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Off topic question (clock repair)

Discussion in 'Electronic Repair' started by klem kedidelhopper, Nov 24, 2012.

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  1. Sorry to post this question here but I really didn't know where else
    to address it to. It is obviously not electronics related however I
    was hoping that someone could never the less help me.

    I was given this really nice wall clock. The clock was missing the
    pendulum and the winding key when I received it. The clock is supposed
    to chime once on every half hour and then appropriately the correct
    number on every hour.

    A friend who does clock repair gave me a small pendulum and a key. He
    said the size of the pendulum is not too critical and so he thought
    that the one he gave me should work. Well it does however the clock is
    really running slow. It sounds like it's in perfect beat though, and
    although I've run the pendulum up the stick pretty high now it's still
    a few minutes slow over a two hour period. I've tried adding some
    weight to the pendulum but that didn't seem to make any difference.

    The clock doesn't look gummy but it is dry. I had planned to spray the
    movement down with a no residue cleaner and then oil every thing that
    moves with a light oil. I just didn't want to possibly introduce
    another problem into the equation before I fix the current one.

    So I had some questions. i don't know what this pendulum that he gave
    me is from. Is the pendulum weight and length critical? My friend says
    no, however the loss of several minutes over the course of two hours
    seems really excessive. Is it possible that the incorrect pendulum is
    causing the current problem and that perhaps there might not even be a
    problem if I had the correct pendulum? Could the need for a cleaning
    and lubrication cause such a speed error?

    The movement seems to be a fairly nice one and primarily is of brass.
    Above the manufacturers name, (Mason and Sullivan Co.) there is a
    number 75. Below that it reads: "no (0) jewels" next line: "Made in
    West Germany" Below that: " unadjusted" and below that : "141-070".
    Then on the bottom line there is the following:


    If anyone has some advice for me as to my questions and how to proceed
    with this project I would be very grateful. Thanks for any advice on
    this. Lenny
  2. I meant that it produces an even "Tick, Tock", as opposed to a "Tic
    Tic, Tock", or "Tic, Tock Tock" sound. Lenny
  3. hr(bob)

    hr(bob) Guest

    Finally a worthwhile suggestion/comment.
  4. tuinkabouter

    tuinkabouter Guest

    The length of the pendulum should be reduced. Usual there is a nut at
    the underside of the pendulum. Turn the nut to get the weight closer to
    the clock. T = 2 Pi sqrt(L / g)
    where L is the length of the pendulum and g is the local acceleration of
    gravity. It is independent of the mass.

  5. josephkk

    josephkk Guest

    The bottom number is the length and mass of a proper pendulum. Use a
    search engine to find one.

  6. josephkk

    josephkk Guest

    Can't be. Almost every pendulum clock (not controlled by line frequency
    or a crystal) is adjustable by moving the weight along the length of the
    pendulum. Thus it must be the moment arm instead of the pure length.
    Check the units of the equations.

  7. Guest

    Terminology is interfering with communication. There are two
    'lengths' of a pendulum. The obvious one is the physical length. The
    important one for timekeeping is the effective length (or as you
    describe it, the moment arm). This is the distance from the pivot
    point of the pendulum hook to the center of mass of the pendulum.

  8. josephkk

    josephkk Guest

    Thanks. I knew that something wasn't getting across.

  9. Thanks for all the great advice guys. I cleaned and lubricated the
    bushings, it now runs great and I am slowly creeping up on the
    correct pendulum position. Lenny
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