[KenWittlief]

I was thinking instead of making it infinately variable, you could use the same concept and have maybe 3 wheels (three speeds).

This would also allow you to make the smaller diameter wheels have wider treads, for more traction, and have the taller wheels wearing skinny tires.

and you could angle each of the three wheels to keep the tread parallel to the floor when it is rotated into positionl