Dear Paul,

I have some questions regarding a spiral tube layout silencer system that
you have apparently developed for rotary engines.

I am very interested to hear more about this because I am currently building
a range of rotary engines for aircraft with Paul Woelfle from Germany. He
mentioned that you had actually made one and tested it.

Could you offer me any advice on this.

Look forward to hearing from you and thanks very much,

All the best, Gilo

http://www.youtube.com/watch?v=TMWyrzisRjY

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We have several designs that work. The basic principle is; don't put anything
in the muffler that is not cooled. It could melt and block the exit causing
the engine to reduce power. We have had one crash where this has happened.
The rotary exhaust runs a few hundred degrees F hotter than the piston
engine so material specs are critical. If weight is critical, and it seems
it is in your application, the best choice is sheet Inconel about .035
inches thick.

Ram air is fed through the center pipe to cool it. The diameter of the exit
pipe controls the noise. The smaller the diameter the quieter. On a 250 HP
13B p-port engine 2 inches in dia. is very quiet.
Square entrance and exit pipes are better than round.

Here are a few ideas.

Paul, I was curious about the Russian design as well. Does it too have the
central cooling tube? Would adding (thought exercise) cooling surface area
within this passage (say, cruciform vane structure, or a number of
longitudinal vanes) improve the characteristics?
Lastly, where does that beautiful hemi-doughnut on the ends Jerry's muffler
come from?
I'm planning to base my muffler on the Russian pattern, but perhaps with
some improvements, and or a combination of Russian square tube and fish tail
features.
C. Smith

Cruciform would be good Hush kits on turbo jet engines use that idea.
It is called a multilobe exhaust mixer.

Paul Lamar