Jerry Hey wrote:

It has always been a problem to find a way to fit the exhaust systems.
Usually there are conflicts with the motor mounts that lead to strange
compromises.  My own muffler that Ed built is a good example.
Originally the 3 inch round exhaust pipe was supposed to exit straight
down but it could not because of a motor mount tube.  So we ended up
running it out the side because that is the only place it could go.
Suddenly I had a hole in my cowl I did not want.  Further, the exhaust
pipe after being moved to the side,  could "see" a small portion of the
intake port with the potential for direct flow out the exhaust  pipe
without first becoming disorganized.   The whole concept of the simple
tangential muffler was compromised.

However, with the rectangular pipe, it was possible to shape the
exhaust pipe to fit the situation.  The exhaust pipe went back to the
six o'clock position.    The narrow "slit" of the rectangular exhaust
is easy to hide from the initial exhaust blast.  And, as time goes on
and we have a working dyno to  use,  the "slit" opening can be further
tuned. There is a lot of potential there.  Also,    I like Bill's idea
of a flat section that takes the initial direct  exhaust blast. On this
flat we could weld diverters to eventually dictate exactly what the
exhaust gasses will do.  We could make it out of 3/32 to better take
the heat if necessary. I think we are just at the beginning of building
a really good  system that quiets the exhaust, delivers  the power,
fits   inside the cowl  and is light weight.  This has really got me
excited.   Jerry

For the new subscribers.
This reiterates the importance of a complete mockup or 3D drawing of
your project before you start to cut metal. I do 3D drawings for free
if you send me some info on your firewall and cowl.

Here are three I did for Jerry. He changed his mind later. Gee Jerry I would
have done one for your new muffler if you asked. I guess you wanted to try
the trial and error method for a change :)

These first two are with the narrow motor mount. I have always advocated a 
wider motor mount to accommodated the muffle or turbo charger inside the motor
mount tubes. I finally talked Jerry into the wider mount.

I am not saying all this to brag but just to illustrate what we have been
through in the last six years to come up with a rotary installation that works for
a wide range of kit airplanes.

If you do a mockup or 3D drawing and stick to it you will save a year or
two building your installation. 3D's can be done in minutes. Changes to the
3D in seconds. Boeing and Airbus both use 3D drawings to help design airplanes.

Paul Lamar
 
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