ES DIY Motor Challenge

Miles

Miles

100 TW
Joined
Mar 16, 2007
Messages
11,031
Location
London UK
What do you think about the idea of a competition for the diy motor builders on ES?

What would be a suitable goal to work towards?

4Nm of sustainable torque per kg of motor weight - passive cooling only - for a motor weighing under 3 kg?

........................................................................................................................................................

Edit

Goal:

- Over 4Nm continuous torque per kg of motor weight.

Rules:

- Less than 3kg in weight.

- No energy input other than that to the motor itself.

- Capable of practical use on an electric bike.

...................................................................................................................................................

Finalised rules:

Three weight categories:
- 3kg or less
- Over 3kg to 10kg
- Over 10kg to 20kg
- Over 20kg to 40kg

Goal

The initial formula for the continuously sustainable specific torque target, in each category, is:

- Specific torque (Nm/kg) = 0.1 * motor weight (kg) + 3 [This will be adjusted by category (raising the bar), as it's achieved.]

Rules

- No energy input other than that to the motor itself.

- Capable of practical use on an electric bike.


Example:
A motor weighing 1.2kg would need to achieve a specific torque of 1.2 * 0.1 + 3 = 3.12 Nm/kg.
So it would need to be able to sustain a torque of 3.12 * 1.2 = 3.74 Nm.
 
The collaborative environment may suffer if members compete against each other.

Right now, the ES team seems to be winning in the DIY competition versus the rest of the world. :mrgreen:
 
TylerDurden said:
The collaborative environment may suffer if members compete against each other.
Click to expand...
Well, the only prize would be the kudos of breaking the barrier..... If you do it in a secretive way, you lose kudos... :mrgreen:

If we call it a "challenge", is that better?
 
I think we should throw the gauntlet to the other forums. (unless all the brain power are same guys here :p )
but I do like the parameters.
Realisticly, how many motor builders do we have here?
I am a hobby machinest, Jack of all trades and electrical bafoon.
Whats hapening in the axial motor thread is a new adventure for me.
 
Toorbough ULL-Zeveigh said:
it's already a good ol-fashioned space race or rather a safe race.
fess up Miles.
Click to expand...

That's good for a few laughs. :lol: Good thing I don't need to spend so much time explaining things to him anymore. Only just recently did my total post count exceed his.

I recall a few that have built their own motors. It is not a trivial task.
Before the old V forum crashed, there was a guy in Sweden named Honk that was working on a multi-disk ironless axial motor using multilayer PCB boards for the windings. I wonder what ever happened to him?

I've seen several DIY radial designs that failed after the magnets flew off the rotor.

We'll just have to see what the "Idea Incubator" comes up with.
 
I've seen 3 things that are factors leading to invention and innovation.

Dumb luck and/or genius

Hardship

Competition



At the moment, most of us here are only working with the first factor. Anything that applies an additional innovation driving force is a very welcome thing IMO.

Competition is what it took to transform engines from 0.04hp/lbs to +2hp/lbs, AND improve reliability and economy.

Motors need the same sort of innovation driving force.

We need to get some innovation driving trash-talking started between other forums. In the automotive racing world, NOTHING makes us hunt harder for every last 0.5% design improvement we can find more than the need to shut-up another trashtalking team/shop/forum on raceday.
 
How about 10nm/kg continuous and 20nm/kg peak? I found something that might help level the playing field a bit, since it has juicy formulae along with a triple rotor/double stator layout in a hub motor layout with real world efficiency of 93% and 97% highway. http://www.itee.uq.edu.au/~aupec/aupec03/papers/114 Greaves full paper.pdf

I'm all for competition, and if we can figure out some way to blend the competitive drive with the multi-brain and wide ranging experience open source sharing approach pervasive here at ES, it could result in a best of both worlds situation.

John
 
I posted this on Thud's thread: http://www.ornl.gov/~webworks/cppr/y2001/rpt/120491.pdf

A similar design objective, but a radial example.

One more thing to throw into the constraints is cost. Super expensive efficient motors are already out there. We need cheap efficient motors. If you're going to DIY, then there are even more constraints in the availble materials and tools. There are going to be trade-offs in design, so anything Thud or anyone else is likely to come up with may not have super advanced fabrication techniques, but I think we could easily make something with more bang for the buck.

