Running a 750W BBS02 through a nexus or Rolhoff hub?

NeilP

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I have a potential conversion to do on a bike with a internal gear rear hub.

I thought it was a rolhoff..but now thing it may be a Nexus....would a BBS02 be too much for these hubs?

maybe go down or run the units at a lower power level..for an older lady, so no need for speeds about 20 mph or high celebration levels
 
It all depends on the torque out of the BBS02's output into the hub's input. As long as you don't exceed whatever Nm limit they've got on that, it'll be ok. I don't know what hte limit is, though, or what the torque output of the BBS02 is, but it's possible someoen else has already determined those in another thread here on ES (a quick search didn't find it, though).

Limiting the current on the controller (potentially by cutting a shunt if there are several, as one easy method) could help control your torque, or if it is programmable for different phase currents, that would be better.


Altering the gearing ratio of the BBS02's output to the hub's input would also help fix it, by letting it have a faster top speed but a lower torque level.
 
Don't know about the Nexus, but Rohloff specifies gear ratios of at least 2.35:1 for single use or 2.55:1 for tandems or heavy riders. If your rider and drive are both operating at fairly low power, I'm sure the tandem specs would be fine, which means that with the 48t sprocket you could use a sprocket with 18 teeth or fewer.

The Rohloff doesn't shift easily under load, so your rider will need to get used to interrupting the motor torque when shifting, either by touching the brake, which is followed by a pretty long delay before the motor reengages, or by lightly touching the throttle, which allows faster recovery but takes some practice so you don't use too much throttle and end up with more torque than you would have had with the PAS.
 
I am guessing the shifting of the Nexus will be similarly difficult.

The lady has enough difficult with gear shifting with dereailleur, so went with the internal hub s it means you can shift once stopped, she never got that right with the derailleur.
I think that may be a bit too complicated for her.

There were auto hubs available..how do they cope with this sort of system?
 
I'm running an 8 speed Alfine hub with no problems, don't have the brake switches as the brakes on the bike are hydro's. Just stop pedaling as you would normally when changing gears and it works fine. If using the throttle just back off, change cogs and get back on it, works fine.
 
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