Steuart patent electric clock with detached pendulum
Very rare Steuart’s patent regulator. The clock is mounted on a heavy cast iron wall mounted bracket into which fits a 44 inch brass vacuum tank at the top of which is a brass flange levelled by three screws adjusted from under the horizontal part of the iron bracket. Above the tank is a heavy glass pressure dome covering the 9 inch silvered dial with blued steel hands behind which are situated the brass geared motion works and the electric motor which drives them continuously. Both are mounted together vertically and attached by three substantial brass pillars to three vertical steel posts which in turn are attached to the rear of steel bedplate. Below entirely separate and mounted directly on the bedplate is the independent pendulum with a weight tray suspended on a knife edge on hard stone blocks positioned by two steel retractable location points. Mounted next to the clockwork movement and the electric motor is a barometer reading 7 – 12 inches of mercury and a Fahrenheit mercury thermometer.
The essence of the Steuart regulator is that the electric motor drives the clock and the pendulum governs and corrects the speed of the motor. The clock pendulum and movements are designed so they are never actually connected either mechanically, electrically or magnetically; the usual “escapement” or any variations has been completely eliminated. The Steuart regulator clock is unique in its workings. The clock runs continuously driven by an electric motor running on about 4.5 volts fed through a variable resistance which is set to run the motor i.e. the clock work very slightly slow. The pendulum is free and unattached. There are two descending rods to the right of the pendulum. The first one on the left is driven by a rotating oval cam on the clockwork and pushes a second pivoted gravity arm with a horizontal section at its end (mounted separately on the base plate), to its right at the end of each cycle. As the gravity rod descends it provides an impulse to maintain the pendulum. At the end of its descent it makes an electrical connection with the horizontal “stop” at the left behind the pendulum as the pendulum continues to move to the left which shorts out the variable resistance thereby increasing the motor voltage and speeding up the motor slightly until it is moved back to the right either by the returning pendulum or the first rod depending on the latter’s cycle (Note the changing cycle of this rod to the pendulum in the video on Facebook http://youtu.be/kISvRVBkdk4 ) The time of this momentary electrical connection continuously ‘corrects’ the electric motor which drives the clock. In the opinion of ‘Scientific American’ it marked ‘the most important development of clock making which has taken place in modern times’. Alexander Steuart in a talk to the Royal Society of Edinburgh stated that his first clock proved to have an accuracy of “between one half and one second per month” which he claimed “was the limit of its accuracy in air”. To achieve greater accuracy it would have to be run in a vacuum to eliminate the air resistance. Professor R. A. Sampson, the Astronomer Royal for Scotland who had watched the developments with interest and encouragement, was impressed by the originality and ingenuity of the invention and described it “one of the most beautiful pieces of clock making” which he had ever come across.
J & D Meek were clock and watch manufacturers with a shop and workshop at 2 North Bank Street, Edinburgh. John Meek, a friend of Alexander Steuart and probably the finest Scottish clockmaker of the twentieth century, took up the challenge and manufactured this unique example of a Steuart Vacuum Tank Regulator. Made in 1923 it was installed in their shop where it ran continuously until the business ceased. It was claimed that this clock was accurate to “better than a second a year”, a claim which if true made this clock probably the most accurate time piece in the world at the time prior to the invention of Caesium clocks in the 1950s.
BBC Time Signals: because Edinburgh was considered by the Ministry of Home Security in WWII to be a safer location than London, ( in case Big Ben was hit by a bomb giving the Germans a propaganda victory), the BBC’s time signals were sent out throughout the war from the Edinburgh Royal Observatory using a Steuart regulator (in air) for their broadcasts. This clock is now owned by the National Museums of Scotland in Edinburgh.
A few Steuart regulators were manufactured by the firm of James Richie of Edinburgh who made domestic and turret clocks. The Steuart clock could be run by an electric motor of any power making it highly suitable for use in public clocks to successfully defy the worst any snow or wind resistance. A few were made and successfully installed. The patent was then sold to Mercer the chronometer makers who manufactured them. Some were sold to observatories chiefly in South America both as master clocks and also for driving telescopes for which use the continuous motion of the clocks was perfect.
Surviving Steuart regulators are extremely rare because only relatively few were ever manufactured. This was due to their late development in the 1920s. Although the Steuart clock was much cheaper and simpler to manufacture by 1923 most observatories around the world were already equipped with tank regulators made by Shortt, Reiffler and Le Roy and had no need to purchase another whose difference in accuracy in a vacuum was probably only measurable in fractions of a second. Nevertheless the Steuart regulator remains one of the most ingenious and accurate timekeepers ever devised.
The clock comes with a comprehensive file: step by step assembly photos “from scratch”, photocopies of patents and other information.
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