Here’s a perpetual motion machine. It has 16 rare earth magnets. The rotor has all the north sides of the magnets pointing out. The stator has all the north sides of the magnets pointing in. It has a precision ball bearing and is made from nylon bolts and hardboard.
I used Google Sketchup to design the parts. I then laser cut the parts during the talk I did for the Inventors Association the other day. The whole thing just bolts together and the bearing is held in place by friction.
The original plan was that the magnets would be in pairs and would hold each other in place by friction. That didn’t work well because the distance between the pairs was a little large and the 1/8th material doesn’t have enough surface area to get good stability. So I just used a glue gun to stick the magnets on. That worked pretty well.
It turns out to be pretty cool. There is some fairly strong cogging since the magnets come within about 3/32″ of each other.
Interestingly, there are two stable resting points. One is before the magnets pass each other and the other is right after. Intuitively I was betting on one stable resting point that is with the magnets all as far apart as possible. I suppose the attraction of the other poles gets in there and creates two local minimums in the potential energy curve.