Cox's timepiece is a clock developed in the 1760s by James Cox. It was developed in collaboration with John Joseph Merlin (with whom Cox also worked on developing automata). Cox claimed that his design was a true perpetual motion machine, but as the device is powered from changes in atmospheric pressure via a mercury barometer, this is not the case. The clock still exists, but was deactivated at the time of its relocation to the Victoria and Albert Museum in London. [1]
The clock is similar to other mechanical clocks, except that it does not need winding. The change of pressure in the Earth's atmosphere acts as an external energy source and causes sufficient movement of the winding mechanism. This keeps the mainspring coiled inside the barrel. The clock is designed to enable the timepiece to run indefinitely and overwinding is prevented by a safety mechanism. The prime mover, encased in a finely detailed clock body, is a Fortin mercury barometer. The barometer contained 68 kilograms (150 pounds) of mercury (approximately 5 litres). [2]
A similar design is Cornelis Drebbel's circa 1610 device that told the time, date, and season. The gold machine was mounted in a globe on pillars and was powered by changes in air pressure (a sealed glass tub with liquid varied in volume through atmospheric pressure changes, rewinding constantly). It is unknown whether Cox was aware of Drebbel's device.
The Atmos, manufactured by Jaeger LeCoultre is a modern clock which is similar to Cox's clock although the main driving force is generated from temperature differential, instead of pressure differential.
Pressure measurement is the analysis of an applied force by a fluid on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure in an integral unit are called pressure meters or pressure gauges or vacuum gauges. A manometer is a good example, as it uses the surface area and weight of a column of liquid to both measure and indicate pressure. Likewise the widely used Bourdon gauge is a mechanical device, which both measures and indicates and is probably the best known type of gauge.
A 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 harmonic oscillator: It swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates. From its invention in 1656 by Christiaan Huygens, inspired by Galileo Galilei, until the 1930s, the pendulum clock was the world's most precise timekeeper, accounting for its widespread use. Throughout the 18th and 19th centuries, pendulum clocks in homes, factories, offices, and railroad stations served as primary time standards for scheduling daily life, work shifts, and public transportation. Moreover, their greater accuracy allowed for the faster pace of life which was necessary for the Industrial Revolution. The home pendulum clock was replaced by less-expensive, synchronous, electric clocks in the 1930s and '40s, with pendulum clocks now kept mostly for their decorative and antique value.
A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis to help find surface troughs, pressure systems and frontal boundaries.
Perpetual motion is the motion of bodies that continues forever. A perpetual motion machine is a hypothetical machine that can do work infinitely without an energy source. This kind of machine is impossible, as it would violate the first or second law of thermodynamics.
Clockwork refers to the inner workings of either mechanical machines called clocks and watches or other mechanisms that work similarly, using a series of gears driven by a spring or weight.
The history of perpetual motion machines dates at least back to the Middle Ages. For millennia, it was not clear whether perpetual motion devices were possible or not, but modern theories of thermodynamics have shown that they are impossible. Despite this, many attempts have been made to construct such machines, continuing into modern times. Modern designers and proponents sometimes use other terms, such as "overunity", to describe their inventions.
A barograph is a barometer that records the barometric pressure over time in graphical form. This instrument is also used to make a continuous recording of atmospheric pressure. The pressure-sensitive element, a partially evacuated metal cylinder, is linked to a pen arm in such a way that the vertical displacement of the pen is proportional to the changes in the atmospheric pressure.
Cornelis Jacobszoon Drebbel was a Dutch engineer and inventor. He was the builder of the first navigable submarine in 1620 and an innovator who contributed to the development of measurement and control systems, optics and chemistry.
Charles Redheffer was an American inventor who claimed to have invented a perpetual motion machine. First appearing in Philadelphia, Redheffer exhibited his machine to the public, charging high prices for viewing. When he applied to the government for more money, a group of inspectors were sent to examine the machine. It was discovered the machine was actually powered by a device Redheffer claimed was powered by the machine.
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 the mainspring by twisting the spiral tighter. The force of the mainspring then turns the clock's wheels as it unwinds, until the next winding is needed. The adjectives wind-up and spring-powered refer to mechanisms powered by mainsprings, which also include kitchen timers, metronomes, music boxes, wind-up toys and clockwork radios.
The vergeescapement is the earliest known type of mechanical escapement, the mechanism in a mechanical clock that controls its rate by allowing the gear train to advance at regular intervals or 'ticks'. Its origin is unknown. Verge escapements were used from the late 13th century until the mid 19th century in clocks and pocketwatches. The name verge comes from the Latin virga, meaning stick or rod.
Atmos is the brand name of a mechanical torsion pendulum clock manufactured by Jaeger-LeCoultre in Switzerland which does not need to be wound manually. It gets the energy it needs to run from temperature and atmospheric pressure changes in the environment, and can run for years without human intervention.
In fluid mechanics, pressure head is the height of a liquid column that corresponds to a particular pressure exerted by the liquid column on the base of its container. It may also be called static pressure head or simply static head.
Nathan Read was an American engineer and steam pioneer.
John Joseph Merlin was a Walloon from the Prince-Bishopric of Liège in the Holy Roman Empire. He was a Freemason, clock-maker, musical-instrument maker, and inventor. He moved to England in 1760. By 1766 he was working with James Cox and creating automatons such as Cox's timepiece and the Silver Swan. By 1773 he was designing and making innovative keyboard instruments. In 1783 he opened Merlin's Mechanical Museum in Princes Street, Hanover Square, London, a meeting-place for the gentry and nobility. In addition to his clocks, musical instruments and automata, Merlin is credited with the invention of inline skates in the 1760s. He was referred to by contemporaries as "The Ingenious Mechanic". He was friendly with composer Joseph Haydn.
The Barker lever is a pneumatic system which multiplies the force of a finger on the key of a tracker pipe organ. It employs the wind pressure of the organ to inflate small bellows called "pneumatics" to overcome the resistance of the pallets (valves) in the organ's wind-chest. This lever allowed for the development of larger, more powerful organs still responsive to the human hand. These larger organs first flourished in France, e.g., the organ produced by Cavaillé-Coll at St. Sulpice. The first Barker lever was built in the Cavaillé-Coll organ of the Basilica of Saint-Denis.
James Cox was a British jeweller, goldsmith and entrepreneur and the proprietor of Cox's Museum. He is now best known for creating ingenious automata and mechanical clocks, including Cox's timepiece, powered by atmospheric pressure, the Peacock Clock and the Silver Swan.
John Henry Lienhard IV is a professor of mechanical engineering and history at The University of Houston. He worked in heat transfer and thermodynamics for many years prior to creating the radio program The Engines of Our Ingenuity. Lienhard is a member of the US National Academy of Engineering.
Ahasuerus Fromanteel was a clockmaker, the first maker of pendulum clocks in Britain.
Comitti of London is a British company which designs and manufactures handcrafted timepieces.