I wanted to make a bot with this circuit that could swing a full 360°, using some hard drive magnets and the Solarbotics “Major Henry” coil. My first attempt used a stripped CD-ROM motor for the axle, but that had too much damping (even after removing the magnets). I ended up using a VCR pinch roller, which has a very free-rotating bearing (but had to be laboriously stripped of its rubber wheel).
I was lucky to find a hard drive magnet pair in a frame, from an older hard drive. The vertical chassis is from an old VCR. The body of the rotating part is a hard drive head mechanism, which happened to fit nicely over the pinch roller hub. The circuit is mounted on this arm, with some care taken to balance it so that the arm can swing all the way around given enough force.
This is a fun bot to watch. In bright light, it starts swinging almost immediately, and after a few swings just makes it to the top, then over. After that it’ll keep rotating all the way around.