"Trench" watch timing issue

Discussion in 'Watch Repair' started by Roy Horrorlogic, Jul 29, 2019.

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  1. Roy Horrorlogic

    Roy Horrorlogic Registered User
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    Mar 7, 2017
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    I have recently serviced the movement shown in the photos. So far I've not managed to identify it although it resembles some of the Fontainmelon ebauches. I know that the beat error is less than ideal but it's well within the range I've seen with these veterans. The watch was running extremely slow on the original very tired main-spring so I replaced it with a best guess that I already have. Diameter 11.0 (should be 11.5) and length 340 (roughly correct). Power value is 1.35 (old spring appears to be 1.0). Figures are within the same range in four positions.
    Despite this, whilst the amplitude is much greater the watch still runs extremely slow. Snaps attached. All the jewels are good and the wheels are - age considered - OK.
    Clues appreciated.
    Roy

    P7290498.JPG P7290499.JPG P7290500.JPG
     
  2. Skutt50

    Skutt50 Registered User

    Mar 14, 2008
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    I am not quite sure what the values 1 and 1.35 means, but an increase in strength with some 30+ percent is possibly causing the movement to knock. The swing of 325 degrees is high and is getting close to when knocking occurs. This in turn will show odd behavior on the Timegrapher. You could try to wind the mainspring only one turn or so to see if this helps and if so replace the mainspring with a weaker....
     
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  3. Roy Horrorlogic

    Roy Horrorlogic Registered User
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    Thanks.
    What's so odd about this is that the previous very tired spring exhibited almost identical performance also with an amplitude of 250+. Not sure how many springs to sacrifice...
    I'll let the mainspring down or run it out and try just that...
    Roy
     
  4. pocketsrforwatches

    pocketsrforwatches Registered User
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    I would pull the canon pinion off and see if there is any change.

    Roger
     
  5. gmorse

    gmorse Registered User
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    Hi Roy,

    If by 'power' you mean the strength or thickness of the mainspring, then bear in mind that the power delivered is proportional the cube of that value, so as Skutt says, 30% is a significant increase, all other parameters being equal. If the watch showed the same slow behaviour together with a reasonable amplitude before you serviced it and replaced the mainspring, I think you should be looking elsewhere for the cause. Counting the train and then vibrating the balance to see whether they match up is where I'd go next, because sometimes a balance spring has been replaced with one that happens to be available and looks 'about right'.

    Regards,

    Graham
     
  6. Roy Horrorlogic

    Roy Horrorlogic Registered User
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    Thanks everyone
    Roger:
    the CP is not the problem - with it removed the timing is the same. Well worth a try though.
    Graham
    I'm sure you're right. This movement came out of my copious collection of veterans but looked as if it was worth putting some effort into it. I'm going to sideline it for the moment because it actually constitutes displacement activity, enabling me to evade all sorts of things that would be more productive. This is a trap I fall into happily, over and over again. But I always learn something, even if it's not to attempt over ambitious jobs.
    I'm in the fortunate position of having lots of very low value watches accumulated by myself and an old friend over decades. So I've been teaching myself by restoring watches that have minimal resale value. It still gives me a lot of pleasure to see something that was in the junk box actually working, even half decently.
    I wish I'd started learning horology, properly, much earlier. Having passed into my 8th decade now that's a reflection, among many, that rises up at regular intervals.

    The expertise shared here is much appreciated. I hope one day to be able to reciprocate - just don't hold your breath!
    Roy
     
  7. Skutt50

    Skutt50 Registered User

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    Perhaps you did this during service but another simple action to try is to demagnetize the watch.
     
  8. praezis

    praezis Registered User

    Feb 11, 2008
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    Looking at your pictures:
    - the Timegrapher shows a fast watch, not slow
    - your regulator is in "fast" position

    What thickness has your new spring?

    Frank
     

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