timekeeping

cronometraggio s.m. timing, timekeeping: cronometraggio manuale, elettronico, manual, electronic timing.

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pl. -gi [kronome'traddʒo, dʒi] sostantivo maschile time-keeping

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cronometraggio

pl. -gi /kronome'traddʒo, dʒi/

sostantivo m.

time-keeping.

Zeit·mes·sung f

timekeeping

• time study

• timekeeping

clock/time/ timekeeping card, employee/labor time card, work ticket

reading, time study, timekeeping, timing

1.clock 2.dial

1  timekeeping; 〈 sport ook〉 timing, recording of times

SUBJECT AREA: Horology, Telecommunications

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Alexander Bain was born into a crofting family in a remote part of Scotland. He was apprenticed to a watchmaker in Wick and during that time he was strongly influenced by a lecture on "Heat, sound and electricity" that he heard in nearby Thurso. This lecture induced him to take up a position in Clerkenwell in London, working as a journeyman clockmaker, where he was able to further his knowledge of electricity by attending lectures at the Adelaide Gallery and the Polytechnic Institution. His thoughts naturally turned to the application of electricity to clockmaking, and despite a bitter dispute with Charles Wheatstone over priority he was granted the first British patent for an electric clock. This patent, taken out on 11 January 1841, described a mechanism for an electric clock, in which an oscillating component of the clock operated a mechanical switch that initiated an electromagnetic pulse to maintain the regular, periodic motion. This principle was used in his master clock, produced in 1845. On 12 December of the same year, he patented a means of using electricity to control the operation of steam railway engines via a steam-valve. His earliest patent was particularly far-sighted and anticipated most of the developments in electrical horology that occurred during the nineteenth century. He proposed the use of electricity not only to drive clocks but also to distribute time over a distance by correcting the hands of mechanical clocks, synchronizing pendulums and using slave dials (here he was anticipated by Steinheil). However, he was less successful in putting these ideas into practice, and his electric clocks proved to be unreliable. Early electric clocks had two weaknesses: the battery; and the switching mechanism that fed the current to the electromagnets. Bain's earth battery, patented in 1843, overcame the first defect by providing a reasonably constant current to drive his clocks, but unlike Hipp he failed to produce a reliable switch.

The application of Bain's numerous patents for electric telegraphy was more successful, and he derived most of his income from these. They included a patent of 12 December 1843 for a form of fax machine, a chemical telegraph that could be used for the transmission of text and of images (facsimile). At the receiver, signals were passed through a moving band of paper impregnated with a solution of ammonium nitrate and potassium ferrocyanide. For text, Morse code signals were used, and because the system could respond to signals faster than those generated by hand, perforated paper tape was used to transmit the messages; in a trial between Paris and Lille, 282 words were transmitted in less than one minute. In 1865 the Abbé Caselli, a French engineer, introduced a commercial fax service between Paris and Lyons, based on Bain's device. Bain also used the idea of perforated tape to operate musical wind instruments automatically. Bain squandered a great deal of money on litigation, initially with Wheatstone and then with Morse in the USA. Although his inventions were acknowledged, Bain appears to have received no honours, but when towards the end of his life he fell upon hard times, influential persons in 1873 secured for him a Civil List Pension of £80 per annum and the Royal Society gave him £150.

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See also: Bakewell, Frederick C.

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SUBJECT AREA: Horology

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Burgi entered the service of Duke William IV of Hesse in 1579 as Court Clockmaker, although he also assisted William with his astronomical observations. In 1584 he invented the cross-beat escapement which increased the accuracy of spring-driven clocks by two orders of magnitude. During the last years of the century he also worked on the development of geometrical and astronomical instruments for the Royal Observatory at Kassel.

On the death of Duke Wilhelm in 1603, and with news of his skills having reached the Holy Roman Emperor Rudolph II, in 1604 he went to Prague to become Imperial Watchmaker and to assist in the creation of a centre of scientific activity, subsequently becoming Assistant to the German astronomer, Johannes Kepler. No doubt this association led to an interest in mathematics and he made significant contributions to the concept of decimal fractions and the use of exponential notation, i.e. the use of a raised number to indicate powers of another number. It is likely that he was developing the idea of logarithms at the same time (or possibly even before) Napier, for in 1620 he made his greatest contribution to mathematics, science and, eventually, engineering, namely the publication of tables of anti-logarithms.

