Small smooth very hard plate material?

[homebrewed]

There are other ways to skin this cat. I was looking at pivot designs for seismometers and came across an approach that was claimed to beat out knife-based approaches. Called an x-roll pivot, the reference can be found here , along with a spreadsheet and PDF that cover the geometry.

 

[zondar]

You want sapphire. https://www.swissjewel.com/

Wow, that looks like a good solution too. Sapphire (which is basically an aluminum oxide) is, I believe, the second hardest substance known to man, though it's pretty easy to shatter (not an issue for this application).

I'll take a serious look at it. Thanks - I hadn't thought of that at all!

 

[zondar]

There are other ways to skin this cat. I was looking at pivot designs for seismometers and came across an approach that was claimed to beat out knife-based approaches. Called an x-roll pivot, the reference can be found here , along with a spreadsheet and PDF that cover the geometry.

People have tried that for clock pendulums with mixed success. The gentleman whose photo I included earlier tried it too and has a prototype shown on his page.

I'm not sure what this technique's difficulty is for normal time-keeping pendulums. But for seismography, one usually uses a horizontal pendulum with an extremely long natural frequency of oscillation (could be minutes), whereas a time-keeping pendulum typically has a period of a second or two.

I'll study those concepts a little. Thanks for the heads-up on it!

I'm blown away at the broad knowledge and ideas one finds here!