraulic pump).
We need a fluid flow of 900 liters per minute.
Accordingly to the calculator above, I would only be able to provide 0.04 gallons of hydraulic fluid, which is 0,1514165 liters.
I need 43.2 liters to actuate all muscles at once.
I guess I will be forced to severely increase the pressure inside the acumulator (or find a better calculator).
The thing is that I don't actually need to make the pressure inside the accumulator to be the same as the final pressure in the muscle (0,4), I can increase the pressure of the liquid more more when it is inside the accumulator and then use a pressure gauge to reduce the flowing pressure to just 0.4-0.8 mpa.
The problem is that I can only produce 4 bars with the pump...
Maybe I will need to use an hydraulic pump fill the hydraulic accumulator, and then a pneumatic pump to fill up tires that achieves 300 PSI (2 MPa or 20 bar) to fill the bladder. And then when the accumulator is empty, I will need to empty it with a solenoid valve and repeat the entire process. Again.
By the way, if I increased the pressure up to 300 PSI in the first calculator, I would get 1,72 gallons, or 6 liters.
Now I finally get the severity of the situation I've put myself in...
All of this work and headache, for a single actuation of all muscles in a single second.
43 liters per second... 900 liters per minute...
It seems I will need to use that 3000 watt/hour 1 horse power electric motor to generate enough pressure for a couple of contractions for every minute.
Oops, I just forgot, it is not 43 liters, it is 5 liters to actuate all the muscles at once.
We are back on schedule bois!
dang...
Now I need to figure out how many pancakes I would need. Since only one pancake is meant for 1 second of actuation of all muscles at full strength, which won't happen, but it is a good margin of error.
So, if one pancake has 40 liters of capacity and the hydraulic pump that I plan to use has 10 liters per minute of capacity, I would need 4 minutes just to fill up the damn thing and more 8-10 minutes to fill the pneumatic bladder. I say 8-10 minutes because the mini-air compressor that fills up tires normally says they can fill a tire (of unknown size) in 8 minutes or less, but knowing what marketing does, it is probably more, way more.
However, these same mini-compressors are like, 50-80 brazilian bucks (more or less 10 dollars), so I can use multiple of them on the same bladder. So I can actually reduce the charging time to 5 minutes or something.
10 minutes of charging for 3-5 steps...
Then I need 2 hydraulic pumps, with 20 liters per minute, and 4 fricking air compressors.
Then I will reduce the time of charging to 2-5 minutes... And increase the cost of energy to...
Assuming each one of those consumes something around 100-200 watt hour, I would consume 800-1600 watts in an hour.
Well, I kinda feel like I would need the air compressor anyway, because:
I don't need the hydraulic pump to work all the time.
I don't actually need to make the entire system flow that fast.
I would do the same thing of filling the bladder after filling the hydraulic accumulator with hydraulic fluid.
Assuming that these are working full throttle, non stop, for an hour...
Which won't happen, the stupid mini air compressors require something around 10 minutes of" rest" because their electric motors overheat (accordingly to the sellers themselves).
Well... It seems that the "bottle neck" here is the air compressor, ironically, the hydraulic compressor... That were meant to stop the bottle neck of the hydraulic pump...
I guess I will be forced to use 3000 Watt hour electric motors with hydraulic pump...
... Which may also not work.
Simply put, this consumes 3000 watt hour producing 900 liters a minute at pressure of 4 bars or less. This means that the hydraulic accumulators won't be able to hold enough pressure to spill enough hydraulic juice. I need to keep that fricking thing at 300 psi in order to produce 6 liters a minute.
If I where to increase the pressure inside the hydraulic accumulators, I would need to increase the pressure in the hydraulic fluid, and to increase the pressure in the hydraulic fluid, I would need to reduce the rpm and increase the torque of the hydraulic pump.
... For 6 liters per minute of fluid flow...
Also: I didn't finish watching the videos teaching how to size a hydraulic accumulator, nor did I include the fact that it is a pancake hydraulic accumulator, which translates the large area of pressure into faster fluid flow with lower pressure.
Actually, I will just ask around, this time there is no way people will get mad at me saying the question is stoopid.
(I already got a post removed from one of the websites I asked lol)
On this reddit question, someone said that this pancake hydraulic accumulator would produce 15 liters at 4 bars if I filled the bladder with 8 bars.
So, 4 minutes to fully fill the pancake, but that is kinda wrong, it doesn't have actually 40 liters of space inside that, because the bladder is occupying space.
So, let's say, 2-3 minutes to fill a single pancake that would allow for fully actuate all 72 muscles for a second 3 times. Which would allow for 6 actuations if half the muscles were actuated instead of all of them. And since this is 3 actuations per second, I would have ±2 seconds of autonomy.
So, if my brain is preoperly working (it is not), I would need around 60 pancake hydraulic accumulators and 60 pumps to fully work for 2 minutes without stopping.
Yeah, forget this system completly based on hydraulic accumulators guys...
I feel like I'm not putting enough effort on this project log, for some reason...
As google put it into better words:
Its function is not meant fo be used in the place of a hydraulic pump.
It would be meant for a "jump" or something like that in the case of a mech.
Besides, 3 actuations per second is the maximum number I estipulated if this thing where to be running at maximum speeds.
It could be only using 5 liters per second or even less while walking.
Anyway, If I where to use 3000 watts per hour (assuming it is actually 3000 watts and not a lesser number), I would need 1 car battery per hour.
Of course, if I were to work lifting weight, run and fight aliensall day, I would need 24 car batteries that have 3000 watts per hour of capacity.
Obviously, for matter of costs and practicality, I would be limited to 4-6 car batteries (or a battery pack with 18000 watts hours to consume 3000 hours throughout these 6 hours of ful "throttle" working.
Now we are reaching another bottle neck, I need to properly calculate the energy requirement for the hydraulic pump.
The problem is that I can't find that damned stupid dumb 1 hp DC motor from Project Log 16.1.
By the way, assuming the 1 horse power of that big ass DC electric motor that I showed on Project Log 16.1 actually consumes 743 watt hour and it is its actual power consumption, these 6 car batteries would allow for more or less 24 hours of work if you were to actuate all muscles at once continiously, without losses due to efficiency and so on. But since you won't actuate everything at once, you would probably be able to last even more.
Also, another note: I do have plans on using DIY Thermoelectric Generators (also known as "Seebeck effect generators"), solar panels and maybe DIY Stirling Engines in order to squeeze more autonomy and cheaply recharge over time.
Or using the Galinstan-Aluminium-Water Hydrogen generator I talked about in the Off-topic part. But that is a headache for another time.
I just found this direct current 1 horse power 745 watt hour that can achieve 3000 RPM, however, I will keep it at 1000 RPM.
The details:
Motor 24V DC - 750W
Voltage 24 Volts DC
Current (min) 4.5A
Current (max) 40A
Power 750W
Speed 3000 RPM
Torque 1.75 Nm
right/left rotation
Weight 4 Kg
Welp, it looks like a good candidate.
2. Costs:
Okay, one problem that I severely overlooked was the expandable braided sleeve. You know, the "core" of a McKibben artificial muscle.
Yes. I'm stoopid.
Basically, assuming that I will make every single one of the 72 muscles the same length (30cm) and without making mistakes (which I will), I would need 2160 cm of braided sleeving. Or 21,6 meters.
Which is not that much...
... If I weren't in use of costumized artificial muscles.
But as I said on Project Log 14: I would need muscles that have 14 cm of diameter.
I can only find at maximum 1 inch diameter braided sleeves made of nylon, which means I would either need to make it myself, or pay supplier for costumized braided sleeves out of steel.
However, there is another option, that I also don't like very much...
I could use any kind of fabric, including those steel woven wire mesh screens:
Of course, I was thinking on using the 400 mesh.
But, as you could see in the first image: I would need to sew its sides, which will diminish the rate of contraction and it will be the first part to fail.
Well, right now I'm sending an email to some braided sleeve suppliers that I could find. Let's se how much it will cost...
And no, I definitely cannot buy or make a reliable braiding machine at home, just look at this thing working:
These two options could help me out:
The first is a handle, which I don't know if it would be suitable for expanadble sleeving.
The second is the Chinese Finger Trap that I talked about before.
The problem is that both are too different from the original McKibben sleeving, and could drastically change the final result.
But taking into consideration the points of failure and disadvantages each brainding method has, I believe that a single metal rope like in the first example.
Well, I received their answer today, and basically, they all say that "it is too big of a diameter to be able to make it custom" ( ͡° ͜ʖ ͡° ), and they also don't have the capacity of testing if such thing will be able to withstand 5 tons.
Well, hand made it is...
... Or maybe not.
You see, one problem of McKibben Muscles where the outer sleeve doesn't have holes smaller than 1 is that the inner bladder rubs itself on the sleeve; which increases the chances of rupture.
This shows a good example.
A solution would be to actually use multiple layers of net/sleeving in order to decrease the space inbetween the holes.
But it would come at the cost of increasing its resistance to expand the outer sleeve.
And yes, I'm also considering the Chinese Finger Trap braid. But again, it will come at a cost/disadvantage that I don't fully know yet...
ANYWAY, the actual subject: Costs.
Like every fricking Project Log, I will only make assumptions here.
DC Electric motor 1hp 750 Watts = 1000 Reais (188,93 dollars)
Each muscle uses around 2 meters of steel wire/cable/rope, so 144 meters of steel in total = a random bobbin of steel 2,4mm of diameter with 200 meters is 250 reais (50 dollars). Actual winch rope that can withstand around 6 tons made of nylon or polyethylene is 200 reais per 10 meters, so 1440 reais (272,06 dollars) in total for all muscles (if I don't make mistakes and end up wasting rope). Well, I added this last part because maybe that's the better option for redundancy, and also I don't actually need the rope to withstand 6000 kg, simply because there will be a lot of cables in a single muscle. Only by testing I will have a definitive answer.
Each piston pump is a pneumatic piston that may or may not break during the extreme 1000 rotations per minute of continuous work = 50 reais (9,45 dollars) each. I need 10 = 500 reais (94 dollars) in total.
Each car battery costs 1000 reais (188,93 dollars), I need 4 to 6 = 4000 reais (755,71 dollars) to 6000 reais (1133,56 dollars).
So, 1000 + 250 + 500 + 4000 = 5750 Reais (1086,33 dollars) the hydraulic system alone. Or 1000 + 250 + 500 + 6000 = 7750 Reais (1464,19 dollars). Or 1000 + 1440 + 500 + 6000 = 8940 Reais (1689,01 Dollars).
