you right tho 
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Ah! This is your 1s idea. Interesting. A lot of challenges ahead, but exciting nonetheless!
Whoever would like to send me motors to dyno, I’ll get more benchmarks on the power you are actually putting to the ground with your setups. Just because you’re running 2000W limits doesn’t mean you’re getting it to the ground.
If you guys want, I will design a motor exactly to your preference, but I can’t guaranntee it will cost less than $500 per pair.
How about 107mm? I could do that. That’s a wheel size that would match well to abec11s.
How many people would put down $2k for a 4WD setup these days? What is the going rate?
What is it about the thick thane that you want? Better ride quality? Do you want large diameter or thick thane? What is too wide of a wheel in your opinion?
it so happens i simulated a one cell hub motor with the same performance characteristics as a pair of @hummie 73kv hubs w/100a motor current limit the other day…
what ESC do you plan to use that allows 1250a motor current?
what connectors and wire gauge will you use when pulling 1400a from your 3.7v battery?
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I don’t know where you get your numbers for your model. Maybe I could have a closer look at your stuff.
it’ll be a 200-300A motor current limit, with a custom controller my buddy and I are working on.
@Hummie can I dyno a pair of your hubs? Need to borrow VESCs and battery to do it.
yes please do. Give me a week to finish things n then
sure, let’s suppose we use 1250a motor current limit with a 900kv motor…
60 / (2 * pi * 900 kv) = 0.01061 newton meter per motor amp = KT 0.01061 nm/a * 1250a = 13.26 nm torque (13.26 nm torque * 1000mm) ÷ ((1 / 2)× 84 mm tire diameter) = 315.71 newtons thrust per motor 315.71 newtons * 0.2248 lbs force per newton = 70.97lbs thrust per motor at 1250a motor current
^70.97lbs thrust per motor requires 1250a motor current
now let’s compare to 73kv @hummie hub w/ 100a motor current…
60 / (2 * pi * 73 kv) = 0.13081 newton meter per motor amp = KT 0.13081 nm/a * 100a = 13.081 nm torque (13.081 nm torque * 1000mm) ÷ ((1 / 2)× 84 mm tire diameter) = 311.45 newtons thrust per motor 311.45 newtons * 0.2248 lbs force per newton = 70.01lbs thrust per motor at 100a motor current
^70.01lbs thrust per motor requires 100a motor current
conclusion… same thrust as 73kv 100a motor current @hummie hub w/ 900kv hub requires 1250a motor current
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Or quick and dirty, 1/12th the voltage needs 12x the current to yield equal power. People here like to run dual 60a motors, so that puts you at 1440A approximate target current.
Just a question that’s got nothing to do with this particular topic, but does stator size affect torque in any way? Apart from staying cooler at higher amps
There’s no “apart from” staying cooler at higher amps. It’s ALL ABOUT staying cooler at higher amps. Staying cool means more current. More current means more electrical power. More electrical power means more mechanical power (i.e. torque and speed).
Torque = current / Kv, so cooler motors = more current = more torque
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Current isn’t what you’re after… amp-turns is what you’re after. Current by itself is not really worth comparing things by. 1000A through 1 turn is the same as 100A through 10 turns.
cooler motors = more copper volume. More torque is the result of making use of your amp-turns effectively and having a balance of high amp turns and high steel content
Keeping your motor operating at a low current with more copper is how you keep a motor cool.
Well there is, and I realise bigger motors handle more current that’s why I said “apart from”. I was asking if larger sized motors create more torque, which would make sense and is what is generally found
My kind of thoughts are, bigger stator bigger magnets, bigger magnetic forces results in more torque.
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I looked at the numbers again. I was mixing things up. I simulated 4.45Nm/230A = 0.01935 Nm/A
493kv or so, but let me re-sim things.
Thrust should be 4.45Nm / 0.042m = 106N per motor, which is plenty.
This is only 21A/mm^2 current density. It can be increased to about 45A/mm^2 so I expect 660A will work just fine at approx. 12.77Nm. I don’t have any plans to pursue a 660A motor controller, as its another $40 of controller to make.
The thing is, that’s an insane amount of thrust for a skateboard. You have to be strapped in. This is why we need to dyno test Hummie’s motors, because I suspect they are saturating well before your 13Nm number or you guys are just insane. 
If he is truly at 13Nm, that’s great. I think you’re better off though with 4WD and more urethane with that kind of power level.
I might take it up to the 300A level and lengthen a little bit, but I need to model up the ronin trucks first and see what looks good.
And more resistance 
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Yes actually you are right. Turns is correlated with Kt, and torque = kt * current. In most of our builds where our motors basically cannot be over-volted and where gearing is a thing, current is basically the only way that motor selection can affect output power. Voltage is already limited by our ESCs, so the only thing we can play with is finding ways to increase motor current.
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There are so many challenges for this build! Even just wires and connectors desoldering themselves! But it sounds like you know your physics, and I imagine you might have had a few sleepless nights thinking through the engineering. Keep us posted!
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17mph top speed?