In the process of making a bicycle chain clock for the STEM room at a primary school.
AC synchronous motor, laser-cut MDF gears (not cut at SLMS!)
The AC motor (12v for safety!) spins at a constant 5rpm - well, with UK 50Hz mains, anyway. I had to find a ‘real’ transformer to supply the 12v - so many so-called lighting transformers are in reality electronic-based.
The compound gear chain reduces the speed to 1 revolution per hour. The tooth the bicycle chain is running on has 10 teeth, and there are 10 links between each number on the chain - so one number passes by per hour. This photo shows about 10 past three.
It’s quite pleasing in reality - I should upload some video. The motor spins at a nicely visible speed, and the gear chain gradually slows from there until the final gear is hardly visibly moving at all.