Paul,
 Can anyone tell me the temp that the exhaust will reach on a
rotary at full noise, or what temp the muffler will have to handle?
Neil.


About as high as 1800 F at full chat.
Furthermore the pulse frequency is as high as 14,000 pulses per
minute or
233 pulses per second. This is very destructive exhaust system and
mufflers.
Lots of energy in the exhaust. It is why the rotary makes a good
turbo compound engine.

The solution is make them out of .065" 321 SS.
If money is no object make them out of .049" Inconel.
The best thing is to put nothing inside. Inside parts have been known
to melt and block the exhaust causing a crash. If there is nothing
inside that can not happen. Most of the external parts will be
cooled by air convection and or radiation. It is possible to put a
cooling tube in the center of a tangential muffler and pass cooling
air through it. Make it at least .065 thick if 321 SS.

Square or rectangular pipes are better than round.

Here are some configuration that do not use internal parts.


Paul Lamar

At this past weekends EAA meeting at Whiteman airport our quest speaker
spoke to us about powder coatings and things related. One coating he
told us about is a non carbon ceramic coating used to prevent metals
from oxidizing.
  Normally stainless blues from heat. This he said was due to oxygen
transfer in the metal. This new coating prevents oxides from interacting
on the metal surface, keeping it from corroding, preventing stainless
from blueing.
 The German company who makes it applies it to a thickness of about 8
'atoms' thick, (or so he said). It is a new material and may not be
widely available yet. If anyone knows more detail about the inventor and
this invention, it would be useful for our purposes.

Ed Carver


Paul,
On my KIS Cruiser, I installed a 'spintec' muffler under the fuselage.
Worried about the heat of the muffler damaging the fiberglass, so I
installed a heat barrier of 1/8" fiberfrax covered with a sheet of Stainless
steel. The painter ended up painting the stainless (I would have preferred
he not) . After a full power run up on the ground, the paint burned off the
stainless steel .

Bill Schertz
KIS Cruiser #4045
N343BS
Phase one testing Completed

Paul,

After just completing my 40 test hours, I can report that my muffler is running strong, and is still very quiet.  I'm using a Burns Stainless 2-stage muffler, 2 1/2" pipe by 17" long.  The first stage is a perforated liner with stainless steel cloth packing.  The second stage is an open chamber with two welded v-shaped angles in a cross hatched installation across the exhaust tube. It resides under the belly, but does not appear to get so hot as to blister paint or show any other damage.

I tried a small Burns Stainless as well as a spiral flow muffler and the noise was still ear-splitting.

Best Regards,

Steve Thomas
Mistral G-190
Phase II


I would get a Harbor Freight (in Camarillo) inspection camera and keep and eye
on the insides. Home Depot also sells them.

http://www.harborfreight.com/catalogsearch/result?q=inspection+camera

Some times it does not happen right away.

Got any performance numbers on your Glassair you can share?

Paul Lamar



Paul,

As for performance, she is rather slow.  At 50% power, I am seeing about 150K true.  I am going to modify my air scoop to make it a lot smaller.  I think I am seeing a lot of cooling drag and I want to fix that.  My cowl is still being over pressurized, even after increasing the exit area considerably.  So, I'll have to cut that scoop way down.  Cooling is good, with my H2O temps rarely getting over 185 and my oil at cruise at 195.  Better airflow will also help get the oil a little cooler.

As for the muffler, I cannot see inside because there is a stainless mesh at the rear exit that I cannot see past.  I already have one of those inspection scopes from Harbor Freight, but no way to get it past that mesh.  See the photos at: http://www.burnsstainless.com/sm-250-450-17-2s.aspx  I have to remove the muffler to inspect it, which I have been doing every 5 hours or so.

Best Regards,

Steve Thomas

Thanks Steve. Is it still at Camarillo?

We are getting quite a rotary community here. There are two at Camarillo not
counting yours. One turbo Long EZ and one not flying. Plus Randy in
Simi Valley and Mike Wills soon to be at SZP. Pretty soon we will have
enough rotaries for a rotary flyin.

Paul.