I'm always one for making maximum use of available materials. If I can buy something that's close and just modify it, that's easier than starting from scratch. This applies to the pieces as well as the whole.

The 'Sphere has morphed into one of the most open and dynamic idea incubators that I have ever encountered. Members come and go, but all add something along the way. Most of the techinical problems we face are quite solvable, but there just seems to be so many of them it's hard to keep up. I think we've had a large influence on the whole ebike sector either directly or indirectly. Ideas we were bouncing around a couple of years ago are starting to show up in the marketplace. Someday products might actually be built so they work and are reliable.
 
John in CR said:
How about 10nm/kg continuous and 20nm/kg peak? I found something that might help level the playing field a bit, since it has juicy formulae along with a triple rotor/double stator layout in a hub motor layout with real world efficiency of 93% and 97% highway. http://www.itee.uq.edu.au/~aupec/aupec03/papers/114 Greaves full paper.pdf
Click to expand...

Interesting find, John. It's on a completely different scale, though....

I think the 4 Nm/kg target is a more reasonable goal, for us.....
 
Miles said:
John in CR said:
How about 10nm/kg continuous and 20nm/kg peak? I found something that might help level the playing field a bit, since it has juicy formulae along with a triple rotor/double stator layout in a hub motor layout with real world efficiency of 93% and 97% highway. http://www.itee.uq.edu.au/~aupec/aupec03/papers/114 Greaves full paper.pdf
Click to expand...

Interesting find, John. It's on a completely different scale, though....

I think the 4 Nm/kg target is a more reasonable goal, for us.....
Click to expand...

I didn't mean to suggest a change in goal. There just seemed to be a lot of meat in that paper that might eliminate some of the guesswork. Now that you have me trying to think in terms of torque machine instead of motor, it's especially interesting that Greaves talks about only torque in that paper. LFP is going to see that 250nm continuous 500nm peak and want to put it on his bike as is. I can see him now riding around on what is essentially a lipo battery with wheels and one of these monsters inside the back wheel.
 
Miles said:
I can see him now riding around on what is essential a lipo battery with wheels and one of these monsters inside the back wheel.
Click to expand...

LOL @ Lipo battery with wheels, pretty good description of Lukes bike there Miles :mrgreen:
 
In case anyone needs it, the formula for rotary power is:

Power (Watts) = Torque (Nm) x Angular Velocity (radians per sec)

Angular Velocity = 2pi * 60 * rpm

So:
Watts = Nm * rpm * 2pi / 60 , or
Watts = Nm * rpm * 0.105

Solved for torque:
Nm = Watts * 60 / rpm / 2pi , or
Nm = 9.549 * Watts / rpm.
 
lol. im in if you gents are willing to let my ghetto entry in . id like to see a formula that takes into account $ spent and time in for total power out . that said i have no idea how much time ive put into this and dont really worry about that part.

Otherwise consider this a THROW DOWN. :twisted:

Barring any problems i have found most of the things i need to get this done . the magnets get here in the mornin (shipping weight of 1.7 pounds) and i intend to put around 1-2 pounds of copper in it still. no steel , fibreglass structure for the windings.

100_6496.jpg

100_6499.jpg

100_6500.jpg


ill have shots of the rotor in the mornin. just working on dressing it up a bit :) . may get lighter as im waffling on some things but i figure i can always get the drill out again and put more speed holes in the case if i need to make a weight requirement. lol
 
This is so cool!

I am an absolute Moron when it comes to understanding motors. But, I can sit back and watch with pleasure.

I am good at implementing someone else's motor onto a bike. It is cool to see people actually start from scratch and make their own working motor. :)

Come on, Gents, lets see some DIY horsepower!

Matt
 
Enoob, you are in the lead.
I have been looking at weight reduction all day to better atack the parameters Miles laid out. I am curious how the alternator conversions compair to the other motor options.
on a side note I worked on my eddy brake dyno last night. I overheated the magnet rotor & the epoxy flowed. Fail! interesting gizmo though.( I am thinking a simpler friction brake will have to suffice)
E, how are you going to test you motor?
 
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