Well, who would guess that mechs aren't cheap, imma right?
Of course, you could obviously wait for discounts, find parts on scrap yards and so on (which I'm planning to do) make the motors, pistons and batteries by yourself for way cheaper.
There is a lot of shortcuts for the prices, but I'm just listing here.
Anyway, I'm finally done with this god dang Project Log.
But, in summary, the informations that got deleted are:
You can't make an electric motor actuate an hydraulic pump at 1000 RPMs, because when you increase the RPM, you decrease the torque.
So, it would be more or less 200 rpm.
This is bad and good, bad because I won't be able to make a fluid flow of 900 liter per minute, but I can use cheaper and smaller electric motors that have reduction gears.
The recalculation of the pump, counting the space the piston rods occupies on the two motion cylinders gives 15 liters per minute at 3 bars in total. This accound the 5 cylinders used as hydraulic pumps.
Edit²:
Obviously, the pump wouldn't be 100% efficient, so we can cut that flow to lower values, around 10 or 8 liters per minute.
Edit¹:
As you can see in the video, torque/horse power, speed and energy consumption can vary a lot.
If I where to use the big 3 hp 300 watts motor, I would definitely be able to supply the 900 liters per minute without the need of hydraulic accumulators.
But, as you can imagine, it requires more energy, it weights more and it is much more expensive.
And I'm trying to make this thing under a budget, because, you know, I'm broke.
And to worsen things more, I'm almost reaching the maximum weight of the mech. Even though all the muscles can lift at least 5 tons.
As you can expect, everything has weight. All the hydraulic fluid is around 150-200 kg (including the hydraulic accumulators, the batteries, the electronics and the pilot would weight 150 to 200 kg (or even more). I don't know how much the endoskeleton will weight, but a structure that can hold 1 ton will definetly be heavy as heck. At best scenario, 200 kg (if I don't use composite materials, just steel tubes).
So... 600-800 kg in total, even though there are more muscles on the torso and lower part of the body, would it even be able to lift itself?
I mean, there are 6 muscles on each thigh and each leg, each muscle can lift 5 tons... So... 120 tons in total... If we take the general mechanical disadvantage where each muscle would lift just a fifth of its total strength, we would get... 24 tons...
Now that I think about it...
Maybe a 3hp that weights 20-50kg and consumes 3000 watt/hour may not be that... Difficult?
There must be something wrong with my calculations, if it was this easy to lift this amount of weight, we would have seen more mechs out there.
20/12/2022 Sorry for the delay, for some reason my brain refused to work these last 5 days, so I didn't work that much on this project log as I wished to.
23/12/2022
For some reason, it seems like this Project log is so long that the Hackaday website is lagging and bugging, basically, the topics 2 and 3 got deleted, so I will be forced to work on hydraulic accumulators and costs on the next project log.
Just you got an idea, at the end of the project log, the text gets automatically deleted when I add something.
I'm putting here all the subjects that I couldn't talk about in Project Log 14:
Hydraulic pumps and its relation to high pressure artificial muscles. I need to calculate the amount of flow.
My first thought was, like I said in the Project Log 13, using manual hydraulic pumps with electric motors. I thought it was the best option, but the pressure is generated too slowly, so I would need a hydraulic accumulator, and the following reasons will clarify why.
Hydraulic accumulators. Basically, one could simply use a cheap 12V tire inflator/air compressor to fill up a bladder hydraulic accumulator. But these are expensive, and I don't know how long a 300 PSI air compressor for tires will take to fill up homemade sketchy bladders. Also, pneumatics are kinda dangerous, they can explode.
Also, one doesn't really neeed bladders, I could simply use a car spring that is pulled by a electric motor. Like a electric jack/linear actuator. When the spring is pulled, the hydraulic oil will be forced in by vacuum action, then I just need to release the spring and the compression of the spring will compress the hydraulic fluid and that's it.
Kinda of, I need to find a way of calculating that. I remember once reading an scientific paper of a "novel design of hydraulic accumulator" or something among these lines, I need to find it again. Maybe they have a model/equation that I can use to guess how much pressure it will generate, if there isn't already an option that I can buy online. For some reason, the electric jack/lineart actuator is more expensive than the hydraulic jack... Bruh.
Or I could simply use a electric jack directly compressing the hydraulic fluid... I could also make a homemade pulley that pulls the hydraulic accumulator spring. Homemade because the fricking electric pulleys use the same 1hp electric motors the high pressure hydraulic pumps use, so... bruh.
Dunno what is the best option, I will need to calculate every single one of these. I hope the people I invited to this project could be able to give me a hand, we probably know as much as each other, but 4 heads think more than 1.
Costs. I was thinking a little bit here about the overhaul cost of this mech. A single car in Brazil can cost 100,000 Reais, but in the US it costs around 30,000 Dollars (as foretold by google). If we can make this thing under 10,000 Reais (or just 2000 Dollars), doesn't that mean it is actually very cheap to make one in comparisson to cars? hum 🤔 For example, if I used 72 5 ton hydraulic jacks that normally cost 100 Reais (19 Dollars) each, I would be expending 7200 bucks on the actuators alone, more 2000-3000 on the electronic parts including the hydraulic pump. This means this thing would cost kinda okay...? 🤔 (Not okay to me, I'm broke).
Quite the off-topic here, but...
I just love these arts from Theo Stylianides (I took this image directly from their Artstation profile) and I actually often look at their art for inspiration on this project.
Like the modularity of their models.
I know that this is "just" a 3D model for a game or a project of sorts, but one thing that I always liked about their arts/models is that even though it is supposedly meant to be "tacticool" or "only" a concept, it reeeeally feels believable.
Because these are really boxy and "brute" with "function over shape" design that would definitely be a modular piece of equipment in the real world.
Anyway, all of this tangent just to start a discussion on the subject of:
Maybe I should think on the artificial endoskeleton of the mech in this project to be more like hollow "boxes" as shown in the second part of the artwork above this text instead of metal tubes like the 3D model I've made in Project Log 6 and Project Log 10.
The idea is to make the "skeletal boxes" more or less like the concept above this text, so it would be easier to ask for CNC or cutting shops to "just" print these parts would in a 2D plane, and screw the parts together.
It would also be possible to print the 2D design in pieces of papers, glue to metal plates and then "just" cut everything by hand.
The muscles, equipment and wiring would be inside these "boxes", including the pilot, which would be inside a bigger "box".
However, the problem is that it would harder to safely calculate/estimate how much structural tension, force and damage these skeletons would be able to withstand, unlicky predictable and simple tubes.
Also, the mechanical advantage of the "levers" in the body must be taken into consideration, the muscles need space to operate because otherwise they wouldn't be able to move the body.
Another problem is that it would be even less safer to be around other humans, not that my first design would be "that" safer either.
But at least the exposed muscles would be like cushions with liquid inside that maybe would be easier to stand around instead of solid and sharp edges of metal boxes.
It could be more useful if the "hollow boxes" where the endoskeleton itself, like the hollow metal tubes, which would allow for all the wiring to go through them.
But at that point, why not just use the hollow tubes, tho?
Anyway, it would be an interesting military design, but I don't want this to be a military thing, even though mechs are normally meant to be military in sci-fi.
... But thinking better about it, I don't really like screws that much. Because every time I need to disassemble electric motors that were thrown away, I need to use an angle grinder for hours in order to take the damn motor out of its metal compartment.
Literally because the screws get so bent and rusted that they can't be unscrewed normally, so I need to make a huge mess (and damage to the overhaul equipment) just because a single screw is stuck on the fuselage and it is screwing me over.
But nuts and bolts? Now that is the good sh*t.
Too small or too big for your screw driver? Just use a plier. Too rusty? Too bent? Can't be pulled over by a plier?
Just cut it, it is not screwed directly to the fuselage, it is not welded on it. You could even hammer it out and just bring a bigger bolt later and keep everything together.
The biggest problem of every equipment, system or whatever is when whoever is building/developing/desinging them aren't considering that this said equipment will fail and will need to be fixed.
Also², for some reason Theo deleted their deviantart account. I put a star on a lot of their works there y-y
Also, I just found this video, it is not related to this project log, but i believe it is very interesting:
Being honest, for some frickery reason, I'm really interested on continuum robots instead of human-like bone-muscle mechs/robots in general.
Don't get me wrong, I (think) won't throw alway all the progress I've made until now just for a random idea I had (like any ADHD person would do), analysing the prospect of working along-side humans, this seems a more safe and useful idea (and maybe cheaper).
If you don't know what a Continuum Robot (or tentacle robot, or trunk robot) is, let me share some videos:
In summary, they are Doc Ock arms, not all of them, but some of them.
I say that because of the obvious differences in structures:
Some have solid spines (like the Doc Ock above) and some don't have spines, like the festo one above.
The problem is that continuum robots are the f*cking hardest to calculate its movement, also known as "kinematics" or "inverse kinematics". In a normal robot you only need an encoder on the axis of rotation in order to know its position, but how you would do that in a spineless tentacle?
Well, I just had the idea of maybe using a plastic "inner sensor" whenre a bunch of 3D printed rotational articulations with encoders on them would track the entire thing.
For example, just imagine the following continuum robot with its spine's rotational axis with enconders on them:
... Or maybe like a Nintendo 64 joystick.
But wait, how do you lift 1 ton with these continuum robots?
It is easy to calculate with a solid lever (like an arm), but how you do that with a continuum robot?
My idea was to use multiple multifilament steel cables as a spine and a lot of McKibben muscles as muscles. As shown in the illustration I've made on paint bellow, the idea is to make a central spine and an extra spine to each direction you want the tentacle to move, just like Festo and Doc Ock have 3 lines of segments that each allows for a degree of movement. And it would partially allow for retraction and expansion of the tentacles, just like Doc Ock does.
I know it is hard as heck to calculate this, but i think it is worth it. I mean, I do want to walk around with a mech and help people lift heavy stuff.
But you know, I don't want to break someone's feet by accident, or even worse, a toddler excited with the robot walking in my blind spot and getting fatally wounded...
I think it is worth the trouble.
And yes, I'm just saying this because I dreamt this happened, I woke up in a cold sweat.
The broken shape of a toddler in the ground scarred in my mind as I woke up...
I really really don't want that to happen.
I will try to calculate this thing on the next project log.
Edit¹:
So, now that a day have passed, let's just say that I calmed down. That dream really messed up my brain.
