This clock displays the time by the number of ball bearings on the balances. A ball bearing comes out of the top every 15 seconds and goes onto the top balance. Every minute this balance overbalances and one ball goes down to the next balance and the rest go down to the bottom. The other balances overbalance every 5 minutes, 1 hour and 12 hours respectively. The clock is driven by a mains synchronous motor which through gearing and a series of cranks pushes one ball up into the ball lift every 15 seconds. A pawl prevents the balls falling back down again.
This is a very good exhibition model and always attracts attention from the public.
It is based on the model shown in Constructor Quarterly issue 22 but I added an additional balance at the top to provide more interest at exhibitions.