{{unreferenced, date=September 2009 Used in mechanical watches and

clock A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and t ...

s, a barrel is a cylindrical metal box closed by a cover, with a ring of gear teeth around it, containing a spiral spring called the

mainspring 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 ...

, which provides power to run the timepiece. The barrel turns on an arbor (axle). The spring is hooked to the barrel at its outer end and to the arbor at its inner end. The barrel teeth engage the first pinion of the

wheel train In horology, a wheel train (or just train) is the gear train of a mechanical watch or clock. Although the term is used for other types of gear trains, the long history of mechanical timepieces has created a traditional terminology for their gear tr ...

of the watch, usually the center wheel. Barrels rotate slowly: for a watch mainspring barrel, the rate is usually one rotation every 8 hours. This construction allows the mainspring to be wound (by turning the arbour) without interrupting the tension of the spring driving the timepiece.

Types

; Plain barrel: I.e. without teeth, used in fusee watches and clocks. A chain, or cord, was wound around the plain barrel, connecting it to the fusee. ; Going barrel: The form used in modern watches, is wound by turning the arbor and drives the watch movement by a ring of teeth around the barrel. This enables the mainspring to continue running the watch while it is being wound. Invented by

Jean-Antoine Lépine Jean-Antoine Lépine (L’Pine, LePine, Lepine, L’Epine), born as Jean-Antoine Depigny, was an influential watchmaker. He contributed inventions which are still used in watchmaking today and was amongst the finest French watchmakers, who were c ...

. ; Hanging barrel: A version of the going barrel that to save space is supported by the movement only at its upper end. ; Motor, or safety, barrel: Used in

pocket watch A pocket watch (or pocketwatch) is a watch that is made to be carried in a pocket, as opposed to a wristwatch, which is strapped to the wrist. They were the most common type of watch from their development in the 16th century until wristw ...

es around 1900, a reverse variant of the going barrel in which the spring is wound by turning the barrel, and turns the watch movement by the central arbor. The purpose of this arrangement was that if the spring breaks, destructive recoil forces would not be applied to the vulnerable

gear train A gear train is a mechanical system formed by mounting gears on a frame so the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission ...

References

External links

FH glossary
Timekeeping components