Koma, what suspension string?

Discussion in '400-Day & Atmos' started by jurgenclocks, Sep 23, 2019.

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  1. jurgenclocks

    jurgenclocks Registered User

    Sep 23, 2019
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    Hi,

    I'm trying to get a Koma anniversary clock to work, I need a new suspension string, here is a picture of the back.

    What type of suspension string do I need to get?

    Thank you!
    Jürgen

    20190923_155614.jpg
     
  2. jurgenclocks

    jurgenclocks Registered User

    Sep 23, 2019
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  3. jurgenclocks

    jurgenclocks Registered User

    Sep 23, 2019
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    I think I only need the string, because I have the forks.
     
  4. KurtinSA

    KurtinSA Registered User
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    Nov 24, 2014
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    Welcome to the message board! Hard to tell with the suspension guard in place, but pretty sure the back plate is #1392 from the repair guide. The guide says that either 0.0032" or 0.003" springs are used. It's unclear why the different thicknesses...the guide says suspension unit 14A takes the 0.0032" while 14B takes the 0.003"...but these two suspension units appear to be the same length. It appears it might have to do with the size of the main spring, either 13mm across or 15mm across. You might need to buy the thicker spring and if the clock runs too fast, then thin the spring down to get it to a point where you can adjust the time.

    Kurt
     
  5. jurgenclocks

    jurgenclocks Registered User

    Sep 23, 2019
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    Allright! Thank you very much!
     
  6. jurgenclocks

    jurgenclocks Registered User

    Sep 23, 2019
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    I have ordered some, I'm new to these types of clocks, I have worked on other regulator wall clocks before.
    When I receive these springs I need to cut them to the correct length, someone showed this on a YouTube video, he was putting his spring on to a book were his guides were showed.
    Do you know where I can get some sort of guide sheet/pdf?

    Is it very important to cut them not to short or not to long, but exact, or can you be a tiny bit of?

    Thank you for your help!
     
  7. KurtinSA

    KurtinSA Registered User
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    Nov 24, 2014
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    Yes, the repair guide I was referring to has to-scale diagrams of the suspension units. It is the 400-day repair guide by Terwillger. Of course if too long, the pendulum will drag. So the length needs to be short enough so the bottom of the pendulum clears the base of the clock by around 1/8 of an inch...maybe a quarter of an inch. Too short and the clock will run fast. So start too long then figure out how much to cut to be about right. It can be a bit off...but too long is a no-no!

    Kurt
     
  8. MartinM

    MartinM Registered User

    Jun 24, 2011
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    You can use the two pieces from the old spring as a guide for proper length.
     
  9. jurgenclocks

    jurgenclocks Registered User

    Sep 23, 2019
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    Thank you for your information!
     
  10. jurgenclocks

    jurgenclocks Registered User

    Sep 23, 2019
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    Will do! Thanks!
     
  11. jurgenclocks

    jurgenclocks Registered User

    Sep 23, 2019
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    Hi,

    So I have changed the suspension spring, the clock runs for maybe 3 minutes and then stops, but I noticed something strange:
    when the pendulum swings back to the left I see the minute hand move backwards for a tiny bit, I think I need to check the hands? Or is it normal that it does that "flick"?

    I also leveled the clock with the built in leveler, and the pendulum is not touching the bottom guide piece, and it runs for maximum 3 minutes.
    And when I remove the pendulum the clock ticks realy fast, so there is (I think) no problem with the gears.

    I think there is something wrong with the hands, they seem to be right, because when the pendulum is removed they behave normal, strange...

    Thanks!

    Jürgen
     
  12. jurgenclocks

    jurgenclocks Registered User

    Sep 23, 2019
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    I think I fixed it! I moved the fork up a tiny bit and it's still turning (30 min), the time is ticking too fast for the moment, but I have turned the dial to the fastest setting on the pendulum.
    I'm going to let it run for a night and if it keeps running I'm going to tweak the time keeping.
     

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