Fixing the cuckoo clock

 

The cuckoo clock works by pulling up a weight on a chain. As the weight falls, gravitational stored energy is transferred to the pendulum which would otherwise lose energy due to friction and air resistance. The problem was that the pendulum kept stopping. I noticed that if I pulled gently on the hanging weight, the tick was louder and it didn't stop so I added an improvised weight as water in a bottle so that it could be changed to find the correct amount. Apparently using a bigger weight is a known way of making an elderly cuckoo clock last for a few years more. I'm not sure how the gravitational energy gets to the pendulum - there could be a spring involved or maybe it is a gear mechanism that is getting worn.