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Thread: Pendulum Wobble

  1. #16
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    Default Re: Twistig Motion of Pendulum (By: smike)

    Quote Originally Posted by smike View Post
    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! 8-)
    I prefer the words "adjusting" or "calibrating"...but sure "bending" works

    David
    David S

  2. #17

    Default Re: Twistig Motion of Pendulum (By: David S)

    Quote Originally Posted by David S View Post
    I prefer the words "adjusting" or "calibrating"...but sure "bending" works

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

    RC

  3. #18

    Default Re: Twistig Motion of Pendulum (By: R. Croswell)

    Quote Originally Posted by R. Croswell View Post
    I believe that "reforming" is the choice of preference in some circles, but everyone knows what bending means, so sure, that works.
    RC

    yes... 'reforming' ... dang auto-correct! 8-)
    i collect antique clocks because i get all that extra time...

  4. #19

    Default Re: Twistig Motion of Pendulum (By: clockman230@comcast.net)

    Quote Originally Posted by R. Croswell View Post
    ... Rate adjusters can also be an issue if the 'chops' are loose and wobble side to side or uneven...
    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.

    Attached Thumbnails Attached Thumbnails P1030676.jpg  
    "Every Nation gets the Government it deserves." -Joseph Marie de Maistre...
    ...and Bruce Alexander






  5. #20

    Default Pendulum Wobble (By: clockman230@comcast.net)

    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 ?
    pamacm

  6. #21

    Default Re: Pendulum Wobble (By: clockman230@comcast.net)

    Quote Originally Posted by clockman230@comcast.net View Post
    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 ?
    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

  7. #22
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    Default Re: Pendulum Wobble (By: R. Croswell)

    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

  8. #23

    Default Re: Pendulum Wobble (By: Tinker Dwight)

    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°.
    A man with a clock always knows the time. A man with two clocks is never sure.

  9. #24

    Default Re: Pendulum Wobble (By: clockman230@comcast.net)

    Quote Originally Posted by clockman230@comcast.net View Post
    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 ?

    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!!!!!! 8-)

    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.
    i collect antique clocks because i get all that extra time...

  10. #25
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    Default Re: Pendulum Wobble (By: smike)

    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.
    Matthias in B.C.
    ------------------

  11. #26
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    Default Re: Pendulum Wobble (By: matthiasi)

    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

  12. #27

    Default Re: Pendulum Wobble (By: clockman230@comcast.net)

    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

  13. #28

    Default Re: Pendulum Wobble (By: Willie X)

    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 ?
    pamacm

  14. #29
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    Default Re: Pendulum Wobble (By: clockman230@comcast.net)

    Not likely.
    Matthias in B.C.
    ------------------

  15. #30

    Default Re: Pendulum Wobble (By: clockman230@comcast.net)

    Quote Originally Posted by clockman230@comcast.net View Post
    The pendulum is held to the suspension spring with a tapered pin.
    Could we see a picture of how that connects?
    A man with a clock always knows the time. A man with two clocks is never sure.

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