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.