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Question about length of suspension spring

marylander

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I have a question about the length of suspension spring.
If the clock suspension spring 17.5X8.0mm 0.005mm thick is replaced by a 18.5mmX8mm 0.005mm thick suspension spring, without readjust the pendulum length, would the clock run slower? If so, how much slower will it be.
Ming
 

bangster

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It won't run any slower, but it may not run as long before needing a re-wind.
 

harold bain

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If the pin to hook the leader, or pendulum is 1 mm further down, yes it will run slower as the effective length of the pendulum will be 1 mm longer. As long as you have enough regulation room to raise the pendulum that much, it shouldn't be a problem.

Bang, suspension spring, not mainspring:whistle:
 

eskmill

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Bangster misunderstands the question about the effect of a longer suspension spring not mainspring.

The simple answer is yes, the pendulum clock will run a little slower with the longer suspension spring given that the center of flexiture of the suspension spring will be slightly lower if the replaced suspension spring has the same bending strength as the original. Thus the length of the pendulum is increased.

For what it is worth, Goodrich's "The Modern Clock" has a handy table on page 16 that provides the answer if you know the number of beats per hour of the original pendulum length. It also depends on geological altitude or the local force of gravity.
 

R. Croswell

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I believe (but I may be incorrect) that effect of the longer suspension spring will have on the rate that the clock runs will be greater for clocks with short pendulums. The 1 mm extra length will produce only a small error but I believe that error will be multiplied with every beat. If the clock has a seconds beating pendulum (approximately 1 meter long) the effect will be very small, but if the clock has a shorter pendulum and beats several times per second it seems that the error would be multiplied - that is, a short pendulum clock would introduce the error more times per minute than a long pendulum clock. Still one mm is probably within the range of adjustment for most clocks.

RC
 

marylander

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The top and bottom blocks of both suspension springs are identical. Only the s.s. center spring is 1mm longer than the other. There is enough room for pendulum bob to move up. Thank you all for the help and education. I will replace the s.s. soon. I think the center of the suspension spring to the center of the bob is only 0.5mm longer. Am I correct?
Ming
 
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shutterbug

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Yeah, but that's not really relevant. The distance from the suspension point to the center of the bob is what you need to consider, so you have a 1mm difference that you'll have to make up by moving the bob up.
 

Tinker Dwight

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I believe (but I may be incorrect) that effect of the longer suspension spring will have on the rate that the clock runs will be greater for clocks with short pendulums. The 1 mm extra length will produce only a small error but I believe that error will be multiplied with every beat. If the clock has a seconds beating pendulum (approximately 1 meter long) the effect will be very small, but if the clock has a shorter pendulum and beats several times per second it seems that the error would be multiplied - that is, a short pendulum clock would introduce the error more times per minute than a long pendulum clock. Still one mm is probably within the range of adjustment for most clocks.

RC
Hi
As RC says, the amount slower will depend on the total length of the pendulum.
A 1 second beat pendulum would be slow by about 43 seconds a day.
A 1/2 second beat pendulum would be slow by about 1 minute 26 seconds a day.
It might be slightly more because with less restoring force of the spring.
A slight additional slowing will be added.
The other problem is that the inflexion point of the spring will move down by 0.5mm.
This will increase friction between the crutch and the pendulum, slightly ( assuming
it was dead on right to start with ).
Tinker Dwight
 

bangster

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If the pin to hook the leader, or pendulum is 1 mm further down, yes it will run slower as the effective length of the pendulum will be 1 mm longer. As long as you have enough regulation room to raise the pendulum that much, it shouldn't be a problem.

Bang, suspension spring, not mainspring:whistle:
Oopsie. Color my face red.
 

marylander

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Thank you all again for the discussions and help.
The clock is regulated and keeps time now. I did have to move the bob up a little to make the clock keep correct time.
I did not measure how much I had to move the bob up.
Ming
 

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