On Tue, 11 Mar 2008 11:01:30 -0700, charlie wrote:

"Tim Wescott" wrote in message
...
More design questions:

I need a stick-like thing, about 30 inches long, to go from a pivot
point to a little electric motor. It needs to be moderately rigid,
light and inexpensive in lots of 50 each or so. It would also be quite
nice if it's moderately attractive -- mill finish aluminum without too
many scuff marks is just fine for this. Prettier is better.

I'm thinking that thin-wall aluminum* tube of about 5/8" diameter will
work well, and I'm getting ready to be shocked once again by how much
things cost these days. While I'm waiting for quotes, I thought I'd
solicit the group for suggestions.

Fiberglass? Carbon fiber? Phenolic? Other plastics? Titanium**?
Extra thin-wall steel? Balsa wood comes to mind, but while it is low
tech I suspect it'll cost more than aluminum. Cooked spaghetti is too
limp, and uncooked is too brittle.

Anyone have suggestions? Do you have supplier names to go with your
suggestions?

* Alloy isn't terribly important. Even dead soft would work, although
harder would be better.

** OK, maybe it's more expensive than aluminum.

pvc pipe? venetian blind replacement rods? wooden dowels? you don't give
a lot of specs on size or what kinds of forces it has to withstand,
whether it has to be weatherproof, etc.

Your "venetian blind rods" turned into "polycarbonate tube".

McMaster sells polycarbonate tube -- they have some 1/8 wall 5/8 OD tube
that should be OK, if a bit more brittle than I'd really like. They want
less than $2.50 a foot, and I should be able to get it for much less
elsewhere if I dig. I'll see what else they have.

Thanks.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html