Well, a bit of wobble can indeed
break apex seals - that is one of the failure modes. Its just I didn't
think my seal slots were that worn - however after finding the were in
some cases past the 0.15mm limit set by Mazda, I think it possible that
the stresses from the "leaned over" profile broke the brittle seal. I
had not measured the compression since last year at the annual
inspection - so don't know what it was, but I agree it seemed good
based on the rpm and power. However, a slop apex seal slot will not
necessarily show up as low compression - it may still seal - but under
more stress due to the angle.
However, it could have been an
foreign object, don't know what it would have been at 7000 msl. Don't
see where anything could have laid around in the intake through my max
power take off and then break loose. Besides, there is nothing
missing. The things it could have been was a chunk of my plastic
manifold - no pieces missing, the epoxy shaping the secondary intake
ports in the lower manifold - inspected and all there.
I could find not scrape mark or
impression on the rotor housing with the broken seal - which surprised
me. I will inspect the rotor housings more carefully after I get the
engine back together in case I missed it.
I looked at the four spark plugs
again yesterday for missing pieces of ceramic cone, chunks of
electrode, etc. These are Racing plugs and seem fairly well
constructed and nothing was missing. I will be sticking them back in
the new engine - after I found their electrode is at least 5mm from
the combustion chamber. Just a coincident that the engine broke right
after I put the new spark plugs in - perhaps I was generating more
power with the new unshrouded plugs and broke the seals {:>).
So may never know for certain -
could have been just a combination of things adding up, weak fractured
seal, sloppy apex slot, etc. could have been the dust.
Ed
-----
Original Message -----
Sent:
Friday, April 22, 2005 11:27 PM
Subject:
[FlyRotary] Re: All Parts have arrived, Whew!
You all have to remember that Ed has a knack for finding and exploring
all possible failure modes - known, unknown, and yes, even the
impossible :)
Something that no one has memtioned is the gears (end housings/rotors).
Also rotor bearings/e-shaft clearance.
What's the consequences of out-of tolerances here?
I just can't see that a bit of wobble of the apex seals in their
grooves could cause a seal to break.
Also, how could you have such excellent compression with worn
seals/grooves?
Sounds more like a fluke or foreign object to me. Any chance that some
carbon build-up near exhaust ports could break loose and get jammed
between seal and edge of exhaust port?
Any telltale on the rotor housing as to where the seal broke?
Did you *thoroughly* inspect the four sparkplugs? Any piece of metal or
porcelain missing at all?
Finn
Ed Anderson wrote:
Well, George, I would not take
the conclusion that far. We have folks flying with several hundred
more hours than I have with no apex seal failures. In fact to the best
of my knowledge, I am the only one I am aware of other than Chuck
Dunlap who's rotary engine swallowed a 1/4" dia steel bolt (it was
retained - so we know) to have an apex seal failure in an aircraft.
However, I do believe that folks need to be more aware of the true
condition of their used engine components - I know all probably did was
look at it and not seeing any obviously defects or dings said - "good
to go!"
As you know, Leon is
convinced my apex seal failure was also due to foreign object ingestion
- I certainly can not prove it was something else (like the apex seal
slop) although I don't believe a foreign object to be the case -
belief is not a fact {:>).
Ed