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Thanks Tracy (and all),
That is kinda what I was looking for, just a quick rundown.
I have left a message with Laura to get my new seals.
I am pretty certain that my current issue is likely due to bent seals as Tracy has mentioned, thus keeping the compression low in the rear chamber.
IIRC, the Haynes manual calls for 80 psi, which is what I am getting in the front chamber. But I am only getting 60 psi in the rear. Since I am confidant in my assembly, the bent seals seem to fit the evidence. To address Lynn's
comments, yes, I do have an IVO three blade prop turning and two non-auto batteries for power. Thus, the not coming up to 100 psi as Lynn mentioned, seems expected under load.
I would love to have gotten the apex seals (and O-rings) to use this weekend, but shipping, while good, it not quite that good. Once I get the parts, the tasks should go fairly quickly. The hard part is getting out to the hangar. I am the caretaker
for my mom (cancer and bad spine) and I have to work around doctor appointments. etc.
I hope to get the time to first try new plugs...and then tear down the engine to confirm my suspicions.
Chris
Houston
From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of Tracy [tracy@rotaryaviation.com]
Sent: Wednesday, February 16, 2011 8:02 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Ceramic Apex Seals....curiosityREceramin/carbon/steelst
What I know (and don't know) about apex seals:
I have never used ceramic seals but I do talk to a lot of car racers who have. (98% of RWS customers are car guys, not aviation folks).
The Pros: From their feedback it sounds like ceramics will last virtually forever, their lower weight allows higher rpm limits and they are kind to the chrome on rotor housings.
The Cons: They are strong but brittle. Detonation in turbo engines will break them just like stock seals. Worn out rotor grooves will break them in NA engines. They cost a lot.
If I were building an engine that had nice fresh parts AND had an extra $1800.00 to spare, I'd use ceramics but only for the feel good / cool factor.
I have used stock and RA seals and never come close to wearing either of them out. Stock seals were worn about 30% of allowable limits after 956 hours of flight time. RA seals were about 25% worn after 560 hours of flight. I do not know the percentage of
wear that happens during break-in period but it's probably not linear. Rotary engines have a longer break-in period than piston engines based on the compression tests I've run at annuals. Mine took 250 hours to get highest compression readings. The new
2 piece stock seals will probably last a bit longer than RA seals but if anything bad does happen to stock seals (fracture due to rotor wear, FOD, detonation, etc) they take expensive parts along for the ride. RA seals can and do fail but the failure modes
are non destructive to other parts of the engine. That is the main reason why the car guys use them. They would not care if the wear life were only 50% of stock because they never expect to get anywhere close to that.
Tracy
On Tue, Feb 15, 2011 at 8:29 PM, Dustin Lobner
<dmlobner@gmail.com> wrote:
For what it's worth, I called Adam at
www.rotaryengines.com and had a half hour discussion with him about things. He was remarkably open about putting it in an aircraft (a lot of other places won't give you the time of day if they hear "aircraft" as I'm sure some of you know). I said that
for an aircraft he wouldn't put in ceramics because they're more there for super-high stress situations like drag racing, but for an aircraft the cost:benefit ratio isn't there. Plus, he's not 100% convinced on the reliability.
Dustin
On Tue, Feb 15, 2011 at 6:26 PM, <Lehanover@aol.com> wrote:
Heck, tearing down my engine seems to be a routine event as of late <sigh>
That was my understanding too....about being nicer to the housings.
I was just wondering about what I don't know or what could be expanded on.
Like Dave said, minding parameters is the proper course but I would like to have as clear an understanding as possible for my own edification.
Ceramics have now come of age in many areas. Any machine shop has tooling in the form of ceramic triangles that clamp into tool holders. It maters not if the work piece is heat treated, or harder than Chinese arithmetic, the ceramic bits go through it
like it was butter. The bits are cheap, and discarded if fouled or dulled.
Ceramic apex seals are the gold standard of apex seals. No detectible wear on the seals or the housing chrome. In our case for two seasons of racing. Stronger than steel. Oblivious to high temperatures.
And for racing, track the housing shape at any RPM, using doubled springs, and even with twice the spring pressure, have less than half the drag of a carbon seal, and far less than stock steel seals. An automatic 5 HP over steel seals. Ceramics are so
light that you cannot help but grin when you pick one up.
Ceramics do survive detonation events that would put all steel seals in the muffler. But not for long.
I have read that RA seals also hold up well. Ceramics are used in nearly all pro racing applications.
I sold a used set to another racer for $500.00. They were identical to new seals after two years of service.
The down side is cost. And for one piece seals, typical of racing applications, you must be sure you have the minimum end clearance, about .0015".
There have been efforts to develop a two piece seal that is less sensitive to length variations, as they run at zero end clearance for much better cold starting.
Mazda competition sells racing ceramics, probably Linetties. There are other manufacturers.
Here is one.
Lynn E. Hanover
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