Urgos Pendulum Length - I want to Change it

Discussion in 'Clock Repair' started by Torre, May 9, 2017.

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  1. Torre

    Torre Registered User

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    #1 Torre, May 9, 2017
    Last edited: May 9, 2017
    Good afternoon. Noob here with a question regarding pendulum length for an Urgos grandfather clock movement. More specifically, I’d like to swap out a 100 cm pendulum with a 114 cm pendulum and I need to know what mods I would need to make to the movement to make it run properly?
    Am I correct in assuming I simply need to replace the escapement wheel with one that matches the new pendulum?
    I have two pendulums now (one at each length) and the only difference between the two is the length of the neck piece.
    Thank you.
    Mark
     
  2. shutterbug

    shutterbug Moderator
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    Changing the EW is one approach. It would probably be better to find a movement made for the longer pendulum.
     
  3. Tinker Dwight

    Tinker Dwight Registered User

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    You need to change the number of teeth someplace.
    Changing the escapement wheel tooth count requires
    changing the anchor to match.
    Tinker Dwight
     
  4. MARK A. BUTTERWORTH

    MARK A. BUTTERWORTH Registered User
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    The escape wheel is the one thing that never changes. In this movement the 2nd wheel is what is changed.
     
  5. Willie X

    Willie X Registered User

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    What movement? Unless you have a nearly new movement the parts will not be available (except from old scrap movements). Urgos has been gone for probably 15 (?) years, taken over by Hermle. Hermle has redesigned the present movements to use mostly Hermle parts.
    Bugs approach would probably be your best option, buy an identical movement made for the 114cm pendulum and either use it, or transfer the needed parts to your original movement. This could be 1 to 4 parts (?) and there are variations. No company makes the exact same movement for very long, even though the main identifier numbers may remain the same for many years. The UW03 and UW32 go back to the late 1950s, and the UW66 series goes back to the mid 1980s, hundreds of changes have been made along the way.
    So, your job may be fairly easy or maybe not ...
    Willie X
     
  6. MARK A. BUTTERWORTH

    MARK A. BUTTERWORTH Registered User
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    We actually have a stock of the original UW03 series 2nd wheels [as well as chain wheels] if anyone is interested.
     
  7. David S

    David S Registered User
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    Mark, why do you want to lengthen the pendulum?

    David
     
  8. Tinker Dwight

    Tinker Dwight Registered User

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    If you put a weight at 1/2 the effective length of the pendulum.
    of about 7% of the bobs weight, it should speed the
    pendulum up by about the right amount.
    The effective length is about from the center of the suspension
    spring to the center of the bob.
    So, say you had a 3 lbs bob, you'd add a 3.4 oz weight.
    Tinker Dwight
     
  9. Willie X

    Willie X Registered User

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    Along the line of Tink's thinking, making a new top piece from 1/4" brass stock would be easily doable. Just remember that it will need to be longer by (??).
    Willie X
     
  10. Tinker Dwight

    Tinker Dwight Registered User

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    I should note that adding the weight at the center ( 1/2 way ) is
    the most effective way to speed up a pendulum.
    Other locations take larger amounts of weight.
    This still assumes a simple pendulum. A pendulum with other weight
    distributions may have other maximal effect points.
    I could show the math if anyone is interested.
    Tinker Dwight
     
  11. Torre

    Torre Registered User

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    Thank you for all the replies.
    First of all the movement is a UW03042B – 9 bell movement taken from a crappy 80’s vintage Emperor clock. I also have a 1980 Sligh Centennial which has the same movement but stamped UW03052B and it has the longer pendulum. I’m assuming that is the reason for the “5” vs the “4” in the model number?
    If I put the longer pendulum on the movement in question it will simply stop after a few minutes.
    I have considered the idea of reducing the weight of the bob to see what happens. I actually have a Hermle pendulum at the correct length with a smaller bob. It should hang on the leader OK for a test.

