The escape wheel is the last wheel in a watch or clock movement. It has notched teeth that the escapement catches and releases in time with the swing of the balance or pendulum. This is where the power of the spring or weight is let out, a little at a time.
How does an escape wheel work?
The escape wheel sits at the end of the wheel train. In a lever watch, the train passes the turning force of the mainspring through gears to the escape wheel. Left alone, the wheel would simply spin. The anchor of the escapement stops that. It catches a tooth, then lets it go, over and over. Each release lets out a small amount of energy. This is how the escape wheel controls the energy coming from the mainspring. The wheel spends most of its time locked. Even so, it turns on average at about 10 revolutions per minute or faster.
What does an escape wheel look like in a lever watch?
In the lever escapement, a typical escape wheel has 15 teeth. With rare exceptions, it is made of steel. The teeth come in two shapes: ratchet-shaped or club-shaped. Either way, they act on the two pallet jewels of the lever. Some makers have moved to a different material. Ulysse Nardin brought out a watch with a silicon escape wheel in 2001. Patek Philippe followed in 2005, and Zenith in 2013.
Where it comes from
The escape wheel is as old as the mechanical escapement itself. The earliest known kind, the verge, was invented in Europe in the 13th century. It was the first fully mechanical escapement. Its escape wheel was shaped like a crown, which is why the verge is also called the crown wheel escapement. The escape wheel is also called the lever wheel.
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