Paxolin rod/bar anything similar?

Gallery, Projects and General > How do I??

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75Plus:
Chris,

See if you can find a suitable piece of Invar. It is a nickle/steel alloy that is known for it's resistance to thermal expansion. Invar is used on a number of precision regulators most of which have a one second period. i.e 60 beats a minute. At that length (36" +/-) thermal expansion can become a problem.

If your pendulum length is only 6 inches you will not see a great variance even if you had the clock located outside so it was subjected to much wider temperature swings than indoor environments.

SPiN Racing:
Another place to check, that has lots of information about the products, is http://www.onlinemetals.com/ They have a nice selection.. granted they are on the US side of the pond.. its worth looking at for info at least.

Also I have found in the past Fleabay has tons of stuff in the plastic lines, as well as metal, lots of Drops. I have purchased lots of drops that are ULTRA cheap, and are perfect for making suspension bushings, as well as a wide variety of plastic, delrin, plastic and other parts.

Scott

raynerd:
Well chaps, thanks for all the info. I`ve spent many hours looking and I now have ordered a 400mm length of Invar36 as well as the tufnol (it`ll come in useful at some point). I hear that Invar is sun of bitch to cut and I think I`m going to have to thread it.

I ordered the invar because I was looking at the thermal expansion co-efficients and Tufnol was 1.9 x 10e-5 which seemed quite high. I believe the expansion on Tufnol is primarly along the laminate and I think the tufnol rod is bound in rings to make up the bar and so I`m guessing expansion along its length (and therefore causing the period to change) could be tiny? - which is why it could be OK to use.

Anyway, for the sake of £3 I have got a length of invar as well so I guess I can choose which I use.

Thanks again for all the detailed info
Chris

Lew_Merrick_PE:

--- Quote from: craynerd on May 21, 2011, 07:04:22 PM ---I ordered the invar because I was looking at the thermal expansion co-efficients and Tufnol was 1.9 x 10e-5 which seemed quite high.
--- End quote ---

Chris,

What units are you using? 1.9 X 10^-5 as in/in/°F is different from m/m/°C. Most steels run about 6 X 10^-6 in/in/°F (1.08 X 10^-5 m/m/°F). Most aluminums run about 12 X 10^-6 in/in/°F (2.2 X 10^-5 m/m/°C). The "length/length" part is always the same regardless of units, it's the degrees of temperature that make the difference.

raynerd:
That is a good question Lew, I am pretty sure it was m/m/oC.

So tufnol at 1.9 x10e-5 m/m/oC which would make it a little less than aluminium!

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