Shortt, William Hamilton

SUBJECT AREA: Horology

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b. 28 September 1881

d. 4 February 1971

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British railway engineer and amateur horologist who designed the first successful free-pendulum clock.

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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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Principal Honours and Distinctions

Master of the Clockmakers' Company 1950. British Horological Society Gold Medal 1931. Clockmakers' Company Tompion Medal 1954. Franklin Institute John Price Wetherill Silver Medal.

Bibliography

1929, "Some experimental mechanisms, mechanical and otherwise, for the maintenance of vibration of a pendulum", Horological Journal 71:224–5.

Further Reading

Obituary, 1971, Proceedings of the Institution of Civil Engineers 56:396–7.

F.Hope-Jones, 1949, Electrical Timekeeping, 2nd edn, London (a detailed but not entirely impartial account of the development of the free-pendulum clock).

See also: Marrison, Warren Alvin

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