- Pierre Le Roy chronometer, 1766, Musée des Arts et Métiers
- Pierre Le Roy chronometer, 1766
- Pierre Le Roy chronometer mechanism
- Plans of Le Roy chronometer
|Pierre Le Roy|
|Died||26 August 1785 (aged 67–68)|
Pierre Le Roy (1717–1785) was a French clockmaker. He was the inventor of the detent escapement, the temperature-compensated balance and the isochronous balance spring. His developments are considered as the foundation of the modern precision clock. Le Roy was born in Paris, eldest son of Julien Le Roy, a clockmaker to Louis XV who had worked with Henry Sully,in which place Pierre Le Roy succeeded his father. He had three brothers: Jean-Baptiste Le Roy (1720-1800), a physicist; Julien-David Le Roy (1724–1803), an architect; and Charles Le Roy (1726–1779), a physician and encyclopédiste.
In 1748, he invented a pivoted detent type of escapement,or detached escapement, which makes him the inventor of the detent escapement: "The invention of the detached escapement belongs to P. Le Roy". This should not be confused with the detached ‘lever’ escapement which was invented by Thomas Mudge circa 1755.
He was distinguished principally in his mastery and improvement of the clock and chronograph, above all of the marine chronometer, in which he carried forward the pioneering work of John Harrison. He took a different approach from that of Harrison, believing that the way to achieve seaworthiness was to detach the escapement from the balance.He also differed from Harrison regarding his temperature compensation method, which used the variation of the rotation radius of the balance by modifying the diameter of the balance through bi-metallic components, a method which would become a standard in chronometers. His technique for temperature compensation was highly efficient in that it worked without changing the length of the spiral balance spring, which he had discovered to be isochronous only at a precise given length (i.e. when frequency is independent of amplitude, so that a mechanical clock or watch runs at the same rate regardless of changes in its drive force, so it keeps correct time as the mainspring unwinds).
After having designed plans in 1754, he constructed his first chronometers by 1756, and accomplished his masterpiece in 1766.This remarkable chronometer incorporated a detached escapement, a temperature-compensated balance and an isochronous balance spring, innovations which would be adopted in subsequent chronometers. Harrison demonstrated a reliable chronometer at sea, but these developments by Le Roy are considered by Rupert Gould to be the foundation of the modern chronometer. Pierre Le Roy's chronometer had a performance equivalent to that of the Harrison H4 chronometer.
In 1769, after his chronometre underwent testing aboard the corvette Aurore, he was awarded the double prize offered by the Académie française for the best method of measuring time at sea. He succeeded in giving his instruments the greatest possible regularity by the discovery of the isochronous spiral spring, in which he was in competition with Ferdinand Berthoud, but which he published first.
He was the author of several valuable publications on the art and science of clock-making and chronography, among them the Étrennes chronométriques of 1760. He also became Horloger du Roi in 1760.
The work of Le Roy was not fully recognized in France however, and his contemporary Ferdinand Berthoud became more famous, obtaining the prestigious title of Horloger de Marine, which left Le Roy disillusioned and led him to retire.He died in Vitry in 1785.
John Harrison was a self-educated English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of calculating longitude while at sea.
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 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. Each swing of the pendulum or balance wheel releases a tooth of the escapement's escape wheel, allowing the clock's gear train to advance or "escape" by a fixed amount. This regular periodic advancement moves the clock's hands forward at a steady rate. At the same time, the tooth gives the timekeeping element a push, before another tooth catches on the escapement's pallet, returning the escapement to its "locked" state. The sudden stopping of the escapement's tooth is what generates the characteristic "ticking" sound heard in operating mechanical clocks and watches. The first mechanical escapement, the verge escapement, was invented in medieval Europe during the 13th century, and was the crucial innovation which led to the development of the mechanical clock. The design of the escapement has a large effect on a timepiece's accuracy, and improvements in escapement design drove improvements in time measurement during the era of mechanical timekeeping from the 13th through the 19th century.
Ferdinand Berthoud, was a scientist and watchmaker. He became master watchmaker in Paris in 1753. Berthoud, who held the position of Horologist-Mechanic by appointment to the King and the Navy, left behind him an exceptionally broad body of work, in particular in the field of sea chronometers.
A balance wheel, or balance, is the timekeeping device used in mechanical watches and small 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 torsion spring, known as the balance spring or hairspring. It is driven by the escapement, which transforms the rotating motion of the watch gear train into impulses delivered to the balance wheel. Each swing of the wheel allows the gear train to advance a set amount, moving the hands forward. The balance wheel and hairspring together form a harmonic oscillator, which due to resonance oscillates preferentially at a certain rate, its resonant frequency or 'beat', and resists oscillating at other rates. The combination of the mass of the balance wheel and the elasticity of the spring keep the time between each oscillation or ‘tick’ very constant, accounting for its nearly universal use as the timekeeper in mechanical watches to the present. From its invention in the 14th century until tuning fork and quartz movements became available in the 1960s, virtually every portable timekeeping device used some form of balance wheel.
