I built this clock in response to the Secretaries Challenge — to make a model using only curved or circular parts. I also chose to make the mechanism as simple as possible.
The time-keeping is achieved using a 5 RPM mains synchronous motor so will keep as good a time as the electric company maintains the mains sine wave cycles. A 5:1 reduction in the base causes one of the vertical shafts to rotate at 1 RPM and the drive is then taken off at 60:1 reduction via worm gear and 60T gear to the minute hand. The hour hand is conventionally driven by a 3:1 and 4:1 reduction train. A ratchet and pawl were added — hidden in the base — to give the clock a satisfying tick.