Chronometer Problem

Discussion in 'Chronometers' started by Jerry Freedman, Feb 19, 2019.

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  1. Jerry Freedman

    Jerry Freedman Registered User
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    Sep 16, 2000
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    I have a Russian chronometer that will not run. I have not wound since it was moved and was jolted during the move. I decided to wind it and found it was not working. The balance was not corked when moved.

    The balance swings freely and no ticking sound is heard. The balance staff appears to be OK. Any thoughts?

    Jerry Freedman
     
  2. Jim Haney

    Jim Haney Registered User
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  3. gmorse

    gmorse Registered User
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    Hi Jerry,

    If the locking stone is broken there's nothing holding the escape wheel and if there's any power at all on the train it should be whizzing round, so if this didn't happen I suspect something else is holding it up. I suppose your instrument doesn't have any type of train locking device like the part #29 in the Hamilton drawing?

    Regards,

    Graham
     
  4. Jerry Freedman

    Jerry Freedman Registered User
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    I forgot to say that hands are not moving when the balance wheel is oscilating.

    Jerry Freedman
     
  5. Tom McIntyre

    Tom McIntyre Technical Admin
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    If the escape wheel is locked, it is the unlocking jewel that is most likely missing. If it only needs the jewel (unlikely) anyone familiar with them should be able to repair it. If it needs an overhaul and repair, it would be rather less expensive to purchase another one, I think.
     
  6. Kinpol

    Kinpol Registered User

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    Hi,
    In my workshop overhaul and repair costs usually 300-400$... But I'm in Poland...
     
  7. Dr. Jon

    Dr. Jon Registered User
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    If the locking jewel broke, the movement unwound and the fusee chain will be off. If so, you may get by with a replacement locking jewel which is not too hard to come by but there can be other damage. This is the most common way these get busted. It is possible this happened before you got it back and chain is off. In this case winding put no power on the mainspring so nothing happened to move the hands or escape wheel.

    If the fusee chain is still in place and under tension, you may have been lucky. In this situation, the roller has either had the jewel broken or the roller has either come off or come loose. Sometimes the entire roller assembly is loose and spins out of angle. It may have had the jewel come out or it may have broken. If you have chain tension and the balance is not operating the detent there is very little risk in taking out the balance to check the roller. The risk in removing the balance is accidentally moving the detent and breaking off the locking jewel. If the balance is not operating moving the detent, removing the balance will not likely do it. Of the roller is loose on the balance staff it will either by lying near the bottom of it or still on teh staff but turn easily. If so you can fix it but pushing it back into place and turning it to the beat position and pressing it toward the balance until it is tight . Unless this makes sense to you; don't try it. Replacing the balance with an operational roller requires some care and caution.

    I had this happen with a fine lever watch I took for a run, The balance swung but the escapement did not operate. The roller was loose and had turned so far out of position that it would not operate the lever.

    If the chain is still under tension, it is probably the roller and not too hard to fix.
     
  8. Jerry Freedman

    Jerry Freedman Registered User
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    Thanks Dr. Jon. I will check it out.
     
  9. Jerry Freedman

    Jerry Freedman Registered User
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    Dr. Jon: I had the movement inspected, and it appears all the jewels are in place. However, the roller jewel is not making contact with the
    detent. I will hear more later.

    Jerry Freedman
     
  10. Tom McIntyre

    Tom McIntyre Technical Admin
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    The gold passing spring could be broken off. Or, the roller could be displaced down so that the jewel misses the passing spring. More likely the first, but I think that is pretty uncommon unless someone's fingers got in there.
     
  11. Dr. Jon

    Dr. Jon Registered User
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    Diagnosis without seeing it is always risky but I took a look at mine. The roller jewel works against the passing spring. It is weak spring that just flips aside on one direction and presses the detent away in the other direction. In this chronometer this spring is secured by a single screw. If that screw was not tight enough, a jar could move the passing spring out of the path of the roller jewel. It is very hard for this spring to get broken except by mishandling on the bench.

