Automatic Transmission

Came across this in the shop the other day. It's an auto shifting bike. I've certainly seen bikes that shift on their own before, the Trek Lime for example. The front hub of that bike measure the bike's speed and electronically shifts an internally geared hub at the back. It only has three gears but the transitions are quick and nearly seamless.

This bike on the other hand is automatic in an entirely mechanical fashion. Three black plastic pieces on the rear spokes are connected to a disk that goes around the freewheel and rests right up against the rear derailleur. As the wheel spins faster and faster, the centrifugal force spreads the plastics tags further apart, which in turn force the disk to push on the derailleur towards a harder gear.

It's really cool to see it in motion so I took a video!

It's great on the upshifts but the downshifts take a wee bit longer, not exactly ideal when you're coming up to a hill. Still though this is all controlled by the wheel, there are no shifters on the bike and the only thing we're doing in this video is turning the crank