> 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.

Who welded up the failed rig?<<

A guy here in Seattle who is a master welder - it was an excellent job. The
welds themselves didn't fail. It was the inconel on the 6" tube all around
the area where the 2" tubes connected. There were spider cracks emanating
from where the inconel cracked next to the welds.

If inconel is used it MUST be supported and made rigid so there is
absolutely no unsupported flex. It does not handle flexing at all without
cracking and breaking. The flexing can even be small amounts from the
exhaust pulses themselves - not just overall engine vibration.

I wish I'd had the presence of mind to take a picture of the cracked exhaust
before I was welded - I guess I was pre-occupied with trying to figure out
what to do since I was in the middle of nowhere. But, attached is a picture
after it had been welded but before I buttoned things up. Note the melted
bottom of the throttle position sensor - that's what all the wires looked
like too!  I had an aluminum heat shield - primarily for keeping any
dripping fuel away from the exhaust. Next time it's going to be stainless!!
(you can see holes blown through the heat shield on the right)

Joe Hull
Cozy Mk-IV N31CZ (65 hrs - Rotary 13B NA)
Redmond (Seattle), Washington

That is interesting. What was the wall on the Inconel.
Dave Atkins has been flying an .035" Inconel muffler like that
for years. First picture was taken 7 years ago. As far as
I know he is still flying it.

Perhaps the guy that tig welded it used the wrong
rod or something like that. I am no welder but there is something
about migration as I recall.

I see your exhaust flanges to pipe joints are welded incorrectly.
I am surprised those did not fail before the pipe to can joint.

We talked about making the can in two pieces with a slip joint.
There is a temp. diff.  between engine and can.