clock stops at 10 to

Discussion in '400-Day & Atmos' started by tracerjack, Feb 23, 2019.

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  1. tracerjack

    tracerjack Registered User
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    Jun 6, 2016
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    I'm working on a Konrad Mauch standard with a miniature movement. It initially stopped several times while lifting the minute hand, usually around 10 to the hour. While turning the minute hand by hand, it turns easily with light tension from 12 to 6, then has quite a bit more tension from 6 to 12. I thought it might have a bent minute arbor, and was going to check that once it stopped again. Wouldn’t you know it, it’s now been running for 3 days. While I am waiting for it to stall, I thought I would ask if there might be another reason why there is different tension when manually turning the minute hand.
     
  2. Harry Hopkins

    Harry Hopkins Registered User
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    Nov 16, 2011
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    Sometimes the tension washer is bent in just a way that it slides easier when the minute hand is in a certain position. Make sure the tension washer is installed the correct way... the hole should be inserted first on the arbor and make sure it is resting on the shoulder of the arbor and not touching the front plate. Also ensure the minute hand and the hour hand are not touching each other anywhere during their rotation. As far as stopping at 10 minutes till the hour these clocks just don't have a lot of extra power and when the power is marginal the extra weight of the hands can cause the clock to stop.
     
  3. tracerjack

    tracerjack Registered User
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    Thanks for the tips. I've never before felt a hand change tension while being moved, so could only guess as to what might cause that. I'm waiting for the right suspension spring size to arrive, so decided to just leave it running until then, which it is still doing nicely. When I go to change the spring, I'll now have a better idea what to look for. I read in the guide that Koma had to go to a bigger spring size and barrel because of weak power. This one had one of the strongest springs I've come across in a miniature movement. .
     
  4. MartinM

    MartinM Registered User

    Jun 24, 2011
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    Any of the above conditions and add a burr on the cannon pinion to the mix.
     
  5. tracerjack

    tracerjack Registered User
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    Well, whatever it is, it hasn't stopped the clock since my original post. When I first started the clock, it stopped three times in the same place, so I assumed a problem. It must have been something minor for it to now chug away without a hitch. Still, I am definitely going to follow through with all the suggestions when I change the suspension spring.
     
  6. tracerjack

    tracerjack Registered User
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    While replacing the suspension spring, I check all the things suggested. This one has a flat spacer washer between the cannon pinion and the plate. At least, that is where it was when I took things apart, and without it, there isn't enough tension on the hands. The only domed washer shown in the Guide, goes over the minute hand. I couldn't find anything to account for the different tension, no burrs, etc. As I explored, the different tensions moved to different places on the dial, and sometimes were gone. I'm not positive, but changing the relationship of the minute hand to the cannon pinion, where it fits over the square head, seemed to be where the problem was. Why, I haven't a clue. Since it is again working beautifully, with a full 360 rotation and an inch of over swing, I can live without knowing. I realize the amount of rotation isn't relevant, but it does put on a nice show with the pendulum. Here is a photo of it.
    komadeco.JPG
     

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