Can you please upload that video in a format we can all enjoy?
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2 mechanically connected motors on 2 independent controllers is fine, even 2 mechanically connected motors on 1 singular controller is feasible, the phase timing must be aligned prior to being connected mechanically however.
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Well I dont wanna say I told you so buuut… 
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Yes, you did. 
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Finalized gearbox v1
Dual 5065
7.8:1 gearing
This should be a lot lighter and less expensive to power.
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In your last video it looks like the power really surges as the paddle grips or hits ice. I wonder if a planetary gear drive would be better than a single spur gear. I could see it easily chip a tooth when the paddle goes from spinning fast and then abruptly stopping when it gets traction. Although I don’t think you could do the planetary gearing with two out runners in the hub, maybe it could be Incorporated into a hub motor design? I have an ebike with a DD rear hub and a Geared hub in the front, and the front motor has more than double the torque even though it’s less than half the size and weight.
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Planetary geared (and reasonably silent) hubmotors has been a wet dream on this forum since forever.
Its no easy feat. maybe bit easier at that size but still Think best route would be to take one of those bafang motors that are planetary geared that has been developed for a few years and retrofit em to a skate. They’re s’posedly real solid.
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up to the snail race? they are like <10KV and also the gearbox is made for super low RPMs (planetary gearboxes are usually all made for low speeds, like max 5kRPM input)
I played around with some neugart ones, but problem is always the same: high RPM => noisy + fast wearout
low RPM => heavy and not really an advantage vs investing weight and money of gearbox into a bigger/better motor
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We have a few planetary hubs, tried to go that route but they are all too slow. 400RPM
(Tring to avoid stamping our own stators if possible.)
I was thinking we could add a 2nd idler gear to the other side of the pinion giving it more bite.
Yeah, bafang hubs are really high quality from my experience. These pics are of the ones that battery clearing house was selling. They come stock with nylon planet gears but I was able to find some steel replacements on alibaba for 25 bucks. If you are worried about speed it would be easy to just make the motor a higher kv… Just wire with fewer turns and you wouldn’t have to do custom stator stamping. It would be easy to throw two of these motors in the paddle wheel, just would need a custom machined axle and then put the ring gear into the custom hub.
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Where are you getting your information? For example the motors used in Porsche EV’s and Ford EV’s use motors that spin up to 15k rpm and use planetary gearboxes. (Motors and gearbox designed and built by the Shaeffler group) Why would planetary gears be more limiting with speed than traditional spur gears?
Another high speed planetary gear application is any cordless drill. They output ~1200-1600 rpm from a ~18-20k rpm motor by using multiple stages of planetary reductions.
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Okay, sure you can develop an application optimized in the period of 2-3years, purchase numbers in the 100k range and then get to a price >>500$ per piece.
But even the premium off the shelf parts: parker, neugart, dunker, etc. all are rated way below 10k RPM; just browse the datasheets and product categories.
Planetary gearboxes come with more constraints regarding precision (they all must align well to meet in the center), otherwise they get loud quickly and you get lot of wear.
Just try it yourself, build 2 stage spur gears and 1 stage planetary, I guess your spur gears come fully working out of the 3D printer, for the 1 stage planetary gears you are probably not even able to assemble them, and if you loosen up your tolerance till you can, it will be really noisy…
Cordless drills are an exception I guess, to be honest I don’t know where the compromise/magic for drills is (I only seen some motors burn, never saw a gearbox failure…yet).
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i agree with the KISS principle here.
a hub motor is cheaper, 1 moving part, very little to go wrong.
Creating that planetary system from scratch? Much much more expensive and move moving parts to fail.
Why not up the amperage on startup? Unless your vesc is already maxed out?
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I think he’s fully saturating his motor causing heating, additionally there’s a really sharp ramp in torque when the blades gain traction.
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Sounds like a gearbox kinda problem. Or in this use cane where slipping is acceptable a CVT.
Simulations:
I know nothing about these little can motors. What can we expect from them in real-world usage? 5065
Any quality vendors we should source?
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Not to crap on your design or anything, its really beautiful. But I think the best way to prototype this would be to have the driving motor external. Leaving you lots of flexibility to experiment with gear ratio and size of motor. (You might have done this already, I have only skimmed thru some of the info here)
Once a motor size and gear is estabished sufficient for intended use. One could iterate abit better on this information to something you’ve modelled above. I think realisticly you’d be able to draw maybe 1kW of peak power per motor from those motors. Since they’re isolated from free air as I understand it, you’re more looking at the cooking pot scenario, yeilding a decrease in avaible performance depending on outside factors, such as heat dissipation and ambient temp.
Regarding the brand, if they’re in the same pricerange, they wont differ alot. The avrage generic outrunner is anywhere from 80-150 buckaroos and the upper span isn’t necessarly any better then the lower span. Theres some german brands out there that are 4x the price of the chinese ones. I have no idea if they’re any better tho.
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Albeit they’re expensive, Hoyt’s tiny motors are surprisingly powerful (56x53 though):
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If I was designing this personally, I would stick with a single, larger motor. Alter the design / add more gears if need be. Would be simpler, which is usually better. Means you only need a single ESC too.
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Figured the biggest differences would be bearing quality and how tight they are wound.
I purchased some to test.
The goal is to cool them in ATF fluid. The rotor is frozen from the ambient conditions.
I am worried about eating gears, tried dual idlers but they wouldn’t mesh. Went with the largest idler that would fit.