Mainspring size for Kundo

Discussion in '400-Day & Atmos' started by Elliott Wolin, Dec 5, 2019.

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  1. Elliott Wolin

    Elliott Wolin Registered User

    Nov 18, 2019
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    I measure the barrel as 0.580" deep (not including the lip that the cover fits into) by 1.278" diameter. This seems closest to 14mm x 32 mm without going over.

    On Esslinger I see springs measuring 14mm x 30mm and 13mm x 32 mm. Which way should I go, one for a slightly narrower barrel (30mm vs 32mm), or for a slightly thinner barrel (13 mm vs 14 mm)?

    I just noticed Horolovar has a 14mm x 32mm, for a few dollars more.

    Does it even make a difference? I don't have the Horolovar book to cross-check anything.
     
  2. sjaffe

    sjaffe Registered User

    Dec 25, 2012
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    If the spring you use is either longer or shorter than ideal, it will affect the run time of the clock and you will get something less than the 400 days expected. Going to a narrower spring will result in a decrease in power. You also need to consider the thickness of the spring. The power goes up by the cube (T*T*T) of the thickness so this can have a bigger influence than the width.

    Stan
     
  3. KurtinSA

    KurtinSA Registered User
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    Nov 24, 2014
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    What is the back plate number? Can you share pictures of the clock?

    Kurt
     
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  4. Elliott Wolin

    Elliott Wolin Registered User

    Nov 18, 2019
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    See below for backplate picture, didn't have it when I made the first post, but should have:

    20191205_164718[1].jpg
     
  5. Wayne A

    Wayne A Registered User

    Sep 24, 2019
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    Looks like a plate 1406H. Guide shows 14x30 mainspring.
     
  6. Elliott Wolin

    Elliott Wolin Registered User

    Nov 18, 2019
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    Thanks, I have to get the guide. Does it say anything about the thickness...earlier posts pointed out that the thickness is very important. Timesavers lists the 14mm x 30mm as 0.0142". Horolovar doesn't list a thickness.
     
  7. Elliott Wolin

    Elliott Wolin Registered User

    Nov 18, 2019
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    Also, when I buy a new mainspring, do I have to clean and lubricate it? Or is it ready to go from the vendor (probably Timesavers, but I have a list of stuff to buy so I'm checking out multiple vendors)?
     
  8. Wayne A

    Wayne A Registered User

    Sep 24, 2019
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    Guide has a chart that lists the 14x30 at .014 thick and 32" long.
     
  9. Wayne A

    Wayne A Registered User

    Sep 24, 2019
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    I like to clean and lube new springs.
     
  10. KurtinSA

    KurtinSA Registered User
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    Nov 24, 2014
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    I wonder if you've measured your spring barrel accurately enough. You said that the diameter was 1.278" which is 32.46mm. Typically, I've found the diameters I measure to be fairly close to the required spring given in the book. Recently, I was measuring for a 19x38 spring and got the barrel depth at 20.4mm and 38.6mm diameter. Certainly the spring width has to be somewhat less than the measured depth. But my barrel diameter was not far off the required spring diameter. For you to need a 14x30, seems like you're measurement is quite a bit larger. If you barrel is really 32.46mm, then I think you need to 14x32. Unless I'm missing something!

    Generally, I trust what The Horolovar store supplies. The book doesn't show two barrels with the same dimension that have different thicknesses. If you have the barrel dimensions right, then you get the right spring. The repair guide is the reference for all these details.

    Kurt
     
  11. Elliott Wolin

    Elliott Wolin Registered User

    Nov 18, 2019
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    Kurt, you are correct, many thanks. The correct measurement is 1.178" to 1.182" in multiple places around the barrel (I must have had a senior moment when reading my dial gauge, thanks for catching this!). This converts to 29.9mm to 30.02 mm, very close to 30mm. So 14mm x 30mm looks like the correct size. And I understand it's best to clean and re-lubricate the spring before installation.
     

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