And maybe I should give up on the idea of continuum robot mech.
For some reason, the hamster in my brain has gone full throttle trying to think in solutions to the "spaghetti body that can't lift 1 ton" problem of spineless continuum robot bodies.
And I couldn't find any.
For example, think of the illustration I've made: if it where to lift 1 ton weight at, let's say, 60 cm of distance from the shoulder, even if all the muscles where fully actuated and tensioned, it would still bend in unpredictable directions.
Because these are cables, how to you stop cables from bending? It is like trying to build a bridge with ropes without connecting both sides.
Now pretend that the rigid horizontal concrete line is just a big rope?
It will act like a giant spaghetti and fall to the ground.
Then I "tried" (in my mind) to imitate the human shape body, adding more cables and rubber/flexible resin, stiffening the limbs and letting the joints flexible, like a compliant endoskeleton.
Imagine it like those plastic hinges on pencil cases:
It is almost solid in most part, but in the point it needs to bend is quite slim. That's the idea.
The problem is that, even if I did that, how I would be able to lift 1 ton at 30 cm in an horizontal line? (you know, like an arm)
All of this would be done to increase stiffness of the structure, but you would innevitably reach such leves of stiffness in order to lift 1 ton, that you would literally become completely solid.
And all the problems would still stay even if I used the suggestion bellow as a basis, because I did use that as a basis.
Maybe I would have better ideas if I made rope 3D models on Blender, but I'm still working on Project Log 16, not on spagetthi project log.
This video of the robotics department of disney is very promising, but, again: in order to lift 1 ton, one would need such amounts of resistance for bending (stiffness), that the structure would eventually be rock solid (or "metal solid", in this case).
And yes, I could use the Festo design of spineless continuum robot, because it is the most promising (for my gut feelings) at being able to lift 1 ton and still be compliant and safe...
However, the muscle needs a lot of space inside of it, space thta needs to be filled with either air or hydraulic fluid.
I would need too fricking much fluid to actuate it, so much that I don't even know if it would be viable.
I don't even know if hydraulic accumulators would be able to supply them.
And yes², I could use some kind of spine/bones with some kind of structure, but I feel that it defeats the porpuse.
Because these "bones" (disks, tubes or spheres) would need to be strong enough to withstand 1 ton or more, and these would be the rigid and hit like a metal chain whip.
Of course, this is just my rationalisation and conclusion, you would probably have a better idea than me.
Edit²:
You know, a good alternative is to look up to Air planes fuselage.
Aerospace engineering is about making the less amount of material to be able to support the biggest amount of stresses and loads.
I would need big ass balloons made of polyurethane all over the mech's body and on the feets...
I think a good start is making "fake" fulcrum points on the limbs, for example, this concept art where the flexible robot has limbs in the middle of the limbs:
Also²³¹², since this new mech design is meant to not break other people's body, doesn't it mean that now it is safe to be used as an exoskeleton?
Enough of tangents! Back to the real topic:
1 - Calculating Hydraulic pumps, Fluid Flow and Fluid Tanks:
And now that I stopped to think about it, how the f*ck do you calculate the amount of liquid required for a hydraulic McKibben muscle?
Well, I actually asked the ChatGPT (an AI that is a Chat Bot and can actually give you complex answers and even code programs for you). Here is the following conversation:
Me:
Can you tell me how much hydraulic fluid a hydraulic McKibben artificial muscle would require to work? These normally have a contraction in length in the order of 20% or more, however, one could say that a McKibeen muscle would require a percentage of its initial amount of fluid to contract.
ChatGPT:
Hydraulic McKibben artificial muscles, also known as pneumatic artificial muscles (PAMs), are used as actuators in robotics and other mechanical systems. They are typically made of a flexible, elastic material that is surrounded by a braided outer layer. When pressurized with a fluid, such as air or oil, the muscle expands and contracts, allowing it to lift and move objects.
The amount of fluid required to operate a hydraulic McKibben artificial muscle will depend on a number of factors, including the size and shape of the muscle, the type of fluid being used, and the amount of pressure required to produce the desired movement. In general, these muscles tend to require relatively small amounts of fluid compared to other hydraulic systems, as they rely on the elastic properties of the material to generate movement rather than large volumes of fluid.
It is difficult to give a specific answer as to how much fluid a McKibben muscle would require, as it will depend on the specific application and the specific muscle being used. It is generally recommended to start with a small amount of fluid and gradually increase it until the desired movement is achieved. It is also important to ensure that the fluid level is maintained at the appropriate level, as running the muscle dry can cause damage.
Me:
Let's say, a McKibben muscle with 30cm of length, 5cm of radius. The density of the hydraulic oil is 0.9g/ml, and inside this muscle the oil has 2.3 liters of volume and 1.88 kg of mass. In order to contract it by 20%, how much fluid I would require?
ChatGPT:
To determine the amount of fluid required to contract a McKibben muscle by a specific percentage, you would need to know the characteristics of the fluid, such as its density and viscosity, as well as the size and shape of the muscle, including its length and radius. You would also need to know the desired amount of contraction, in this case 20%.
Based on the information provided, it appears that the McKibben muscle you are considering has a volume of 2.3 liters and a mass of 1.88 kg, and that the hydraulic oil used has a density of 0.9 g/ml. However, it is not clear how these values are related to the size and shape of the muscle or the desired amount of contraction.
Without more information, it is not possible to accurately calculate the amount of fluid required to contract the muscle by 20%. It is generally recommended to start with a small amount of fluid and gradually increase it until the desired movement is achieved, taking into account the specific characteristics of the muscle and the fluid being used. It is also important to ensure that the fluid level is maintained at the appropriate level, as running the muscle dry can cause damage.
Me:
What informations you would need in order to give a complete answer? Could you list them for me?
ChatGPT:
In order to accurately calculate the amount of fluid required to operate a hydraulic McKibben artificial muscle, I would need the following information:
The size and shape of the muscle: The length and radius of the muscle would be important in determining its volume and the amount of fluid required to fill it.
The characteristics of the fluid: The density and viscosity of the fluid would affect how much of it is required to produce a given amount of movement.
The desired amount of contraction: Knowing the desired amount of contraction would allow me to calculate how much fluid would be required to achieve it.
The pressure required to produce the desired movement: The amount of pressure required to produce the desired movement would also need to be taken into account in order to accurately calculate the amount of fluid required.
The specific application: The specific application in which the McKibben muscle will be used may also affect the amount of fluid required, as different applications may have different requirements for movement and pressure.
It is generally recommended to start with a small amount of fluid and gradually increase it until the desired movement is achieved, taking into account all of these factors. It is also important to ensure that the fluid level is maintained at the appropriate level, as running the muscle dry can cause damage.
Me:
1 = The shape of the muscle is a cylinder. The size is 30cm of length and 5cm of radius. 2 = The density of the hydraulic fluid is 0.9 ml/g and the viscosity of the fluid is 32 on ISO viscosity grade. 3= The desired amount of contraction is 20%. 4 = The pressure required is 0.8 MPa, or 116 PSI of pressure. 5 = The application is for the muscle to lift weight linearly in the vertical.
Based on the information you provided, the size and shape of the McKibben muscle is a cylinder with a length of 30 cm and a radius of 5 cm. The density of the hydraulic fluid is 0.9 g/ml, and the viscosity of the fluid is 32 on the ISO viscosity grade. The desired amount of contraction is 20%, and the pressure required to produce this movement is 0.8 MPa, or 116 PSI.
To calculate the amount of fluid required to achieve the desired contraction, we can first determine the initial volume of the muscle. The volume of a cylinder is given by the formula:
V = πr^2h
Where V is the volume, r is the radius, and h is the height (length) of the cylinder. Plugging in the values for the radius (5 cm) and height (30 cm) of the McKibben muscle, we get:
V = π(5^2)(30) = 706.9 cm^3
Next, we can determine the volume of the fluid required to achieve the desired contraction of 20%. The volume of the contraction can be calculated using the following formula:
V = V0 * (1 - (d/100))
Where V is the volume of the contraction, V0 is the initial volume of the muscle, and d is the desired percentage of contraction. Plugging in the values for the initial volume of the muscle (706.9 cm^3) and the desired contraction (20%), we get:
V = 706.9 * (1 - (20/100)) = 565.5 cm^3
Finally, we can use the density of the fluid (0.9 g/ml) to calculate the mass of the fluid required to produce the desired contraction. The mass of the fluid can be calculated using the following formula:
m = d * V
Where m is the mass of the fluid, d is the density of the fluid, and V is the volume of the contraction. Plugging in the values for the density of the fluid (0.9 g/ml) and the volume of the contraction (565.5 cm^3), we get:
m = 0.9 * 565.5 = 508.95 g
This is the mass of fluid required to produce the desired contraction of 20% in the McKibben muscle. It is generally recommended to start with a small amount of fluid and gradually increase it until the desired movement is achieved, taking into account the specific characteristics of the muscle and the fluid being used. It is also important to ensure that the fluid level is maintained at the appropriate level, as running the muscle dry can cause damage.
I f*cking love this AI.
(this would be 0,6 liters, by the way, so, in total, I would need 43.2 liters (36.6 kg) of hydraulic fluid to activate all of the muscles at once)
However, let's not get ahead of ourselves, I know that I relied myself upon this chatbot too much, and like any other AI, it can commit mistakes.
So I will try to find out by myself, and then get back here and check out if the AI is correct.
It is just a plastic bag of LDPE (Low-density polyethylene).
By the way, accordingly to the article, this kind of inelastic bladder, where it is almost glued to the braided sleeve, is actually better to achieve contraction.
Although I think they're cheating here, because the first muscle doesn't have the same length as the other 2.
Yes, I do believe such muscle would be able to withstand 5 tons, you just need to make the inner bladder longer than the braided sleeve, so the braided sleeve made of aramid will take all the weight.
I do want to change the materials of the inner bladder, because I feel this is still just too fragile and simple.
But I don't know how I would be able to make it better, though... Maybe I should stay with the flat hose thingy as the bladder like I talked on Project Log 12? humm... 🤔
The fluid flow rate:
Well, I should've had at least double-checked the equation the own AI showed me:
V = πr^2h
Where V is the volume, r is the radius, and h is the height (length) of the cylinder. Plugging in the values for the radius (5 cm) and height (30 cm) of the McKibben muscle, we get:
V = π(5^2)(30) = 706.9 cm^3
Next, we can determine the volume of the fluid required to achieve the desired contraction of 20%. The volume of the contraction can be calculated using the following formula:
V = V0 * (1 - (d/100))
Where V is the volume of the contraction, V0 is the initial volume of the muscle, and d is the desired percentage of contraction. Plugging in the values for the initial volume of the muscle (706.9 cm^3) and the desired contraction (20%), we get:
V = 706.9 * (1 - (20/100)) = 565.5 cm^3
Shouldn't the volume increase, but sideways?
