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William Hamilton Shortt No. 84

An English mahogany, copper and brass free pendulum observatory regulator. Circa 1925
No VAT will be charged on the hammer price, but VA… Read more
William Hamilton Shortt No. 84 An English mahogany, copper and brass free pendulum observatory regulator. Circa 1925

Details
William Hamilton Shortt No. 84

An English mahogany, copper and brass free pendulum observatory regulator. Circa 1925
The copper vaccuum tank with wall suspension brackets, glass plate to the base with vaccuum tap to the side, the top brass collar applied with two rectangular silvered plaques engraved Designed By WM. HAMILTON SHORTT M.inst. C.E. IN ASSOCIATION WITH THE SYNCHRONOME Co. Ltd. ALPERTON Nr. LONDON. CLOCK SHORTT No. 84, electric contact nodes to the right side, the brass four-arm pendulum suspension bracket with six milled adjustment screws, silvered brass plaque secured to the top for thermometer and barometric reading, the pendulum suspended from the centre having lead bob with weight tray to the shaft and receiving 30 second impulses via a complex electro-mechanical circuit, the slave with rectangular mahogany case having foliate carved spandrels around the circular silvered dial with regulator format signed SYNCHRONOME PATENT No. 187814 to the centre, outer minute ring with Arabic five minute markings and XXIIII-hour ring, all hands of blued steel, silvered rectangular sub-dials below with two XII-hour dials engraved FREE P & SLAVE, both with blued steel spade hands, the complex electro-mechanical system with flanking bakelite dials with large adjustable knobs with calibrated white painted calibration; SERIES SECONDS - PARALLEL SECONDS - SLAVE - FREE PENDULUM
Slave clock: 55¼ in. (140 cm.) high
Tank: 51 in. (129.5 cm.) high over glass dome
Literature
F. Hope-Jones, Electrical Timekeeping, 2nd. ed., 1949, N.A.G. Press, pp. 166-174
Special Notice

No VAT will be charged on the hammer price, but VAT at 17.5% will be added to the buyer's premium which is invoiced on a VAT inclusive basis

Lot Essay


The Shortt free pendulum clock was a quantum advancement in the field of electrical horology and after its trials in Edinburgh it was regarded as the most advanced timekeeper to date giving an astonishing accuracy of less than one second a year/

Frank Hope-Jones, Electrical Timekeeping op.cit.

...fortunately in 1921 he (Shortt) hit upon a means of two pendulums swinging together in PRECISE sympathy vis. 'the hit and miss synchroniser'......I rank this invention as one of the very few of outstanding importance in the application of electricity to horology; it was the last thing needed to produce a practical free pendulum since it enabled two synchronome clocks to be firmly held in synchronisation. .......The first free pendulum clock was made by Mr Shortt with his own hands and was erected by him in the Edinburgh observatory in the christmas of 1921.....the free pendulum itself being in a cylindrical copper case from which the air was exhausted. It is known in the astronomical world as SH.O and the report of Professor Sampson on its first year's run created a sensation

In 1912 the watch trials at Kew were transfered to Bushy House in Teddington where the new National Physical Laboratories were set up. In its basement was an old beer cellar which was converted into a rating room with small rooms constructed alongside for maintaining cold, normal and hot temperatures. In March 1927 the laboratory installed the Shortt free pendulum clock No. 13 to be used as the standard timekeeper. This was the replacement for a master clock by J. Morrison & Sons. It was bolted to the 3 ft. thick cellar wall and final regulation was attained by adjusting the air pressure, enabling rates of under one second a year to be attained. Its time was transmitted by the slave clock to the three rating room's impulse dials. Eventually it was replaced by a quartz clock about 1955 and the Shortt clock was dismantled. Later given to the Liverpool City Museum where it remains.

Seventy six Shortt Free Pendulum vacuum clocks were built, all for observatories all over the world. For decades they were the most accurate form of timekeeper known until they were superseded by Atom clocks.
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