Close

Project Log 59: DIY Electric Motor² (and other stuff).

A project log for DIY Mech/Exoskeleton suit.

Mechs are not viable, nor cheap, so I will try to design and build one alone anyway.

fulanodetailFulanoDetail 07/08/2023 at 12:450 Comments
Saturday, 08/07/2023, 09:37.

Well, I just woke up and I'm already done with this project log, I will take a few days off and I'm not in the mood...


Edit¹:

Forget everything I said in this project log.

Just now I understood what I was taking 50 newton meters of torque instead of 500 nm.

I'm quite stoopid and bad at math, if you didn't notice it.

I would only achieve 50 nm if I were to use the 10x10cm electric motor with the addition of a gear reduction of 10:1.

I would only achieve 500Nm with a 100:1 (or two 10:1 reduction boxes), which is exactly what I was trying to avoid.

So, the motor's stator would need to be 10 times higher, and thus giving it around 8cm of height with 50 newton meters and 300 rpm by itself and then with a gearbox of 10:1.

Actually... I correctly made the proportions, I just missunderstood the output torque. lol

____________________________________________________________________

Although I was thinking on using 6 of this 27cm wide electric motor on each limb for the mech, I was wondering what should be the size of a small brushless motor with 1500 watts and 50 Nm of torque in order to fit in a exoskeleton capable of lifting 1 ton.

Of course, I wouldn't like to be inside such thing, but if I can find a way of making an even smaller electric motor, it may be beneficial for the mech thingie. After all, I would need way less material for a smaller motor, and thus, less money. >.>

Ironically, I had the idea of using that Eagle power electric motor used by James bruton that I talked so much.

https://grabcad.com/library/x8308s-outrunner-motor-1

Or maybe this one:
https://grabcad.com/library/t-motor-u8-lite-1

Early I gave up on the idea because I was thinking on using the electric motor without the gear reduction, so I simply multiplied its height until the torque matched with the torque I required (50 Nm), so I would need around 25 or 30 of both aforementioned motors, which would give something with 80cm of length or even 1 meter. Because these motors only have 2 to 4 Nm of torque.

But, of course, it never crossed in my mind that I should use the gear-box instead of a motor by istelf. So it would give 10 times more torque (although I would need to take the 20% loss into consideration).

So, I would need around 3 to 4 times the height of the motor, which would be around 13cm of height and 9-10 cm of diameter. More or less a 10x10 package. Way more compact than the fricking 27cm wide electric motor.

Also, I could even change the AWG of the brushless motor so it doubles or triples the amperage, and thus, the torque.
If I'm not incorrect, the normal motor would need around 49 amps to achieve the 2-3nm of torque, so I would need around 2 wires of 7-8 AWG for the same power and 40 wires to multiply the torque 25 times to 50 Nm and increase the amperage to 1225amps.
Well, dunno about you, but I don't want to come close to a 1225 amps electric motor.

If linus tech, with all their knowledge and experience were afraid of doing something with 250 amps, I don't think I'd like to mess with 1225 amps. >.>

Well, the good part is that I don't need to 3D model anything.

---------------------------------------------------------------------------------------

And honestly, just now I noticed that I never actually calculated the amount of metal powder I would need.

I will try to use blender to tell me the volume, then calculate how much it would weight if it was nickel/iron/ferrite powder.

So, this stator alone would have 14497.7245 mm³ (of course, the stator of the eagle power 3D model from grabcad I posted above), which would be 14,497 cubic centimeters, I will round up to 15 because whatever.
Assuming that google is correct and the density of nickel powder is 8.9 g/ml, iron powder is 7.85 g/cc and ferrite is 5.18 g/ml, I would need 133.5 grams of nickel, 117.75 grams of iron and 77.5 grams for ferrite powder.

So, since I would make 4 stators for every motor and then need around 30 motors of these in total, I would need 16 kg of nickel 14kg of iron and 9 kg of ferrite. 

For some reason I can't really find ferrite powder, only ferride transformer cores.
5 units of a transformer core that weights around 115 grams, so 575 grams, costs around 120 reais (24 dollars), so 9kg would cost around 2160 reais (443 dollars).

Pure iron powder, for some reason, I found properly made for magnetic core for 50 reais the kilogram. Which would cost around 700 reais (143 dollars) in total.

For nickel powder, unfortunately, 100 grams of nickel powder costs twice as iron powder. 1kg of nickel wire that I was thinking on using for electroplating costs 600 reais (123 dollars).

Welp, sh*t. I should've thought on this issue sooner.

Even thought I'm using graphite/graphene, I would still need to infuse 16kg of nickel on the graphite/graphene and the same for iron...

... Now I have to think in a solution...

I either switch to sputtering or keep going with silicon steel and iron using muriatic acid (hydrochloric acid) and/or sulfuric acid...

Both are extra hard on their own ways...

---------------------------------------------------------------------------------------

Obviously, this project log won't just end here, I will first try to make the DIY electroplating with graphite/graphene.

First, I need to convert graphite into graphene in a DIY configuration, for that I would need bovine serum albumin and lactoglobulins.
However, I couldn't find it by itself, only egg albumin.
So I thought on simply using milk in powder, which every good brazilian has at least 10kg of packages at their home to drink with coffe every day.

