There is a set of bike pedals attached to each seat. The chain on each one drives a sprocket attached to the chair’s pivot point. Spinning the pedals tilts the chair and the entire frame reacts by rotating. They only had one set of pedals attached, but it was more than enough to spin the wheel at a pretty good clip. It did look like some damping on the chair pivots would help, since the chairs would swing pretty wildly. I’m sure adding two more chairs would help as well.