I thought about the two speed version, and after evaluating the single speed version that I tried out a while back, I wouldn't be happy without assist capabilities over a wide range covering very low speeds to relatively fast speed over 20mph. That might be something like 6:1 variability, which I wouldn't want in just two steps.
The design that I have been thinking about lately has the drive wheel on the motor being able to move higher or lower on the multidiameter drive roller, which itself can move left or right on the bike tire. This dual action can give the much wider reduction range that provides low speed grunt while not limiting top speed assist much. However I'm thinking now that freewheeling should be included in the assembly to prevent pedaling energy having to turn the drive, even though that wouldn't allow it to provide braking.
If that dual action mechanism were to be used on a three stage roller, if I figure right, that should give five speeds. (On a two stage roller, it would give three speeds.) I haven't figured out an easy way to do it on my bike, however. I have a strong feeling that I won't be going anywhere with building it this year.
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