Helsbro wristwatch mainspring

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  • #50029
    mclark3617
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    • Topics Started: 28
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    I have a Helbro Invinsable 21 wrist watch that appears to have a broken main spring, Is there a way to get that out without taking out the centerwheel. I have the bridge off but the centerwheel doesn’t seem to want to let it go.

    #64758
    randy
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    • Topics Started: 39
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    Hi Hank

    Often you can grab the mainspring barrel arbor and gently work the mainspring assembly out from under the center wheel…but not always.
    Just depends on the design and tolerances in the plates.

    Try to ease it out , but if you run into interference,..you’ll just have to remove the bridge…

    Best of luck

    Randy

    #64759
    mclark3617
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    I took the Bridge off but it looks like the center wheel is goin to stop it. but I don’t think its a broken mainspring anymore. the watch was stored many years with the spring fully wound up, it will only run for about 7 1/2 hours. would being fully wound for so long do that?
    also while messing around with it I found the cannon pinion not pressed all the way down. that may have been the cause of earlier problems

    #64760
    randy
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    • Topics Started: 39
    • Total Posts: 594

    Hello Hank,
    The weakest of mainsprings should run a movement at least 24-30 hours in my experience. Yours may not be broken, but it’s probably taken a “set” and won’t produce much power.
    If you are going to get this one out,..I’m guessing you’ll have to further disassemble the watch.
    Pull the canon pinion to release the center wheel so you can get the barrel out..etc.etc.

    Randy

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