- Remontoire
In mechanical
horology , a remontoire, (from the French "remonter", meaning 'to wind') is a small secondary source of power, a weight orspring , which runs the timekeeping mechanism and is itself periodically rewound by the timepiece's main power source, such as amainspring . In precisionclock s andwatch es it is often used to place the source of power closer to theescapement thereby increasing the accuracy by evening out variations in drive force caused by unevenness of thefriction in the geartrain. In spring-driven precision clocks a gravity remontoire is often used to replace the uneven force delivered by the mainspring running down by the more constant force of gravity acting on a weight. Inturret clock s it serves to separate the large forces needed to drive the hands from the modest forces needed to drive theescapement which keeps thependulum swinging. A remontoir should not be confused with amaintaining power spring, which is used only to keep the timepiece going while it is being wound.How it works
Remontoires are used because the timekeeping mechanism in clocks and watches, the
pendulum orbalance wheel , is neverisochronous ; that is its rate is affected by changes in the drive force applied to it. In spring driven timepieces, the drive force declines as themainspring runs down. In weight driven clocks the drive force, provided by a weight suspended by a cord, is more constant, but imperfections in the gear train and variations in lubrication also cause small variations. Inturret clock s, the large hands, which are attached to the clock's wheel train, are exposed to the weather on the outside of the tower, so winds and accumulations of ice and snow apply disturbing forces to the hands, which are passed on to the wheel train.With a remontoire, the only force applied to the clock's
escapement is that of the remontoire's spring or weight, so that it is isolated from any variations in the main power source or wheel train, which is just used to rewind the remontoire. 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. This frequent rewinding is another source of accuracy, because it averages out any variations in the clock's rate due to changes in the force of the remontoire itself. If the rate of the clock varies as the remontoir spring runs down, this variation will be repeated again and again, each time the remontoire goes through its cycle, so it will have no effect on the long term rate of the clock. [cite encyclopedia
title = Clocks
encyclopedia = Encyclopedia Britannica, 11th Ed.
volume = 6
pages =
publisher = The Encyclopedia Britannica Co., Cambridge
date = 1910
url = http://books.google.com/books?id=6jcEAAAAYAAJ&pg=PA544&dq=remontoire
id =
accessdate = 2008-06-08 p.543-544]History
The gravity remontoire was invented by Swiss clockmaker
Jost Burgi around 1595. Usually the "Kalenderuhr" (Three month running, springdriven, calendar-desk-clock) Burgi made forWilliam IV, Landgrave of Hesse-Kassel (or Hesse-Cassel) (Now Inventory No. U 47 at the Naturwissenschaftlich-Technische Sammlung in Kassel) is considered the oldest surviving clock with a remontoire, even if it does not provide power to the escapement during the few seconds of the daily cycle where the remontoire weight gets wound up by the spring. [Karsten Gaulke: Der Ptolemãus von Kassel; Kassel: 2007; ISBN 978-3-931787-43-1, Page 143 ] Today remontoire mechanisms are all designed to deliver power to the escapement during the remontoire reset cycle.The spring remontoire was invented by English clockmaker
John Harrison during development of his H2marine chronometer in 1739.Many French and Swiss
pocketwatch es after 1860 were stamped on the back with the word "Remontoire". This merely meant that it didn't have to be wound with a key (i.e. they were wound by the then novel winding crown inside the pendent). Ethymologically the term is correct, the mainspring is "rewound" by some other force than a key, but these watches usually do not contain a remontoire as the word is used today. [cite web
last = Fried
first = Henry B.
authorlink =
coauthors =
title = What is a remontoire?
work = Modern Masterpieces of Horology
publisher = Heritage, Jeweler's Circular Keystone, Cahner's Business Information
date = July 1995
url = http://jck.polygon.net/archives/1995/07/0795horo.html
format =
doi =
accessdate = 2008-06-23]Types
Remontoirs are distinguished by their power source:
*A "gravity remontoir" is one that uses a weight for power. It is used in precisionpendulum clock s.
*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" can be either a gravity or spring type. In it, the weight or spring is rewound electrically, with a motor orsolenoid . It is used in clocks with traditional mechanicalmovement s which are run on electricity. They can also be classified by where in the wheel train the remontoire is located:
*In an "escapement remontoire" the remontoire applies its force directly to the escape wheel of the escapement. Spring remontoires were usually this type.
*In a "train remontoire" the remontoire applies its force to one of the wheels upstream from the escapement, usually to the wheel that drives the escape wheel.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.Footnotes
External links
* http://www.my-time-machines.net/wagner_detail.htm
* http://www.antiquorum.com/html/vox/vox2002/remontoire/remontoire.htm
Wikimedia Foundation. 2010.