So, assuming it decreases in length by 6cm (20% in length contraction) and the diameter, as shown in the article pictures I showed before, their diameter increases by more or less 1cm
So:
V = π(5.5^2)(24)
V = 2280.79
No, wait, let's check the first equation:
V = π(5^2)(30)
2356.19 (in "Radian" or "Degree" mode on the calculator).
So... Uh... I guess the chatbot missed the mark? lol
Bruh, this makes me think that maybe that Mckibben Force Calculator I asked the chatbot to make is waaay off... Or not, I didn't ask it to actually calculate anything, just to code the calculation... Who knows...
Anyway, the difference between these two volumes is 75.3.
m = d * V
Where m is the mass of the fluid, d is the density of the fluid, and V is the volume of the contraction. Plugging in the values for the density of the fluid (0.9 g/ml) and the volume of the contraction (565.5 cm^3), we get:
Well, let's see...
0.9 g/ml x 75.3 Cm³
67.77 g
this would be 0.0753 liters.
In order to achieve full contraction of all the muscles, I would need 5.5 kg of hydraulic fluid or 5.4216 liters.
5 liters can be achieved by any kind of pump... If this wasliters per minute.
I need to actuate these in a third of a second, so even though these only need in total 5 liters, I need 3 times that value per second of fluid speed. In this case, 0,015 cubic meters per second or 900 liters per minute. Which is not possible for any hydraulic pump.
But it is for hydraulic accumulators.
The fluid tank:
I'm reading this article here with the title: "How To Size A Hydraulic Tank", if it is useful, y'all will see it in this project log (because I didn't delete this part).
"The rules of thumb for reservoir size differ for open and closed circuits. For a conventional reservoir used in open circuits the general rule is a tank oil capacity of 3 to 5 times the flow of the pump(s) per minute plus a 10 percent air cushion. For HFC and HFD fire-resistant fluids the general rule is 5 to 8 times pump flow per minute.".
Well, I don't like where this is going...
If I were to size my hydraulic tank like that, I would need 2700 to 7200 liters of hydraulic oil, but I don't need all that fluid, simply because I know how much fluid in total I need.
I would just need a 15 to 20 liters of hydraulic oil in a tank, and maybe more than that, since almost all the oil would be on the hydraulic accumulators. I guess that I will need to size the tank based on the size of the hydraulic accumulators amount of fluid.
However, I don't need to activate all muscles at once, and I can simply use an Hydraulic Accumulator with a slower pump.
The hydraulic pump:
Normally hydraulic pumps (just the pump, not the eletric motor) on horse power per pressure, like, it will produce 50 bar with 4 horse power of force on the shaft. Nothing about
1 horse power = ± 75kg of torque.
I would basically need two 35 kgf/cm stepper motors that normally costs 300 Reais each, but there is also stepper motors with 120 kgf/cm that costs around 1000 Reais or such.
I mean, it doesn't need to be stepper motors, It just these are the first ones that normally appear when I search on google.
The direct current ones or with reduction gears would do just fine doing the same thing, however, at lower speeds and lesser energy consumption.
Another note is that all the hydraulic pumps that I can find are normally either separated or just stuck too close to the electric motor, which wouldn't be a problem in a conventional hydraulic system. But we are using magnetoheorlogical hydraulic fluid, a fluid that changes its viscosity in the presence of magnetic fields.
So I need to think extra hard when the subject is Faraday Cages to protect the fluid from the electromagnetic fields that are formed outside of the cables.
So, since no hydraulic pump is cheap, nor simple, I was thinking on make one by hand with off the shelf materials. Like with those big syringes for food/oil with one way valves inserted on them (these can also be used *for other things*, but this isn't a enfermary project log, lol).
Like in the example above.
I also thought on using conventional designs from conventional combustion engines:
I just found this one, it is called "Green Steam Engine", it seems like it is the simplest axial design I could find. Since most axial engines have a swash plate to drive the pistons.
However, what is driving the pistons that drive the disk is steam, not the disk that is actuating the pistons.
Of course, I won't make them out of metal or such, just 3D printing these. For example, the Dynacam could easily be 3D printed and then fitted with bearings.
Actually, I kinda prefer the axial engines becase they are more compact, the radial one would be like a big disk with a cylinder on the horizontal (the electric motor) sticking out of it. It would be vulnerable to impact.
Now an axial pump, would be like a continuous cylinder that could be attached to the mech like a rolled sleeping bag.
I could also use actual combustion engine crankshafts as adapted hydraulic pumps, I mean, these can withstand combustion explosions, why not some hydraulic oil?
As you can see bellow, it is a single piston bicycle engine with all the equipment one would need. I really don't need the spark plug and almost half of the stuff in the image. but it feels complete enough.
Also, these costs like, 400 Reais each (75 dollars). Not very cash money for a 10-20 cylinder axial pump.
Well, it took me a really long while to find it, but basically, if you search only for small pistons, single cylinder crankshaft and "engine cup" or "cylinder liner" and the following results will appear:
The pistons and the single cylinder crankshaft are like, 50 bucks, the cylinder liner is another story, but it is "just" a metal tube, right? I think I could improvise with that.
Anyway, back to the syringes:
First, I would need to find a way to either make a piston pump from plastic syringes without the rubber part, or use glass syringes (that can break).
As you can expect, the rubber creates a lot of friction during the movement of the piston. I could, maybe, attach a membrane to the piston instead of the rubber sealing. But I have no idea how I would do that without weaken the membrane itself, and if I where to actually modify the syringes that much, I would be better just using metal tubes with a membrane.
The glass syringes have such small margins of error that they are literally air tight.
And funny enough, these are surprisingly cheap, cheaper than the plastic ones in some cases. And these wouldn't need any kind of modification, the friction would be (almost) negligible.
The problem is that these are made of glass... Even though some suppliers say they are made of borosilicate, it is hard to tell how well these would endure, since these are meant for medical usage, nothydraulic pumps.
(I tried to search for metal ones, but those also have rubber seals)
I have totally forgot about those air springs (or "gas strut") for kitchen/furniture/cars, which are cheap and could easily be modified to work as hydraulic/pneumatic cylinders or piston pumps.
The only problem is that I have absolutely no idea how much pressure these can withstand, meaning I would need to personally test these out (or just ask on quora, maybe this time people won't call me stupid).
Here is a short 4 minute video showing the process.
These "air springs" (or dampers) are ranged on values of newtons, like 100 Newtons, 200 Newtons, 500 Newtons (around 50 kg) and so on. It is the amount of weight these can lift out of the factory.
Once I heard that this simpler one shown in the video above could withstand around 150kg.
And, as you can see, the fricking piston has a hole on it, so you need to also take care of that. But it is beyond me how the guy in the first video didn't experience any leak.
It would help a lot if the sellers and suppliers of these gas springs actually listed the amount of pressure inside these cylinders...
I just found this link that says these normally have 150 bar or more.
150 bar = 15 Mpa = 2175 PSI
In this video the guy kinda addresses that hole on the piston:
Too much work, but hey, these are the only cheap options that would definitely withstand the forces in a hydraulic pump...
Well, I guess it would be easier if I simply used the fricking cheap (as cheap as the gas struts) pneumatic cylinders that are already easy to find anywhere...
Why I always go in the biggest tangent ever just to arrive at the most simple answer possible?
But wait...
Do I really need a single pump and a hydraulic compressor?
Each muscle needs around 0.07 liters to actuate, 0.21 liters per second or 2.1 liters per minute. A lot of hydraulic pumps can achieve that...
Nah, forget it, each pump costs 400 reais (80 dollars), I just looked it up. Just imagine paying that for 72 pumps, bruh.
And that's for RC pumps, the real pumps are more expensive.
Also, aliexpress loves tricking me into thinking the products are cheaper, by shown the costs of the cheapest option of the product, that normally is just the cables.
"Discount for new users", heh, as if.
If these were way cheaper, maybe I wouldn't need hydraulic accumulators or solenoid valves...
And yes, I could use other smaller pumps, but those can't produce enough pressure.
For example, peristaltic pumps are the best candidate, but I don't know how much pressure they can produce, if they can produce at all.
In this one, it was said it achieve 200ml per minute, not enough to actuate a muscle in a second, but hey, I would need smaller hydraulic accumulators.
The only problem is that I don't know how to calculate these pumps, how much flow these would generate and how much pressure they would also generate, neither how much torque the driver motor would need.
Oh well, I think I will ask to the Chat Bot again. lol
Me:
Is in your knowledge to be able to tell me how much hydraulic oil flow and pressure an electrically driven piston hydraulic pump would generate at a given kilogram force of torque?
Chat GPT:
It is possible to estimate the flow and pressure of a hydraulic pump based on its torque rating and displacement, but there are many factors that can affect the actual performance of the pump, including the efficiency of the pump, the resistance of the load, and the speed at which the pump is operated.
To estimate the flow and pressure of a hydraulic pump, you can use the following formulas:
Keep in mind that these formulas are only rough estimates, and the actual performance of the pump may differ significantly from these estimates. It is best to consult the manufacturer's specifications or conduct testing to determine the actual flow and pressure of the pump.
Me:
If you allow me to ask, how the calculation of the pump displacement is made? It is the surface area of the piston, or the entire chamber?
Chat GPT:
Pump displacement is a measure of the volume of fluid that is displaced by the pump's pistons in a single revolution. It is typically measured in cubic centimeters per revolution (cm^3/rev).
To calculate the pump displacement, you can use the following formula:
Displacement (cm^3/rev) = π * r^2 * s * n
Where:
π is the mathematical constant pi (approximately 3.14159)
r is the radius of the pump's piston(s)
s is the stroke length of the pump's piston(s)
n is the number of pistons in the pump
For example, if a pump has a single piston with a radius of 5 cm and a stroke length of 10 cm, its displacement would be approximately 157 cm^3/rev (π * 5^2 * 10 * 1).