Thomas Earnshaw was an English watchmaker who, following John Arnold's earlier work, further simplified the process of marine chronometer production, making them available to the general public. He is also known for his improvements to the transit clock at the Royal Greenwich Observatory in London and his invention of a chronometer escapement and a form of bimetallic compensation balance.
John Arnold was an English watchmaker and inventor.
Used in antique spring-powered mechanical watches and clocks, a fusee is a cone-shaped pulley with a helical groove around it, wound with a cord or chain which is attached to the mainspring barrel. Fusees were used from the 15th century to the early 20th century to improve timekeeping by equalizing the uneven pull of the mainspring as it ran down. Gawaine Baillie stated of the fusee, "Perhaps no problem in mechanics has ever been solved so simply and so perfectly."
A balance spring, or hairspring, is a spring attached to the balance wheel in mechanical timepieces. It causes the balance wheel to oscillate with a resonant frequency when the timepiece is running, which controls the speed at which the wheels of the timepiece turn, thus the rate of movement of the hands. A regulator lever is often fitted, which can be used to alter the free length of the spring and thereby adjust the rate of the timepiece.
Charles Frodsham was a distinguished English horologist, establishing the firm of Charles Frodsham & Co, which remains in existence as the longest continuously trading firm of chronometer manufacturers in the world. In January 2018, the firm launched a new chronometer wristwatch, after sixteen years in development. It is the first watch to use the George Daniels double-impulse escapement.
Julien Le Roy (1686-1759) was a major 18th-century Parisian clockmaker and watchmaker.
In mechanical horology, a remontoire 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 a few precision clocks and watches 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 sometimes 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 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. A remontoire should not be confused with a maintaining power spring, which is used only to keep the timepiece going while it is being wound.
A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation. It is used to determine longitude by comparing Greenwich Mean Time (GMT) and the time at the current location found from observations of celestial bodies. When first developed in the 18th century, it was a major technical achievement, as accurate knowledge of the time over a long sea voyage is necessary for navigation, lacking electronic or communications aids. The first true chronometer was the life work of one man, John Harrison, spanning 31 years of persistent experimentation and testing that revolutionized naval navigation and enabling the Age of Discovery and Colonialism to accelerate.
A chronometer is a specific type of mechanical timepiece. In Switzerland, only timepieces certified by the Contrôle Officiel Suisse des Chronomètres (COSC) may use the word certified chronometer or officially certified chronometer on them. Outside Switzerland, equivalent bodies, such as the Japan Chronometer Inspection Institute, have in the past certified timepieces to the same internationally recognised standards, although use of the term has not always been strictly controlled.
The history of timekeeping devices dates back to when ancient civilizations observed the Sun and the Moon as they moved across the sky. The current sexagesimal system of time measurement dates to approximately 2000 BC from the Sumerians.
Henry Sully (1680–1729) was an English clockmaker. He was an apprentice and then journeyman for celebrated English clockmaker and watchmaker Charles Gretton. He lived in France for many years.
Jean-Antoine Lépine, 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 contemporary world leaders in the field.
The échappement naturel was the invention of Abraham Louis Breguet, one of the most eminent watchmakers of all time. Following the introduction of the detent chronometer escapement with a temperature compensated balance, very close rates could be achieved in marine chronometers and to a lesser degree in pocket chronometers. This achievement was due, other things being equal, to the minimal interference with the balance during unlocking and impulse. A further key advantage of this escapement was that there was no need for oil on the escapement's working surfaces and hence no deterioration in the friction between the working surfaces as the oil aged. A drawback was that the detent escapement as it was used in pocket chronometers was prone to stopping as a result of motion. Most escapements are capable of being stopped by a sudden movement but the detent escapement gives an impulse to the balance only when it is moving in one direction. The escapement is therefore not self-starting. The lever escapement, as used in most modern mechanical watches, avoided this problem. In common with most other escapements it gave an impulse to the balance in both directions of the balance swing. This creates another problem in doing so because the introduction of a lever between the balance and the final (escape) wheel of the escapement requires lubrication on the acting surfaces.
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Aurore was a corvette or snow, designed by Nicolas Ozanne. Built privately on the personal funds of François-César Le Tellier de Courtanvaux, she was commissioned by the French Navy and used for scientific purposes. She performed the first measurement of longitude using Marine chronometer.