I'm pursuing it - I finished boring rotor housings last weekend. Hopefully
I'll have tubes in and the slide throttle done by next week. If that all
goes well and the housings still look good - I'll order a complete rebuild
kit and put it all together the week after that.
Since the 13B in my airplane is waiting for a re-built exhaust system to
replace the one that cracked off - I've got time on my hands and figured I
go ahead and take a shot a rebuilding this second 13B into a P-Port.
Thanx,
Joe Hull
Cozy Mk-IV N31CZ (65 hrs - Rotary 13B NA)
Redmond (Seattle), Washington
Congratulations Joe. Since you are already flying and all
you need do is swap out the engine, I think you will be
the first true homebuilder to fly a p-port of your own build
since Everett Hatch. There are going to be a lot of
envious RV'ers your neck of the woods as you flash past
them in the sky.
It was easy wasn't it? Hey, got any pictures of the boring
process? Here are a few picturs of Joes airplane for the
new guys.
Where did the exhaust crack Joe?
Paul Lamar ...No rotor no motor.
Pictures - Nope! I was going to take pics but forgot the camera. My friend
has a huge Cleveland milling machine in his shop and tons of different
cutters. So I started off with a 1/2" face cutter to flatten the area - i.e.
the knob where the manifold stud sticks out. Then I bored progressively
larger holes with three drills and then used what-cha-ma-call-its (big
cutters with blades on the face and the sides) to cut 3 stepped holes 2 1/8,
2 3/16, and 2 7/32. I wanted a notch in the inner face and another in the
outer face to seat the tubes and provide another barrier to water leaks -
the 2 1/8 hole goes all the way through. The tube I'm using is 2" OD x 1/4"
wall.
Next I'll turn the tube to match the steps and also a little lip on the
outside edge to help capture the rubber tube that will join the manifold to
the P-Ports.
Exhaust - I was on my way to OSH and about an hour east of Cheyenne,
Wyoming, over Nebraska when I felt a slight change in the vibration of the
airplane. All the temps, pressures and RPM were fine - just a slight change
in the vibration. So I figured I better get on the ground and see what was
up. I landed at a little ranching town (population 267) with a 4000ft runway
(since I need lots of runway to land) and after landing and running up the
engine - the engine quit DEAD. The paint on the cowling started to bubble
and burn - not good. I pulled the cowling and found that the big tube of
the tangential muffler had broken off both of the 2" runners that come off
the exhaust flange. The hot exhaust had melted the wires together to the
injectors and other wires in that area - that's why the engine quit.
Fortunately this little town had a great welder - and even on Sunday
afternoon he welded it back together. I pealed the injector and other wires
apart and wrapped them all up in electrical tape and silicone rubber tape
and took off for home the next morning.
I'm abandoning the tangential muffler and inconel - too prone to cracks
(this is my second) and am going with .049" 321 stainless tubes. The noise
will be higher but so will HP (I'll also have way less back pressure) - and
hopefully more reliability too!
Joe Hull
Cozy Mk-IV N31CZ (65 hrs - Rotary 13B NA)
Redmond (Seattle), Washington
Thanks for the report Joe.
That is interesting. Who welded up the failed rig?
This is the second pusher rotary engine muffler failure
we have heard of. Many people make the mistake of welding
the tubes to the exhaust flange on the outside of the flange rather
than the inside of the flange. There is vibration causing
fatigue due to the mass of the large muffler cantilevered off
the tubes. The weight of the muffler can must be supported by a strap
to the engine and not just by the tubes.
This was discussed on Mark Wrathal's best practices web site which
is linked to the ACRE NL site. Everybody building an airplane please
read this site.
http://www.wankel.org/
Also check out
http://www.rotaryeng.net/interesting.html
Too bad I did not know about it sooner Joe. Sorry.
Paul Lamar ...No rotor no motor.
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