Message
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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