Lars and I plan to build a sort of perpetual motion machine for the 2008 World Ice Art Championships. This is a simplified diagram of the mechanism, notably missing gear teeth. The big red thing is a heavy half gear that powers the sculpture. It is shown here nearly at the starting position. The weight of the half gear pulls it downward, turning the little red pinion as it goes. The red pinion is connected to the large yellow gear which turns the yellow pinion. The yellow pinion is connected to the large green flywheel.
Once the half gear completes a quarter turn to the bottom position, the flywheel should have enough angular momentum to keep the half gear moving until it slows to a stop opposite from its starting position. With any luck, the half gear will be high enough that gravity will pull it back toward the center position, repeating the whole process in reverse. Our goal is to produce oscillatory motion that lasts for as long as possible, perhaps a few minutes.