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Searching for hub motor options

Old 09-01-21, 08:37 AM
  #1  
alias5000
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Searching for hub motor options

Hi all,
I am not super familiar with the ebike market and am considering what benefits and options there would be to upgrade one of my bikes with an ebike kit. Rough requirements as I can tell:
  • Would be mounted on a 700C hybrid bike, QR & 135mm OLD + disc brakes at first. Square taper BB
  • Later on, the need for it on the 700C bike might go away, so it might make sense to transition it over to my cargo bike/tandem. That would be a 20in wheeled bike with QR & 135mm OLD, disc brakes. Square taper BB for now
  • I am a year-round commuter, so corrosion resistance is very important
I am a bit hesitant about mid-drive motors of the bafang/tongsheng kind. They seem to be lots of steel and I'm not sure how well they would fare in Ontario salty winter conditions day in and day out. Furthermore, I've been having difficulties confirming that a tongsheng would fit on the cargo bike frame which has some weird tube installations in the bottom bracket region.

So I've been thinking that a rear hub motor could be a very nice drop-in option that preserves most of the drivetrain and possibly encapsules the system better in bad weather (?), and makes it simpler to move the system around different bikes that have different drive trains - as long as I'm okay rebuilding the wheel between 700C and 20in (that's fine by me).

Couple of requirements I can think of:
  • I think I would like to preserve the normal cycling dynamics as much as possible - i.e. torque-based pedal assist, not speed sensor or throttle.
  • Range: 60km (hill assist, boost cruising speed by a little bit)
  • Ontario regulations: 32km/h, 500W.
  • The motor should fit the 20in wheel, so it can't have an outstandingly large diameter to build a feasible wheel.
I'm aware of the bafang offerings and something along the line of H630 might possibly work? Yet, it does not list 20in as compatible. Also, what is listed on their website is not very consistent with what I can find on aliexpress/ebay/etc. Where can you source current bafang designs?
What other systems are out there that would fit this application?

Thanks!
alias5000
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Old 09-01-21, 09:07 AM
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There is a religious divide between hub and mid drive advocates, but if you are thinking of a hub motor, I would check out ebikes.ca. They have many options and there is plenty of info on their site, so even if you decide to go somewhere else, it can give you lots of ideas.

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Old 09-01-21, 09:16 AM
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20” hub drives have different windings and spoke counts from 26 or 700C wheels. Unfortunately, AFAIK, Bafang does not offer any 20” rear hub drives, only front ones, so not currently an option for your cargo bike. Not to mention they are not compatible with torque sensors (or would require a needlessly complicated, pricey, special controller and fugly display unit.) Perhaps though a front hub drive would work okay with your cargo/tandem bike. Others have had success that way; I have a 20” Bafang front hub drive on my LWB ecumbent that performs well but that bike also sports a TSDZ2 for good measure.
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Old 09-01-21, 09:26 AM
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Originally Posted by andychrist
20” hub drives have different windings and spoke counts from 26 or 700C wheels. Unfortunately, AFAIK, Bafang does not offer any 20” rear hub drives, only front ones, so not currently an option for your cargo bike. Not to mention they are not compatible with torque sensors (or would require a needlessly complicated, pricey, special controller and fugly display unit.) Perhaps though a front hub drive would work okay with your cargo/tandem bike. Others have had success that way; I have a 20” Bafang front hub drive on my LWB ecumbent that performs well but that bike also sports a TSDZ2 for good measure.
Thanks for this. That's unfortunate regarding 20 vs 700C. Does this apply generally across the board, or is this bafang-specific? Does bafang offer a torque option (they have this bottom bracket that senses something - is that torque? Does it use that for pedal assist?)
According to the cargo bike manufacturer, a front hub system would not work as the fork is not rated for that load (and they say that there have been actual accidents from people ignoring that advice).
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Old 09-01-21, 09:50 AM
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Good advice above. IMO the biggest challenge and as andychrist said, the motors for 20" and 700c probably are different. If the motor RPM for 700c provides 15 mph, what would it be for the same motor with a 20" wheel? Wild-assed-estimate: 10 mph. As snookum stated, ebikesca is an excellent, if expensive, resource. The guys there are the smartest that I've encountered plus do the most research.
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Old 09-01-21, 09:59 AM
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Came across grin many years ago. I'm impressed how much their website and resources have grown since. I'm reading and reading
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Old 09-01-21, 10:19 AM
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Originally Posted by alias5000
Thanks for this. That's unfortunate regarding 20 vs 700C. Does this apply generally across the board, or is this bafang-specific? Does bafang offer a torque option (they have this bottom bracket that senses something - is that torque? Does it use that for pedal assist?)
According to the cargo bike manufacturer, a front hub system would not work as the fork is not rated for that load (and they say that there have been actual accidents from people ignoring that advice).
yeah, can't use a 700c motor in a 20" wheel, or vice versa. (well, I do, so there is that).

