Remontoire
Encyclopedia
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
. It was used in precision clock
s and watch
es to place the source of power closer to the escapement
, thereby increasing the accuracy by evening out variations in drive force caused by unevenness of the friction
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. In turret clock
s 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. 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.
or balance wheel
, is never isochronous
; that is its rate is affected by changes in the drive force applied to it. In spring driven timepieces, the drive force declines as the mainspring
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. In turret 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 remontoire 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.
(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. 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 H2 marine chronometer
in 1739. Harrison's working drawing of the device is preserved in the Library of the Worshipful Company of Clockmakers in London, England.
Many French and Swiss pocketwatches 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). Etymologically 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.
They can also be classified by where in the wheel train the remontoire is located:
, 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.
Horology
Horology is the art or science of measuring time. Clocks, watches, clockwork, sundials, clepsydras, timers, time recorders and marine chronometers are all examples of instruments used to measure time.People interested in horology are called horologists...
, a remontoire, (from the French remonter, meaning 'to wind') is a small secondary source of power, a weight or spring
Spring (device)
A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...
, which runs the timekeeping mechanism and is itself periodically rewound by the timepiece's main power source, such as a mainspring
Mainspring
A mainspring is a spiral torsion spring of metal ribbon that is the power source in mechanical watches and some clocks. 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...
. It was used in precision clock
Clock
A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece...
s and watch
Watch
A watch is a small timepiece, typically worn either on the wrist or attached on a chain and carried in a pocket, with wristwatches being the most common type of watch used today. They evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were...
es to place the source of power closer to the escapement
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
, thereby increasing the accuracy by evening out variations in drive force caused by unevenness of the friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
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. In turret clock
Turret clock
A Turret clock is a clock mounted in a tower or turret, usually to show the current time on a dial with hand or to announce the time by strike, or both. It can also have more than one dial to show days, moon phases, and other astronomical data.-Sundials:...
s it serves to separate the large forces needed to drive the hands from the modest forces needed to drive the escapement
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
which keeps the pendulum
Pendulum
A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position...
swinging. A remontoir should not be confused with a maintaining power
Maintaining power
In horology, a maintaining power is a mechanism for keeping a clock or watch going while it is being wound.-Huygens:The weight drive used by Christiaan Huygens in his early clocks acts as a maintaining 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 pendulumPendulum
A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position...
or balance wheel
Balance wheel
The balance wheel is the timekeeping device used in mechanical watches and some clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral spring, the balance spring or hairspring...
, is never isochronous
Isochronous
Isochronous : From Greek iso, equal + chronos, time. It literally means regularly, or at equal time intervals. In general English language, it refers to something that occurs at a regular interval, of the same duration; as opposed to synchronous which refers to more than one thing happening at the...
; that is its rate is affected by changes in the drive force applied to it. In spring driven timepieces, the drive force declines as the mainspring
Mainspring
A mainspring is a spiral torsion spring of metal ribbon that is the power source in mechanical watches and some clocks. 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...
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. In turret clock
Turret clock
A Turret clock is a clock mounted in a tower or turret, usually to show the current time on a dial with hand or to announce the time by strike, or both. It can also have more than one dial to show days, moon phases, and other astronomical data.-Sundials:...
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
Escapement
In mechanical watches and clocks, an escapement is a device that transfers energy to the timekeeping element and enables counting the number of oscillations of the timekeeping element...
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 remontoire 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.
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 for William IV, Landgrave of Hesse-KasselWilliam IV, Landgrave of Hesse-Kassel
William IV of Hesse-Kassel , also called William the Wise, was the first Landgrave of Hesse-Kassel . He was the founder of the oldest line, which survives to this day.-Life:...
(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. 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
John Harrison
John Harrison was a self-educated English clockmaker. He invented the marine chronometer, a long-sought device in solving the problem of establishing the East-West position or longitude of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age...
during development of his H2 marine chronometer
Marine chronometer
A marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation...
in 1739. Harrison's working drawing of the device is preserved in the Library of the Worshipful Company of Clockmakers in London, England.
Many French and Swiss pocketwatches 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). Etymologically 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.
Types
Remontoires are distinguished by their power source:- A gravity remontoire is one that uses a weight for power. It is used in precision pendulum clockPendulum clockA pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is a resonant device; it swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates...
s. - A spring remontoire 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 remontoire can be either a gravity or spring type. In it, the weight or spring is rewound electrically, with a motor or solenoidSolenoidA solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...
. It is used in clocks with traditional mechanical movements which are run on electricity.
They can also be classified by where in the wheel train the remontoire is located:
- An escapement remontoire applies its force directly to the escape wheel of the escapement. Spring remontoires were usually this type.
- A train 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 solenoidSolenoid
A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create...
, 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.