Hi Mike
Metallic "O" rings are not new, they just seem like a closely guarded
secret.
Made from .062" dia, .010" wall Inconnel X 750 tubing, formed into a hoop
and then welded and ground at the weld. During the manufacturing process
they fill with a high pressure gas Nitrogen I think. A company called
Helico Flex, in S. C. produces them in lots of sizes, but actually makes
them to my (or your) specification. They are expensive. When ordering 25
or more the price is/was $24 each. These type of parts are used to seal
very high pressure steam at Nuclear plants and are very well engineered.
The O ring sets in a step in the bore rather than a groove. With big bores
there just isn't room so a counterbore does just fine.
The logic, behind the design is the metal O ring provides a very high unit
load to seal high pressure combustion gas, and as temperatures increase and
the properties of the metal decline, the high pressure gas has expanded and
supports the original sealing (unit load). They work well, and of course
provide a metal/metal clamping joint that is much more stable than the
typical gasketed joint. If you flow water and oil thru this joint you still
need elastomer O rings at each location. If anyone is interested in
specifics, I can take some photos and post. (Glenys just got a new digital
camera).
Even for us crazys, most of us don't need this kind of approach to sealing.
Roush used this in the 2.5L GTO motors they used in the 80's and never had a
problem. What was interesting about that program is they never had any type
of engine failure in public. Except one pilot burning down one engine when
he lost coolant after a shunt. He didn't DNF though....
I was very fortunate that late in the program Lee White, then the manager of
the GTO program shared some of the non propriority items with me. I'm not
too proud to copy.....especially the good ones.....
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