At Prague he continued the series of accurate clocks and instruments for astronomical measurements that he had begun to produce at Kassel. At that period clocks were very poor timekeepers since the controller, the foliot or balance, had no natural period of oscillation and was consequently dependent on the driving force. Although the force of the driving weight was constant, irregularities occurred during the transmission of the power through the train as a result of the poor shape and quality of the gearing. Burgi attempted to overcome this directly by superb craftsmanship and indirectly by using a remontoire. This device was wound at regular intervals by the main driving force and fed the power directly to the escape wheel, which impulsed the foliot. He also introduced the crossbeat escapement (a variation on the verge), which consisted of two coupled foliots that swung in opposition to each other. According to contemporary evidence his clocks produced a remarkable improvement in timekeeping, being accurate to within a minute a day. This improvement was probably a result of the use of a remontoire and the high quality of the workmanship rather than a result of the cross-beat escapement, which did not have a natural period of oscillation.

Burgi or Prague clocks, as they were known, were produced by very few other makers and were supplanted shortly afterwards by the intro-duction of the pendulum clock. Burgi also produced superb clockwork-driven celestial globes.

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See also: Briggs, Henry

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SUBJECT AREA: Horology

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Graham's father died soon after his birth, so he was raised by his brother. In 1688 he was apprenticed to the London clockmaker Henry Aske, and in 1695 he gained his freedom. He was employed as a journeyman by Tompion in 1696 and later married his niece. In 1711 he formed a partnership with Tompion and effectively ran the business in Tompion's declining years; he took over the business after Tompion died in 1713. In addition to his horological interests he also made scientific instruments, specializing in those for astronomical use. As a person, he was well respected and appears to have lived up to the epithet "Honest George Graham". He befriended John Harrison when he first went to London and lent him money to further his researches at a time when they might have conflicted with his own interests.

The two common forms of escapement in use in Graham's time, the anchor escapement for clocks and the verge escapement for watches, shared the same weakness: they interfered severely with the free oscillation of the pendulum and the balance, and thus adversely affected the timekeeping. Tompion's two frictional rest escapements, the dead-beat for clocks and the horizontal for watches, had provided a partial solution by eliminating recoil (the momentary reversal of the motion of the timepiece), but they had not been successful in practice. Around 1720 Graham produced his own much improved version of the dead-beat escapement which became a standard feature of regulator clocks, at least in Britain, until its supremacy was challenged at the end of the nineteenth century by the superior accuracy of the Riefler clock. Another feature of the regulator clock owed to Graham was the mercury compensation pendulum, which he invented in 1722 and published four years later. The bob of this pendulum contained mercury, the surface of which rose or fell with changes in temperature, compensating for the concomitant variation in the length of the pendulum rod. Graham devised his mercury pendulum after he had failed to achieve compensation by means of the difference in expansion between various metals. He then turned his attention to improving Tompion's horizontal escapement, and by 1725 the cylinder escapement existed in what was virtually its final form. From the following year he fitted this escapement to all his watches, and it was also used extensively by London makers for their precision watches. It proved to be somewhat lacking in durability, but this problem was overcome later in the century by using a ruby cylinder, notably by Abraham Louis Breguet. It was revived, in a cheaper form, by the Swiss and the French in the nineteenth century and was produced in vast quantities.

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See also: Barlow, Edward; Guillaume, Charles-Edouard

SUBJECT AREA: Horology, Ports and shipping

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John Harrison was the son of a carpenter and was brought up to that trade. He was largely self-taught and learned mechanics from a copy of Nicholas Saunderson's lectures that had been lent to him. With the assistance of his younger brother, James, he built a series of unconventional clocks, mainly of wood. He was always concerned to reduce friction, without using oil, and this influenced the design of his "grasshopper" escapement. He also invented the "gridiron" compensation pendulum, which depended on the differential expansion of brass and steel. The excellent performance of his regulator clocks, which incorporated these devices, convinced him that they could also be used in a sea dock to compete for the longitude prize. In 1714 the Government had offered a prize of £20,000 for a method of determining longitude at sea to within half a degree after a voyage to the West Indies. In theory the longitude could be found by carrying an accurate timepiece that would indicate the time at a known longitude, but the requirements of the Act were very exacting. The timepiece would have to have a cumulative error of no more than two minutes after a voyage lasting six weeks.

