I am looking for an o-ring to place on a rectangular shaped cavity rim. Not rectangular as in the cross sectional shape of the O-ring (which is all that keeps popping up), but rectangular as in the shape of the cavity's rim perimeter.
Anybody done this before? Years ago, I'd just whip out the ol' Thomcat register..
Google is sometimes so worthless.
umeroUno:
normally you just put a reasonable corner radius on the groove and use a regular o-ring, I think Parker suggest a corner radius of something like minimum 3-6 times the o-ring cross section
-Lasse
You will probably need to have it made for you. I had something like that done about 20 years ago by these people:
I am not associated with them.
Yeah, it can be done, BUT you don't get a good seal unless you control all the dimensions (width and depth of 'cavity'), to suit the particular O-ring dimensions you use. So, it's generally easier to just cut a round cavity.
You can also get die-cut gaskets in the rectangular shape, it just takes some tooling. Search on "steel rule die".
My first try for this sort of thing would be McMaster-Carr. George H.
Vulcanized gaskets can made on the fly, you just get the basic material on a roll and do the hot spice.
Neophrene also can be spliced and got on a roll.
There is also a rather new produce that forms gaskets much like silicone compound for high temp. Those can peel off easy to reform a new gasket if needed and many times can be reused if you don't fully tighten down while curing.
Jamie
I've seen many commercial cases designed this way. What is your concern? As someone said, they give the groove rounded corners at each turn. I'm not sure they worry about the cross section of the groove. Looks like they are often rectangular. I believe there is a specific degree of compression required, both a min and a max.
On Sun, 13 Mar 2016 15:59:46 -0700 (PDT), George Herold Gave us:
Sorry, but that triple overpriced reseller is my LAST place to look, and they will not be having a 23 x 15 inch O-ring gasket for me.
I will be better off determining the overall length and buying a round tank o-ring and fitting it to the compression groove.
On Sun, 13 Mar 2016 19:51:53 -0500, M Philbrook Gave us:
It isn't food, ya dope, and NO a spliced seal media is NOT going to work at diving depths.
It has to be a proper compression gasket medium.
On Sun, 13 Mar 2016 19:51:53 -0500, M Philbrook Gave us:
There is no H in 'neoprene'.
You have appeared to be a bit more drunk lately. Or maybe the doc upped your meds.
On Sun, 13 Mar 2016 21:58:14 -0400, rickman Gave us:
With what you said in the subsequent lines, I have my doubts. And this is not a walkie talkie sized instrument case, it is nearly two feet long and nearly a foot and a half wide.
Learn to read.
No s*it. I was gonna be dumb like you and make sharp, right angle cuts in the design.
I am quite sure that you cannot provide even a hint of useful information about it.
You completely missed every aspect of the post. I do not need a seminar on how round seals work in rectangular grooves.
And YES *they* worry about the groove shape AND the gasket shape. There are ovals, squares rectangles, ad infinitum. But as my post clearly states, I am looking for the overall perimeter shape, not the shape of the seal media itself, and they are NOT "often rectangular". "Rectangular" is but ONE of the many methods employed and it all depends on what one needs to keep out... or in.
Most such applications use O-rings that are made by splicing a length into a circle. You buy a spool full of rubber strip and a vulcanizing machine, and you go to town with it.
Uh... you do know that the case will not remain rectangular if you apply pressure? Like, at 20 psi, that 'panel' will have 20 x 25 x 18 = over four tons of applied force.
Make the container cylindrical, and the seal round, this will be less of a problem.
On Mon, 14 Mar 2016 00:00:48 -0700 (PDT), whit3rd Gave us:
Not if the interior is pressurized with nitrogen gas or helium it wont.
And you got the shape wrong. It is only 3 inches deep.
"That panel" will be 3/4 Delrin plate and the underside will be honeycomb cut like a giant telescope lens, yielding a huge subtraction in weight yet nearly the same physical strength.
And it is only 22 x 15 now as I have been nesting things more tightly inside.
McM-C will sell you o-ring cord, cut to length and splice the ends. (I'm not sure how the ends are bonded.)
George H. (The good thing about McM-C is they always have stock and it arrives in the mail the next day.)
If you do really intend the case to have its own pressure regulator and gas supply, the glued-up O-ring will work fine; it won't have any particular pressure to seal against. Without regulator, prepressurizing to 20 psi puts the initial pressure on the flat surface of a side, OUTWARD. It's still a few tons. For a 15 x 22 inch panel, 15 x 22 x 20 = 6600 lbs (three and a half tons). I wouldn't do that with Delrin.
Wow, I found a supplier today...
On Tue, 15 Mar 2016 02:39:23 -0400, rickman Gave us:
What are you making?
I've seen things that squirt liquid plastic into groves to make arbitrary complex o-rings. If your box has no outer rim, some tape or something would help until it cures.
On Tue, 15 Mar 2016 10:48:52 -0700, John Larkin Gave us:
Absolutely unacceptable for a seawater immersion military instrument.
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