Pendulum Wobble

Discussion in 'Clock Repair' started by clockman230@comcast.net, Mar 6, 2017.

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  1. clockman230@comcast.net

    clockman230@comcast.net Registered User

    Jan 30, 2005
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    Twisting Motion of Pendulum

    In a long case clock, the pendulum has a twisting motion rather than a motion in the same plane. Could this stop the clock? How can one fix this ?
     
  2. harold bain

    harold bain Forums Administrator
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    Re: Twistig Motion of Pendulum

    It could be the suspension spring is twisted or partly broken. May be time to call a repairman to fix it.
     
  3. shutterbug

    shutterbug Moderator
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    Re: Twistig Motion of Pendulum

    The suspension spring and crutch need to be in line and the crutch loop needs to be parallel to the floor. There should be a tiny bit of wiggle room where the pendulum hanger passes through the crutch.
     
  4. R. Croswell

    R. Croswell Registered User
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    Re: Twistig Motion of Pendulum

    In a tall clock the pendulum my be suspended from a bracket mounted to the case. The movement must be parallel to the back of the case and the path of the pendulum. Would help to see pictures of the suspension spring and how the crutch contacts the pendulum. A bad suspension spring (already mentioned) can be the problem sometimes even if it looks OK.

    RC
     
  5. bruce linde

    bruce linde Technical Admin
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    Re: Twistig Motion of Pendulum


    hmm... the previous posters are the guys who really know what they're talking about.

    on the other hand, this newb has discovered that he needs to check all of the following, each time:

    - movement parallel to back of case (which, hopefully, is perpendicular to the floor... which, hopefully, is also level)

    - suspension spring not kinked or funky

    - pendulum hanger (if applicable) hooks parallel and lined up with each other so they hang on the bottom of the suspension spring hooks (if applicable) evenly. if it's a standard tall case suspension spring with a brass block at the top keeping the pendulum assy from slipping down through the suspension block, make sure there's not too much play in-between the suspension block extensions that spring sits between

    - crutch pin (where it goes through the crutch plate/pendulum rod) perpendicular to the pendulum rod and parallel to both floor and sides of case

    - pendulum bob mounted snuggly to pendulum rod... not able to twist on the rod because the top is loose

    not talking big adjustments to any of the usual suspects... just suggesting you call them all in for questioning. heavier bobs tend to be more forgiving of slight alignment issues, just as a heavier car will have a smoother ride over a rough rode than a light car.

    this is all theoretical without photos and/or a video of the actual wobble.
     
  6. shutterbug

    shutterbug Moderator
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    Re: Twistig Motion of Pendulum

    Note to RC - I'm pretty sure smike was including you in the "previous posters" :) He quoted you as a good example, but on reading it you could possibly think otherwise....at least I did and had to read it a couple of times.
     
  7. bruce linde

    bruce linde Technical Admin
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    Re: Twistig Motion of Pendulum


    my intent was to expand on rc's answer, but make it clear that he and the previous posters were the posters with actual credibility
     
  8. shutterbug

    shutterbug Moderator
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    Re: Twistig Motion of Pendulum

    Yep, knew that, smike. Just wanted to be sure RC didn't read it like I did the first time through :)
     
  9. bruce linde

    bruce linde Technical Admin
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    Re: Twistig Motion of Pendulum

    rc knows i respect both his knowledge and skills, as well as the consistently high road manner in which he presents his comments. he's one of my favorite teachers here for both clocks and learning how to communicate well with others.
     
  10. clockman230@comcast.net

    clockman230@comcast.net Registered User

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    Re: Twistig Motion of Pendulum

    Thanks for all the advice; however, I followed all the suggestions and the pendulum still does not have acceptable motion in one plane. I am baffled by this.
     
  11. BLKBEARD

    BLKBEARD Registered User
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    Re: Twistig Motion of Pendulum

    Does the floor bounce much when someone walks across the room?
     
  12. dad1891

    dad1891 Registered User

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    Re: Twistig Motion of Pendulum

    I have had cases where the suspension spring looked fine, but it was in fact causing a wobble.
     
  13. R. Croswell

    R. Croswell Registered User
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    Re: Twistig Motion of Pendulum

    RC read it as complementary (perhaps more than deserved) as intended. Glad to have my comments expanded on. Pendulum wobble can be a most exasperating issue to solve. I've seen suspension springs that look fine cause a problem (as already mentioned) as well as some that looked like they had been through a meat grinder run perfectly. Rate adjusters can also be an issue if the 'chops' are loose and wobble side to side or uneven. Sometimes a suspension post slot may be wider on one end and narrow on the other where someone 'pinched' it. and on and on.

    RC
     
  14. R&A

    R&A Registered User

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    Re: Twistig Motion of Pendulum

    Why don't you post some pictures of the situation in question. Will give a better understanding of what we are actually trying to pin down??
     
