How does an automatic watch hold a power reserve?

Question

And how does mere movement power it? Cheers

In: 3

Answer 1

Mechanical watches have a spring inside that you wind up, the spring then powers the movement throughout the day.

Automatic watches still use this same system, but instead of having to manually wind the spring everyday there is a heavy weight inside that spins freely as you move your hand. This weight is then attached to the winding spring system and effectively winds the watch as it spins around all day.

Many automatic watches have a glass window in the back and you can see this weight freely moving as you turn the watch.