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Speedmaster Moon watch suddenly became accurate

  1. rollee Mar 1, 2016

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    My 2011 3570.50 has been running slow -10s/ 24h for the past year, and I plan to have a service this year.
    Recently I tried not fully winding the watch, but only 20 turns a day. The watch is suddenly dead accurate, in the past 5 days I lost 2.5s total.

    Given everything else was normal, and there was no change in my wearing habits.
    Any reasons?
     
    Edited Mar 1, 2016
  2. Horlogerie EU based Professional Watchmaker Mar 1, 2016

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    Less winding means less power from the mainspring reaching the escapement and balance, result? a lower amplitude for the balance wheel.

    The lower amplitude, in your case, is causing the balance to run faster. Amplitude changes always result in a change of rate of the watch.

    Isochronism, in a perfect watch would be that the balance wheel rotations are equal lenghts, no matter the amplitude, but this doesn't happen.

    A handwind watch should always be fully wound off the wrist before wearing it, a full wind gives the movement a full charge and it is designed to perform at it's best in this state (why auto's work so well, they are at full wind most of the time when worn).

    I think the watch is trying to tell you something, by partial winding to make up for it's slow running, your not doing the movement any favors, time for a service I believe...

    Rob
     
    Edited Mar 1, 2016
    lando, watchknut, flyingout and 3 others like this.
  3. Kobus Mar 1, 2016

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    Can search elsewhere, but while on the topic; what is acceptable or the norm. My new Speedy is +15s/24h.
     
  4. dsio Ash @ ΩF Staff Member Mar 1, 2016

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    As Rob suggests it might be time for its first service, if the watch is a 2011 model its due about now.
     
  5. italy1861 Mar 1, 2016

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    Spec is -1/+11 sec per day..
     
  6. Horlogerie EU based Professional Watchmaker Mar 1, 2016

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    It should be -1 to +11 seconds per day, so you are a bit outside of the tolerance.

    Many factors affect the rate, mostly what happens to your wrist while wearing the watch, active? stationary? bit of both etc, all affect the rate.

    And of course most important, what is the state of condition of the movement.

    Rob
     
  7. rollee Mar 2, 2016

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    Thank you Rob for your reply, it is very helpful and informative.
    I will book an appointment for it to be serviced, and I thank all other members here for sharing your experience.
     
  8. Perseus Mar 8, 2016

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    What if you're watch has stayed the same and time itself is speeding up?