![]() The original Synchronome clock was invented by George Bennett Bowell in 1895 and developed and distributed by Frank Hope-Jones. Until the 1960s they were used as master clocks in large institutions and factories which required a precise timekeeper to control all the clocks on the premises. Once every 30 seconds the count wheel of the master clock releases gravity arm which pushes the pendulum and sends an electrical pulse to move the hands of all the slave clocks. It also switches on two electro magnets that reset the gravity arm ready to give the next push. Synchronomes also served as slaves for the famous Shortt-Synchronome clocks which were the world's best timekeepers in the 1920s and 30s, installed in many observatories. These were the first clocks that were more precise than the rotations of the Earth itself. Since the 1940s they have been replaced by quartz clocks and later by atomic clocks. In the meantime, a Shortt-Synchronome under test has been found to have an error of one second in 12 years. |
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Like the original Synchronome, the pendulum is powered by a gravity arm pushing down on a pallet but the rest of the mechanism is different. My version is driven by a weight whereas the Synchronome was powered by an electro-magnet.
Time keeping: My clock has an unvarnished wooden pendulum with a lead bob (weight 5.3 kg) swinging in an arc of 3° with a Q value of about 25,000. It keeps time to about one second from day to day but drifts with changes in humidity, temperature and atmospheric pressure. It is the most accurate clock I have made so far but might be improved by giving the pendulum rod a coat of yacht varnish or by replacing it with a carbon fibre or invar rod.
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![]() The count wheel was made
The rim and hub were turned from a disc of plywood glued to a scrap-wood faceplate held in the chuck of the lathe. The holes for the spokes, the pins and the original 8 x 5 mm ball-bearing were made with suitable drills mounted on the tool-post. I used a strip of Ikea ½ millimeter tape wrapped around the chuck, and some arithmatic, as a dividing head. The spokes were fitted and the wheel was then cut free from the sacrificial faceplate.
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