----- Original Message -----
Sent: Sunday, April 17, 2005 2:09
AM
Subject: [FlyRotary] Apex Seal Groove
Wear and Air Filters was Re: [FlyRotary] Re: New rotors, New housings
Hi Guys,
Just need to clarify something that I have been
discussing off list with Ed. I don't THINK (but I'm not really
sure) that his apex seal collapsed and did the damage. The grooves are
not badly worn enough, nor are the seals sufficiently thin enough to
turn in the grooves. Apex seals don't normally break unless clouted by
some obdurate object, and we can't blame insane RPM or detonation as the
culprit either. So while the jury remains out on it, I
remain of the opinion that his engine swallowed something solid in the
shape of the diamond impressions left in his rotor.
Further, I thought I'd offer a little
diatribe/rant on "Ingestion of Foreign Objects" based on 32+ years of
observation and experience with Wankel engines. As an aside, I
cracked up when I read a "Japlish" exhortation that was included in the
instructions of a HKS turbo kit I purchased back in the early '80s. It
said: "Prease being careful not to allow any alien into port"
Prescient advice indeed!
Now over the years, I have found that the
major cause of apex seal groove wear is ingestion of abrasive material.
The air ALWAYS contains a certain amount of fine dust, except just after
a rain storm. Proof of this is the patina of crud left by said rain on
any shiny surface, most obvious on car duco. Here in Oz, we
often get thick orange/brown dust deposits from dust storms originating out in
the desert hundreds of miles west of the city on the other side of
the Great Dividing Range.
Now that very same dust, invisible though
it may be, will act as a fine lapping paste: if allowed into the
engine, will, depending on the concentration, sooner or
later eventually chop out the apex seal grooves, and the corner seal
grooves. It will accumulate in the grooves and the lapping action gets
worse over time as the paste gets thicker.
Ed has told me that there is
some construction work going on near his hangar, and his aircaft is
often covered with a film of dust. That dust will also be all over the
tarmac, taxiways, on the grass verges, and in the air
itself. If you are following another aircraft, you are GUARANTEED
to cop a lung full of fine dust, whether you can see it or not. It
stands to reason, seeing that any engine is just an air pump, that
it will act as a very efficient vacuum cleaner.
Which gents, is why you should always
supply your engine with nothing but clean filtered air AND fuel.
Most people wouldn't THINK about running a fuel system without a fuel filter
and a water trap.
Additionally, a decent filter will also
stop the rocks and pebbles, and grains of sand that can get thrown up by
the prop wash of the preceeding aircraft, as well as the almost
ubiquitous fine dust. Wankel engines in particular are not very
tolerant of being fed a meal of anything solid. One small pebble,
or a decent sized grain of quartz sand or bluestone is sufficient to take out
an apex seal. (And please dont' tell me it can't happen as I've seen the
results with my own eyes on more than one occasion).
I realise that there will be a bunch of
people on this list who feel air filters are un-necessary, but we
can all become the victims and prisoners of our own (often false) belief
systems, no matter how passionately and sincerely they are held.
(I've no need to remind you that there once was a bloke who said that EWPs
COULDN'T cool a rotary).
So even if you do fly off water, you
still can be exposed to the products of dust storms from other parts of the
country, or volcanic ash (both often invisible - ask the guys in the BA
747 some years ago!).
As a corollary, on many occasions, I
have pulled down engines that have had up to 550,000 kms on them (mainly 12A
RX7 engines). Those that have had regular servicing (regular oil and
[air oil, & fuel] filter changes) invariably have pristine
rotors, that show little or negiglible apex seal groove wear.
OTOH, I have seen engine "chop out" in as little as six months when run
with a faulty air cleaner, and run in dusty environments.
Two things are important to prevent groove
wear. Proper lubrication - if the surfaces don't touch, they
cannot wear - and elimination of abrasive particles - which, when mixed
with lubricant, acts as a VERY efficient lapping compound..
Further, everyone should be scrupulously
paranoid about loose objects getting into the inlet tract. In the past
32+ years, I've seen the sad results of just about everything being
ingested - nuts, bolts, studs, spring & flat
washers, carby check balls, paper clips, lock wire off-cuts, bits
of cardboard, plastic, alloy trimmings, metal filings and
turnings etc, as well as sand, pebbles, and small
rocks. NOTHING good has EVER come of feeding a Wankel with any of
this sort of detritus. So please be extremely paranoid about inlet tract
cleanliness after working on it.
While I'm on this topic, I should also
exhort you to treat the exhaust system with the same degree of
cleanliness. Untill the engine actually fires, it doesn't really know
that the exhaust port is an egress apeture. I've have seen stuff sucked
up out of exhausts (particulalry weld spatter, and even pieces of rag
used to prevent stuff falling INTO the exhaust and inadvertently left
there!).
So that's my additional palm full of Roubles
for today.
Cheers,
Leon
----- Original Message -----
Sent: Sunday, April 17, 2005 11:54
AM
Subject: [FlyRotary] Re: New rotors,
New housings
Hi Ken,
I really, really have no interest in running
for your title, believe me! {:>). I am inclined to agree
that milling out the slot may indeed take you pass some metal hardening that
lessens the wear. While I must admit that I am still a bit skeptical
about the dust doing it to me in 150 hours, I think the rotors had been run
hard when I got them but just didn't know what to check for. But, in
any case I am going to add a filter figuring it probably won't
hurt. Besides, If I didn't add a filter and something happened
again, I'd never hear the end of it from my friend, Leon.
New rotors and housing are ordered. I
figured depending on how Jerry Hey and his PP project turns out, I might use
them to practice cutting PP port and then turn two of my good NA
housings into PP housings - down the road.
Ed
----- Original Message -----
Sent: Saturday, April 16, 2005 4:40
PM
Subject: [FlyRotary] Re: New rotors,
New housings
I would look into getting 85-85 GSELE rotors with the 3 mm
seals, you would also need the weights to match them, then machine out
your rotors for a spare engine, you may need one to bale you out in the
future, if you keep this up you may knock me off the seat as president of
the dead stick club.
I am now running rotors machined out to 3 mm seals and at
about 400 hrs on them I can tell by checking through the exhaust port that
the seal grooves are getting V'ed out and getting sloppy so I am now
putting another engine together, on this one the rotors are in prime shape
so I think I will run Tracy's 2mm seals.
Also I think that the groves may be hardened and by machining
the groves out makes them softer as they shouldn't have worn out in only
400 hrs.
Ken
Well, the
decision has been made. Thanks in part to the wife's continued
interest in my warm body on cold winter nights, the decision has
been made to purchase new rotors and rotor housings. $$ but
apparently I am worth it {:>)
I looked into
milling out the slots to 3mm and that would have been the cheaper
approach - but cheap approach is probably partly responsible for me
being in this situation - so going to try a different approach this
time. Besides leery of using a rotor which clearly has been
subjected to sufficient loads to scrape metal off its surface and peen
over apex slot.
In the process
of getting quotes.
Ed
Ed
Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com