Mechanical watch

A mechanical watch is a watch that uses a mechanism to measure the passage of time, as opposed to modern quartz watches which function electronically. It is driven by a spring (called a mainspring) which must be wound periodically. Its force is transmitted through a series of gears to power the balance wheel, a weighted wheel which oscillates back and forth at a constant rate. A device called an escapement releases the watch's wheels to move forward a small amount with each swing of the balance wheel, moving the watch's hands forward at a constant rate. This makes the 'ticking' sound characteristic of all mechanical watches. Mechanical watches evolved in Europe in the 17th century from spring powered clocks, which appeared in the 15th century.

Mechanical watches are typically not as accurate as modern electronic quartz watches, and they require periodic cleaning by a skilled watchmaker. Since the 1970s, quartz watches have taken over most of the watch market, and mechanical watches are now mostly a high-end product, purchased for aesthetic reasons, appreciation of their fine craftsmanship, or as a status symbol.

The internal mechanism of a watch, excluding the face and hands, is called the movement. All mechanical watches have these five parts:

Additional functions on a watch besides the basic timekeeping ones are traditionally called complications. Mechanical watches may have these complications:

The mechanical watch is a mature technology, and most ordinary watch movements have the same parts and work the same way.

The mainspring that powers the watch, a spiral ribbon of spring steel, is inside a cylindrical barrel, with the outer end of the mainspring attached to the barrel. The force of the mainspring turns the barrel. The barrel has gear teeth around the outside that turn the center wheel once per hour — this wheel has a shaft that goes through the dial. On the dial side the cannon pinion is attached with a friction fit (allowing it to slide when setting the hands) and the minute hand is attached to the cannon pinion. The cannon pinion drives a small 12-to-1 reduction gearing called the motion work that turns the hour wheel and hand once for every 12 revolutions of the minute hand.

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