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  1. #1

    Default Pendulum Drop Length

    I am a newbee. I was told by the repair person, the pend.drop would not fit the case. How can you decide the required drop by looking at a movement?

  2. #2

    Default Re: Pendulum Drop Lenght (RE: superfine_7d04f4)

    Can you attach a photo of you clock and movement?

  3. #3
    Forums Administrator harold bain's Avatar
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    Default Re: Pendulum Drop Lenght (RE: swankyman)

    Hi SF, welcome to the message board. Many movements have the pendulum length stamped on the movement.
    harold bain, Member ch 33
    "If it won't "tick",
    let me "tock" to it"

  4. #4
    Registered User Scottie-TX's Avatar
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    Default Re: Pendulum Drop Length (RE: harold bain)

    One cannot tell the pendulum length required by looking at the movement. Sometimes stamped on it, PL - Pendulum Length - often in cm - centimeters - is only a guide or estimate. One needs also to know whether the spec. was made from the suspension point or centershaft, as mfr. specs. vary.
    Pendulum length can be estimated with movement disassembled by counting the teeth and pinion leafs on certain wheels, applying them to a ratio formula that yields a product of BPM - beats per minute - from which length can be derived.
    Briefly, it's not as simple as looking at the movement.

  5. #5
    Forums Administrator harold bain's Avatar
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    Default Re: Pendulum Drop Length (RE: Scottie-TX)

    But it can be that simple, Scottie. If he is trying to stuff a three train movement with a 93 cm pendulum stamped on the movement, into a two foot wall clock, it ain't gonna go
    harold bain, Member ch 33
    "If it won't "tick",
    let me "tock" to it"

  6. #6
    Registered User Scottie-TX's Avatar
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    Default Re: Pendulum Drop Length (RE: harold bain)

    EXcellent point, HAROLD!
    There are of course, clear cut cases - instances - when the answer is patently obvious such as Harold's example.
    I was referring to the less obvious when the consideration may be as little as plus or minus an inch or two.

  7. #7

    Default Re: Pendulum Drop Lenght (RE: harold bain)

    Quote Originally Posted by harold bain View Post
    Hi SF, welcome to the message board. Many movements have the pendulum length stamped on the movement.
    Thank you for the reply. You have peek my curiosity and I have taken a book titledd ""Practical Clock Repairing" by De Carle. There is an extensive chapter on Pendulum length and a chart to shown lenghts.

  8. #8
    Registered User Scottie-TX's Avatar
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    Default Re: Pendulum Drop Length (RE: coolyus)

    Yep! We find it interesting also. Pendulum length is a linear function described by a constant, 141,120. That constant divided by BPM squared yields PL!

  9. #9

    Default Re: Pendulum Drop Length (RE: Scottie-TX)

    Well, curious minds want to know. What are you attempting? Some pictures will help a lot. If it is indeed not going to work, we can help you find a movement that will

  10. #10
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    Default Re: Pendulum Drop Length (RE: Scottie-TX)

    Quote Originally Posted by Scottie-TX View Post
    Yep! We find it interesting also. Pendulum length is a linear function described by a constant, 141,120. That constant divided by BPM squared yields PL!
    Hey, Scottie - the gravitational constant actually isn't (not by much, I grant, but maybe by enough for a really accurate clock) So does the pendulum length multiplier (1/141120) also really change by a small amount relative to gravity? Just a thought.

    I think it's time for more wine.

  11. #11
    Registered User Scottie-TX's Avatar
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    Default Re: Pendulum Drop Length (RE: Dave B)

    Yes, I would think it would change as gravity changes.

  12. #12

    Default Re: Pendulum Drop Length (RE: shutterbug)

    Quote Originally Posted by shutterbug View Post
    Well, curious minds want to know. What are you attempting? Some pictures will help a lot. If it is indeed not going to work, we can help you find a movement that will
    I am looking at the movements for sale on ebay. You would have to ask the drop of the pendulum or the type of clock the movement came from. Does that make sense?
    I have been reading Conover's book on Clock Repair. He gives a chart and formula based on beats per minute. Therefore you would have to count the teeth on the escapement wheel, use the formula and look in the chart for the length of the pendulum.
    Am I on the right track.

  13. #13

    Default Re: Pendulum Drop Length (RE: coolyus)

    Quote Originally Posted by coolyus View Post
    I am looking at the movements for sale on ebay. You would have to ask the drop of the pendulum or the type of clock the movement came from. Does that make sense?
    I have been reading Conover's book on Clock Repair. He gives a chart and formula based on beats per minute. Therefore you would have to count the teeth on the escapement wheel, use the formula and look in the chart for the length of the pendulum.
    Am I on the right track.
    I'd leave Ebay out of this one What you'll probably get is a movement that doesn't work (why would it be out of the clock?). Better to determine how much room you have in the case, determine the best pendulum length for it, then get a new movement. You'll be happier in the long run.

  14. #14
    Registered User Scottie-TX's Avatar
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    Default Re: Pendulum Drop Length (RE: shutterbug)

    You're on the right track but there's a little more. In addition to no. of EW teeth, you'll need to know number of pinion leaves on EW, No. of teeth and pinion leaves on all the wheels back to the centerwheel, excluding it's pinion count. The math begins there.

  15. #15
    Forums Administrator harold bain's Avatar
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    Default Re: Pendulum Drop Length (RE: shutterbug)

    Quote Originally Posted by shutterbug View Post
    I'd leave Ebay out of this one What you'll probably get is a movement that doesn't work (why would it be out of the clock?). Better to determine how much room you have in the case, determine the best pendulum length for it, then get a new movement. You'll be happier in the long run.
    Only if he is also making new cases. I know I wouldn't be very happy having an antique case with a Hermle movement.
    harold bain, Member ch 33
    "If it won't "tick",
    let me "tock" to it"

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