Chime Unlocking Problem

Discussion in 'Clock Repair' started by bangster, Apr 14, 2019.

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. Our Donation Service is back after a brief absence to fix the payment service. Please give it a try! Donate
  1. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    18,426
    190
    63
    utah
    Country Flag:
    Region Flag:
    You who have been following me through the vicissitudes of this adventure will remember the SethThomas mechanical/electric, ST 124E, whose motor gave out on me and I had to hunt for a replacement.

    Finally found a replacement, installed it in the movement, and (after testing), put it in the case, attached the hands and hoped. It seemed to run OK, but once in a while it would skip a chime. Took mvt back out hooked it up and before long the once-in-a-while turned into all-the time.

    By keen observation, I discovered that the three short lobes on the center cam weren't raising the lever enough to lift the chime locking piece out of the notch far enough to unlock the train. They barely budge it.

    Hasn't always been this way. Used to run just fine. Something has happened over time to make it do this. AND I CAN'T THINK OF WHAT!

    So I'm calling on y'all who are smarter than me to get into the discussion. Possible cause #1: the center cam wore down so it can't lift the lever enough. Possible cause #2: the end of the lifting lever wore down so the cam cain't lift it enough.

    Neither of those seems plausible. An obvious sledgehammer remedy would be to solder a piece of brass to the end of the lever, to increase the lift.

    But before I go modifying parts, I thought I'd seek your opinions and advice. What do y'all thing think might have caused it? And what do y'all think the proper cure would be?

    Ideas, please.

    Chime mechanism 001.jpg
     
  2. Uhralt

    Uhralt Registered User
    NAWCC Member

    Sep 4, 2008
    2,572
    191
    63
    Country Flag:
    Region Flag:
    Maybe the set screw at 10 has become loose changing the angle between 18 and 23?

    uhralt
     
  3. Time After Time

    Time After Time Registered User
    NAWCC Brass Member

    Feb 22, 2010
    4,953
    213
    63
    Male
    Retired DDS
    Country Flag:
    Region Flag:
    And/or the Quarter Cam on the front plate as well. Uhrait's suggestion certainly fits your description of the symptoms.
    How about it bangster? Set screw slipping?

    btw, glad you found a suitable replacement motor.
     
  4. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    18,426
    190
    63
    utah
    Country Flag:
    Region Flag:
    No, because 18 and 19 aren't attached to the shaft. They roll free on it.
     
  5. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    18,426
    190
    63
    utah
    Country Flag:
    Region Flag:
    Setscrew got nothing to do with them levers. They are loose on the shaft and totally gravity operated.
    :(
     
  6. Isaac

    Isaac Registered User

    Aug 5, 2013
    500
    56
    28
    Male
    Student
    Country Flag:
    Region Flag:
    #6 Isaac, Apr 15, 2019
    Last edited: Apr 15, 2019
    If the lever 18 does not move lever 23, then one of those levers most likely are loose on their arbor. Maybe lever 18 shifted enough on its arbor after a while of running the movement so that the lever doesn't fully engage with the center cam.

    Very curious if this is the issue.
     
  7. Time After Time

    Time After Time Registered User
    NAWCC Brass Member

    Feb 22, 2010
    4,953
    213
    63
    Male
    Retired DDS
    Country Flag:
    Region Flag:
    The activation and warning levers are loose on the shaft but the the chime lock lever, which is held in place by the set screw, has a pin going through the front plate which is lifted by the activation lever. The position and movement of that entire lock and maintenance assembly is dependent on the settings achieved by the set screw as uhrait pointed out initially. Are you saying that you've checked the set screw and settings and found nothing wrong? :?|
     
  8. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    18,426
    190
    63
    utah
    Country Flag:
    Region Flag:
    Here's what I see. 18 and 19 are all one piece. Star cam is supposed to raise 18, which raises 19, which is supposed to raise the pin on 10, the chime lock piece, to unlock the train. But it doesn't raise it far enough --barely at all.

    Chime lock piece is a single part. It's orientation is fixed when the tab goes into the notch on the locking plate. Can't go any further down than that. Setscrew would allow it to fall less deeply into the notch, but that would simply move the pin further away from 19.

    There's no way to move the pin any closer to the contact point with 19. Unless I wanted to file the 4 notches deeper which I don't want to do. The setscrew also allows the drop lever 23 to be adjusted with respect to the chime cam. But they are part of the chime correction business, and play no role in the normal unlocking of the train.

    I know of a way to remedy the symptom (doesn't raise the pin) by soldering a bit onto the end of 18 to raise the lift. But proper procedure tells me I should first try to find the cause of the symptom, and fix that.

    And here I'm stuck. It used to work. It no longer works. What could have happened to make it no longer work? The only two possibilities seem to be either worn parts, or mis-adjustment in the mechanism. The latter is most likely. Y'all have given suggestions on readjustment, but so far none of them will achieve the goal of RAISING THE DANGED PIN! I continue to hope that y'all will eventually figure out what must have happened, because I surely cain't. In the end, I may be reduced to soldering. But I want to put that off as long as I can. :(
     
  9. David S

    David S Registered User
    NAWCC Member Donor

    Dec 18, 2011
    6,972
    166
    63
    Male
    Professional Engineer - Retired
    Brockville, On Canada
    Country Flag:
    Region Flag:
    Are 23 and 18 a friction fit on the same arbour? If so is it possible that 23 got rotated and is preventing 19 from falling down far enough?

