> The approach I adopted is mechanically as simple as you can get. It uses an "outrunner" motor designed for electric skateboards. With such outrunners, the cas

> The approach I adopted is mechanically as simple as you can get. It uses an "outrunner" motor designed for electric skateboards. With such outrunners, the case of the motor rotates. Driving the bike with it merely requires mounting it to the frame in such a way that the case is in contact with the rear wheel. I haven't crunched the numbers, but this[0] Low Tech Magazine article from 2011 about the reverse process (generating electricity with stationary bikes) gives me the impression this adds quite a bit of inefficiency to this set-up: > One reason [for inefficiencies] is the use of a so-called friction drive - the rear bicycle wheel acts upon the small roller of the motor/generator. While chain and belt drives (used in late 19th century pedal powered machines) have an efficiency of up to 98 percent, a friction drive is only 80 to 90 percent efficient (and wears much faster). Whether or not you think that this is important is a different discussion of course, but I think 10-20% less range is quite significant. [0] https://www.lowtechmagazine.com/2011/05/bike-powered-electricity-generators.html https://www.lowtechmagazine.com/2011/05/bike-powered-electri...