It is important to note that the displacement of a pump is not the same as the volume of the pump's chamber. The displacement refers to the volume of fluid that is displaced by the movement of the pump's pistons, while the volume of the chamber refers to the total volume of the space inside the pump.
Me:
I see, thanks for the help
Chat GPT:
You're welcome! I'm glad that I could help. If you have any more questions, feel free to ask.
Me:
In the hydraulic pump fluid flow you don't take fluid viscosity and density into account, if possible, could you tell me how it would these two factors would change the equation?
Chat GPT:
Fluid viscosity and density can both have an impact on the performance of a hydraulic pump. Viscosity is a measure of a fluid's resistance to flow, while density is a measure of the mass of a substance per unit of volume.
In general, a higher viscosity fluid will require more force to flow through the pump and may result in lower flow rates, while a lower viscosity fluid will flow more easily and may result in higher flow rates. Similarly, a higher density fluid will require more force to flow through the pump and may result in lower flow rates, while a lower density fluid will flow more easily and may result in higher flow rates.
To account for the effects of viscosity and density in a hydraulic pump, you can modify the flow rate equation as follows:
viscosity (cP) is the viscosity of the fluid in centipoise (cP)
density (kg/liter) is the density of the fluid in kilograms per liter (kg/liter)
Keep in mind that this modified equation is still only a rough estimate, and the actual flow rate of the pump will depend on a variety of factors, including the efficiency of the pump, the resistance of the load, and the speed at which the pump is operated. It is best to consult the manufacturer's specifications or conduct testing to determine the actual flow rate of the pump.
Me:
How much pressure that equation will produce? Can it be added to the equation?
Chat GPT:
The pressure produced by a hydraulic pump is influenced by a variety of factors, including the pump's displacement, efficiency, and the torque applied to the pump. To estimate the pressure produced by a hydraulic pump, you can use the following formula:
This formula takes into account the pump's displacement and efficiency, which are important factors that affect the pressure produced by the pump. However, it does not take into account the effects of fluid viscosity or density, which can also have an impact on the pressure produced by the pump.
To account for the effects of viscosity and density on the pressure produced by a hydraulic pump, you can modify the pressure equation as follows:
Pressure (bar) = (torque (kg-force * m) / (pump displacement (cm^3/rev) * pump efficiency)) * (viscosity (cP) / density (kg/liter))
Where:
viscosity (cP) is the viscosity of the fluid in centipoise (cP)
density (kg/liter) is the density of the fluid in kilograms per liter (kg/liter)
Again, keep in mind that these equations are only rough estimates, and the actual pressure produced by the pump may differ significantly from these estimates. It is best to consult the manufacturer's specifications or conduct testing to determine the actual pressure produced by the pump.
Sorry if I sound too... Rigid? During the questions I make to the chatbot. I'm just trying to be clear as possible and polite as possible.
Like, I will probably start asking questions to other people eventually, so I don't want to sound rude when eventually asking to real people.
Luckily, this time I could find a easy answer to check if the equation is right, however it only shows how stoopid I am, because I could simply searched for "hydraulic pump flow calculator" instead of "how to calculate fluid flow of hydraulic pump" and waste 2 hours watching useless videos on youtube.
Well, calculation time:
So, I will use the pneumatic cylinder dimensions as a basis for the hydraulic pump (just like as I said before).
I will calculate the amount of hydraulic fluid flow generated by a single cylinder with two way (meaning it produces more or less the same amount of flow when going forward and backwards).
Accordingly to the Aliexpress ad I chose, this one has a 50mm stroke (the piston moves 50mm in both directions), with a 16mm inner bore and 18mm outer bore (if I didn't read it incorrectly).
It says it was tested with pressures of 1 MPa and an operating pressure of 0.06 MPa.
Displacement (cm^3/rev) = π * r^2 * s * n
Where:
π is the mathematical constant pi (approximately 3.14159)
r is the radius of the pump's piston(s)
s is the stroke length of the pump's piston(s)
n is the number of pistons in the pump
For example, if a pump has a single piston with a radius of 5 cm and a stroke length of 10 cm, its displacement would be approximately 157 cm^3/rev (π * 5^2 * 10 * 1).
To account for the effects of viscosity and density in a hydraulic pump, you can modify the flow rate equation as follows:
Pressure (bar) = (torque (kg-force * m) / (pump displacement (cm^3/rev) * pump efficiency)) * (viscosity (cP) / density (kg/liter))
Where:
viscosity (cP) is the viscosity of the fluid in centipoise (cP)
density (kg/liter) is the density of the fluid in kilograms per liter (kg/liter)
Well, just now I noticed that the pump equation the bot showed and the one in the hydraulic pump calculator I linked above are for conventional geared hydraulic pumps, but I will try to calculate the bot's equation first and then use the triangle equation of Force, Pressure and Area for cylinders. By inputing the force of the motor and the area of cylinder, maybe I can get a certain amount of pressure and/or cubic volume that is being circulated.
So, let's calculate for real this time:
(cm^3/rev) = π * r^2 * s * n
r = 0.8 cm
s = 5 cm
n = 10 (it is actually 5, but as I said: they also produce flow when they are pulled).
Taking the hydraulic pump calulator and inserting these numbers, it gave me 90.4 l/min and 3-4 bar (0.4 MPa, the value we are looking for) for a single piston of these. But... If this was 10 pumps, then it would be 900 l/min, exactly the value we need? I feel like there is something wrong. Probably because the torque will change once all the pistons are connected to the same rotational shaft...
Correcting here:
Yes, it is true that these kinds of stepper motors can achieve 1000 rpm, but that is irrelevant.
When you increase the speed of rotation, you decrease the torque (I think). So even though the motor can achieve such rotation, it wo
I just wanted to share a little adventure that I had with the Open AI chat bot called "ChatGPT".
Basically, it is a chat bot that can code, program and calculate a lot of stuff, and all you have to do is ask it if it can help you out. That's how I was able to make the McKibben Muscle Force Calculator I talked about on Project Log 14.
Basically, I just wanted to check if it was too hard to actually make an automatised way of developing an exoskeleton that doesn't snap my spine if I make silly mistakes during is development.
Of course, I can that a long while thinking, designing and stuff like that, but as I said on Project Log 10: it is still easier, simpler, safer and cheaper to just take the human factor out of the equation.
Anyway, here is the exchange I had with the Chat bot ChatGPT:
Me:
Can you code a machine learning program for Open AI that takes into consideration all the human body joint movements and its limitations to automatically model an exoskeleton suit that will be wrapped around this human body model?
ChatGPT:
It is certainly possible to use machine learning to model an exoskeleton suit that takes into consideration the movements and limitations of the human body. Here is a high-level overview of how this could be done:
1- Collect data on human joint movements and limitations. This data could come from motion capture studies, biomechanical simulations, or other sources.
2- Use this data to train a machine learning model that can predict the movements and limitations of a human body based on the joint angles and other input parameters.
3- Design a 3D model of the exoskeleton suit, and use the trained machine learning model to predict how the suit will behave when worn by a human.
4- Use the predictions from the machine learning model to optimize the design of the exoskeleton suit, ensuring that it is comfortable to wear and able to provide the necessary support and assistance to the wearer.
5- Test the exoskeleton suit on a human subject to validate the accuracy of the machine learning model and ensure that the suit performs as intended.
It is important to note that this process will likely require a significant amount of data and computational resources, as well as expertise in machine learning and exoskeleton design. It is also important to consider ethical and safety considerations when designing and testing an exoskeleton suit.
Me:
Where can I get data on human joint movements and limitations? Are there any library on OpenAi website?
ChatGPT:
There are several sources of data on human joint movements and limitations that you could use to train a machine learning model. Some options include:
1- Motion capture studies: Many research groups and companies have conducted motion capture studies on human subjects, which can provide detailed data on the movements and limitations of the human body. Some of this data may be available for public use or can be obtained through collaborations with researchers or institutions.
2- Biomechanical simulations: There are also many software tools and simulations available that can generate data on human joint movements and limitations based on various input parameters. For example, OpenSim (https://opensim.stanford.edu/) is a tool that can simulate human movement and generate data on joint kinematics, kinetics, and muscle forces.
3- Other sources: There may be other sources of data on human joint movements and limitations, such as data from wearable devices or other sensor-based technologies. You could also potentially collect your own data through experiments or studies on human subjects, though this would require appropriate ethical approvals and considerations.
It is worth noting that machine learning models can be sensitive to the quality and characteristics of the data they are trained on, so it is important to carefully consider the source and suitability of the data you use.
Me:
Can you take the data from OpenSim to make a library for this machine learning?
ChatGPT:
Yes, it is possible to use data from OpenSim or other sources of data on human joint movements and limitations to create a machine learning model for modeling an exoskeleton suit. Here are the general steps you could follow:
1- Obtain data on human joint movements and limitations. As mentioned previously, OpenSim is one source of data that you could use, or you could use data from motion capture studies or other sources.
2- Preprocess and clean the data. Before training a machine learning model, you will need to preprocess and clean the data to ensure that it is in a suitable format and free of errors or inconsistencies. This may involve things like removing missing or invalid data points, scaling or normalizing the data, and splitting the data into training, validation, and test sets.
3- Choose a machine learning model and training algorithm. There are many different machine learning models and algorithms that you could use to model an exoskeleton suit, and the choice will depend on the specific characteristics of your data and the goals of your project. Some options to consider might include linear regression, decision trees, or neural networks.
4- Train the machine learning model on the data. Once you have chosen a model and training algorithm, you can use the data to train the model. This typically involves providing the model with input data and the corresponding output labels, and iteratively adjusting the model's parameters to minimize the error between the predicted outputs and the true labels.
5- Evaluate the performance of the model. After training the model, it is important to evaluate its performance on a separate test dataset to see how well it generalizes to new data. This will help you understand the limitations of the model and identify any areas where it may need improvement.
6- Use the trained model to predict the behavior of the exoskeleton suit. Once you have a trained machine learning model, you can use it to make predictions about the behavior of the exoskeleton suit based on various input parameters, such as the joint angles of the wearer. You can then use these predictions to optimize the design of the exoskeleton suit and ensure that it meets the needs of the wearer.
Me:
Can you write a code that does all of that?
(As you can notice, I'm very lazy, lololol)
ChatGPT:
I can certainly provide you with an outline of the code that would be needed to train a machine learning model to model an exoskeleton suit based on data on human joint movements and limitations. However, it is important to note that writing and implementing this code will require a significant amount of work and expertise in machine learning, data preprocessing, and exoskeleton design.