Also, I was thinking about the relation of milk in powder with the vinegar salt solution. When these two combine, wacky things happen, so a thick layer of bioplastic will simply form around the thing.
I was thinking on after making the graphene, I would just heat it up to hundreds of degrees so the milk is converted to plain carbon powder.

I found one of these rechargeable mixer/shredder thingies, so luckily I won't need to use the mixer in my house. I don't even know how I would clean it after using the graphite powder >.>
(I said "luckily" because I really don't know if it will be fast enough)

But this crap needs to recharge, and it takes a while... And it was not worth it, this thing is too slow...

Also, I just now opened my graphite powder that I received on the mail and... I don't know if it is a thing with the camera/photos, but it is gray as hell, not black...

I also don't have deionized water in hand...
Not because I'm too broke or anything like that, it is just because the shipping fee for this stuff is a fricking crime. You have like, a liter of deionized water costing 10 reais (2 dollars), then the shipping fee is like, 50-80 reais (10-16 dollars).
Like, bruh, I will just use destilled water, thank you.

Well, my improvised setup is that I put an empty smaller pan inside a bigger pan full of water, the water will evaporate into the lid of the bigger pan and fall into the smaller pan.

The problem is that I've been trying to make this for 2 hours now and no water formed in the fricking smaller pan. I can't believe I'm so bad at DIYing that I can't even make a fricking boiled water bowl.

... And the light is off.
Great.

(it just came back and some electronics in my house are broken, bruh²).

__________________________________________________________________________________________________________________________________________

Well, bruh³, I completly forgor to take into consideration²³³²³²² the hydrogen storage, it is a problem for a good reason.

"Under ambient conditions, a cubic metre of hydrogen provides some 3 kWh, equivalent to 0.003 kWh per litre. Pressurised hydrogen contains about 0.5 kWh/litre at 200 bar, 1.1 kWh/litre at 500 bar and 1.4 kWh/litre at 700 bar."
Source. https://www.idealhy.eu/index.php?page=lh2_outline#:~:text=Under%20ambient%20conditions%2C%20a%20cubic,kWh%2Flitre%20at%20700%20bar.

In other words, even if I had 100% efficiency of energy extraction out of hydrogen, and used only 18 kilowat hours for the mech/exosuit, I would still need a 180 liter hydrogen tank with 500 bar of pressure to work for 10 hours.

But since I will have around 30% efficiency, I would only extract the equivalent of 54 liters out of 180, which means that I would need around 3 to 4 times more hydrogen in order to achieve the 10 hour mark.
I would need a 540 liter tank of hydrogen.

This one hydrogen tank has 850 liters of capacity at 600 bar.

I would either need hydrogen hydride tanks or a conventional combustion generator.

Again, I would suggest to use Digital TG4000I Toyama generator, it weights only 30kg and it delivers 4.4 kilowatt hour. But it costs 3000 reais (616 dollars).

Initially I choose hydrogen fuel cells because you can extract hydrogen from anywhere and on top of that, you can make the hydrogen fuel cells by yourself.

I just forgot a very important detail: you absolutely cannot make the hydrogen tanks by yourself.

Seriously, I don't want to risk my life just to make a hydrogen tank for a big toy.

I've seen DIY videos teaching how to convert fire extinguisher tanks to scuba tanks and whatsoever, but you still are limited to its original pressure rating, which is around 20 bars (2 MPa).

The other way would be hydrogen hydrides, but these are equally as dangerous, since you have to heat the hydride that holds the hydrogen to hundreds of degrees.

And yes, they are twice as expensive as conventional hydrogen tanks.


__________________________________________________________________________________________________________________________________________

However I could make conventional combustion engines in a somewhat DIY manner using 3D printing and I could make an electric generator in a DIY manner.
However, I will have to make a few researches on the subject and see how I would pull that off in a practical manner.

I think I would have to use ceramic polymer composites (such as teflon/kapton that can withstand up to 300ºC or more) and/or sodium silicate with ceramics in the engine in order to actually do that. Which is not that big of a deal.

I could still use hydrogen gas for the fuel...

I could try using the most amount of trics for efficiency that I could find, like the elko Elsbett engines, which were a kind of semi-adiabatic engine (adiabatic engines are the top efficiency of all internal combustion engines) that used hollow piston heads with a vortex generator direct injection and ingnition, which created an air separation layer between the piston head and the gas inside the engine, which in turn avoided the heat exchange between the fuel, air and piston, creating a somewhat adiabatic combustion.
Thus the name.
It could run with pure oil and diesel, with any kind of fuel, in fact. It was said to be 65% efficient, but I doubt, it would probably be, at best, 40% efficient.


__________________________________________________________________________________________________________________________________________

In any case, I don't feel like I can just handwave my way into a conveniently cheap energy source and/or equipment.

If it was this simple to make a composite engine, there would be more of those.

If it was this simple to make soft magnetic composite electric motors, there would be more of those.

I just hit a new roadblock because of my own negligence and incompetence.

Discussions