Clockwork refers to the inner workings of either a mechanical clock (where it is also called a movement) or another device that operates in a similar fashion (such as a dial indicator). Specifically, the term refers to mechanisms utilizing a complex series of gears. One of the earliest known examples of a clockwork mechanism is the Antikythera mechanism, a first-century BC geared astrolabe device for calculating star positions, recovered from a Greek shipwreck.
A clockwork motor is a clockwork device mechanically powered by a mainspring, a spiral torsion spring of metal ribbon. Energy is stored in the mainspring manually by winding it up, turning a key attached to a ratchet which twists the mainspring tighter. Then the force of the mainspring turns the clockwork's gears, until the stored energy is used up. The adjective wind-up refers to mainspring-powered clockwork devices, which include clocks and watches, kitchen timers, music boxes, and wind-up toys.
Often power for the device is stored within it, via a winding device that applies mechanical stress to an energy-storage mechanism such as a mainspring, thus involving some form of escapement; in other cases, hand power may be utilized. The use of wheels, whether linked by friction or gear teeth, to redirect motion or gain speed or torque, is typical; many clockworks have been constructed primarily to serve as visible or implicit tours de force of mechanical ingenuity in this area. Sometimes clocks and timing mechanisms are used to set off explosives, timers, alarms and many other devices.
The most common examples are mechanical clocks and watches. Others include:
- Wind-up toys – often as a simple mechanical motor, or to create automata. These may be either key-wound, or a simpler pullback motor.
- Most leaf shutters use a clockwork mechanism not unlike that of wristwatches to time the opening and closing of the shutter blades.
- Mechanisms to turn the lens of lighthouses before electric motors.
- Mechanical calculators, used before electronic computers were developed around World War II. Among the most complex were Babbage's difference and analytical engines, which were mechanical versions of computers.
- Astronomical models, such as orreries whose history spans hundreds of years.
- Music boxes, which were very popular during the 19th century and at the beginning of the 20th.
- Almost all phonographs built before the 1930s.
- Hand-powered electrical equipment, such as a clockwork radio, where an energy-storing spring accounting for much of the size and weight of the device spins a much smaller electric generator; such equipment is very popular where batteries and mains power (house current) are scarce.
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