  15. bruce linde

    bruce linde Technical Admin
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    Re: Twistig Motion of Pendulum

    funny, i have a used-to-be-a-grandfather-clock-but-now-it's-hanging-on-the-wall-without-the-base-or-top seconds clock and i noticed the pendulum was wobbling ever so slightly as it swung to the far left... and thought of this thread.

    i swapped out the suspension spring, but no go.

    what i ended up doing was:

    - closing the two parallel pendulum hooks (hanger assy: make a peace sign with your index and middle fingers and then curl your fingers forward) at the top of the pendulum so they were a little snugger to the suspension spring pins... essentially curled them a little more

    - moving the pendulum hooks a little closer together, so the suspension spring had less slop between the two pendulum hooks... bring those two fingers a little closer together

    - held the suspension spring and pendulum assy carefully in my hands while watching the pendulum swing back and forth... using the straight lines of my hardwood floor as a guide. i noticed that when the suspension spring was perfectly perpendicular to the floor boards, the pendulum rod (and bob) were not... they were torqued a little, with the right side a little farther away and the left side a little closer to me.

    - grabbed the base of the pendulum hanger assembly with needle nose pliers and twisted the assy slightly until the rod and bob were perfectly perpendicular to the suspension spring... making sure the two pendulum assy hooks were still aligned correctly.

    - re-installed original suspension spring, all good.

    as my clock mentor often says: it usually comes down to bending stuff! :cool:
     
  16. David S

    David S Registered User
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    Re: Twistig Motion of Pendulum

    I prefer the words "adjusting" or "calibrating"...but sure "bending" works :)

    David
     
  17. R. Croswell

    R. Croswell Registered User
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    Re: Twistig Motion of Pendulum

    I believe that "reforming" is the choice of preference in some circles, but everyone knows what bending means, so sure, that works.

    RC
     
  18. bruce linde

    bruce linde Technical Admin
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    Re: Twistig Motion of Pendulum


    yes... 'reforming' ... dang auto-correct! :cool:
     
  19. Time After Time

    Time After Time Registered User
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    Re: Twistig Motion of Pendulum

    I've found this to be so common a problem with American Mantels that I'm in the habit of carefully evaluating the chops as part of my overhaul. I've even had a loose regulator suspension cause intermittent stalling of a Seth Thomas 124 movement. Attached is a photo of a temporary aluminum "shim" which fixed the problem. The clock belongs to us. The next time I overhaul the movement I may "reform" the base of the chops or perhaps I'll just replace the Aluminum shim with one made of Brass. Doubt that chops present problems in most Tall Case Mechanisms though.

    [​IMG]
     

    Attached Files:

  20. clockman230@comcast.net

    clockman230@comcast.net Registered User

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    Long case clock has a wobble that is synchronized with the beat of the pendulum such that, when the pendulum moves to the right its right arc moves to the back of the case. This wobble continues on the left side in the same manner also. I have replaced the suspension spring, stabilized the clock case, and put the clock into beat. Can there be a problem with the crutch pin as it gives its pulse to the pendulum ? Where else can I look to solve this wobble ?
     
  21. R. Croswell

    R. Croswell Registered User
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    Yes if it is not perpendicular to the pendulum stick. In a clock like this you might swing the pendulum with the movement out of the case and make sure the pendulum is swinging true and parallel to the back of the case.

    RC
     
  22. Tinker Dwight

    Tinker Dwight Registered User

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    Most tall clocks have a large disk. Is it straight for the intended travel.
    It has aerodynamics as does a wing.
    Also check that the suspension spring isn't so tight that it traps the suspension spring.
    Forward and backwards should be free such that gravity controls the hang.
    It does rob some power but a good movement shouldn't have an issue but it is
    often erratic and takes a little from a steady beat. Just to be 1 second of a day,
    it has to be better than about 1 part in 100,000.
    It doesn't take much to do 1 part in 10,000.
    Tinker Dwight
     
  23. shutterbug

    shutterbug Moderator
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    Everything must be straight. Crutch loop 90° to the front plate, and horizontal to the floor. Pendulum bob straight, running horizontal to the wall. Crutch loop running centered with the hanger, and a slight amount of wiggle room. A tiny drop of oil at the friction point might help. In the case of the crutch interfacing with the pendulum by a slot cut into the pendulum ... metal on each side of the slot is best. Straight slot, crutch at 90°.
     
