By Andrew Hooper
West Dean College has recently included electrical horology within the Clock Conservation course. Electric clocks were developed in the 1840's onwards by Alexander Bain, Charles Shepherd and others. This post is one of an occasional series on electrical horology.
Gent No. 1240
On the 7th May 1912, three weeks after the loss of the RMS Titanic, a clockmaker at the Gent factory in Leicester, England, examined clock No.1240 and signed and dated the label pasted inside its case. This procedure would be followed for each of the next 14,000 or so master clocks produced by Gent until production ceased of this model in 1980. However, No.1240 is currently the earliest known numbered and dated clock.
No.1240 is not actually a clock; as this term comes from the French word cloche, meaning bell, it implies striking. A clock that does not strike but simply tells the time is a timepiece. No.1240 doesn't even tell the time, as it has no dial or hands, but is does very accurately and reliably send an electric pulse every 30 seconds to all the impulse (or slave) dials attached to it and the time is read from these. Gent called it a Time Transmitter and this was produced in two versions, known as the 'C6' and 'C7', without and with a pilot dial respectively (Figure 1).
Figure 1: Gent 'C7' Time Transmitter No.1812, 27 Nov. 1919
© Lacy Scott & Knight, Auctioneers
No.1240, a 'C6' Time Transmitter without a pilot dial, came from Dunecht House, near Aberdeen. The house, with its 24 bedrooms surrounded by 59,000 acres, was purchased in 1910 by the first Viscount Cowdray. Around 1913 a series of major internal and external alterations were made to the house and it is likely that No.1240 was installed as part of this refurbishment.
During the 20th century, Gent master clock systems were installed throughout the British Empire. The master clock synchronised the associated dials so that the activities of factories, schools, hospitals, railways and other institutions were co-ordinated. Large installations comprised several hundred slave dials; see examples of 12", 15" & 18" dials in Figures 2-4 respectively. Some of these dials on public buildings were immense, such as the four 25-foot dials on the Royal Liver Building in Liverpool.
Figure 3 shows the impulse dial that accompanied No.1240. This has similar hands and case to the 1905 example in Figure 2, but the has had a new dial fitted similar to the ca. 1923 example in Figure 4.
The accuracy of a master clock derives from its free-swinging pendulum that is essentially doing no work and is only disturbed every 30 seconds by a gravity arm, giving the pendulum a gentle push to maintain its arc. The gravity arm is reset by electromagnets and at the same time an electrical pulse is transmitted to all the connected slave dials to increment them by half a minute.
Predating the National Grid or any form of reliable mains electricity, master clocks work at low voltages, typically 4-6 volts, supplied by banks of batteries. These tough industrial clocks are more accurate than most, if not all, the exquisite astronomical regulators produced in previous centuries. However, they are rarely used as domestic clocks due to the noise made when the gravity arm resets every 30 seconds.
Gent of Leicester started manufacturing master clock systems in the late 1890s. Two key patents in 1907 led to a new robust and reliable design entering production in 1908. These early clocks were not marked, but it seems that each one had a production number associated with it, as can be seen in Figure 5. The extrapolation of known clock numbers suggests that the first 'C6' or 'C7' produced in 1908 was probably No.1000 and not clock No.1.
The production rate, or requirement, for these Time Transmitters is surprisingly constant over the period shown by Figure 5, with essentially no reduction in output throughout the First World War. For every Time Transmitter dozens, sometimes hundreds, of impulse dials had to be made, installed and wired together.
In the 75 or so years that the 'C6' and 'C7' Time Transmitters remained in production, various modifications were made to the movement. The principal changes are illustrated in Figures 6-14. The bracketed alphanumeric references are those of the corresponding illustrations drawn by Derek Bird in his 1987 Antiquarian Horology paper "The 'Pulsynetic' System and its place in the History of Electric Clocks-An Introductory Study." This paper describes in detail the development of the Gent master clock system.
No.1240 (Figure 8) is the only known dated Time Transmitter with the short contact arm, on the left of the movement, which had only previous been known on undated clocks.
Master clocks, and especially 'C6's with no pilot dial, were often connected to one or more impulse dials. As these dials were usually in far more prominent positions than the master clock, their designed changed rapidly with fashion throughout the 20th century.
Many Gent master clocks ended their working lives being dumped in skips to be replaced by the ubiquitous quartz clock. However, by numbering and precisely dating its clocks, Gent has provided a rich historical legacy of technical development and style.
100 years ago, on Tuesday 7th May, 1912, a machine gun was fired from an airplane for the first time; the House of Commons discussed the National Health Act; a British Wreck Commissioner's Inquiry sat to investigate the loss of the Titanic; and a clockmaker signed a little piece of paper (Figure 15).
I wish to express my thanks to those who permitted their clocks to be photographed, to those who made clock date data available and to Derek Bird for sharing his knowledge of these clocks.