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Sunday, December 18, 2011

Powerchair Motors for Bikes...Brushless this time

I used to run CrazyBike2 on brushed powerchair motors with right angle reduction gearboxes, and that was ok, with the only real problem being the repeated chain and sprocket mangling from the incredible torque I could get out of them, and misalignment problems I had due to frame twisting (because of said torque).

Well, now I've got a *brushless* powerchair motor, direct drive rather than gear reduced, to try out.  This thread on Endless Sphere documents my exploration, modification, and testing of that motor, and will eventually show it's first tests on CrazyBike2, and it's later testing on the bike it's intended to be one of the various experimental power sources for. 

That bike is not yet named, and isn't finished yet due primarily to not having a reliably-working welder anymore, and secondarily from not having enough time to do everything yet.  There's a thread on it's evolution over on Endless Sphere, showing it's current progress.   The main thing I needed from this frame was stiffness, to prevent the flexing and twisting issues I had with CrazyBike2 with chain-drive motor power, whcih I still have issues with when carrying heavy cargo.  It'll use a mid-mounted NuVinci 171 developer's kit with autoshifting for a "transmission", to help keep power usage down (although it might not actually make it any more efficient due to the losses the NuVinci itself incurs internally). 

Also, to start it out from beginning as a full-suspension, since CrazyBike2 has broken lots of rear wheels while loaded down because of unavoidable bumps, potholes, and road debris, which shouldnt' cause such problems on a suspended wheel.  It will also use a motorcycle (Suzuki dirtbike, acually) rear wheel, which will take a lot more abuse than the bicycle wheels I have used so far.  I just need a good narrow "slick" tire for it, as the wide knobby it has now isn't really suitable for my purposes.

That's my update for now, hopefully I can keep coming back and adding info to the blog more frequently--but if you are a reader of it, and need more, I tend to post on at least one of my project threads on Endless Sphere ebike forums every day, and sometimes on several of them. 


  1. High torque from brushed motors is interesting. I like how the timing is synced so simply. I recently got some more Pittman brushed motors that are half the size of my present ones. I would like to make a low power project that can brake from regen. it would have a very small battery whose function would be kinda like a super capacitor. The motor would be mostly for braking and short assistance boosts.

  2. More thought on the regen braking idea leads me to wonder about this being a case when a brushless motor is called for (Alas!). It might be a case when the small drag from the brushes is too much, given that the motor will need to be small and always turn at high RPM even though most of the time it won't be powered. It won't be able to use a freewheel, though a clutch could ease the motor requirement somewhat. That would add complexity and weight, however.

  3. This motor has captivated me now. I'm thinking about getting the courage and opportunity to say something about it on ES.

    It might be a way to build a simple assist. First stage would be through a 3mm pitch belt.


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