I've been thinking about making my own apex seals for a while now(3mm, 2piece seals for the 12a). The machining of them is not a problem at all, but what material to use is. I could just get a stock seal, run some tests on it, and make my seals out of the same material. But I don't want to do that, since they are only safe up to 8500rpm. I want the seal to be safe until at least 9500prm, and be able to handle a decent amount of boost too(20-25psi). I was thinking some type of high-carbon steel would be a good choice, but I can't decide on any material yet. Seal life won't matter that much, as long as they don't do any significant wear on the housings.

If I can get some seals made and tested in my engine, then I would start making them for all the rotarys and start selling them(for less $ than other places of course).

 

I know the stock apex seals are cast-Iron, but I don't know any more than that

If you can get it, why not use titanium?

 

Titanium? There was a thread a while back about titanium apex seals.

 

Titanium is wicked abrasive(sp?) The guy that made it in the previously mentioned thread said after brief opperation of the engine it was torn down and the housing's looked Very Very old by a wear standpoint to the point that the engine couldn't maintain compression

 

Why not get the rotaryaviation seals and see what material that is? They seem to make tall claims and a few forum members have backed them up on it.

 

makes me wonder... would it be possible to coat both the housings and seals with a molycoat? Slippery stuff..

 

Also, titanuim likes to gall. So after when you turn off the engine, the seal could stick to the housing and cause damage to the housing when you re-start the engine, or it could just crack the seal if it's stuck bad enough.

 

what about ceramic coated steel
they will still chatter, but they wont leave marks,hmm nexty time i rebiuld ill have to talk to scalliwag

 

Or (if you can afford it!!) get a thin strip of titanium, and get it coated in several layers of ceramic to bring it up to the desired thickness

 

mostly I was thinking of treating old seals and selling them cheap
liek 50 a peice

 

Well... choosing a material isn't really that easy there are alot of factors you need to act for...
is the material FCC, BCC. Which one do you want to use? What has been used and what is currently being used? what are their advantages/disadvantages. Err.. Fracture toughness. Hardness. Coefficient of thermal expansion. I guess as far as chatter goes you will have to design for the best natural frequency which I think should be closely related to density with other factors.

 

I've been working on this for some time now and in may it's off to Woodburn local drag stip. the engine does run with good comperssion

 

Hmmm, brass.... I know my dad mentioned something about using brass when I asked him what he thought would work good. Let me know how they work and what kind of revs they will take.

 

Won't brass expand like a **** under extreme heat causing all kinds of problems?

 

Err.. what type of egt's does the rotary engine see?
The melting point of Brass is about 900C and it's an FCC material which means there are more slip planes and it is more ductile and deforms more when heated.

 

damn, is this for real or are you jerking o ur chains?

 

Yeah.. i wouldnt personally use brass. face centered cubic, when you really want BCC. HA! i learned *something* from engineering.