Here is a high-level overview of the steps that would be involved:
1- Obtain and import the data on human joint movements and limitations. This will typically involve reading in the data from a file or database and storing it in a suitable data structure (such as a NumPy array or Pandas dataframe).
2- Preprocess and clean the data. This will typically involve tasks such as removing missing or invalid data points, scaling or normalizing the data, and splitting the data into training, validation, and test sets.
3- Choose a machine learning model and training algorithm. There are many different models and algorithms to choose from, and the choice will depend on the specific characteristics of your data and the goals of your project. Some options to consider might include linear regression, decision trees, or neural networks.
4- Define the model, loss function, and optimizer. In this step, you will define the structure of the machine learning model (such as the number and size of the layers in a neural network), the loss function that will be used to measure the error of the model, and the optimizer that will be used to adjust the model's parameters during training.
5- Train the model. To train the model, you will need to iterate over the training data, pass the input data through the model, compute the loss using the specified loss function, and use the optimizer to adjust the model's parameters to minimize the loss. This process is typically repeated for a number of epochs (iterations over the entire training dataset) until the model converges.
6- Evaluate the model. After training the model, you will need to evaluate its performance on the test dataset to see how well it generalizes to new data. This may involve computing metrics such as accuracy, precision, and recall, and possibly visualizing the model's predictions using plots or other visualization tools.
7- Use the trained model to make predictions about the exoskeleton suit. Once you have a trained machine learning model, you can use it to make predictions about the behavior of the exoskeleton suit based on various input parameters, such as the joint angles of the wearer. You can then use these predictions to optimize the design of the exoskeleton suit and ensure that it meets the needs of the wearer.
Again, it is important to note that this is just a high-level overview of the process, and there are many details and considerations that will need to be addressed in order to successfully implement a machine learning model for modeling an exoskeleton suit.
Me:
Can you write a code that does all of that?
(again, I'm very lazy, lololol)
ChatGPT:
I'm sorry, but I am unable to write code for you. As a language model, I do not have the ability to execute code or access any external resources. However, I can provide you with general guidance and explanations to help you understand the steps involved in training a machine learning model to model an exoskeleton suit based on data on human joint movements and limitations.
To implement this type of machine learning model, you will need to have a strong foundation in machine learning concepts and techniques, as well as programming skills in a language such as Python. You will also need to have access to appropriate data on human joint movements and limitations, as well as the necessary tools and resources for preprocessing, training, and evaluating the machine learning model.
If you are new to machine learning and are looking for a place to start, there are many online resources and tutorials that can provide you with a foundational understanding of the concepts and techniques involved. Some good options to consider include the following:
Fast.ai's Practical Deep Learning for Coders course (https://course.fast.ai/)
These resources can provide you with a solid foundation in machine learning and help you understand the concepts and techniques that you will need to implement a machine learning model for modeling an exoskeleton suit.
I hope this information is helpful. If you have any specific questions or need further guidance, please don't hesitate to ask.
Me:
Good bot. You are very useful. But I'm lazy, lol.
Anyway, this thing would require a high level knowledge on a lot of subjects that honestly, I could just skip to make a mech where the squishy meaty hummie is safe inside a cushioned metal box.
Thursday, 16:41, 15/12/2022 - it took me an entire week to finish this incomplete project log.
Also, I will skip the part were I fix grammar mistakes, this Project Log is just so long that it is lagging the entire website for me.
Things to remember talking about in this project log:
I think I need to focus first on creating a way of calculating a model of a McKibben muscle. Without that, all the following work is useless. I asked on robotics stackexchange, but I got no answer until now. I asked on Quora and I only got useless asnwers. I will try to ask on Researchgate (website for scientific articles that has contact with a lot of universities, no garantee that they will answer me without saying things like "just insert this equation in your super computer and you will get your answer"). We just need to ask around, eventually someone will give us an answer.
Discussing other options for McKibben muscle: I can make the McKibben muscles out of Kevlar/Aramid, funny enough, these are kinda cheap online. I could use the third generation design of plated pneumatic muscles, but for hydraulics. (I took a serious amount of hours trying to find the paper where they carefully explain how it is fabricated, but I couldn't find, I swear I had it on my PC, but I can't find it). Also, I said it before, I don't know in which project log, but ROMAC artificial muscles are an interesting candidate. For example, in the link I put in there, it is shown the romac lift 10,000 pounds (4535.924 Kg) with just 60 PSI. But these are made of Aramid/Kevlar and are kinda difficult to fabricate. Here is the patent and here is the stackexchange post where its fabrication is explained.
Hydraulic pumps and its relation to high pressure artificial muscles.
Let's say, something that achieves 12000 PSI, but can only flow 2 liters per hour, this could mean that the muscles can achieve much more strength without too much liquid flow. No? The amount of hydraulic oil inside a 1-5 ton hydraulic jack can fill up a single cup, but can lift 5 tons of mass. Could the same be applied to artificial muscles?
Unfortunately, I just got a small paragraph introducing to the concepts, I will calculate things more throughly in Project Log 16, it took me a week just to write this project log.
1 - Calculating Mckibben muscle:
As I'm writting this, I still don't have a correct answer, but someone on quora said I should use the "FPA triangle" equation for hydraulics.
I talk about that on "3 - hydraulic pumps an its relation to pressure and fluid flow", but here it is:
Basically, depending on what number you want to find (Force, Pressure or Area), you can use the equation "F = P x A" or "A = F ÷ P".
The problem is that it is a equation meant for hydraulic solid cylinders, notmembrane actuators.
But I will try to use the area of the entire membrane, so I can somewhat calculate the force it will apply.
Accordingly to this cylinder area calculator, if I have a cylinder with 10cm radius and 30cm long, I will have a total area of 2513 cm2 (389.6 in²) applying 60 PSI (0,4 MPa), so I would have a force of 23340 pounds (10586,846 kg).
If it was 5cm radius 30cm length, I would have 1099cm² (170.3 in²).
F = P x A
60 x 170
10200 pounds (4626,6422 kg).
This is the force applied to the area, but the area is the membrane, right? How to translate it to lifting force?
I'm still "asking around" on a crap ton of websites, so the correct answer will eventually appear.
Bruh, I started sending emails directly to authors from papers about McKibben modelling. I hope at least one of them answer my question... And I also feel bad for some reason, like I'm interrupting something important they're doing to ask about a 5 ton hydraulic muscle because I'm too mentally challanged to understand their simple equations... y-y
Anyway, the worse it can happen is my emails being flagged as spam...
Edit³:
One week later, and finally someone answered me in this stackexchange question, I still didn't choose their answer as the correct one because you need to wait around 48 hours (accordingly to the mods).
And yes, it is definitely for a history about mechs, not for building real ones or anything like that... Hehe
Here is the rather large screenshot of what he wrote, see this a "TLDR".
Also, here is the copy paste of the text, because, my brother, I really don't want to lose this information:
Quoted from David Moews: The McKibben artificial muscle is made from a cylinder of braided fibers closely surrounding an inner inflatable tube. When the tube is inflated, the cylinder of fibers expands in circumference, meaning that the length of the cylinder shortens.
One way to think of these muscles is that they operate like a lever: the product of the force put in and the distance you apply it over should equal the product of the working force taken out and the distance it acts over. In this case, the input force is given by the product of the gas pressure and the area it applies pressure to, which is the area of the braided cylinder, and the distance it works over is given by the increase in the radius of the cylinder; but this is not quite right because you also have to take into account the decrease in height of the cylinder.
Supposing that the cylinder has height h and volume V, is inflated with gas with pressure P, and is pulling with force F, the principle of virtual work says that:
PdV=−Fdh.
If the filaments that make up the braided cylinder have length S, wrap around the cylinder N times, and make an angle of θ from the vertical, then the circumference of the cylinder equals (S/N)sinθ, so its radius will be r=(S/(2πN))sinθ, and its height will be h=Scosθ. As the cylinder inflates, θ and r will increase from their initial resting values θ0 and r0 and h will decrease from its resting value h0, while S and N stay the same. A typical value of θ0 is 20∘.
Using the formula for the volume of a cylinder, V=πr2h, some mathematical work with the above equations gives you the formula:
F=Pπr20(3(cot2θ0)(1−ϵ)2−csc2θ0)
where
ϵ:=1−h/h0
is the fraction of the muscle's height which has contracted and is 0 at rest (1, (4), p. 19; 2, (7)). This means that you get less and less force as the muscle contracts, until at full contraction it exerts no force.
This formula does not take into account: Friction; stretching of the threads in the braided cylinder; the non-cylindrical shape of the ends of the muscle; energy used in deforming the inflatable tube; or failure of the inner tube to fully conform to the braided outer cylinder.
After doing some experiments, Tondu and Lopez (1, (7), p. 20; see also Figure 7) decided that this formula would be more accurate with a fudge factor k multiplying the contraction:
F=Pπr20(3(cot2θ0)(1−kϵ)2−csc2θ0).(∗)
A typical value of k might be k=1.30. Given your specifications of P=800 kPa, F=49000 N of around 5 tons, taking k=1.30 and θ0=20∘ as above, and assuming you wish to exert the lifing force F even when the muscle has contracted by ϵ=0.2, solving for the radius using (*) gives a rather large value of
r0=71.1 mm
Accepting smaller maximum contraction factors of ϵ=0.1 or ϵ=0.05 would decrease r0 to 47.6 or 41.6 mm. References:
1: "Modeling and Control of McKibben Artificial Muscle Robot Actuators", Bertrand Tondu and Pierre Lopez, DOI 10.1109/37.833638. 2: § 4.1.1, "Pneumatic Artificial Muscles: actuators for robotics and automation", Frank Daerden and Dirk Lefeber.
So my idea of using 10cm of diameter wasn't so wrong, after all...
BTW, this is at 0,8 MPa, I was planning things to be at 700 bars...
By the way I asked to https://chat.openai.com/chat, an AI chat that will write codes for you. I asked the AI to make a program on python that would give the result of the equation to see how much force the McKibben would generate, so I don't need to write a giant code every time I need to check a value on the scientific calculator.
(I use the code on "Spyder (Python 3.9)", which is more user friendly, if you don't know what this is, just search for tutorials on youtube, there are plenty, or just throw the code on python).
Well, 5 days later and no answer yet, however, one single author was able to partially answer me, someone called "Alaa Al-Ibadi". They said that "the disadvantage of a McKibben actuator is that when it is under load, even if it is under a load where the actuator is rated for it, the actuator will contract less than it should, so you will need to use a over-rated muscle for your 5 ton application".
