Originally Posted by
cnczoner
Well, I was trying to narrow down the problem to simplify it, but here's the situation in more detail...
I will have a shaft (~1/4"-3/16" dia) with a hole axially through it, and a vacuum will suck air through the tube. But the tube needs to rotate (via a stepper motor), so to create an air-tight swivel joint, my plan is to drill a few holes on the side of the tube and create a small "chamber" around that part of the tube. Sealing the ends of the chamber is what I need these seals for.
The chamber will have some vacuum in it, which should essentially the same as there being positive pressure on the other side of the seal (or bearing or o-ring). The seal will only see a difference in the pressure from one side to the other. I'm thinking -20 inHg (though I should measure that), which is roughly 10 PSI.
FWIW, I tried a test with just a shielded bearing yesterday, and it was *okay*, but I'm sure I can do better with a seal or o-ring.
Geof, which side of a seal is the higher pressure side? The side with the garter spring?
One company I spoke with told me to get a "spring energized teflon seal" and pointed me to balseals.com as a source. I've yet to contact them.
I'm going to run a couple tests with some O-rings also.
Cheers,
-Neil.