    As for why I want to do this? I found this beat up Emperor about a year ago and removed the movement. After cleaning it and replacing a weight cable, it has run flawlessly on a stand for a year. Fast forward to now and I acquired a beautiful limited edition 1985 vintage Howard Miller “Charleston Manor” which is a big clock with an unusually tall cabinet and glass door. It too had an Urgos but a simple rod chime version. I was able to swap movements and keep the original dial of the “Charleston Manor”. The clock runs great but the pendulum is too short so it looks strange in that tall cabinet. Photo attached.
    [​IMG]

    Incidentally, I did this same exercise a couple of years ago with a newer Hermle – 9 bell movement taken from a crappy Colonial Times clock. I put it in a beautiful Ridgeway “Victory at Yorktown” cabinet. The bells barely fit into the narrow wasted cabinet but it was a success and one of my favorite clocks now. (another photo attached).
    [​IMG]

    Thank you again,
    Mark
     
  12. Tinker Dwight

    Tinker Dwight Registered User

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    The movement stopping with the longer pendulum is
    not a fault of the pendulum.
    It may not be in beat.
    The movement may be marginal in running.
    The connection between the pendulum and the leader
    may not be solid.
    And such.
    Tinker Dwight
     
  13. Torre

    Torre Registered User

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    You are correct in that it was simply out of beat.
    I tried the longer pendulum again yesterday. Set it in beat and it has been running for over 24 hrs. at approx. 5 seconds slow per minute.
    I am going to try your center weight (10% bob weight) idea over the weekend and see what happens.
    Thanks again,
    Mark
     
  14. Torre

    Torre Registered User

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    I actually have a UW03 movement which used the 116 cm pendulum. I could steel the wheel from it.
    Do you think these wheels would fit any 03 (B) series movements?
    Thanks
     
  15. MARK A. BUTTERWORTH

    MARK A. BUTTERWORTH Registered User
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    they should. The one difference could be in the diameter of the shaft going through the front plate, but a bushing will solve that.
     
  16. Torre

    Torre Registered User

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    I tried adding weight to the center of the pendulum and there was no discernable difference in tempo.
    The 10.5” bob weighs 28 oz. so I attached 2 oz of steel shot to the center of the pendulum, halfway between the suspension spring and the bottom of the pendulum. After 24 hrs. the clock was exactly the same as before I added the weight (i.e 1 hr. 48 mins slow). I moved the weight up a bit thinking the “center” should be to the center of the bob. This too made no difference. Maybe a minute or two after 24 hrs.
    Thanks for the tip but it does not work. At least not for me. This is a lyre pendulum so I’m sure the weight distribution is not as simple as a stick.
     
  17. Tinker Dwight

    Tinker Dwight Registered User

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    The calculation was for a simple bob pendulum. The mass distribution
    of a lyre pendulum is quite different.
    Can you send me a rough measurement of the grid iron frame
    and weight as well as the location and weight of the bob part.
    I can do another calculation to see about where and what
    can be done.
    We are not beat yet.
    Tinker Dwight
     
  18. Torre

    Torre Registered User

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    Tinker,
    I truly appreciate you helping me out with this.
    The new photo I have attached shows the longer pendulum so you may compare it to the first photo of the clock I posted.
    [​IMG]

    The longer pendulum’s geometry is as follows:

    Overall length (not including the adjustment knob) = 42.5”
    Overall weight = 59.0 oz.
    Dia. of Bob = 10.5”
    Weight of Bob = 28.0 oz.
    Center Mass = 30” from top/12.5” from bottom
    The leader is 7” long so you can add another 7” to the suspension spring.

    Thanks again!
    Mark
     
  19. Tinker Dwight

    Tinker Dwight Registered User

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    I did some calculations but I'm still not sure about the
    grid iron geometry and its CG. I estimated it from the overall
    CG.
    Anyway, a 1 to 2 ounce weight mounted about 2 inches below
    the joint between the leader and the pendulum rod.
    This was using your 5 seconds per hour number.
    Tinker Dwight
     
  20. Torre

    Torre Registered User

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    Thanks Tinker.
    That is quite a bit higher up!
    I'll give this a try tomorrow and report back.
    And I think you meant to say 5 seconds slow per "minute" not per "hour".
    Per hour I could live with.
    Thanks again,
    Mark
     
  21. Tinker Dwight

    Tinker Dwight Registered User

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    #21 Tinker Dwight, May 17, 2017
    Last edited: May 17, 2017

