Sunday, August 22, 2021

Short notes on clock calibration

Here are some notes from calibrating and comparing the two clocks.

The A26 clock is supposed to run at 3600bph. I calibrated it to this value when I set it up. After leaving the clock without running it for a few days, I then set it going and found that it was gaining about 30 seconds in 5 hours (6 seconds per hour). Just before I stopped the run, I measured it 3640 bph. It's probably quite temperature sensitive due to the use of a brass rod for the pendulum.

The Peterson clock is intended to run at 5850bph. I set it that way originally and it has run continuously for around 10 days since then. On a test over 30 hours or so, it gained around 2 minutes (4 seconds per hour), and I measured it at 5870bph.

Both measurements of how fast the clocks ran could be very inaccurate as they rely on judging the time by eye.

Another data point. In one hour, the weight on the A26 clock fell 120mm. So you would need a lot of height or to double up the weight chain to get a good run time. The weight was about 300g with a 30g counterweight.

The weight for the Peterson fell about 5mm in one hour. So with a four foot drop, you should be able to get 10 days from it. The weight is 7 pounds 12 ounces, with a doubled weight cord.

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