Steel or Invar pendulum

Discussion in 'Electric Horology' started by markiemark, Jun 6, 2019.

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  1. markiemark

    markiemark Registered User

    Nov 21, 2017
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    Is there a way to tell if a pendulum shaft is made of steel or invar?

    thumbnail_IMG_0886.jpg
     
  2. novicetimekeeper

    novicetimekeeper Registered User

    Jul 26, 2015
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    There isn't that much difference in density, 7.85g/cm^3 compared to 8 g/sc^3 for mild steel and both are ferromagnetic
     
  3. Allan Wolff

    Allan Wolff Moderator
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    Mar 17, 2005
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    I purchased a piece of Invar for my last clock build. If it had not come with a certificate, there would have been no way for me to differentiate it from regular steel. It machined like steel, is magnetic, etc. There are probably laboratory tests that can be run, but I am not aware how the typical clock repairer or home machinist would know. If someone knows how, I would love to hear it.
     
  4. Jim Hartog

    Jim Hartog Registered User
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    Jan 6, 2010
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    Hello,

    Wikipedia says Invar is about 1/3 nickel. Wikipedia does say anything about corrosion resistance, but the Ni content should make it rust free, like stainless steel. Try rusting it in some acid.

    Jim
     
  5. gloos

    gloos Registered User
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    Nov 19, 2002
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    Does anyone know if a Synchronome pendulum is made of invar?
    Thanks, Gayle
     
  6. Snapper

    Snapper Registered User

    Nov 30, 2014
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    Synchronome pendulum rods are invar.
     
  7. steve323

    steve323 Registered User

    Sep 25, 2018
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    Does the rate of the clock change when you change temperature?

    Steve
     
  8. Peter

    Peter Registered User

    Jan 28, 2010
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    What I did:
    Clamped rod at one end on a rigid surface ( used my milling machine table, but any counter top would work), supported it in a couple of v blocks down its length, put a dial indicator on the other end. Heated along the length with a heat gun(hair dryer). I had negligible change in length from room temperature to warmer than I could comfortably hold onto it. Invar!

    -Pete
     
  9. Peter

    Peter Registered User

    Jan 28, 2010
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    Kevin W. likes this.
  10. rogerj

    rogerj Registered User

    Dec 21, 2014
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    I once bought a much neglected Mk2 Synchronome that had plenty of surface rust on the rod....
     
  11. Snapper

    Snapper Registered User

    Nov 30, 2014
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    Agreed. I was fortunate that my Synchronome was in superb condition when I acquired it as it had been in a church rather than a factory. Even so there was surface rust on the pendulum rod.
     

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