The accuracy of cuckoo clocks.

I am often contacted by people who are having the problem of a cuckoo clock either gaining or losing time. The subtext of the question is usually “what the f am I doing wrong – surely the bloody thing tells the time as well as entertains”.

Well the answer is yes. In fact, a recently serviced, or even a not so recently serviced cuckoo clock, can be accurate to within the same tolerances as say, a medium priced mechanical clock. A minute or three out per week but easily adjusted for when you wind the clock up daily. One day cuckoo clocks are more accurate than most 30 hour mechanical wall clocks for instance. There are a few reasons for this.

Firstly the time gearing is well seated with thick pinions. They have a longer functional lifespan so the clock therefore remains in the same frictional dynamic for a stretched out period. About 25 years on a 20th century clock with servicing when performance starts to degrade. Generally that’s anything from 3 pet hair exposed years to a clean pollen free and clean room level of environment.

Secondly, the pendulum is made out of wood. Wood doesn’t stretch over time as metal does. It’s treated wood so it stays in shape and simply hardens over decades. Also wood isn’t known for its expansion under heat and the pendulum is so short it would need to expand like a balloon for it to make any real difference. Lastly the centre of gravity is simpler because the wooden pendulum rod, providing its the length the movement was designed for, is light. The bit that carries the momentum and mass is the wooden leaf shaped (normally) pendulum bob.

The last reason cuckoo clocks can be quite accurate is because they are so simple to adjust in terms of running fast or slow (regulating a clock). You just slide the leaf up and down until you work out exactly where the sweet spot is.

This is the point where you can’t quite work out if the clock is running a minute fast or a minute slow over one day. You can put up with a minute a day adjusted for. Fiddling could achieve watch level accuracy. Sometimes.

Regulation on an 8 day clock takes longer. It’s the same method but with the time difference check weekly when you pull the weights up. You could do it daily but let the pendulum settle into it’s normal arc of swing before starting the timer.

Anyway when you pull the weights up most people knock the pendulum, stop the clock and have to reset the time anyway. It’s just what happens. I do it all the time on test jobs which can be annoying. Just take it easy, like I don’t enough, when you pull the chain. Don’t try and do a Tarzan on it like the grandkids / nephews.

Lastly, because this blog is about insight and helping people ill tell you the method you use to quickly and accurately regulate any pendulum based clock. It’s called “the rule of dividing halves”. Google it.

Just remember that to use the rule, you have to know that moving the leaf up the wooden shift speeds up the swing and therefore the speed of the clock. Just remember “up,faster” and because they are superlative in nature you will remember.

Obviously the opposite applies for moving the leaf down. To be fair, if you didn’t already realise that I genuinely congratulate you on finishing this article.

Cuckoo clock repairs. How can this even be interesting to anyone.

Next time I’ll explain how cosmology works in relation to quantum physics and prove, on the basis of probability, the inevitability of what you mortals call God. Nobel prize stuff. Tune in.