My Kern clock stopped working :-(

Discussion in '400-Day & Atmos' started by berntd, May 16, 2018.

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  1. berntd

    berntd Registered User
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    Jun 21, 2009
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    Hello

    I repaired it 4 years ago. It had a badly worn bush.
    Has been fine ever since with about 7 months winding intervals.
    Then, a few weeks back it stopped.

    I started it, wound it etc but it always stopped again after hours or days.

    Last weekend I stripped it. The oil still looked great. Wear and pivots not much different than 4 years ago.
    I cleaned it and re-oiled it.
    I also opened the barrel and oiled the spring as well.

    All great. Re-assemled.
    It ran for a few hours without the dome so I replaced it.
    Found it stopped. This jeeps repeating. It goes for some time but just stops.

    I cannot see any problem and now I am not sure what next.


    Any ideas anyone?


    Regards
    Bernt
     
  2. roughbarked

    roughbarked Registered User

    Dec 2, 2016
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    Counting the beat?
     
  3. shutterbug

    shutterbug Super Moderator
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    Oct 19, 2005
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    Check your over swing. That's really important. Lowering the fork increases over swing while decreasing total rotation.
     
  4. KurtinSA

    KurtinSA Registered User
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    Nov 24, 2014
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    "Opened the barrel and oil the spring...". Is this all the service that the mainspring has received? It may be time to completely remove the spring, clean, and reoil. I had a clock that just wouldn't run. I had tried everything. I finally decided to use a new spring. Problem solved.

    Kurt
     
  5. Harry Hopkins

    Harry Hopkins Registered User
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    Nov 16, 2011
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    With problems like this I always start with removing the hands, dial and motion works then see if overswing improves and if it will continue to run. If there is no improvement then I tear it down and inspect just as you have. On a recent similar problem I found the front pivot of the center wheel arbor very gray and rough looking so I polished that pivot and smooth broached that hole and the clock was as good as new. I assume you are using the same suspension spring without changing the position of the fork but check for the fork binding on the anchor pin.
     
  6. sjaffe

    sjaffe Registered User

    Dec 25, 2012
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    It takes very little pivot friction to keep this type of clock from running. If yours was on the hairy edge of just barely running, a slight increase in pivot friction would prevent it from running. Split the plates and remove all the wheels. Install each on separately. When one is in place, tighten the plates and spin the wheel. It should continue to spin for several seconds and glide to a stop. If it does not spin this long, or when it stops it does so abruptly, that's a problem. Polish this wheel's pivots and smooth broach the plate pivot holes, then test again. If it still does not pass, check for a bent pivot or a rough surface on the inside of the plate where it contacts the end of the arbor. When all the wheels pass this test, install them in pairs and test all the different combination of pairs using the same test. Once they all pass this test, your clock should run. Since it had been running, I would not change the fork height.
    Stan
     
  7. KurtinSA

    KurtinSA Registered User
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    Nov 24, 2014
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    I've been doing the same tests as Stan suggests with an additional one...with just the center arbor between the plates, put on the motion works and hands then rotate the center wheel to get a sense of the meshing there. Harry's suggestion does this for after the clock is put completely together.

    I've also incorporated the 2-click test when assembling a clock after overhaul. I do exactly as Stan says, then assemble without the motion and the anchor, I see how many clicks it takes to get the escape wheel to spin. Most times it will spin quite freely...that's the best. A few times, the escape wheel will spin a number of revolutions and then slow down. If it takes more than 2 clicks for this to happen, then I go back and look at all pivots and bushings.

    Kurt
     
  8. Randy Beckett

    Randy Beckett Registered User
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    May 23, 2012
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    Start out by simply removing the hands and see if it runs like that. Could just be something simple like the hour bushing rubbing on the inside of the dial hole. At any rate, removing the hands takes this, as well as the motion works, mostly off the list of possibilities.
     
  9. berntd

    berntd Registered User
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    Jun 21, 2009
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    Thanks everyone.

    The important clue here is that whatever went wrong with it, happened by itself. Either suddenly or perhaps over some time period until it no longer worked.

    Regarding the over-swing:

    When the clock was still working, it always had more than 1/2" 12mm over-swing each way. Possibly 16mm.
    I now was not able to check it since it won't go for enough time for the swing and beat to settle properly.

    I will try and check this again on the weekend but my guess is that the over-swing will probably just decrease until the clock stops.

    The spring seems fine and shiny and it's barrel is clean. It was all done just 4 years ago.

    There is a bit of slop in the bush of the centre wheel back but when I ran a broach into it carefully, it appears the hole is round and not oval.
    The pivots look great actually.

    Regards
    Bernt
     
  10. roughbarked

    roughbarked Registered User

    Dec 2, 2016
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    Mostly it is the escapement that needs looking at but we don't know the whole story yet. Re-reading your initial post you mentioned a badly worn bush. These clocks are rarely bushed. Did you do the repair? A badly worn bearing usually means a worn pivot as well. perhaps this is the place to look?
     
  11. berntd

    berntd Registered User
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    Jun 21, 2009
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    Yes, it was the front bush on the wheel after the barrel. I repaired that and polished the pivot years ago.
    ago. 15265469756971330114068.jpg 1526547022089-1062812071.jpg 15265470542711421216659.jpg

    Here are some pictures.

    Regards
    Bernt
     
  12. roughbarked

    roughbarked Registered User

    Dec 2, 2016
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    Often this is the worst place for wear. Perhaps after you get it going again, try not winding it all the way up. Try stopping a bit short of full power. There is plenty of reserve there.
     
  13. KurtinSA

    KurtinSA Registered User
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    Nov 24, 2014
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    How bad does this bushing need to get to create issues with running the clock? The only time this gets any wear is when the clock is being wound. Once wound, the barrel spins around the arbor.

    Kurt
     
  14. roughbarked

    roughbarked Registered User

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    ;)
     
  15. berntd

    berntd Registered User
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    So last night, I ran it without hands.
    The overswing was almost 22mm 7/8".
    I set the beat and it went for several hours withe freat overswing.

    I replaced the hands. Checked them for problems. Started it and again great swing still after 2 hours.

    Went to bed.
    This morning it had stopped again.


    Regards
    Bernt
     
  16. KurtinSA

    KurtinSA Registered User
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    Nov 24, 2014
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    BTDT! Now you have to see if there's something about the hands/motion works that's causing a problem. Where was the minute hand when it stopped? If you were to restart the clock as is, does it stop with the minute hand in the same position? That would be a clue. You may need to check for binding of the motion works gears/pinions.

    Kurt
     
  17. roughbarked

    roughbarked Registered User

    Dec 2, 2016
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    oil the canon pinion?
     
  18. berntd

    berntd Registered User
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    Jun 21, 2009
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    Not sure.
    It stopped at 2min before 10.
    I did oil the canon pinion.

    After a lot of fudfling, I found nothing.
    I re-started it an it has been going all day so far 8h. Excellent overswing.

    I wonder if low temperature at night could be a problem.

    Will keep you postet...

    Regards
    Bernt
     
  19. berntd

    berntd Registered User
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    And so it continues...
    Since my last post, mentioning the re-start, it has NOT stopped going all weekend and was still at it this morning when I left.
    Swing is good, time is good so now I am still stumped :-(
     
  20. Uhralt

    Uhralt Registered User
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    To me this sounds like the barrel bushing might need to be replaced. Is the barrel arbor snug in the bushings of both sides of the barrel? If there is play, so that the barrel can tilt a bit, that might be the problem.

    Uhralt
     

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