Maker's Name: 
Synchronome Electrical Co of Australasia, Brisbane.
Where made: 
Where used: 
UQ Teaching Labs
circa 1955
15 × 27 × 126 cm

This clock was made in Brisbane  in 1955. The Synchronome Electrical Company of Australasia built clocks in Brisbane under licence from Frank Hope-Jones' Synchronome Company in England. They also built the clocks in the towers of South Brisbane Town Hall (1904) and Brisbane City Hall (1930), among many others.

This clock has a grey wooden case with a glass door. It has two dials, the lower dial has the seconds hand and the upper dial has the hours and minutes hands. Inside the case is a pendulum with a period of two seconds and a countwheel which advances one tooth with each swing of the pendulum. Every 30 seconds the countwheel trips a detent and an L-shaped lever falls. The lever carries a roller which impulses an arm attached to the pendulum restoring the energy lost in the previous half minute. A moment later, the L-shaped lever also closes a circuit. The current that flows, energises an electromagnet that resets the lever, breaking the circuit again, sending a pulse to the upper dial through a series circuit. This means that the minute and hour hands only move every 30 seconds. The seconds dial is controlled by a separate seconds counter so that its hand ticks with every swing of the pendulum. Note that neither dial has any mechanical connection to the pendulum.

On the left side of the case is a small crank that can be turned once either way. Turning the crank lowers a weight onto a circular platform on the pendulum. Adding a small amount of weight to the middle of the pendulum moves its centre of gravity upwards, which has the effect of shortening its length. Because the time taken for the pendulum to complete one swing is proportional to the square root of the length, decreasing the length will slightly decrease the time taken and the clock will speed up. This was very useful if a clock was running slightly late but the owner did not want to completely reset it. They could simply lower the weight onto the platform, allow the clock to catch up to the correct time and then wind the weight back up, allowing the clock to resume its normal timekeeping.

Synchronome pendulum clocks were widely used in the University to operate slave dials in lecture rooms and to control bells and timers. When the clock sends the pulse to the hours and minutes hands every 30 seconds, it can also send the same pulse to any number of connected slave clocks. This particular clock was used to drive the slave clocks for the Parnell Building from 1955 to the 1970s. It was also connected to a program timer which controlled the building's bell system. The program timer is mounted below this clock in the Physics Museum. A similar clock was used to time and control ionospheric observations at the Moggill field station, starting in the International Geophysical Year in 1958.

This item is part of the UQ Physics Museum ‘100 Years of Physics at UQ’ Tour
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This item is part of the UQ Physics Museum Electric Clocks Tour
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