    Don't bother. I don't know why I thought it was per hour but that was
    my calculation. 5 seconds per minute will be quite different.
    I won't be able to look at the calculation again until Monday.
    If while waiting, can you get me the CG of the grid iron, without the bob
    and the measurments to the ends of the grid iron from some reference
    I'll need a better number than "about" 5 seconds per minute. Can you measure
    over a longer period?
    Tinker Dwight
     
  22. Torre

    Torre Registered User

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    Ha. No problem. Yeah 5 sec. per hour could be adjusted by turning the adjustment knob on the bottom a half turn.
    I have measured the slowness over a 48 hr. period and it was 214 min. (and some seconds) which equates to 4.45 mins./hr. and 4.45 sec./min.
    I have removed the bob and took measurements of only the “grid iron” section with the neck piece.
    This center of gravity is 22.5” from the top (add 7” for the leader). The dimensions of the grid iron section is 18.875” long x 3.5” wide.
    Another thought I had was to try and duplicate the center of gravity of the shorter pendulum which came with the movement. Both pendulums have virtually the same overall weight at 59.0 oz as they are identical with the exception of an extended neck piece.
    The comparison of center mass is as follows:

    Longer Pendulum = 30” from top/12.5” from bottom
    Shorter = 23.25” from top/13.25” from bottom

    I would think a good experiment would be to try and raise the center mas of the longer pendulum by 6.75” so that is duplicates the shorter one which works. I will try this over the weekend and let you know what happens.
    [​IMG][​IMG]

    Thanks again,
    Mark
     
  23. Willie X

    Willie X Registered User

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    Probably be a lot easier, and better, to change the wheels in the movement.
    To do what you are trying to do will probably require exchanging the present bob for a dummy bob, just the brass or plated aluminum cap/disk.
    Willie X
     
  24. Tinker Dwight

    Tinker Dwight Registered User

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    Contrary to common thinking, the center of gravity is only
    part of the controlling factor of the pendulum.
    In fact, we will most likely be lowering the center of gravity to speed
    it up, not raising it.
    It is the moment of inertia that slows it down. The lower you can get the
    center of gravity without increasing the moment of inertia the faster
    the pendulum will be.
    The equation for a complex pendulum ( any pendulum without a simple
    ball at the bottom ) is:

    Period = 2*Pi* ]SquareRoot( SumMomentsOfInertia/(SumOfCgFromFulcrum*g) )
    The SumOfCgFromFulcrum is the distance from the fulcrum times that mass
    at the center of gravity.
    So, you can see that lowering the CG by itself actually speeds the pendulum
    up.
    The problem is that after, around the center of the pendulum, adding mass
    increases the SumMomentsOfInertia faster than the SumOfCgFromFulcrum.
    Having the grid iron throws this off a little so I need to hunt for the minimum
    with a spread sheet.
    So, matching CGs may actually make the pendulum slower, depending on the
    amount of mass you add and where.
    We want to find the most effective point to add mass and how much to add.
    Above or below that optimal point will just be wasting weight that could be
    more effective elsewhere.
    Wait till Monday when I get back to a machine that has a spread sheet.
    Tinker Dwight
     
  25. Torre

    Torre Registered User

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    Thanks gentleman,
    I am still hopeful there is some way to modify the pendulum to make this work based upon your equation.
    While I agree changing the second wheel is the "right" way to go it is suck a PITA to take apart a tubular bell movement.

    I cannot change the center of gravity to match the shorter pendulum anyway as it would require nearly 16 oz. of weight added near the top. Or I would have to drastically decrease the weight of the bob. Not a realistic.

    Thanks again,
    Mark
     
  26. Tinker Dwight

    Tinker Dwight Registered User

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    Adding the weight at the top of the pendulum would
    have almost zero effect on the rate of the pendulum.
    It is the center of gravity relative to the fulcrum that
    counts. Adding weight at the fulcrum has no effect, since
    it is at the center of the rotation. It would slow the
    clock a little because it would add to the rotational moment
    of inertia, because it would have to have some diameter,
    larger than zero.
    Remember I said, the idea is to lower the center of gravity,
    without increasing the rotational moment of inertia. Adding
    at the top of the pendulum does neither in the right direction.
    Tinker Dwight
     
  27. Torre

    Torre Registered User

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    #27 Torre, May 22, 2017
    Last edited: May 22, 2017
    It's an interesting experiment for sure but no doubt the right way to go is to change out the second wheel as suggested.
    I have another Urgos movement from which the longer pendulum actually fitted to. I'm not sure where the second wheel is? I am assuming it is near the back of the movement? Most photos of movements I see show it directly behind the clock hands. I don't think this is the case on these movements.
    Thank you.
     
