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Discussion in 'Electric Horology' started by markiemark, Jun 6, 2019.
Is there a way to tell if a pendulum shaft is made of steel or invar?
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
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.
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.
Does anyone know if a Synchronome pendulum is made of invar?
Synchronome pendulum rods are invar.
Does the rate of the clock change when you change temperature?
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!
Previous thread with picture:
Confirming Invar Pendulum Rod
I once bought a much neglected Mk2 Synchronome that had plenty of surface rust on the rod....
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.