Clockwork refers to the inner workings of either mechanical devices called clocks and watches (where it is also called the movement) or other mechanisms that work similarly, using a series of gears driven by a spring or weight.
A clockwork mechanism is often powered by a clockwork motor consisting of 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 gears, until the stored energy is used up. The adjectives wind-up and spring-powered refer to mainspring-powered clockwork devices, which include clocks and watches, kitchen timers, music boxes, and wind-up toys.
The earliest known example of a clockwork mechanism is the Antikythera mechanism, a first-century BC geared analogue computer, somewhat astrolabe-like, for calculating astronomical positions and eclipses, recovered from a Greek shipwreck. There are many other accounts of clockwork devices in Ancient Greece, even in its mythology, and the mechanism itself is sophisticated enough to indicate a significant history of lesser devices leading up to its creation.
At some point, this level of sophistication in clockwork technology was lost or forgotten in Europe, and only returned when brought from the Islamic world after the Crusades, along with other knowledge leading to the Renaissance. Clockwork finally recovered the equivalent of pre-Roman technological levels in the 14th century.
As in Greek mythology, there are ambitious automation claims in the legends of other cultures. For example, in Jewish legend, Solomon used his wisdom to design a throne with mechanical animals which hailed him as king when he ascended it; upon sitting down an eagle would place a crown upon his head, and a dove would bring him a Torah scroll. It's also said that when King Solomon stepped upon the throne, a mechanism was set in motion.
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A spring is a device consisting of an elastic but largely rigid material (typically metal) bent or molded into a form (especially a coil) that can return into shape after being compressed or extended. Springs can store energy when compressed. In everyday use the term often refers to coil springs, but there are many different spring designs. Modern springs are typically manufactured from spring steel. An example of a non-metallic spring is the bow, made traditionally of flexible yew wood, which when drawn stores energy to propel an arrow.
An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy to the clock's timekeeping element (usually a pendulum or balance wheel) to replace the energy lost to friction during its cycle and keep the timekeeper oscillating. The escapement is driven by force from a coiled spring or a suspended weight, transmitted through the timepiece's gear train.
A mainspring is a spiral torsion spring of metal ribbon—commonly spring steel—used as a power source in mechanical watches, some clocks, and other clockwork mechanisms. Winding the timepiece, by turning a knob or key, stores energy in the mainspring by twisting the spiral tighter. The force of the mainspring then turns the clock's wheels as it unwinds, until the next winding is needed. The adjectives wind-up and spring-powered refer to mechanisms powered by mainsprings, which also include kitchen timers, metronomes, music boxes, wind-up toys and clockwork radios.
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