We'll I finally got some time off to check out my airplane after the
round trip from Everett to Medford. The heat cooked my left brake
line, and I suspected the muffler had too much back pressure, so I
resolved to investigate. Here's what I found when I removed my
Hushpower from the airplane. There is way too much heat coming off my
muffler- the powder coating on my engine mount is cooked near the
exhaust pipes, even though I coverd them with fiberfrax and placed a
SS heat sheild to cover the tubes from view of the exhaust. The
muffler was making like a baby rattle so I cut it open and this stuff
came out of the inlet side. I'll send more pictures of the innards.
What I have is an RV-4 with the radiators and oil cooler hung
underneath the plane in a scoop that is reminiscent of a P-51. I had
the muffler submerged under the fuselage. I"m thinking that it would
be better to have the exhaust pipes exit the side of the cowl, in a
reverse scoop that would vent a huge amount of heat from the cowl. The
muffler would be a straight 6 foot muffler like the one Paul outlined
about a week ago. It would be mounted along the side of the fuselage.
I hate to ruin the clean lines of an RV-4, but nothing would ruin it
more than having a mechanical failure due to excessive exhaust heat
bringing the plane down. My biggest worry about this rotary conversion
is excessive exhaust heat and how to manage it effectively.
Here is the muffler cut open. The red chunks are what is left of the
melted insulation material between the perforated inner case and
outer. The outer case showed signs of bulging. The perforated inner
case was split on the seam closest to the camera. The inner cone
material which is also perforated was mostly gone, but big chunks were
still left inside the muffler and undoubtedly were causing some
obstruction.
Here's the split in the inner perforated case. Not real confidence
inspiring.
Crap that I shook out of my baby rattle/Hushpower muffler.
Brian Trubee
That will work out OK but I would put it on the bottom like Mike did.
I think you could get the rad under the engine.
Either that or use a narrower rad and put it next to the rad under the
fuse.
Paul Lamar
If you ever replaced mufflers on a 2nd or 3 gen RX7 you would know
that Mazda built heavy, massive mufflers. I have a couple around here.
Wonder what the inside design is like? Maybe I should cut one open.
Marc Wiese
That would be interesting. Measure the sheet metal thickness.
Paul Lamar
maybe something like this coating both inside and outside of the
exhaust
system would be useful to reduce heat.
http://www.jet-hot.com/coatings/jet-hot-extreme-2500/
chris smale
Paul and Brian,
It is great watching your "Big Pictures Minds" working together.
Listening to ideas on turbo compounding, peripheral ports, etc.
From my perspective of working on GE, Allison/Rolls Royce, and P&W
turbines for 35 years here are a few ideas to add to the mix.
I am suggesting using a 8" by 12" muffler called a turbo.
Ideally for power to weight a turbine engine would be best for the hobbyist.
The hardest part would be making the gear reduction, fuel control,
governor and burner can.
A turbo actually turns a normal engine (recip or rotary) into a turbine
engine (An old perspective from Hugh MacInnes).
We then have a compressor and turbine section with the exiting engine
becoming the gear reduction, burner can, Fuel Control and Governor.
..... *and with your peripheral port it actually becomes a power
recovery compound turbo by blowing directly on the rotor!*
The exhaust is quieted by removing energy and heat.
The real problem is controlling heat. We would need to use surplus
compressed air to cool the exhaust. One place air could be injected at
the exhaust sleeve.
We would use a balanced system that could operate 'theoretically" with
no wastegate like the original GM Corvair. (using a extra large exhaust
housing AR of about 1.34 or larger).
Your thoughts,
Barry
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