How do Rolex watches spin without batteries?
In: Technology
There are two key mechanisms that make a watch work.
The first is what’s known as an [escapement](https://en.wikipedia.org/wiki/Escapement). This is a device that allows a very slow unwinding of a spring, harvesting a bit of that spring’s energy with each tick. That’s the device that governs the actual ticking action of a watch.
The second is a [balance wheel](https://en.wikipedia.org/wiki/Balance_wheel). This is a lot like a pendulum, but instead of a weight that sways back and forth and is pulled towards the center by gravity (as in a grandfather clock) it’s a ring with weights that spins forward and in reverse, being pulled back into position by a spring. The period of this oscillation is extremely consistent and is based on the stiffness of the spring and the mass of the wheel.
Those two pieces can be combined to keep time: the balance wheel oscillates forward and reverse, with each half stroke allowing the escapement to advance a half tick. A stiff spring gives the balance wheel a small kick as the escapement advances, making sure the balance wheel doesn’t stop. As the escapement advances it is hooked up to progressive gears which convert the frequency of the ticks into the motion of the second, minute, hour, and date indicators.
There are various refinements to this design that super luxury watchmakers like Rolex use, but the fundamental concept remains the same.
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