[jyl]

Hey, I noticed something else - tell me if this sounds correct.

If this drive produces constant force (20 N) all the time that it is turned "ON", then it produces constant acceleration all the time. Whether you want it or not. When you are coasting fast down a steep incline, when you are holding position amidst other riders in the peloton, when you are trying to slow down for a turn - you don't want acceleration, but you will get it anyway. It is like a car with a stuck throttle. The only way to stop the constant 20 N is to turn the drive off. But when the drive is turned off, the wheel is very imbalanced as discussed above.