Tuesday, June 2, 2009

Horology 101

Last month I bought a 400 day torsion pendulum clock at an antique store. They are more commonly known as an "anniversary clock." After setting it up at home, it would not tick more than a few times. After a bit of investigation on horology web sites, I measured the timing of the ticks on either side of neutral point when it is doing nothing. It turned out that the swing on one side was much greater than on the other side. Making the swing equal is known as setting the beat, and, is essential for making the clock to run accurately or even to run at all.

It turns out that none of the web sites show how to set the beat. Finally I figured out that the thing from which the pendulum torsion wire is suspended can be made to rotate by first loosening an adjacent screw. I turned it until the tick swing was about equal to the tock swing. Now it runs and now you know how to get an anniversary clock running.

Sometimes someone starts an anniversary clock with too much swing and this kinks the torsion wire. In a case like that the wire must be replaced, and that is expensive. My clock did not require a wire replacement and all it needed was to set the beat. It now runs fine, and, I am now in the process of adjusting its timing.

Setting the beat on a swing pendulum clock is similar to setting the beat on the torsion pendulum. Make the tick equal to the tock by tilting the clock. Then adjust the setting so it will do that while level. Move the setting toward the high side of the tilted clock.

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