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)