Just so you know, I did quite a bit of ground testing before I flew with
this oil cooler. I had a way of securing the plane to the ground and could
run the engine/prop up to flying speed (half power @ 4000 rpm). In this
way, I could watch if anything was not properly secured, vibrating, or
overheating. It helped me find some problems on the ground, and I recommend
you do the same.

The thing it didn't do was provide flying airflows across the radiators
(both oil and water). I can't prove it, but just like it is outlined below,
the oil cooler was isolated from engine vibration, but the 3/4" (OD) flex
SS oil hoses going to the oil cooler were in the airstream flow exiting the
cooler inside the engine cowlings, and I think they we're working back and
forth on the cast aluminum cooler until it cracked (in about 1-2 hrs(4
t/o's) of flying). There was no indication of impending failure, nor could
you have pressure tested and found it.

What I have determined that I did wrong was at least the following things:

1. Didn't use a heavy duty oil cooler like the one Maxda uses on all their
rotary engines. Don't use a cast aluminum type. They may have superior
cooling numbers, but they can't handle vibration.

2. Don't locate the oil cooler in an area, such that if it breaks or leaks
that it will be carried onto the hot exhaust pipe. Put it on the cold side
of the engine (spark plug side), or out of the engine compartment (consider
in the wing).

3. Secure the hoses going to the oil cooler, plus any other hoses inside
the engine compartment because there's a lot of air currents inside the
cowlings. Same goes for wiring. It may look like it won't be able to move
much, but even an inch is too much.

Chuck Harbert

 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org