I know o-rings are used in hydraulics as seals, wipers.
But what about in a dry environment?

Imagine a 3/4" sq bar freely sliding inside a square tube, nominal 3/4" id,
with the id smooth but unpolished, and not a great material, like alum...
no flashing.

I see two possibilities: o-ring material itself with a square xsection, in
a groove around the 3/4 material. But the corners would have a radius,
unless I could find o-ring stuff with a square xsection and also for
square/rect rod.

Square xcection o-ring material can be found here
http://www.epm.com/square_cut.htm
but round bar/rod, not sq or rect. bar.


Or, on the END of the 3/4 bar, take a nominal 3/4 sq pc of some compressible
(but hopefully low-frcition) material, and screw it to the end end of the
3/4 bar, the tension of the screw (and washer/plate) squeezing out the wiper
material for a suitable "fit" on the inner wall of the tube.

Compressibility (rubber) and low friction *seem* to be mutually exclusive
properties, but not sure.
Some kind of leaf spring steel/brass wiper could do as well, altho I
wouldn't want stuff too mechanically fragile.

Or just screw some felt/cloth to the end of the 3/4 bar???

The logic, rationale behind this is that the 3/4" bar needs to slide freely
but be reasonably low tolerance (.005 to .010), which could allow grit to
jam it in the tube. Ergo the wipers. A square fuzzy o-ring for rect. mat'l
would be ideal.

Idears, leads?
--
EA