Just wanted to add these two pictures, as close-ups of the shifting mechanism. There are three weights that slide outwards , by centrifugal force, as the wheel spins faster, and moves a black plastic disk, to push the chain into a higher gear. The counterweights slide on the spokes. I think there are two or three threads with the Autobike, and I used these photos in one of the other threads. I think it best to compile them here.