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  1. #1
    Registered user. ANDY YALE's Avatar
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    Default A common watch symptom - what might it mean?

    I have had several movements that run with poor amplitude, but if the mainspring is fully wound, and you give the crown another little twist, tightening the spring a bit more, then hold the crown there, they take off and run with a good swing. Until you release the crown.
    I've seen this in 2 Illinois 12s movements and a Waltham 16s movement.
    My first thought was weak or set mainspring. I had 2 spare barrels for the Illinois but switching them out didn't change the behavior.
    I think it must be an indication of some resistance in the movement, but all of them run well on the high speed test and the balances spin freely with the pallets out.
    Can I draw any kind of generalized conclusion when I see this?

  2. #2

    Default Re: A common watch symptom - what might it mean? (By: ANDY YALE)

    You're basically adding more power when you do this. This will overcome faults in the train. Many watches that need service will start running when you put winding pressure on the crown but will stop immediately when you back off. So, basically, you're not getting enough power through the train for one reason or another. Incomplete cleaning, cracked train jewel, etc. etc.

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    Default Re: A common watch symptom - what might it mean? (By: Dave Coatsworth)

    I agree with Dave, resistance somewhere in the gear train.

    When you have the pallet out you can see if you get some backlash of the escape wheel. Wind the watch half a turn with the crown and observe the escape wheel. It should spin, come to a halt and then reverse! If it does, the gear train runs smooth and your problem is elsewhere to be found. If you don't get any back lash (or at least an attempt of a back lash) you need to check the gear train.

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    Default Re: A common watch symptom - what might it mean? (By: Skutt50)

    Quote Originally Posted by Skutt50 View Post
    I agree with Dave, resistance somewhere in the gear train.

    When you have the pallet out you can see if you get some backlash of the escape wheel. Wind the watch half a turn with the crown and observe the escape wheel. It should spin, come to a halt and then reverse! If it does, the gear train runs smooth and your problem is elsewhere to be found. If you don't get any back lash (or at least an attempt of a back lash) you need to check the gear train.
    Much neglected seems to be at the beginning. ie: mostly I see wear on the bridge or the barrel.

  5. #5
    Registered user. ANDY YALE's Avatar
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    Default Re: A common watch symptom - what might it mean? (By: roughbarked)

    Guys - thanks for the input. I already understood that it was resistance. Now I'm understanding that if the train runs smooth up to the pallets without the extra pressure on the crown, and doesnt run when you put the balance back in, the problem must be in the balance, jewels, or hairspring.
    I got the Waltham that was showing this behavior sorted last night. The hairspring stud was just a trifle low in the balance cock and it was rubbing on the hairspring and knocking it out of the regulator pins. Once this was corrected, the watch began to run properly.
    I generally test a movement at each step of assembly to find any problems. What this teaches me is a balance can run smooth in the movement with the pallets out on test, but act entirely different when engaged with the pallet.

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    Default Re: A common watch symptom - what might it mean? (By: ANDY YALE)

    How do you measure if the gear train is running "smooth" (I'm assuming you are talking about loss of power) without seeing amplitude? You could still be losing a lot of power in the going train due to dirt or worn pivots and bushings. Not to mention deformed tooth profiles and out of mesh issues.

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    Registered user. ANDY YALE's Avatar
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    Default Re: A common watch symptom - what might it mean? (By: karlmansson)

    Just a visual based on the escape wheel - does it have a little bit of reverse motion when the train runs down.
    I read that was a measure of the train being in good shape.

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    Default Re: A common watch symptom - what might it mean? (By: ANDY YALE)

    Everything is relative. I think a high speed test will give you mostly information about if there are any gear teeth out of line or if something is binding. But you don't really load the train when doing a high speed test. Lateral pressure on the pivots becomes much greater with the escapement installed and the spring fully wound.

    Also, not all movements are designed in such a way that they will have backlash. And slop in the bearing surfaces (excessive side shake) will show a very free gear train but it will shift under pressure causing the tooth profiles to mate in a way that will cause power loss.

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    Default Re: A common watch symptom - what might it mean? (By: karlmansson)

    It just occurred to me that an additional factor as to why a backlash test wouldn't give you the whole story is that starting friction is normally much higher than moving friction. A 18000bph watch is starting and stopping 5 times a second. So any imperfection spotted during a high speed or backlash test will be amplified as the watch is running as it's built to do with impulses every 1/5th of a second.

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    Default Re: A common watch symptom - what might it mean? (By: karlmansson)

    Got it. Thanks, Karl. The watch is such a dynamic machine and I keep applying static analytics to it.
    Going to go stick my head in running water.

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