Pendulum rubbing-ST Mantel

Discussion in 'Clock Repair' started by grm9, Mar 5, 2011.

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  1. grm9

    grm9 Registered User

    Feb 12, 2011
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    I am a complete newcomer to the mechanisms inside clocks. I have this Seth Thomas mantel clock (#89) which hasn't run in about 24 years, and I'm finally getting around to looking at it. As you can see in the photo, the pendulum is in contact with the back edge of the milled-out recess (and yes, the clock is on a level surface). The only way I can correct this is by putting 1/4" thick spacers under the back feet. Can anyone tell me if the pin or post from which the pendulum is suspended is adjustable in and out, and if that would be the right way to correct this? I searched the posts and I didn't find anything related to this kind of issue. Any help would be much appreciated.
    Regards,
    George
    View attachment 5003
     
  2. Steven Thornberry

    Steven Thornberry User Administrator
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    George:

    That pendulum looks awfully low. How good a timekeeper is it?
     
  3. Kevin W.

    Kevin W. Registered User
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    Apr 11, 2002
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    George did the suspension spring come out of place?
     
  4. grm9

    grm9 Registered User

    Feb 12, 2011
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    Steve, I bought the clock from a friend in 1975 and it never kept good time. It would run for a few hours at best.
    -> posts merged by system <-
    Veritas, as to the suspension spring coming out of place, it doesn't appear to be out of place, but I am very inexperienced with clocks. It is loose in the slot in the horizontal post (if wrong terminology, I'm sorry) that holds it, but there is some feature in the spring- a very small pin, I think-that keeps it from slipping out. I can move the spring up, and in and out to a certain degree, though I can't move it in enough to get the pendulum to clear the edge of the recess.
     
  5. Kevin W.

    Kevin W. Registered User
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    Apr 11, 2002
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    Likely not in beat and pendulum way too low.Can you show a picture of the back of the movement, the suspension spring?
     
  6. Willie X

    Willie X Registered User

    Feb 9, 2008
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    George,

    Is the clock movement tight and parallel to the front of the case where it attaches? A picture of the pendulum hanger might help too. Are all the feet the same height? Clearance cut looks original but there is something that is out of kilter by about 1/4".

    Just keep up the good pictures, we can eventually figure it out.

    Willie X
     
  7. grm9

    grm9 Registered User

    Feb 12, 2011
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    Thanks for looking. Do these help?

    View attachment 5004
    View attachment 5005
    View attachment 5006
    -> posts merged by system <-
    Willie X, yes, the movement is firmly attached to the front of the case, and the feet are all the same height. There does seem to be very slight wear on the slots of the screws, so I'm guessing someone had the movement out at some point, but that's not to say that's when the problem started. The clock has been packed up and moved several times in the last 25+ years, and it's possible something got knocked put of whack.
     
  8. Randyd

    Randyd Registered User

    Dec 2, 2004
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    George,

    It looks like your crutch (the brass wire with the loop in the end) is bent and may be pushing the suspension spring away from the movement. The rod should be dropping thru the middle of the loop in the crutch and not touching the back or the front of the loop. If the suspension spring rod is touching the back of the loop bend the crutch wire so that the rod falls thru the middle of the loop.

    Randy
     
  9. shutterbug

    shutterbug Moderator
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    The pendulum hanger seems to be hooked up correctly. The fact that it's dragging the bottom of the case indicates (to me anyway) that it has been replaced incorrectly. Here's what I'd do:

    Take off the bob, and pull the suspension spring out of the slots and remove it from the movement. Cut the bottom hook off at the loop, and re-bend it into a hook. That will make the pendulum about 1/2" shorter. Start the clock and be sure it's not hitting the bottom of the case, and see how it keeps time. Report back on the findings.
     
  10. grm9

    grm9 Registered User

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    Thanks to all for the help! Something curious happened when I finished up with the photos last night. I put the clock back on the shelf and it started running. That was roughly 12 hours ago, and it's still running, but lost 17 minutes. Apparently, I must have re-positioned the spring enough that the pendulum is just clearing the recess.
    To answer Randyd, yes, I did look at that, and the suspension spring does seem to be pretty much in the center of the loop. I will take another look this morning.

    To answer shutterbug, that sounds like a good suggestion. That spring looks like spring steel shim stock, and I'm going to see what I can find "at work" in case I have a need to make one.

    2 remaining questions:

    1. It sounds like it's on beat, at least to my untrained ears, however there is occasionally a third sound that comes and goes, so the clock is doing this: tick ta-tock tick ta-tock, with the "ta" relatively quiet.

    2. The S-F adjustment is approximately in the middle of its range. Is 17 minutes in 12h, or 1:25 per hour within the range of adjustment? If not, then it seems to me that shutterbug's suggestion to shorten the suspension spring will help make the clock run faster.
     
  11. Willie X

    Willie X Registered User

    Feb 9, 2008
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    grm9,

    Sounds like you are on the right track. Many times the problem lies in the sum of a bunch of small problems.

    FYI, 1/4" clearance is a good rule of thumb for pendulum clearance and that pendulum hook should face the rear of the clock but if it makes hanging the pendulum easier, I would leave it facing the front; that will not effect the clearance issue. The clearance could be a bit closer on a smaller clock like you have but there should be no chance of the pendulum brushing anything, even if the case is a good bit off level.

    Willie X
     
  12. shutterbug

    shutterbug Moderator
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    Just so I wasn't misunderstood, you cut the wire, not the spring :)
     
  13. grm9

    grm9 Registered User

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    Once again, thanks to all for sharing their knowledge. And yes, I had misunderstood, so it was good to get the clarification on which part to shorten.
     
  14. Willie X

    Willie X Registered User

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    grm9,

    On short pendulum clocks, if you cut the whole hook off the outcome will likely be a to short pendulum rod. So, you may want to try making the cut a little around the crook as it turns back up toward the tip. Then reform the hook in the opposite direction. This will result in a nicely formed hook with a little reverse bend at the tip to make it easier to hang the pendulum.

    Willie X
     
  15. Dave B

    Dave B Banned

    Jun 7, 2008
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    #15 Dave B, Mar 7, 2011
    Last edited: Mar 7, 2011
    That is a replacement suspension spring and pendulum rod. The Seth Thomas #89 movement used a narrower suspension spring, which could be slid a little further into the suspension post. I you take yours out, and grind a little off the inside edge (the edge toward the movement), you can probably get just enough room to clear the recess in the bottom of the case. While you are messing around with looking for solutions to the problem, check the bottom to see if someone has had it off at one time, and put it back on backwards. If I remember correctly, the routed out recess for pendulum bob clearance is not in the center of the bottom board.

    Also, grinding a little off the back edge of the suspension spring will make it a little bit weaker, allowing the pendulum to make a wider swing with each impulse. That will slow the clock down, allowing you to raise the bob slightly from the bottom. When I put replacement suspensions in those movements, I use the ones that are a one piece rod and "feather, which are a little narrower, and seem to be a little weaker than the "universal" ones such as that in oyur clock. When I use those two-piece ones, I grind both edges of the spring, so that it is about 1/8" wide.
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    re: hook forming - The hook should be a smooth curve, with a reverse bend in it, so that centroid of the bob is in the same plane as the suspension spring and rod. Here's a photo of a correctly formed bend. 76109.jpg
     

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