On Tue, 5 Feb 2013 15:52:04 -0800 (PST), jon_banquer
wrote:

On Feb 5, 3:39*pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:
Searcher7 fired this volley in news:370407bd-
:

This is not plausible with conventional camera stands. So I'm trying
to decide on the best metal to make the moving parts out of. A metal
that will best retain it's dimensions under changing temperature
conditions.

To start. Would cast Iron be a plausible candidate?

It's a fool's errand to try and find a metal you can work with that won't
expand and contract with changes in temperature.

Instead, you should be 'focusing' on a design where the various
dimensional changes don't affect the aim angle. *For instance, where the
camera pivots at the exact centroid of all the expansion or contraction.

That, and a solid base, like granite, to hold all the other stuff.

Even granite changes dimensions with temperature... G

LLoyd

Wrong, Loud. He should be focusing on both. I've machined a lot of
parts out of Invar for Coordinate Measuring Machines:

http://en.wikipedia.org/wiki/Invar

He's not trying to make a CMM, more like an index or dividing head.

There's no engineering reason to use an exotic material with a low
CTE. There's plenty of reason to look at runout in bearings and that
sort thing.