Remontoire
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In mechanical horology, a remontoire, (from the French remonter, meaning 'to wind') is a small secondary source of power, a weight or spring, which runs the timekeeping mechanism and is itself periodically rewound by the timepiece's main power source, such as a mainspring. In precision clocks and watches it is used to increase accuracy by evening out variations in drive force caused by the mainspring running down, or friction in the gear train. In turret clocks it serves to separate the large forces needed to drive the hands from the modest forces needed to drive the escapement which keeps the pendulum swinging.
Remontoires are designed to rewind frequently, at intervals of 15 seconds to an hour. The rewinding process is triggered automatically when the remontoire's weight or spring reaches the end of its power. The remontoire and the clock's timekeeping mechanism together can be thought of as a 'subclock'. The only force applied to the timekeeping mechanism is that of the remontoire's spring or weight, so it is isolated from any variations in the main power source. Variations in the remontoire's force may cause short term variations in the clock's rate, but because of the frequent rewinding these are averaged out and have no effect on the clock's long term rate.[1]
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[edit] Types
- A gravity remontoir is one that uses a weight for power. It is used in precision pendulum clocks.
- A spring remontoir uses a spring. It is the only type which can be used in watches, since the force of a weight would be disturbed by motions of the wearer's wrist
- An electric remontoir is one in which the spring or weight is rewound electrically, with a motor or solenoid. It is used in clocks with traditional mechanical movements which are run on electricity.
A remontoir should not be confused with a maintaining power spring, which is used only to keep the timepiece going while it is being wound.
[edit] Electric remontoires in automobile clocks
Before the common use of electronic clocks in automobiles a low energy power spring would be wound every few minutes by the short motion action of a solenoid, powered by the vehicle's service battery and activated by a simple switch upon low power spring tension. Such clocks were, however, notoriously inaccurate, typically being made as cheaply as possible.
