Jacot Pendulum repair

Discussion in 'Clock Repair' started by woodlawndon, Jan 15, 2020.

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  1. woodlawndon

    woodlawndon Registered User
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    This is the second Jacot I have come across, fortunately the first one was working perfectly and just needed cleaning. This one from a New Haven shelf clock is in a little rough shape.

    The cord inside is broken and I can't quite figure out how a new one would be attached. I am assuming that the cord is wrapped around the indicator pointer and then tied to the notches on each end of the rectangle.

    How tight should the cord be tied and how many wraps around the indicator is normal? Anything else? Any guidance is appreciated, thanks.
    Don

    fullsizeoutput_578.jpeg
     
  2. Kevin W.

    Kevin W. Registered User
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    Thats a new one for me Don. I had no idea what was inside .
     
  3. shutterbug

    shutterbug Moderator
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    You only need a couple of wraps around the center. Note that the dial is for determining how much you moved the adjustment nut. It does not affect the adjustment. It's often easier to leave the dial non-functional than to try to get it working right again.
     
  4. Jim Hartog

    Jim Hartog Registered User
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    Hello Don,

    Did this some years ago but I did take pictures. Pics below. The little slots are to anchor the string.

    Jim

    NH bob 004.JPG NH bob 005.JPG NH bob 006.JPG
     
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  5. woodlawndon

    woodlawndon Registered User
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    That's perfect Jim, thanks. That's what I figured but hadn't done it before. It's snowy out there today, think I'll give this a try.
    Don
     
  6. Uhralt

    Uhralt Registered User
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    Interesting, this looks quite similar to what was used in old radios to move the capacitator to dial into the various radio stations. I wonder if there should be a small helical spring to keep tension on the string, like it was in the radios?

    Uhralt
     
  7. Willie X

    Willie X Registered User

    Feb 9, 2008
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    I'm thinking the same thing. Pretty sure it will need a spring there somewhere, to keep the line snug. It looks rather Mickey Mouse, with or without a spring ... :) Willie X
     
  8. Jim Hartog

    Jim Hartog Registered User
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    Hello,

    No spring. The string is "snug" on the post so that there is enough friction to rotate the indicator. Two wraps would produce more friction but one seems to be enough. It can be tested before the back is soldered back on.

    Jim
     
  9. Jim Hartog

    Jim Hartog Registered User
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    Hello again,

    Looking closely at my third photo (I did do this years ago) there seems to be a slot in the post that may serve as an anchor point for the string. I may have two wraps on there. One wrap on each side of the anchor point?

    Jim
     
  10. woodlawndon

    woodlawndon Registered User
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    I just wanted to follow up on this. My first attempt worked but not very well, it seemed the cord wasn't providing enough friction. I spread a very thin layer of wax on the cord, this seemed to stiffen it enough and it's working well. I can't imagine there is any accuracy whatsoever with the scale, it's just a visual indicator, which is fine, I think it looks kinda cool.

    Also, I researched this pendulum a bit more, turns out there is no spring inside, just wrapped with cord. I found this patent diagram courtesy of David Labounty.
    Don

    puHj7S5HT3qtphRlTtrPig.jpg IMG_5710.JPG jacot.jpg IMG_5709.JPG
     
  11. Jim Hartog

    Jim Hartog Registered User
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    Hello Don,

    There was no little slot in the indicator post to snuggle the string into?

    Jim
     
  12. woodlawndon

    woodlawndon Registered User
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    I didn't see one Jim. There just seemed to be some small grooves on the post where I presumed the cord was meant to wrap around.
    Don
     
  13. Jim Hartog

    Jim Hartog Registered User
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    Hello Don,

    If you look closely at my third photo, you can see how the string appears to "disappear" into a slot on the post. That would pinch the string and add friction. I may have stuck some glue in there, too. Hmmm.

    Jim
     
  14. Willie X

    Willie X Registered User

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    #14 Willie X, Jan 18, 2020
    Last edited: Jan 18, 2020
    So the cord is loose around the little drum? A tightly braded string rubbed with rosin might help your action a bit. Won't need to be too tight with two turns. Interesting ... :) Willie X
     
  15. woodlawndon

    woodlawndon Registered User
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    Yeah I do see that. OK, I'm curious now and if there is a slot, that would definitely be the correct method. Attempt number 3 coming up.
    Don
     
  16. woodlawndon

    woodlawndon Registered User
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    I just wrapped it loose Willie, but Jim is suggesting that there is a slot in the drum that you tuck the cord into to hold it fast to the post. That makes sense and I'm going to have another look. If there isn't one on my post for some reason I'm going to try your rosin suggestion.
    Don
     
  17. Uhralt

    Uhralt Registered User
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    The patent figure 4 seems to describe the slot.

    Uhralt
     
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  18. Jim Hartog

    Jim Hartog Registered User
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    Hello Uhrait,

    Figure 4 shows a hole through the post for the string. That would work well, but, that is not what I had. I had a slot in the side of the post. The hole or slot or nothing idea may be the evolution of the design. It would be easier to cut a slot than drill a hole and the do nothing thing would have been even easier.

    I had the Gilbert version of this apart once and I think it had a rack and pinion arrangement.

    Jim
     

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