    David
     
  10. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    18,426
    190
    63
    utah
    Country Flag:
    Region Flag:
    23 is more than friction fit; it's solidly attached to the arbor. It gets adjusted to the cam by loosening the set screw, turning the arbor, re-tightening the screw.
    !8 and 19 aren't friction fit; the unit is loose and flops around (so to speak).
     
  11. DeweyC

    DeweyC Registered User
    NAWCC Member

    Feb 5, 2007
    1,144
    204
    63
    Watchmaker
    Baltimore
    Country Flag:
    IIRC, the angular relationship between 23 and 18 is important. Also check for wear in the arbor bearing. This sounds a little like where cleaning out the gunk from the bearing changes how the pivot fits into the hole.
     
  12. Time After Time

    Time After Time Registered User
    NAWCC Brass Member

    Feb 22, 2010
    4,953
    213
    63
    Male
    Retired DDS
    Country Flag:
    Region Flag:
    #12 Time After Time, Apr 15, 2019
    Last edited: Apr 15, 2019
    Bangster, be sure to check this. I think that 23 is the chime maintenance cam which keeps the chime lock lever from dropping back into one of the chime lock cam's quarter slots. (See diagram legend) I'm pretty sure that 22 is part of the chime correction mechanism. If the drop lever in 23 is not lifted far enough, your chime train won't stay out of lock when 18 drops out of Warning. Do you have a sufficient Warning Run to get 23 clear of the slot in 24?

    I have to assume that you've checked the set screw and settings, but be sure that you are clear as to what constitutes the chime correction mechanism vs. the chime maintenance functions.

    Assuming that is all correctly set up, are you saying that the chime lock lever itself is barely lifted out of the chime lock plate by the Star Cam? If so, the lift from the Star Cam hasn't changed in such a short period of time. It was working so for some reason the full lift is no longer being transferred to the chime lock lever. That is accomplished via the pin which goes through the slot in the front plate. Is the pin fully engaged by "19"? If so, Is 18 slipping off of the star cam? I think it is set up to deflect if the minute hand is turned counter-clockwise past a chime point. Maybe that needs to be adjusted?
     
  13. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    18,426
    190
    63
    utah
    Country Flag:
    Region Flag:
    19 comes up, bumps against the pin, and goes away. Except on the high cam lobe, the pin get lifted and unlocks the train.

    Here's the pic again.

    Chime mechanism 001.jpg
     
  14. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    18,426
    190
    63
    utah
    Country Flag:
    Region Flag:
    Here's another one.

    Chime mechanism 002.jpg
     
  15. Dick Feldman

    Dick Feldman Registered User

    Sep 1, 2000
    1,972
    46
    48
    Colorado, usa
    Country Flag:
    Region Flag:
    Ho Bangs,
    Masking tape is one of my best friends.
    If you want to try adding to the lever, how about stacking a number of layers of masking tape where you plan to solder the new piece?
    Nothing permanent, and that can be removed quickly.
    Also, I have, in the past, bent levers to adjust their travel distance.
    Dick
     
  16. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    18,426
    190
    63
    utah
    Country Flag:
    Region Flag:
    Good idea, Dick. Before I do anything semi-permanent I'll do it that way. Hard to bend this one since I'd need to bend it edgewise.
     
  17. Time After Time

    Time After Time Registered User
    NAWCC Brass Member

    Feb 22, 2010
    4,953
    213
    63
    Male
    Retired DDS
    Country Flag:
    Region Flag:
    #17 Time After Time, Apr 15, 2019
    Last edited: Apr 15, 2019
    You might also twist 18 axially clockwise so that the tip which is acted upon by the Star Cam is rotated/pointed down slightly. If you don't need too much additional lift this might be a quick and easy (and reversible) adjustment to make. I don't think that it will affect the timing of the drop out of warning. A potential downside would be accelerated wear to the tip of the lever.

    Edit:
    You should also be able to adjust 10/23 so that 8 falls just far enough to ensure a reliable lock.
    10 shouldn't have to hit the bottom of the slots in 11 for lock.

    You probably know all this already...just throwing things out for consideration.
     
    bangster likes this.
  18. Time After Time

    Time After Time Registered User
    NAWCC Brass Member

    Feb 22, 2010
    4,953
    213
    63
    Male
    Retired DDS
    Country Flag:
    Region Flag:
    Something else to consider would be to work on 10 instead of 18. Try twisting or adjusting the lower lever of 10 which holds the pin acted upon by 18. Twist it slightly to angle the lift pin down. This has the advantage of not altering 18 which requires splitting the plates and possibly altering the chime points. It should also be completely reversible if you don't go overboard.

    It's hard to know how much additional lift is required...the slight adjustments described may not be enough...:?|
     
  19. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    18,426
    190
    63
    utah
    Country Flag:
    Region Flag:
    I'm going back to the workroom to try these suggestions and see if any of them do any good. I'll let you know.
     

Share This Page