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Hi Rusty,
I am sorry
to hear about your unfortunate experience with the evap core. I
have been watching your testing with much interest. I have decided
to use either a Mazda cooler or and AC cooler for the oil. Thank
you for the great test report. I just wanted you to know that your
efforts are appreciated by all of us who are trying to get into the
sky.
Joe Berki
Limo EZ
Re-designing cooling system for the third time
At 04:04 PM 12/14/2004 -0600, you (Russell Duffy) wrote:
Greetings,
Well, I got the plane hauled back to the hanger, and
managed to find the problem. I had fully expected to find the oil
cooler (evap core) split at one of the seams in the tank, but I couldn't
see a thing wrong with it. After wiping off the oil, and checking
all the oil components, I still couldn't see anything wrong.
At that point, I drained the pan, and only measured
1/3 quart. This is clearly below the oil pickup, which is at least
a half inch off the bottom of the pan due to the sandwich mount
plate. I proceeded to remove the oil cooler, and inline
filter. The filter wasn't plugged, or collapsed, though there are
some flakes of something in it. Even on the workbench, the
cooler looks absolutely fine, but it isn't. Blowing through it
demonstrates a definite leak at one of the seams on the tank.
If you look at the way these are constructed, the core
is made up of a number of layers, stacked together like slices of
bread. To close up the open ends of the tanks, there's about a
1/16" aluminum plate brazed at the end of the tanks. The seam
between this plate, and the main part of the core is what leaked on both
of my oil cooler cores. The attached pictures show an old
core that Ed sent me to do some testing with a couple years ago. It
had developed a leak from what he believed to be too much
strain/vibration on the hoses.
Both of my oil cooler evap cores leaked at this same
seam. The latest one was on the end of the tank with the fitting
that I welded on. You could suppose that the welding process
overheated the seam, and caused it to leak, however, it sure took it's
time (at least 10 hours for this one, and about 30 hours for the first
one) deciding to leak. You could also suppose that the strain on
the hose caused fatigue. My oil hose is long, and has lots of room
to flex. I just can't imagine that putting any strain on the oil
cooler fitting. The first leaking oil core happened on the end
without the welded fitting, though that one was dented in. In
other words, welding, or strain from a fitting couldn't have been the
cause in that case.
I find it too much of a coincidence that my two water
cores have not had any problems, yet both of the cores I've tried on oil
have leaked at the same point of construction. Of course Ed did
have a water core that leaked at the same point. Bottom line is
that this seam seems to be the weak point of these cores. I can't
explain exactly why they're failing, but I have to conclude that they
aren't so robust as I'd like them to be. I'd be interested to know
if this is where they commonly leak on cars as well.
As for the engine, all 6 rotor faces seem to have even
compression when turned by hand. Unfortunately, I'd have to say
that the compression is considerably less than it used to be. The
engine will definitely have to come apart.
As for the plane, I've already received one email
asking if I want to sell it, so I might pursue that. As you know,
only a couple weeks ago, I was saying that I planned to sell the
RV-3, and transplant the engine into an RV-7. Well, the plane's
apart, and I would end up putting a significant amount of time into
getting it back in the air. With that in mind, I'm thinking that it
might be just as well to go ahead and sell the airframe now.
Haven't decided for sure, but I could see getting the Slingshot back
together in fairly short order with the 912S, then either starting on a
single rotor conversion for the Slingshot, or starting on an RV-7.
Cheers,
Rusty (undecided)
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