In 1730 Harrison went to London with his proposal for a sea clock, supported by examples of his grasshopper escapement and his gridiron pendulum. His proposal received sufficient encouragement and financial support, from George Graham and others, to enable him to return to Barrow and construct his first sea clock, which he completed five years later. This was a large and complicated machine that was made out of brass but retained the wooden wheelwork and the grasshopper escapement of the regulator clocks. The two balances were interlinked to counteract the rolling of the vessel and were controlled by helical springs operating in tension. It was the first timepiece with a balance to have temperature compensation. The effect of temperature change on the timekeeping of a balance is more pronounced than it is for a pendulum, as two effects are involved: the change in the size of the balance; and the change in the elasticity of the balance spring. Harrison compensated for both effects by using a gridiron arrangement to alter the tension in the springs. This timekeeper performed creditably when it was tested on a voyage to Lisbon, and the Board of Longitude agreed to finance improved models. Harrison's second timekeeper dispensed with the use of wood and had the added refinement of a remontoire, but even before it was tested he had embarked on a third machine. The balance of this machine was controlled by a spiral spring whose effective length was altered by a bimetallic strip to compensate for changes in temperature. In 1753 Harrison commissioned a London watchmaker, John Jefferys, to make a watch for his own personal use, with a similar form of temperature compensation and a modified verge escapement that was intended to compensate for the lack of isochronism of the balance spring. The time-keeping of this watch was surprisingly good and Harrison proceeded to build a larger and more sophisticated version, with a remontoire. This timekeeper was completed in 1759 and its performance was so remarkable that Harrison decided to enter it for the longitude prize in place of his third machine. It was tested on two voyages to the West Indies and on both occasions it met the requirements of the Act, but the Board of Longitude withheld half the prize money until they had proof that the timekeeper could be duplicated. Copies were made by Harrison and by Larcum Kendall, but the Board still continued to prevaricate and Harrison received the full amount of the prize in 1773 only after George III had intervened on his behalf.

Although Harrison had shown that it was possible to construct a timepiece of sufficient accuracy to determine longitude at sea, his solution was too complex and costly to be produced in quantity. It had, for example, taken Larcum Kendall two years to produce his copy of Harrison's fourth timekeeper, but Harrison had overcome the psychological barrier and opened the door for others to produce chronometers in quantity at an affordable price. This was achieved before the end of the century by Arnold and Earnshaw, but they used an entirely different design that owed more to Le Roy than it did to Harrison and which only retained Harrison's maintaining power.

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See also: Burgi, Jost; Huygens, Christiaan

SUBJECT AREA: Horology

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Richard, the son of a blacksmith, was adopted by the Prior of Wallingford when his father died and educated at Oxford. He then joined the monastery at St Albans and was ordained as a priest in 1317. After a further period at Oxford studying mathematics and astronomy he returned to St Albans as Abbot in 1327. Shortly after he had been elected Abbot he started work on a very elaborate astronomical clock. The escapement and the striking mechanism of this clock were unusual. The former was a variation on the verge escapement, and the hour striking (up to twenty-four) was controlled by a series of pins laid out in a helical pattern on a drum. However, timekeeping was of secondary importance as the main purpose of the clock was to show the motion of the Sun, Moon and planets (the details of the planet mechanism are lost) and to demonstrate eclipses. This was achieved in a very precise manner by a series of ingenious mechanisms, such as the elliptical wheel that was used to derive the variable motion of the sun.

Richard died of leprosy, which he had contracted during a visit to obtain papal confirmation of his appointment, and the clock was completed after his death. The last recorded reference to it was made by John Leyland, shortly before the dissolution of the monasteries. It is now known only from incomplete manuscript copies of Richard's treatise. A modern reconstruction has been made based upon J.D.North's interpretation of the manuscript.

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SUBJECT AREA: Horology

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Shortt entered the Engineering Department of the London and South Western Railway as an engineering cadet in 1902, remaining with the company and its successors until he retired in 1946. He became interested in precision horology in 1908, when he designed an instrument for recording the speed of trains; this led to a long and fruitful collaboration with Frank HopeJones, the proprietor of the Synchronome Company. This association culminated in the installation of a free-pendulum clock, with an accuracy of the order of one second per year, at Edinburgh Observatory in 1921. The clock's performance was far better than that of existing clocks, such as the Riefler, and a slightly modified version was produced commercially by the Synchronome Company. These clocks provided the time standard at Greenwich and many other observatories and scientific institutions across the world until they were supplanted by the quartz clock.

The period of a pendulum is constant if it swings freely with a constant amplitude in a vacuum. However, this ideal state cannot be achieved in a clock because the pendulum must be impulsed to maintain its amplitude and the swings have to be counted to indicate time. The free-pendulum clock is an attempt to approach this ideal as closely as possible. In 1898 R.J. Rudd used a slave clock, synchronized with a free pendulum, to time the impulses delivered to the free pendulum. This clock was not successful, but it provided the inspiration for Shortt's clock, which operates on the same principle. The Shortt clock used a standard Synchronome electric clock as the slave, and its pendulum was kept in step with the free pendulum by means of the "hit and miss" synchronizer that Shortt had patented in 1921. This allowed the pendulum to swing freely (in a vacuum), apart from the fraction of a second in which it received an impulse each half-minute.

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See also: Marrison, Warren Alvin

1. countdown

2. timekeeping

1. chronometry

2. horology

3. timekeeping

timekeeping