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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
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