SSS 5694 800kv motor + Flipsky 75100 vesc

I already have a well built from scratch eboard😅

BUT!

I’m building a friction drive ebike, this motor I mentioned, will spin a 90mm longboard wheel (15/36 teeth) that will eventually spin the 20 inch bike wheel and I’m encountering a weird (or not) problem with this motor,

After configuration on vesc tool, everything work amazing and crazy fast, the longboard wheel almost explodes, But when I’m applying pressure/holding the longboard wheel with my hand, the motor seems to be struggling very much, almost uncapable to spin
I know I’m not using the full potential of the motor abilities, but I can still generate 5000watt, and yet, very weak.

You know why?

Running 10s, 5ah, 30c,
Limited to 80Ah - if it’s too low, let me know.
ERPM limited to 60,000 - if it’s not ok, let me know.

I would be very happy if you can hint me or provide me any lead.

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800kv motor is going to have very little torque unless you feed it a huge amount of amps
“80ah” is a measure of energy not power. 80 amps to the motor is not much for such a high kv motor

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ERPM limited to 60k. with 10s you’re looking at 200k ERPM with a 800kv motor

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Yeah what hummie said, plus if you gear down the speed the wheel will spin slower but with more torque to overcome resistance and with less of a current load on the motor. Those things want a huge amount of current and cooling, 150~200A from some specs and they’re often water cooled

I think they’re much lower pole count (I saw 6 pole in this size, other inrunners are 4 pole) so it’s more like 100k (edit: 86k max, I must have entered something wrong because I got 100.8 the first time)

You can use Evan’s esk8 force calculator to figure out the torque at 1:1.

Only 11 Newtons @ 80A

Compare that to a standard 190kv outrunner which I can just hold with my hand at 80A

Also the esk8 calculator at the top of this page can calculate the ERPMs, and yeah it’s fine. (77k to 86k)

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You need to gear down that 800kv motor to get any torque out of it bro

Not necessarily. It basically is geared down friction driving a bike wheel.

90mm vs 508mm (20in wheel) is a 5.6:1 ratio. It may work fine on a bike, but will fail the “hand” test.

Also make sure you are running the right firmware for these, and if it’s the aluminum PCB one, you can probably run it at 120A or more.

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To be fair OP is geared 15:36 on a 90mm wheel rather than 1:1 on a 165mm, but obviously with that big disparity in force it’s still gonna be stopped by hand

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Ah good point I missed that part. Thought it was a direct drive from the motor to the esk8 wheel

What’s interesting now is that it still lacks torque compared to a direct drive outrunner

With the inrunner at 15/36 it’s still less than an outrunner in direct drive.


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Not so, with friction drives the force at the perimeter of the driving wheel is the same as at the driven. No real difference in thrust.

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Doesn’t the friction wheel at least need enough torque to drive the bike wheel? If it’s stopped by hand it sure as heck won’t be able to use friction to propel a load with the mass of a human.

I’m having a hard time understanding this. A friction drive is similar to a gear drive, which is a force multiplier, trading speed for torque. With his setup, using a 90mm wheel should accelerate the bike faster, but have a lower top speed than using a 200mm wheel right?

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Holy crap,
I’m reading all these comments and I’m very glad for all you’re willing to assist me, thank you so so much!
it’s very warming!
Please, continue this discussion, maybe we can get any idea.

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My bad, yes the smaller wheel gives more thrust. I just meant the step from driving wheel to bike wheel doesn’t change the thrust.

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Going to need an esc that can do much higher amperage or else a motor wound to a much lower kv to produce the max torque from the motor.

Can you explain a bit more? To me It doesn’t seem likely to happen, just cannot see why and how.

What’s the max speed the vehicle will do assuming no load or wind resistance?

I’d save myself the trouble of the little motor and gearing and just get a premade 20” wheel with a hub motor in it. Leaf hub motors are good.