Really need help wtih o-ring comp for engine application
Really need help wtih o-ring comp for engine application
(OP)
We are designing a small engine cylinder head that will be seated with a rubber o-ring. There are similar designs already out there that work fine. Problem is deciding what o-ring composition to go with. Most people have no idea. So far, we are looking at Viton but there are several variations of the material.
Most companies spout off specs and crap but we really need a well stocked, common compound to hold the price down for an OEM design. Any ideas here? Who do we need to talk to?
Engine operating temp is max 250F
Compression max is 1500psi
fuel exposure is methanol and ethanol and gasoline as well as some oils.
Most companies spout off specs and crap but we really need a well stocked, common compound to hold the price down for an OEM design. Any ideas here? Who do we need to talk to?
Engine operating temp is max 250F
Compression max is 1500psi
fuel exposure is methanol and ethanol and gasoline as well as some oils.





RE: Really need help wtih o-ring comp for engine application
Do not use Viton as a specifier. Viton is a DuPont trademark, using it is meaningless. Learn how to properly specify an o-ring compound using SAE D2000. Buy a copy & spend some time reading it.
I can recommend Precix Inc. They have many compounds with OEM approvals. Something like their F78 would probably meet you requirements. There are many other reputable o-ring manufactures. Stay away from most of the stocking distributors and App!@, they will over charge for material of unknown compounding & origin.
RE: Really need help wtih o-ring comp for engine application
I feel there is a lot of data missing, like:-
Is this an IC engine.
How is it cooled.
Where is the o ring relative to combustion products and cooling media.
Where is the 250F measured relative to the o ring.
Will the o ring be sealing the combustion chamber or water ways or fuel lines fo all we know from your OP.
Regards
Pat
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RE: Really need help wtih o-ring comp for engine application
Engine, liquid cooled IC 2-stroke
static head seal application.
o-ring separated from combustion gas by .050" Al mating surface.
O-ring also subject to glyco based anti-freeze.
dynamic compression not to exceed 1500psi
Methanol a must but rather limited exposer and in vapor form. All fuels vaporized with 2-cycle oils.
RE: Really need help wtih o-ring comp for engine application
I agree, I really should talk with an OEM. The suppliers do not know any more than I do about o-rings. I plan to call Parker tomorrow. Any others?
RE: Really need help wtih o-ring comp for engine application
Another very capable company is SIMRIT. I believe they are based in France. I think they tend to cover the niches that Parker finds uninteresting commercially.
RE: Really need help wtih o-ring comp for engine application
Ted
RE: Really need help wtih o-ring comp for engine application
RE: Really need help wtih o-ring comp for engine application
I'm not familiar with M83248/1, it has been canceled. I doubt the military has any need for methanol compatibility. One problem with the AMS & MIL specs is the requirement for the QPL, Qualified Product List. In my experience most manufactures don't want to have to bother with it.
Talk to Bob Coleates at Precix, 828-724-1775, he can get you headed in the right direction. I have no connection with the company except they supply some of our fuel system o-rings.
RE: Really need help wtih o-ring comp for engine application
It would seem what is already being used in the industry is the standard Fluorocarbon A, Viton 75. I cannot be certain though. We will have to get some samples here for some destructive testing.
Parker has recommended their V0747 or the V1263 for more chemical resistance. At this time, I am thinking we should do testing with the Viton 75 rings and see if we find failures with them.
I am really torn trying to determine if I need a harder compound than 75A. Some say it can make compression set worse, some say it it will resist extrusion failure better. No idea here.....
RE: Really need help wtih o-ring comp for engine application
I am assuming your cylinder head seal is a groove with the o-ring in it and will have metal-to-metal closure when bolted down. No extrusion gap on the side of the groove away from the pressure. No? Yes?
Ted
RE: Really need help wtih o-ring comp for engine application
I think the better way to go is an integral head, like most all small aircooled 2 cycle engines have saves you the sealing problems and fastening etc.
RE: Really need help wtih o-ring comp for engine application
Hydtools, NO extrusion gap here so I really do not see any concerns with that failure mode. metal to metal contact on the head with an o-ring groove in the cylinder.
RE: Really need help wtih o-ring comp for engine application
I find it hard to imagine that a liquid cooled engine would be significantly cooler in an area so close to the heat source, but if that is what you have verified thorough testing or modeling, then it is much more useful than my above statements.
RE: Really need help wtih o-ring comp for engine application
RE: Really need help wtih o-ring comp for engine application
I am sure some testing will be needed here.
RE: Really need help wtih o-ring comp for engine application