  24. bruce linde

    bruce linde Technical Admin
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    you asked 'Can there be a problem with the crutch pin as it gives its pulse to the pendulum?'. the answer is yes. if there is too much slop between crutch pin and crutch slot, you can get additional/unwanted clicking as the pendulum swings back and forth and the pin smacks against the sides of the crutch slot/plate... or you can get wobble.

    again, fixing it is a combination of things... mostly making sure every component in the chain is true and functioning as it should.

    you say you've replaced the suspension spring, but there's more to it than that. how does the spring fit in the slot it's hanging in? how does the pendulum hanger (and hooks) hang on the bottom of the suspension spring... if those hooks are too loose, it can introduce wobble. if they're too far apart, it can introduce wobble. if they're not perpendicular to the pendulum rod, it can introduce wobble. if the pendulum rod is not perfectly true and twists slightly over its length, it can introduce wobble. if the bob is not mounted/seated perfectly parallel to the rod, same.

    at this point, it would help to see some video. can you please shoot some (with reasonable lighting and clarity!) using your mobile phone and upload to this thread?

    i've seen videos from other posters who've claimed their clocks were in beat (and weren't), that things were true (and weren't), etc. i just spent several months trying to figure out why and older (and admittedly beat up) seth thomas movement would either run fine for weeks or stop after 5 minutes... randomly... and finally figured out what bonehead error i had introduced in the one gear i WASN'T suspecting. at least everything else in the train got checked!!!!!! :cool:

    please post some video... and include a sound track to we can hear it ticking. it would be great to see escape wheel teeth hitting pallets (on both sides), suspension holder and spring, crutch pin and plate, the actual wobble, etc. if you can get a view from the side, it would be helpful to see if crutch rod is moving front/back as it swings, or is swinging parallel to the back plate of the movement.
     
  25. matthiasi

    matthiasi Registered User

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    As has been posted previously:
    ensure that the crutch loop (or slot) is at 90degrees to the REAR plate, in the direction of the swing. If it is not, the crutch gives the pendulum a slight sideways impulse, which causes it to swing in an elliptical or figure 8 arc motion.
    If the crutch loop is not parallel to the floor (i.e.- it goes down or up when viewed from the side), it will not give the pendulum a true impulse, however, it isn't as critical as above.

    Also, a "too stiff" pendulum spring can cause the pendulum to make an elliptical or figure 8 arc motion as well.

    Also, ensure that the slot in the pendulum holder (where the spring is mounted) is also at right angles to the rear plate. All too often, especially on the old clocks, where the slot was hand-cut / sawn, these are not always straight and perpendicular.

    I've also seen it caused by a bent / warped pendulum stick (mainly wooden).

    If the pendulum / suspension spring is kinked, replace it. It can't be straightened reliably. The metal structure has been compromised and will not give a perfect swing again, even if superficially straight.
     
  26. Tinker Dwight

    Tinker Dwight Registered User

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    To help define where the problem is:
    If the pendulum hangs from the case, remove the movement and
    swing the pendulum. When free, does it swing poorly.
    If the pendulum swing from a post on the movement, push the crutch
    off to the side or remove it and swing it.
    If it swings true, the problem is how it is driven.
    If not, it is in the pendulum itself.
    Tinker Dwight
     
  27. Willie X

    Willie X Registered User

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    I just quickly scanned this thread, so I might have missed this point. But ... has the suspension spring actually been replaced with a new one?
    Willie X
     
  28. clockman230@comcast.net

    clockman230@comcast.net Registered User

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    I am working on all the suggestions. The crutch pin is slightly elevated. The new suspension spring is held on the movement with a tapered pin. The pendulum is held to the suspension spring with a tapered pin. All the attachments seem stable and tight. I suspended a thread with a weight to see if the clock moves ; the results shows no movement of the lead sinker weight. Can a one degree of elevation be the culprit ?
     
  29. matthiasi

    matthiasi Registered User

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    Not likely.
     
  30. shutterbug

    shutterbug Moderator
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    Could we see a picture of how that connects?
     
  31. R. Croswell

    R. Croswell Registered User
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    Yes, can we see a picture. Generally one would expect the pendulum to hook onto a straight pin. If it hangs on a tapered pin perhaps only one supported at one point rather than across the length of the pin?

    RC
     
  32. bruce linde

    bruce linde Technical Admin
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    clockman230 -

    so far 2000+ words on the subject... including a couple of requests for pictures that would really help inform the discussion.

    i see ads on craigslist where the ad says 'clock for sale... wood'... with no photos... uh huh.

    do you not have a mobile phone you can use to take some photos or videos?

    these guys have sharp eyes... just sayin'/suggesting.

    smike
     
  33. Willie X

    Willie X Registered User

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    Nothing should be "tight". The top of the suspension should be snug in its chops but free to move easily. Everything else should have plenty of freedom to move about. I often take the the complete pendulum assembly out and sight down it from the top. Everything should be as straight as an arrow. Also support the assembly at the hook, this will often show you that the joining point is not supported evenly. (I think this is what RC just mentioned). Often you will see a inward ot outward bow in the rod or stick. This alone can cause dishing.
    When I have one that refuses to do right, I often shorten the suspension spring a bit and lengthen the rating adjustment a like amount. This has somewhere around a 50:50 sucess rate.
    Willie X
     
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