trydis7

Damn- thanks for the update? I think I am going back to stock everything.



There was some discussion regarding the TES orings on the rotaryeng list years ago.



?Did the o-rings only split/fail facing the combustion chamber?



To start off:

Some of the suggested sizes on rotaryeng.net were sligthly off and had to be stretched. The stretching concerned me so I measured and purchased slightly different custom oring sizes from Creavey.com at a slight increase over stock mazda OEM prices. Mine required no stretching and were just slightly larger ID than the inner wall - still a painIA to hold in place when turning a plate over...



Creavey.com had several grades of o-rings, some were good to higher temps 400F/500F. I am not sure if these are the same as the RA orings.



One major concern was the expansion of the orings at temperature in both length(diameter) and thickness.

There was a nasty pic of an (oversized?) oring that expanded and managed to break a large loop of the oring through the iron's groove wall into the water passage.

The TES orings have a fairly high expansion rate and can exert a fair amount of force.

To work the orings need a certain recommended crush (something like .020-25? IIRC). They would conform to the grooves, but you also need to leave enough (20-30%?) room for them expand with temperature in the groove. I had visions of them sliding around inside the groove or forcing the plates apart at temp.



Personally I ordered the inner o-ring with a smaller 0.093 thickness in the 500F variety - and I was concerned there might not be enough space for them to expand.

?Can someone measure the diameter of the RA inner oring? 0.098?



The orings I had were an opaque tubular teflon casing with a reddish silicone core. The only splice joint I could see was one end inserted into the other. The splice joint was placed in the upper intake area.

?Are the RA seals the same?



I'm guessing based on your pics that either the orings were a lower temperature variety or they opened enough of a gap to be exposed to exhaust gases...

?do you know the tension bolt torque used?

?were any of them loose when you cracked the keg?



Thanks

Trydis7

Lynn E. Hanover

The idea of a very specialized "O" ring being required I think, came from the stock ring being made of a number of materials, and for years they came with a metal seal strip that was fitted along the outside of the ring groove, in the combustion area.



"O" ring protectors are common in high pressure hydraulic situations, where the "O" ring is in danger of being extruded into a microscopic gap between the groove and the covering material.



The "O" ring protector is usually a strip of flat plastic several layers deep and looking like a spiral lock snap ring.



So the metal strip in the Mazda kit was to keep combustion gasses from extruding the stock compression ring from extruding into the coolant area. It was on the wrong side of the seal to protect it from the combustion pressure. So, now there is no protector in the kit. Am I to guess that there was never a need for it. Or that materials are now so good that it is not needed? Or, perhaps it never was neede.



It is technically correct to mount round "O" rings in square and rectangular grooves. Any "O" ring catalog will have the rules for groove sizes for each kind of "O" ring material.



There needs to be a bit of space left over after the piece is assembled. The groove surfaces should be flawless. Pressure from the area being sealed can leak into the groove, and force the ring against the outer wall of the groove. This force only makes the seal better, as the ring deforms to take on the shape of the groove walls.



If the "O" ring is known to increase its size with heat, that must be accounted for in selecting the ring thickness for a particular application.



The stock square rings fill the groove nearly 100% and do a great job of sealing combustion gasses when hot. And on cooldown where there is still coolant pressure pushing the other direction, can still seal well enough that coolant is not lost into the combustion chamber or out the intake. There may not be enough pressure to do this with the round "O" ring that has become stiff from heat or long term use.



Also the stock ring is more tollerant of dirt and or damage in the grooves. The round ring needs slick smooth grooves to workat all.



There are often failures of stock rings due to freezing of the coolant, that later has gasses leaking into the coolant, and on inspection looks like a sheared ring during assembly.



If the grooves are spotlessly clean and dead smooth, almost anything will work as the seal. The real work is done at the junction of the iron and the housing faces under several tons per square inch of pressure.



It seems to me that specalized rings are an answer to a question nobody is asking. The stock rings work perfectly and are not all that expensive.



Lynn E. Hanover

banzaitoyota

I chased this problem a while back. Custom made nuclear grade metallic rings are great, but overkill. I tend to spend more time prepping the O-Ring groove than before

j9fd3s

i had a set sit outside for a year, and it did the same thing.



they do have lot numbers on em, might translate to a date if we knew how

BDC

Yep that appears to be it and it was predominately on the sides at TDC and BDC. Some at the 90*ATDC area as well all throughout.





This is what I've encountered on several occasions with these o-rings in the past prior to discontinuing use. I'd had several batches show up that were ever-so-slightly too small and would require "re-molding" of the o-ring into the groove. Needless to say, it caused alot of trouble and made some of my rebuild times go through the roof. This occurred enough times to make me skeptical about what the next o-ring batch would be like -- right on the money or too small.



Remolding the o-ring may not be as problematic on a square-ring land that's facing up, but imagine the concern it raises when placing them on the rear iron housing as well as the front combustion chamber side of the centre plate -- both of which face down during an engine assembly. Gravity has a chance to pull them out.





I believe Creavey is the original manufacturer but I could be mistaken about that. Creavey was referenced pretty much consistently on the ACRE NL list, with regards to TES o-rings, during the same time I was an active member of that list a few years back. Seeing as how Rotary Aviation is comprised primarily of the one, remarkably successful RE aircraft pilot (Tracy Crook) who produces and sells products for the budding RE aviation market, who is (or was) an active member of that same newsletter list and seems to be the "go-to guy" that the newsletter owner promotes, it seems safe in my opinion to assume that the same o-ring manufacturer spoken of on a regular basis back then would be the one that they would turn to to have their rings made. I even spoke to the rep at Creavey.com about 4 years ago about having some o-rings made specifically for my engine based on the dimensions of the different o-rings that were posted up on the list.



