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.
Hello Joe,
Could you clarify the ID dimension of the your P-Port pipe?
You wrote ....."the 2 1/8 hole goes all the way through. The tube I'm
using
is 2" OD x 1/4". Maybe you meant 2"ID?
Thanks
DougFir
I've got 2"ID tubes with .25" wall - so the overall OD is 2.5". I'll turn
the tubes down to fit the holes. I also wanted thick walled tube so I can
cut some sealing notches around the circumference in the water jacket area
and can pack those notches with JB Weld. I want to make it as difficult as
possible for water to get out!
I also figured I would start with 2" OD because it would be easy so reduce
the volume later if I found that 2" was too much. I can always slip another
tube inside the 2" OD tube and pin it to reduce the volume - without taking
the engine apart.
Joe Hull
Cozy Mk-IV N31CZ (65 hrs - Rotary 13B NA)
Redmond (Seattle), Washington
--------------------------------------------------
Joe, Why the edge of the aluminum tube in the wear surface?
I used 2 inch OD .065 wall but the hole through the steel liner
was only 1.875". That left a counter bore that prevented
the square cut aluminum tube from going all the way in and becoming
part of the wear surface. This left a slight gap which was blue taped
over from the inside of the runner when potting.
See the first and second attachments.
We filled it with white, high buck high temp epoxy initially.
Despite a mistake mixing the high temp epoxy,
which left it soft after "cure", it still did not leak coolant
when it was running on the dyno. We know as we had the slide
throttle off and on a couple of times.
Mark disassembled the engine, after a few hours on the dyno and
storing it over the winter, for an unrelated reason and found
the soft epoxy. Again no sign of leaking coolant around the joint
when I saw it. I dug the bad white epoxy out and replaced it with
gray JB Weld.
I am not saying your way won't work. I just wonder what
will happen over time as the apex seal passes over the aluminum
area in the liner area. It will be insteresting.
--
Paul Lamar ...No rotor no motor.
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Copyright 1998-2006 All world wide rights reserved.
Thanks Joe,
If you really want a tight fit I guess you could freeze the insert, heat the
housing and do a press fit like Paul Yaw did. If you also radius the port
to optimize flow and confirm the flow characteristics on a home made flow
bench the apex seal won't be touching aluminum anyway.
Paul,
Now I know why there was epoxy in the inside of the intake pipe. You had a
gap there. Does that gap go through into the water chamber? If so then the
GB weld has to seal the gap between the housing and as well and perform the
function of being part of the inner pipe surface.
DougFir
Yes and it does a good job of it. The path between the epoxy and
the rotor housing water jacket inner surface the water must take
to get inside the intake runner is at least an inch long.
Hundreds if not thousand of road racing p-port rotor housings
have been made this way for the past 30 years with no problems.
BTW no mechanical lock of any kind is necessary as JB Weld
steel filled epoxy has a shear bond strength of 3000 pounds per
square inch. If you take the OD of the tube and one inch wide (it
is actually wider than that inside the water jacket) and multiply
by the circumference of the tube which is 6.28 inches that is
an area of 6.28 square inches. Times 3,000 psi is a force of 18,840
pounds holding and locking the tube in the rotor housing.
Your wings will fall off long before that tube will come out
of there.
Paul Lamar ...No rotor no motor.
The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site.
http://www.rotaryeng.net
Copyright 1998-2006 All world wide rights reserved.