Herschede Pendulum

[robisonl]

Help---I am working on a small Herschede Grandmother clock. It has a name on the inside,"300 Newton" I have no problem with the mov't, it's the pendulum. When the customer rec'd the clock from relatives, it had a Quartz Pendulum. Needless to say this is wrong. My problem is how do I determine the length of the rod and the weight of the bob. I repair clocks for a local jeweler, but their idea is trial and error...I'm sure there is a better way. I've only been repairing clocks for about 5 yrs and learning something new everyday. I'm a member of the NAWCC and have learned from the past, you people are a wealth of knowledge.. Thanks----Larry

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Larry D. Robison

 

[robisonl]

Help---I am working on a small Herschede Grandmother clock. It has a name on the inside,"300 Newton" I have no problem with the mov't, it's the pendulum. When the customer rec'd the clock from relatives, it had a Quartz Pendulum. Needless to say this is wrong. My problem is how do I determine the length of the rod and the weight of the bob. I repair clocks for a local jeweler, but their idea is trial and error...I'm sure there is a better way. I've only been repairing clocks for about 5 yrs and learning something new everyday. I'm a member of the NAWCC and have learned from the past, you people are a wealth of knowledge.. Thanks----Larry

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Larry D. Robison

 

[Dick Feldman]

Larry,
There is a more or less scientific process to fit a pendulum to a clock. A value in beats per hour/minute can be determined for a clock keeping proper time. This number comes from a tooth count of the wheels in the time train of the clock. From there a pendulum length can be determined from a chart. The "hook" is that pendulum lengths from charts are for theoretical pendulums which have only one dimension, length. Theoretical pendulums are devoid of the effects of gravity as well. So, you pick one close and vary the length till the clock keeps good time. The mass of the pendulum (bob)does have an effect on the rate of any pendulum. This effect, however, is smaller than expected. I have found this out by taping coins, etc. to pendulums to slow the rate down. Length has far more effect on time keeping.
I have sent you an email with almost the same information. If you send me a US postal address, I will send you a copy of the formula for determining beats per hour and a copy of the pendulum length chart. (mine came from the directions from my Time Trax and The Modern Clock by Ward Goodrich.)
Regards,
Dick Feldman