    This is more likely than a broken roller jewel because this would only happen if the jar occurred when the roller jewel was in contact and even then there is no way for much force to get transmitted this way.

    If this is what happened the repair is a very simple adjustment; just move the spring back into alignment with the detent.
     
  12. Tom McIntyre

    Tom McIntyre Technical Admin
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    I agree Jon. The loose screw theory occured to me right after I posted the above. If the detent is to be removed, you do need to figure out how to let down the power or use the funky locking screw to take the power off the escape wheel. I would need to take it to someone with much better hands than me.
     
  13. Dr. Jon

    Dr. Jon Registered User
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    If it is a loose screw and passing spring has slipped, I would not remove the detent. I would remove the balance and I would peg or wedge the escape wheel and reposition the passing spring. I would not make the holding screw all that tight, just enough to hold the passing spring in place. If it slips again there is no harm done but it you strain the detent by torquing too much it is bad. The instrument worked fine until it was jarred.

    I would keep the escape wheel locked until the balance was back in place.

    BTW wedging the balance would not have made any difference.
     
  14. Tom McIntyre

    Tom McIntyre Technical Admin
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    Not that I could personally use either approach, but tightening the screw with everything hanging from the detent spring seems a bit scary to me. As you say, a gentle touch may be sufficient. How would you keep the escape wheel locked? At the moment, the locking jewel is the only thing holding it. If it slips while you are tightening the passing spring attachment screw, that is sort of bad news. :eek:

    If it slips and snaps off the locking jewel it is really bad news, isn't it?
     
  15. gmorse

    gmorse Registered User
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    Hi Tom,

    Wedging the escape wheel very securely as Dr. Jon suggests is clearly the first step if you don't want to go as far as letting down the mainspring and the maintaining power, but holding the detent perfectly still to protect its spring whilst addressing the passing spring issue would be a very delicate operation. Depending on the design, removing the detent to correct the passing spring and replacing it again in exactly the correct place may not be a problem; if it's a dovetail mount, that's a different matter.

    Regards,

    Graham
     
  16. Dr. Jon

    Dr. Jon Registered User
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    #16 Dr. Jon, Mar 7, 2019
    Last edited: Mar 7, 2019
    I got the idea for this simple fix from looking at my example. My guess is that the passing spring was jarred just a bit and enough to make it miss the roller. If this is correct the fix I suggest is workable. The detent is mounted to plate and the escape wheel teeth rise close the top plate making it simple to wedge both the detent and escape wheel. The screw is about halfway between the foot and end of the detent just where it narrows down.

    Another examination of mine suggest that my diagnosis is either wrong or detent locking screw is missing. Mine has this screw under the passing spring on one side and the escape wheel on the other side. There is not enough room the the passing spring to slip that far. The entire assembly is easy to see. Here are a couple of photos with indicated parts called out in the first photo.

    If the detent locking screw is engage against the detent there may not be space for the spring to fall out of alignment. If it has it should be easy to see. This is what a good one looks like and how the passing spring is set up.

    The blue arrows in the second photo indicate where wedges can be placed to protect the detent, if force is needed on the passing spring holding screw, and the closeness of the escape wheel teeth to the plate for wedging.

    Parts_sm.jpg Wedge_sm.jpg

    BTW I once broke a locking jewel when the detent slipped as I was letting down a mainspring. My experience is that wedging the escape wheel is safe enough and lot safer than letting down the mainspring with the detent in place. If the passing spring has slipped, I see no reason to remove the detent.
     
  17. Jerry Freedman

    Jerry Freedman Registered User
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    Dr. Jon: Your photo was big help. The watch maker tells me that what he calls the unlocking jewel was loose and out of position but intact. he also
    said that the passing spring needs adjusting. So far so good.

    Thanks for the help.
     

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