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Re: [FlyRotary] 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
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