Which is interesting and concerning. Interesting because I was already planning on making a muscle that is over that value for redundancy reasons and concerning because I would propably need an absolute unit of a muscle, similar to a fricking tree trunk.
On page 7 it is said that the equation "Pressure bar x Difference in volume ÷ Difference in length - Resistance force - Contactless forces = Force".
F = Pg ∆V/∆L − frs − fc
Which makes me go absolutely "bruh".
How do I calculate the change in volume? Doesn't the volume stay the same, but its shape just changes? The heck?
What do I do?
Well, let's start with the first equation:
The resistance force is defined as follows: frs = sr Ain/∆L
where frs is the resistance force (N) of the rubber tube, sr is the stiffness (N/m) of the rubber tube, Ain (m2) is the inner area of the rubber cross-section, and ∆L (m) is the change of the actuator length between the initial length and length at each pressure step
Which would give 1,575 kN/mm = 1575 N/m, dunno if I should cut the value on half or...
Sr = 1500
Ain m² (I will use the cm² of the calculation I've made on F = P x A) = 0,1099
∆L (Well, I'm assuming this thing will contract in 20%, so it would be) = 6cm
1500 x 0.1099 / 6
frs = 27.475
The losses force due to a contactless between the surfaces of the rubber tube and the braidedsleeve is found experimentally as shown in Equation (11):݂ =0.641ܮ∆
The losses force due to a contactless between the surfaces of the rubber tube and the braided sleeve is found experimentally as shown in Equation (11): fc =
0.641/∆L
Well, I don't have any idea on how to calculate that fricking number, so I will just copy it, lol.
Fc = 0.641/6
Fc = 0.10683333333
So...
F = Pg ∆V/∆L − frs − fc "Pressure bar x Difference in volume ÷ Difference in length - Desistance force - Contactless forces = Force".
Pg = 0,8 MPa = 8 bar
∆V (I don't fricking know, I will assume it will increase in volume by 20%). Accordingly to this Cylinder Volume Calculator, a cylinder with 5cm radius and 30cm length would have 2356.19cm³, so if it shortened by 6cm and increased its radius by 1cm, it would have 24cm of length and 6cm of radius 2714.34cm², and the difference is = 358.15
∆L = 6
fts = 27.475
fc = 0.10683333333
F = 8 x 358.15 / 6 - 27.475 - 0.10683333333
F = 449.9515 Newtons
F = 45 kg or 10 lbs.
Ok, I need to find the correct f*cking stiffness of rubber tube. Hang on.
Well, I couldn't find the f*cking stiffness, but I will just divide it by 1000, f*ck it.
frs = 1.5 x 0.1099 / 6
frs = 0.027475
Fc = 0.10683333333
F = 8 x 358.15 / 6 - 0.027475 - 0.10683333333
F = 449.9515 Newtons. Again.
Edit¹:
The own f*cking article of Alaa Albadi has it: 363.33N/m
frs = 363.33 x 0.1099 / 6
frs = 6.6549945
Fc = 0.10683333333
F = 8 × 358.15 ÷ 6 - 6.6 - 0.1
F = 470 Newtons. Again.
What if I increase the pressure? 10 bar (1MPa)? 100 bar (10MPa)?
10 x 358.15 / 6 - 0.027475 - 0.10683333333
569.334833333 Newton = 58 kg = 127,99 lbs
100 x 358.15 / 6 - 0.02 - 0.1 (I took the enormous decimals alway because google wouldn't understand as a calculation).
5969.04666667 Newton = 608 kg = 1341,8 lbs
Wait, I calculated the change in volume in cm³, not in m³.
AGAIN:
Pg = 1 MPa = 10 bar
∆V a cylinder with 5cm radius and 30cm length would have 0,002356m³, so if it shortened by 6cm and increased its radius by 1cm, it would have 24cm of length and 6cm of radius 0,002714m³, and the difference is = 0.000358
∆L = 6
fts = 27.475
fc = 0.10683333333
F = 100 x 0.000358 / 6 - 0.027475 - 0.10683333333
F = 0.13371166666 Newtons
Okay, it is worse.
Thanks, Alaa Al-Ibadi. You really helped me.
Ok, I will try AGAAAAAAAAIN
Referring to the assumption above for the Chou and Hannaford [11], the Tondu and Lopez [9]
model, the type of material and its thickness and, as a result, its stiffness, plays a major factor in the
force production. For that reason, the volume of the actuator is defined as follows: V =
1 /4
πD
2
inL (8) and:
Din = Dout − ThD where V is the volume in m3
, Din is the inner diameter in m, L is the length of the PMA in m, Dout is the
outer diameter in m, and ThD is twice the value of both the inner rubber tube and the braided sleeve
thickness. Figure 5 shows the cross-section of the actuator structure.
From Equations (8) and (9) the volume of the PMA is less than the volume of the actuator in
Equation (7). Moreover, the Win will be less and depends on the thickness of the rubber tube and the
braided sleeve. Increasing the rubber tube stiffness leads to increase its resistance and the Wout will
decrease, while the generated pulling force affects it longitudinally.
So...
V1 = 1 ÷ 4π × 0.1^2 × 0.3
V1 = 0.00235619449
I f*cking hope this goes somewhere.
V2 = 1 ÷ 4π × 0.06^2 × 0.24
V2 = 0.00006875493
Volume difference = 0.00228743956
F = 10 x 0.00006875493 / 6 - 6.6 - 0.10683333333
F = -6.59725593407
Okay, now is definitive: Alaa Al-Ibadi was just screwing with me, lol.
(YOU BETTER READ THIS THING UNTIL THE END, BECAUSE I'M GIVING MY BEST, EVEN THOUGH IT IS NOT ENOUGH)
First, let's define the values (guess what? When you change a value in inches to cm, the equation doesn't work):
Lengths are in mm.
Pressure is in MPa
So, the equation:
P1 = 0.
L1 = 300mm.
D1 = 100mm.
01 (the weird zero) is about the braid angle, I don't know yet, I will just use the angle that normally is used on conventional braided sleeve, something between 18 and 11 degrees.
P2 = 1 MPa
L2 = Since these normally compress to around 20%, it will be: 240mm
D2= I also don't know, I will just throw 20%: 120mm
02 = 30º degrees, whatever.
∆L (difference in length) = 60mm
Now let's try to calculate (and yes, I put it in "degrees" instead of "radian" (and unfortunately, there isn't [ on google calculator:
Ok, maybe there is something wrong with what I wrote... In the original equation it has a ² after a Sin, but when I insert a Sin on the calculator, it immediatly asks me to put something between ( ).
Hum, so it does increase with increase in pressure... 🤔
416,360787027 Newtons is 93,6 pounds or 42,4.
24749,7628004 Newtons is... I don't know, the converters just give an error message. 👀
I had to convert Newtons to KiloNewtons, then convert to other values.
24749,7628004 Newtons
24,7 KiloNewtons
5552,7 pounds
2518.7 kg
humm... Interesting, I feel like I'm on something.
And I also feel like Hackaday is lagging too much, maybe the draft is too heavy? 👀
Now trying the second equation:
F= (πD1²P/4) (3cos²0-1)
(π × 100^2 × 1 ÷ 4)(3 cos(15)^2 - 1)
14129.6122408
Radian = 5744.22289863
There is something wrooooooooong and I don't what it iiiiiiiiiiiiiiiiiiiiiiiis...
Trying each one separatedly:
π × 100^2 × 1 ÷ 4
7853.98163397
3 cos(15)^2 - 1
1.79903810568
(7853.98163397) (1.79903810568)
14129.6122408
Doing again, but in radian:
π × 100^2 × 1 ÷ 4
7853.98163397
3 cos(15)^2 - 1
0.73137717483
(7853.98163397) (0.73137717483)
5744.22289862
NOW I get it, I'm inputting the angle of the unactuated muscle, I need to put it actuated.
(π × 100^2 × 1 ÷ 4)(3 cos(30)^2 - 1)
9817.47704247
Radian = -7293.36026722
huh?!
huh?!
Well, this is taking too long, no one is being able to answer me, I literally offered money on some websites that are specifically meant for hiring engineers/roboticists etc.
I mean, I started the announcement yesterday, so maybe I'm being a little impatient.
Anyway, taking the most realistic value we got until now, the 614 newtons of force, I will try to extrapolate a possible dimension that such artificial muscle would have in order to lift 5 tons.
So, just to remember (because I'm taking days between these line spaces, btw):
waaaaaaait a minute, I forgot to put ² after the diameter (forget it, it gives the same result).
I could increase the pressure until 10,000 PSI or 69 MPa (nice), however, as shown before, this would still not be enough, I would "only" get 2 tons out of this muscle. Not to mention that the more pressure I need, the more energy I need to spend, specially since we are talking about 72 muscles (or more). Even though they would not be fully actuated all the time, but what is the point of having a mech if it won't be working "full throttle"?
So I need to increase its radius or its length, but I don't want to increase its length, because it simply wouldn't fit inside its body, lol.
So, let's try to increase its diameter by more 10cm, a trunk of a muscle.
Innerd diameter is 20cm, the length is 30cm, the oil density is 8 g/ml.
A single McKibben muscle would have 9.4 liters of volume and 7.54 kg of mass.
Since there are 72 of those, everything would weight:
676.8 liters of volume and 542.88 kg of mass.
You know, I thought it would already reach 2 tons or something... Interesting. This seems viable. Specially if you take into consideration the fact that I will fill the muscles with something and then insert the hydraulic oil.
🤔 hum...
I will just try the other equation, with the 10cm diameter, but with 700 bar (or 70MPa or 10152 PSI), because the hydraulic hand pumps are normally rated in that pressure.
But IF the next muscles aren't as easy to calculate, I think I would still stick with the 10cm in diameter McKibben muscle, because these results are a guess, not a precise calculation/simulation of the artificial muscle.
For example, I'm assuming that the braided sleeve will have 15º degrees of angle, and when actuated it will shorten by 6cm and the angle of the braided sleeve will change to 30º degrees. Which could be either shorter than what it will actually actuate, or longer than it will actually actuate.
I will need to buy the pump and the material to make one by hand, and these calculations are only pointing where I should go.
For example, for some reason the equation uses the initial angle, not the final one.
