How do mechanical (automatic) watches keep time exactly when springs exert different amounts of force depending on how tightly wound they are?

Question

I know that mechanical watches have a spring that they wind to store energy, and un-winding the spring produces energy for the watch. But a spring produces a lot of force when it’s very tightly wound, and very little when it’s almost completely un-wound. So how does the watch even that out with high precision?

In: 95

Answer 1

The spring in a watch isn’t like a typical helical spring one normally thinks of, it’s a wrapped up coil of metal. Think of a tiny flat strip wound up really tight. As you wind it it exerts a force. The neat thing is that the elastic force is mostly linear as long as it’s not completely uncoiled.