How to add energy to a spring system?

 I need to make a metronome out of a spring and mass system, one that has a mass on a vertical spring that goes up and down. Here's the catch: it needs to be accurate for more then 2 minutes, so I want to find a way to maybe hit the spring just a bit so that it will keep going. But, I don't have any access to a motor, or electrical source. Does anyone know how to do this? Like mechanically? I was thinking like how a clock conserves energy, but mine moves vertical.

kelseymh7 years ago
Clocks aren't perpetual motion machines -- left to their own devices, they would slow down through friction.  Large pendulum clocks (grandfather clocks) have a weight-and-pulley system which puts energy back into the pendulum, compensating for friction.  Smaller mechanical clocks and watches have springs which do the same thing (and which themselves have to be wound tight).

For your project, you probably want something similar to the gravity escapement used in grandfather clocks.  You should be able to look up those terms in Wikipedia, or look for "build your own clock" plans.
+1. "Escapement" is the key word.
You've answered your own question, you're making a metronome, now they will tick for hours on a single wind. Wonder how they do it ???