American Pendulum Attachment for Seth Thomas 41A...

Discussion in 'General Clock Discussions' started by RobBurkhart, Jul 10, 2020.

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  1. RobBurkhart

    RobBurkhart New Member

    Jul 10, 2020
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    Hi NAWCC!

    I received an antique Seth Thomas wall clock from my mother recently. I believe the clock is fully working, but the pendulum(s) have come off and need some help understanding how to re-attach them.

    To start, I believe it is a 41A regulator movement per the markings. The clock is a large round wall clock. There is a leader hanging with a hook. The issue for me is that there are two pendulums (or a pendulum and a weight?) shown in the pictures, and I have not been able to figure out how they both attach, or even if they do.

    The brass pendulum feels too light to keep the movement going but neither on their own seem to keep the pendulum swinging. It could easily be a balance issue, but I was hoping to be sure I was doing it correctly before trying to troubleshoot balance.

    Happy to answer any other questions if I forgot to add something required to answer the question accurately.

    Thanks for any help!

    -Rob


    movement-41A.jpg Pendulums.jpg
     
  2. Tim Orr

    Tim Orr National Membership Chair
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    Good evening, Rob!

    It may be, of course, that neither of the "bobs" you have is right for the clock. If the bob is not exposed to view when the works is in the case, you'd expect a less decorative bob, like the one on the right in your second photo. But, neither one may be right. In any case, you would only use one bob on the clock, not both.

    Also, the bob doesn't keep the clock running. The mainspring and gear train keep the bob oscillating from side to side. It could be that the works is so dirty and gummed up that there's not enough power left to kick the bob from side to side. It could also be that the clock is out of beat. Do you know how to adjust the beat? There are articles here on that subject, like this one: Beat Setting 101

    In fact, some people will try to run a clock with no bob at all to test it. If you can get it to run that way, it will, of course, run very fast, but it will at least indicate that there's something going more or less right. Still, a heavier bob is not going to fix it.

    Simply, if you hang the bob on the hook at the end of the leader, then push it so it swings back and forth, you want to hear a "tick" and a "tock" evenly spaced apart. If that isn't right, it may be very difficult to get the clock to run for any length of time, especially if it's kinda gummed up and dirty, or has other problems.

    This clock has a stopworks (the two small, funny-looking gears in the winding area that mesh together) on the winding setup, so it's obviously a bit higher grade than the cheapest clocks.

    A diagnostic trick some folks use is to get a little artist's paintbrush and use it to dab a bit of paint thinner / mineral spirits on each one of the pivot holes in the clock plates. This may have the effect of loosening up some of the gummed up oil. It is not a repair technique, but a diagnostic technique. If it works, and gets the clock going, it is pretty good evidence that your clock needs a thorough cleaning – at least.

    Good luck and keep us posted!

    Best regards!

    Tim Orr
     
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  3. shutterbug

    shutterbug Moderator
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    I'm guessing that neither bob shown is the correct one for the clock, but the one on the left would probably work. Does the clock have a time setting adjuster on the front? it may have markings like this: S F A pic of the case might help too.
     
  4. RobBurkhart

    RobBurkhart New Member

    Jul 10, 2020
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    Tim,

    Thank you so much for the information. I will try the tricks above and may come back to the thread based on what I find. Interesting that the bob is not needed to keep it going. I guess that was my misconception, but what you mentioned about the spring does make sense.

    Best regards,

    Rob
     
  5. RobBurkhart

    RobBurkhart New Member

    Jul 10, 2020
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    Tim,

    Great suggestions and I believe all is working now. I m may have some fine tuning on the bob as it seems to be gaining a minute over about a 12 hour period, but I also may be expecting too much precision? Regardless, thank you so much for your sage advice!

    Best regards,

    Rob

    Here's a link to a video of it running. Does it sound right to you?
     
  6. Tim Orr

    Tim Orr National Membership Chair
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    Good afternoon, Rob!

    Sounds to me as though you are still quite a bit "out of beat." If you can twist the clock on the wall, you should be able to hear the beat even out at some point. Try it, making sure first that securement to the wall is solid.

    According to many authorities, being out of beat does not affect accuracy. Instead, it affects the amount of power needed to run the clock successfully. And it sounds lousy.

    Depending on how clean your clock is, how much wear it has, and other service considerations, I would think you could do better than 1 minute in 12 hours (2 minutes a day). You do have stopworks on the mainspring, so that indicates the clock was meant to keep pretty good time.

    I would think that in good condition, properly bushed and lubricated, you could be able to do two or three minutes a week, maybe even less.

    Best regards!

    Tim
     
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  7. one1laner

    one1laner Registered User

    Aug 1, 2020
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    Hi Tim! Can you tell us what a stopworks is? Thank you,

    John
     
  8. Tim Orr

    Tim Orr National Membership Chair
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    Good afternoon, John!

    I've attached an enlargement of one of the original pix. See the two "gears"? If you look closely, not all the "teeth" are the same. And they're kinda funny-looking anyway. The base of one tooth is a different shape from the others. When you turn the key, the two gears mesh until the oddball teeth bump into each other, and that jams the mechanism and prevents the gears from turning any further.

    What this does is limit the number of turns that the clock's key can be turned. The idea is to position the two gears so that the clock gets wound somewhere in the middle of the range of its mainspring – sort of a "Goldilocks" zone. A spring doesn't exert the same force throughout its run. It tends to have a large force when wound tight, and little or no force when it's near the end of its wind.

    So, if the stopworks is set up correctly, the part of the mainspring that gets used can be optimized to be in that "Goldilocks" zone. There are different versions of this concept, some similar to a "Geneva stop" and others looking like a "Maltese Cross," but the idea is to keep the spring tension in the optimal range. Fusee mainspring systems did something different, using a sort of graduated spiral "pulley" to adjust the force over the range of the mainspring. The "stackfried" concept used a sort of "brake" to accomplish this. Not too hot – not too cold – but "just right."
    StopWorks.jpg
    Hope this helps!

    Best regards!

    Tim
     
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  9. one1laner

    one1laner Registered User

    Aug 1, 2020
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    Hi Tim! Wow, thank you for that fine explanation. I understand now. Appreciate the information and education. Before this, I hadn’t heard of it. ☺️
     

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