  28. Torre

    Torre Registered User

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    Is the second wheel the wheel directly behind the winding cable barrel?
     
  29. David S

    David S Registered User
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    It will be the wheel / pinion set that the winding barrel teeth drive (mesh with).

    David
     
  30. Tinker Dwight

    Tinker Dwight Registered User

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    Ok, I ran the numbers again. I don't have all the rotational inertia but this
    is a close ball park number/
    The weight should be added at about 10.25 inches down from the hook at the
    top end of the pendulum ( don't include the leader and spring. )
    The calculated value is 28 oz. or 1.75 lbs. This is most likely a low value
    since I didn't include extraneous inertia, like the width of the grid iron or the
    bob's rotational inertia. These are usually a small factor. I'd start out with trying
    2 lbs of lead. The diameter side to side or up and down should be kept small..
    It is heavy but the movement should be able to handle it.
    Is the bob hollow or lead filled. Reducing its weight can make a big difference.
    grinding some lead out with a bur will help a lot.
    Tinker Dwight
     
  31. bangster

    bangster Super Moderator
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    The method Tink describes is called top-loading. It moves the center of gravity up without shortening the pendulum --makes a longer pendulum behave like a shorter one. The higher up the rod, the faster it runs...until you get to the center of the rod. After that the effect is opposite.
     
  32. Tinker Dwight

    Tinker Dwight Registered User

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    Actually, it is not so much moving the center of gravity as increasing
    the mass without significantly increasing the movement of inertia.
    Since he had a grid iron, the calculation was a little more complicated.
    It was easier to do it with a spread sheet since the calculation
    of the different factors was not too hard but the back calculation
    of the value needed was difficult.
    It was still close to the center where the optimum point was.
    but not quite at the center.
    Tinker Dwight
     
  33. Willie X

    Willie X Registered User

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    Tinker,
    All of these bobs have a curved steel backer with a brass cap spun over the edge of the backer. I would guess that the steel backer weighs 2 or 3 times as much as the brass cap. No filler.
    Willie X
     
  34. Tinker Dwight

    Tinker Dwight Registered User

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    If steel, use a grinding wheel instead of a bur.
    Always watch the temperature. you don't want to discolor the brass.
    Tinker Dwight
     
  35. Torre

    Torre Registered User

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    Thanks again for your consideration.
    I had imagined it would require good bit of weight. I don't see how I could add that much weigh and not have it interfere with the weights dropping. On the back side of the pendulum it would interfere with the bells.
    I will most likely take the movement outside of of the cabinet and mess around with it.
    Thanks.
    Mark
     
  36. Tinker Dwight

    Tinker Dwight Registered User

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    If you can reduce the weight of the bob, I can get away
    with less weight.
    The way it works is by adding the weight near the center,
    you are reducing the moment of inertia faster than you are moving
    the center of mass.
    Inertia is the square of the distance times the mass, while center
    of gravity is just the distance times the mass.
    Once past about the center, you have less and less effect on the
    center of mass so the pendulum slows again.
    You could try a bar of metal perpendicular to the rod.
    An 8 inch by 4 inch piece of 1/4 inch steel will weigh about 2 lbs.
    I think you could stick that behind the pendulum.
    Tinker Dwight
     
  37. RJSoftware

    RJSoftware Registered User

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    Just so we got the horse understood to be before the carriage,

    I have always understood and appreciated that to keep a clock in the original condition (as much as possible) is considered sacrosanct. That being said when it is found that a pendulum length to be incorrect that points to an error with movement and case is a marriage.

    Most marriages (these days) wind up in divorce. It is not good to force together what should naturally be apart. I would alter/damage either pendulum, case or movement to force the union.

    I would research and begin again.

    RJ
     
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