The William Shortt regulator
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The William Shortt regulator


The William Shortt regulator
William Hamilton Shortt, London. No7. Circa 1925
The copper vacuum tank with wall suspension brackets, later glass bell jar to the top and glass plate to the base with vacuum tap and pressure gauge to the side, the top brass collar with electric contact nodes to both sides, the brass four-arm pendulum suspension bracket with engraved and silvered brass plaque secured to the top for thermometer and barometric reading, the pendulum suspended from the centre with weight tray and impulse arm assembly to the invar rod and receiving 30 second impulses via a complex electro-mechanical circuit mounted to the right, the slave with rectangular oak case, engraved and silvered Roman main dial, signed SYNCHRONOME/ELECTRIC with black painted hands displaying time as regulated by the slave and above the subsidiary cream painted Roman dial with black painted hands displaying time as regulated by the master clock, the synchronome movement of typical form with jewelled gathering pin affixed to the pendulum passing over a 15-toothed wheel with steel arm to its arbor giving make-break contact every 30 seconds
The tank--55 in. (140 cm.) high, over bell jar, the slave clock--50½ in. (128 cm.) high
William Hamilton Shortt, thence by descent
Special notice

No VAT will be charged on the hammer price, but VAT at 15% will be added to the buyer's premium which is invoiced on a VAT inclusive basis.

Lot Essay

Frank Hope-Jones, Electrical Timekeeping, 2nd. ed., 1949, London pp.166-174
Klaus Erbrich, Präzisionspendeluhren, 1978, Munich pp.223-234
Derek Roberts, Precision Pendulum Clocks, The Quest for Accurate Timekeeping, Pennsylvania, 2003, pp.157-159

Two English electric observatory regulators by William Shortt have been sold at Christie's, London: No.18, Important Clocks 10 June 1998, lot 32 and No.20, Important Clocks 25 November 1998, lot 412.

William Hamilton Shortt (1882-1971) spent all his working life in the employment of the London and South Western Railway and its successors. In 1908 one of the main problems with trains was to establish their safe speed on curved tracks. An accurate time standard was required which Shortt devised. In 1910 he met Frank Hope-Jones who offered him facilities for making experimental models. Many designs were produced before Shortt invented his 'hit-and-miss' synchroniser for a slave clock and his Free Pendulum.
In 1921 Shortt set up his first Free Pendulum vacuum clock at Edinburgh Observatory; its results astounded the world with revolutionary timekeeping confirmed at a rate of less than one second a year. By 1924 he made clocks for the Helwan Observatory in Egypt, The Royal Observatory in Greenwich and The National Astronomical Observatory of Japan, Tokyo. In all 99 of these clocks were made for observatories, institutions and scientists all over the world and used for accurate time measurement until they were superceded by the invention of the quartz crystal clock.
For his work Shortt was awarded the gold medal from the British Horological Institute in 1929 and made a Fellow in 1932. In 1954 The Clockmakers' Company awarded him the first Tompion Medal.
No.7 was Shortt's personal clock. Made in 1925, it was installed in his house in Exeter where he received the coded Greenwich Time Signal through an old Admiralty receiver from which he could check the clock's accuracy. During the war No.7 was moved for safety to the science block at the then Exeter College until being returned to Shortt's house in 1945 where he continued to monitor it until his death in 1975. It was then removed and has since been in storage.

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