For the motors I use, 32km/hr is about 200 rpm in a 700c wheel, and probably 330 rpm in a 20" wheel. The no load motor speed is determined by windings and is a fixed thing. So, with a major brand (MAC, Bafang, Cute), you have the choice of # of windings - which determines the no load speed. Generally you match that to the wheel size (and load you will be carrying).

If you want to use the same motor for 29" and 20", you are gonna need a mid-drive - where you can use chain gearing to match the speed of the motor/wheel.

I'm not sure that a mid drive is more vulnerable to winter. Certainly it is gonna get a LOT more road spray, so there is that. I use a hub motor in Ontario conditions, and it works for me. The best thing (by far) is that I can use super efficient summer slicks or super inefficient studded tires (600 studs total) and cruise at 32km/hr either way. It really doesn't make much difference. I guess that my range might be reduced in the winter (with the cold and inefficient tires), but I never really run a battery dry in the winter. Wind chill can be an issue though. ;-)
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Old 09-01-21, 10:58 AM
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Maybe wait a few more years?
German company Schaeffler has just revealed an entirely new drive system for electric bicycles that eschews traditional bike chains and belts for an entirely electrical-driven system. The new system is known as the Schaeffler Free Drive and marks the entry of one of the most divergent electric bicycle drivetrains we've seen in years....

https://electrek.co/2021/08/31/radic...GVMr186s4ij5Vs
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Old 09-01-21, 11:42 AM
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Hostel Shoppe can put together a 20” rear hub drive. They are actually a recumbent oriented enterprise but many trikes feature 20” wheels all around and their Burly should fit your tandem/cargo bike.

For your hybrid, either a 700C rear hub drive or mid drive would work.

Last edited by andychrist; 09-01-21 at 02:23 PM.
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Old 09-01-21, 11:51 AM
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I believe that Grin/ebikes.ca has different windings on several rear hub motors. They also specify thermistors and speedos in the hubs they order so you don't damage the motor and don't need a separate sensor for the speed. You get what you pay for.
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Old 09-01-21, 12:19 PM
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20" hub motor conversion kits: https://www.ebay.com/sch/i.html?_fro...Desc=0&_sop=15

700c hub motor conversion kits: https://www.ebay.com/sch/i.html?_fro...Desc=0&_sop=15
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Old 09-02-21, 09:11 AM
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Originally Posted by cat0020
Maybe wait a few more years?
German company Schaeffler has just revealed an entirely new drive system for electric bicycles that eschews traditional bike chains and belts for an entirely electrical-driven system. The new system is known as the Schaeffler Free Drive and marks the entry of one of the most divergent electric bicycle drivetrains we've seen in years....

https://electrek.co/2021/08/31/radic...GVMr186s4ij5Vs
uh, no. That isn't for bikes like this. I mean, you pedal, convert kinetic energy to electricity, run wires to the rear hub, and convert electricity back into kinetic energy? I don't think so. Maybe for a cargo bike, but still...
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Old 09-05-21, 04:57 PM
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Wait a few years:
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