So, if I change the initial angle to either 20º, 30º or 11º degrees:
(and yes, every single calculation you see here I had to write using the mouse, because I don't know how to automatically change the google calculator research to "degree" instead of "Radian")
Is as if it is mocking me...
Also, the "cost of weight":
10cm diameter, 30cm length, 0.8 g/ml, you know the drill
2.3 liters of volume, 1.88 kg of mass
169.632 liters of volume in total and 135.36 kg of mass in total.
Again, I will fill the inner tubing with something (silicon foam, maybe?), so it would weight even less.
However, I still couldn't find the method of fabrication, not that it would make too much of a change, since the blueprints and 3d models aren't available, but it is kinda frustrating still.
uuuuuuh...
I've been looking at these pdfs for the past 2 days and I can't make heads out of this crap.
Funny enough, the third generation has the simpler explanation for the second and first generation of Pleated Artificial muscles. I will try now how to calculate this crap.
(also, you have no idea of how many times I wrote "I give up" throughout this project log and went back to erase it)
Quoted from the article itself:
Since the design of the membrane has not changed, the same mathematical model is assumed for PPAM 3.0 and validated in this section. As derived in the generated force F equals:
F =pL0²n/2π sin(2π/n)f(e,L0/R)
with f(e,l0/R) the dimensionless force function as defined by Daerden. The
contraction is defined as e = L0-L/L0, L0 is the maximum length of the muscle’s membrane and R represents the minimum muscle, radius.
L0/R is called the slenderness,
p is the relative pressure inside the muscle and n is the number of fibres used.
This function f depends only on contraction and geometry as far as the elasticity
of the fibres is neglected. The thicker the muscle, the less it contracts and the
higher the forces it generates in short contractions. Contraction can reach up to 30
54% in a theoretical case with l0 L0/R = ∞, which is bounded in practice because of
minimum space needed to fold the membrane.
Static load tests on real muscles were carried out to validate the proposed
mathematical model of Equation (1). Four standard muscles were tested on different contraction trajectories between 150 N and 3 KN with a test bench at isobaric conditions, while applying three different gauge pressures: 1–3 bar. The
tested muscles are made with 32 pleats, have a maximum membrane length
l0 = 110 mm and unpressurized radius of 15.6 mm at the top of the polyester fabric pleats and R = 11.5 mm for the position of the Dyneema fibres.
So, let's get going with the same procedure: First figuring out the units of measurement, then listing what the f*ck (I think) each symbol represents:
Distance units is mm, Pressure gauge seems to be in bar. Or not?
In page 8 as quoted:
The coefficients of the fitting process for the force function of the third generation PPAM, following the structure of Equation (2), are given in Table 1. The values are valid when the generated force F is expressed in N, the initial muscle length l0 in m, the pressure expressed in bar, and the contraction E expressed in %.
Also, in the first article that this paper refers to, they use pressure in kpa and cm.
L0 = maximum length, maybe the initial length? = 300mm (or 0,3 meters or 30cm).
n = dunno, let's use the example given = 32
f = What the f*ck this little "f" is supposed to mean? It is force? I was reading the first document and it seems to be "Dimensionless force function", and it is something related to the contraction ratio, since I'm assuming this wil have 20% of contration = 0.5
R = radius = 50mm (or 0,05 meter or 5 cm).
e = L0-L/L0 = what the f*ck is the L?) =
Well, this is already going down hill, but let's try this stupid calculation with each set of units.
First mm and bars
Second KPa and cm
third bars and meter and %.
F =pL0²n/2π sin(2π/n)f(e,L0/R)
I don't f*cking know why the "e" is separated by a comma, I can't add that on the calculator.
But I think that is for teh better, as you can see from this illustration from its own patent, it seems that ROMAC actuators are flat actuators.
Meaning that I would need to fill and empty their entire inner volume in order to actuate and unactuate them with hydraulic oil, which would need too much energy and oil flow.
3 - Hydraulic pumps and its relation to pressure and fluid flux/flow:
Well, I will start writting this one (even though it will be the third one for the reader), because I actually found a lot of materials about it.
I will avoid inserting the video player here because there is a lot, and these would eventually make the Project log too long.
"Do Pumps Create Pressure or Flow?" It is a simple and visual video explaining about flow and pressure, in certain cases the pump only produces flow, and in certain cases it only creates pressure.
"Pascal's Principle, Hydraulic Lift System, Pascal's Law of Pressure, Fluid Mechanics Problems". It is a video explaining the basics of hydraulics, it may be useful for calculating McKibben muscles or other types. Like, you could calculate the volume inside a cylinder (the initial state of the McKibben) and the volume inside a bigger cylinder (the actuated state of the McKibben muscle) and guess your way into finding how much weight it would be able to generate.
"Troubleshooting". This is actually a playlist of videos explaining hydraulic principles in a simple manner, I'm still half-way through. In this video of the playlist they explain a "triangle" to help calculate the force applied. In the case of a hydraulic cylinder (not a muscle), it is pressure x surface area = force. I don't know yet if it will be useful for muscles, but...
"Fluids in Motion: Crash Course Physics #15" This is video about fluid dynamics, basically it explains that if there is 1 kg (or liter) of water flowing in a second in a wider tube, it will also have the same 1 liter per second flow in a narrower tube, but in a longer section. It also says that the slower the fluid, the more pressure it applies to the tubing, and the faster the fluid, the lower the pressure it applies to the tube that contains it... Dang.
"Water pressure versus water flow" It is a short video, it shows that even though he limited the water flow by half, the pressure inside of the tube keeps at 7 bars.
"Velocity and pressure" The same as the previous two videos, but a little bit more visual.
I just remembered about a series of "walking trucks" that the US tried to develop during the 60's, there are a lot of interesting designs, but the fact that we don't have one in use today is telling of its effiency and practicality.
The entire contraption weighted around 3000 pounds (1400 kg) and used 50 gallons per minute of hydraulic fluid, which was feeded by an external power source.
50 gallons is a similar number of what I calculated in previous Project Logs for the amount of hydraulic fluid the humanoid mech would use. Although 63 liters per second is 3780 liters per minute, which would be 998 gallons per minute...
Something must be terribly wrong with my calculations...
Also, the driver sit (or standed) 15 feet from the ground, almost 4 meters tall. Operating 4 limbs all at once.
Which is also telling that maybe this mech project could be viable in some way, after all it would weight and stand at almost half (or less) of what this walking truck had.
Although the mech was made to have as little as moving parts as possible, the tip of the feet is more important than you might think. I'm not trying to say that I know more than the motherhecking engineer that made this marble of engineering 80 years ago, but the tip of the feet is the only mechanical lever in the body (that I could find) that actually has mechanical advantage.
As you can see, the lever effort is far away from the fulcrum than the load lever, this "load" being the entire weight of the body.
Of course, this is for the pulling force of a muscle, not the pushing force of a hydraulic cylinder. Even then, you could make some mechanism to do that.
Also, you could easily increase the lever, and thus the mechanical advantage of the feet. It would look weird to see a feet longer in the back than in the front, but whatever.
Not that this is somekind of detail that will "save the walking machines" or whatever, it is just a little help that maybe can help a lot.
Well, as I said on the previous Project Log 12: hydraulic mechs are not viable.
The thing is that I calculated the hydraulic artificial muscle mech, not hydraulic cylinder mech.
THEREFORE, I will try again to calculate how much energy and hydraulic fluid all this mess would need.
I'm completely fine guys, I can do this, lesgooooo!
Like I said on Project Log 7, using 1-5 ton cheap hydraulic jacks can be a great option. These are small, light and I can modify them to receive external fluid.
However, I do have doubts about this.
For example, in the video it is said that his hydraulic jack can achieve 12000 PSI. And in order to achieve such high pressures, I would need a serious amount of power. Just like with the previous artificial muscle.
The thing is: even though one needs this amount of pressure, a hydraulic jack that achieves 12000 PSI can simply be used with a hand crank.
Do I really need a heavy duty electric motor tho?
This guy did exactly what I was thinking: putting an electric motor at the end of the crank of a hydraulic jack.
Okay, I finished watching the video and it takes a lot of time to lift that thing.
Still, since this generates 12000 PSI of pressure, it doesn't mean I would be able to power the mech?
hum... 🤔
Well, I don't know the answer to any of this, but I will try to calculate stuff with water instead of oil. Although I don't know how well the magnetic powder and/or magnetic liquid would change that.
One McKibben tube with 2 inches (5,08cm) diameter and 30 cm length would have 0.405 liters of volume and 0.40 kg of mass. Since there is 10 to 50 groups of muscles for all the 72 groups, it would be 291.6 to 1458 liters of volume and 288 to 1440 kg of mass. And since² one would have to inflate these muscles with 3 to 4 times the amount of liquid to increase the mas, it would be a total of 864 to 4320 kg of mass and 874.8 to 4374 liters of volume.
Now I get why everyone focuses more on pneumatic artificial muscles than hydraulic ones...
Well, I thought on trying a smaller pump with extra higher pressure so I could compensate for the flow, but these also have a liters per minute flow and it is around 0.8 and stuff like this.
This project is too complex for me. bruh
Whatever, I will try the electromagnetic actuators. No bad feelings.
So in order to provide them with 3 times its initial volume, I would need 262.2 liters/second...
This is the oil pump I was talking about, the one that achieves maximum pressure of 0.8 MPa. I'm assuming it produces 0.8 MPa of pressure, not that it only holds to that amount of pressure. Who knows.
I tried the flow calculator again, and it said that it would produce 63 liters per second of flow, although in the description of the pump, it says it only produces 4.0 Liters per minute (0,07 L/s) of water (but it is a oil pump...?).
This means I would "only" need 4 to 5 of those per limb, even so I don't actually need to fully actuate all of them at once.
Which would use 1125 watts of power per hour (if I where to activate all of them at once.
Edit²:
It seems that the flow will increase a little bit from 63 to 98 liters per second if you decrease the pipe diameter to 10 mm.
So this means they are viable?
How my calculations always goes back and forth doing this kind of stupid stuff?
One time these say something, another time these say something completly different.
Edit²:
For some reason the electric oil/hydraulic pumps aren't appearing anymore, only the pump itself.
Not that this is bad, it is actually better.
After all, I will use electromagnetic oil (or Magnetorheological fluid), so keeping the pump too close to the electric motor would cause the fluid to change viscosity under the influences of the electromagnetic fields of the electric motor and cables.
FulanoDetail
Now I "just" need to find a way to avoid the tubes from slipping out of each other like a telescopic tube. lol
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