Again, I could be mistaken about it. Secondly, my intent here in posting my concerns about these o-rings isn't to point a finger at Creavey.com or any other o-ring manufacturer per se; it's to raise an issue of the use of these particular o-rings from this particular, aftermarket o-ring package and to convey that the way this o-ring is made might not be being applied correctly to how are engines are constructed and what they demand from that inner o-ring. I'm still sold on the TES/TEV technology; I just don't think these o-rings here are indicative of a good and well-tested application of that to our 13B's.





One of my fears was whether or not the pressure from the o-ring expanding in a then too-small groove would be the potential breaking of the o-ring land on the iron at certain spots where it's thin.





Theirs has a translucent/clear teflon jacketting with an orange-ish silicone core from what I can tell. They've consistently been like that from what I recall in the past when I first began purchasing from them. I've purchased a few sets of TES o-rings from McMaster-Carr.com (part # 9319 K239; approx $10ea.) that were slightly fatter but looked almost identical to the RA ones.





Approximately 32ft/lbs (starting at 13ft/lbs, then 22ft/lbs, then 32ft/lbs) strictly according to the bolt-torquing pattern shown in the shop manual. I've done it so many times I finally memorized it.



My guess is the same -- Although I'm not skilled in the technical differences between the types of teflon, silicone, and what not that's used in constructing these things, if I do recall correctly, however, there are a few different temperature variations that are available when having these rings constructed. Perhaps the type of teflon used here was a lower temperature type. I don't know. Since there's some blackish around the split area of the teflon jacketting, and since those splits are facing the chamber side rather than the cooling jacket side, my guess is they split from heat and exposure -- I think they were cooked.





On the sides, yes. Otherwise, I had to use a very small, thin, flat-head screw-driver to pop them out.





Hope this has helped.



B



Edit: To Fix quote screwups.

BDC

Lynn, you're amazing.





Exactly -- What's the point of pursuing a super-duper, gee-whiz, ninja o-ring when the stock ones aren't broken in the first place?





B

trydis7

The color was an orange-ish core, not reddish - brainfade. I think they were something like $7 a piece from Creavey for the custom size 500F 0.093 orings.



Was this engine a high powered turbo/race car/daily driver?



Could you measure the thickness, in a few good places, on one of the failed orings - might be useful info.



Thanks

dis7

Lynn E. Hanover

If every you want to try this style of ring material, or some other material, just buy some bulk stock on spools, or made up rings that are to big for the application.



Cut the ring at a steep angle, fit it in the groove, and cut off the excess length at the same steep angle.



Place the junction on the intake side of the engine. If skittish about the seal, just add a drop of silicone to the splice.



The Navy used to have $2,000.00 splice kit, that contained a heating iron with grooves of various sizes and a cover that had the other half of the grooves on a hinge. You would cut off however much bulk material you needed, cut the ends off square and put a drop of goop on each end and push them together and clamp on the cover and turn on the heating element. The goop would cure as if part of the original ring and when pulled to destruction, the ring would never fail at this joint. I discovered a high consumption rate for this vulcanizing set and asked some of the users why they seemed to fail so often.



I discovered that the set had been superceded by another set that included several sizes of bulk material on spools. That set used a drop of super glue to join the ends of the bulk material. There were NSNs for the glue and the bulk spools listed in the kit.



The users still ordered the older vulcanizing kit to get the long heavy duty electrical power cord, which they cut off when discarding the brand new vucanizer, and the fabulous wooden (Maple with dovetailed joints and brass fittings) box the vucanizer kit came in.



I published a new NSN for just the box. (about $30.00) I linked the New kit NSN to the old kit NSN, so no matter which one you ordered, you could only buy the new kit. All approved by the Navy.



The point was that when compressed in its groove the ring trys to get longer, and cannot so it generates a very firm pressure. The part about adding this or that glue is almost a mental trick to help the installer believe this will work. If there is still a worry, make the shelf splice where the ring is reduced by half its width over a half inch or so, and the mating end is also done the same but in mirror of the first end. Glue it if it makes you feel better.



If possible place the joint in a location where a leak will have no, or little effect, and the leak might be detected.



Notice when the rings are removed even for a short time that they grow in length and can not be reinserted into the grooves.



Note that if you forget to pin the grooves in a "J" bridgeport that the ring material extrudes 1/2" into the intake port.



Everything used by the US Government has a special P/N assigned to it. It is known as the National Stock Number, or NSN.



Lynn E. Hanover



US Navy 59-63

banzaitoyota

The "new" navy splice kit from 81-92 had superglue in it

fitzrx7

Sorry I'm a little late on this one, but I just took apart my motor with the RA seal kit, and although it wasn't exibiting any of the coolant loss symptoms, on examining the inner coolant seals I also noticed one o-ring with the exact same damage as to what you posted BDC. Unfortunately I had already removed them from the irons so I don't know on exactly what part they came from, but it is on a straight section of the seal so I would suspect combustions area and not intake side. Anyway just thought I would throw in my 2 cents and also comment that I will not be using a RA rebuild kit (or TE o-rings) or the RA seals as there was a little bit of chrome wear and grooving on my housings so it is back to OEM for me.



Fitz