boinbgboing: ' Christopher Blasius sells plans (€40) to make a Serpina "rolling ball clock" whose timekeeping is accomplished by rolling a ball around a laser-cut wooden frame, causing the frame to see-saw and sending the ball in the opposite direction.

These clocks are popular collectors' items. It makes just fun to watch the ball, rolling down his way and then to see how the Seesaw starts the process all over again. It was not without reason that these clocks were formerly in shop windows to impress pedestrians. Your friends and visitors will be impressed, too.

Rolling ball clocks are primarily great entertainers. Although Galileo Galilei already discovers, that a ball needs on an inclined plane always the same time for the same distance. In practice, however, all rolling ball clocks have a problem with the accuracy, because dust on the seesaw destroys the theory.

The name Serpina is a modification of serpentine and refers to the path traveled by the ball when rolling down the seesaw. '