Here's an idea for fabicating a [tuned] tangential exhaust which might work. It could be made using nothing more than sheet stock. For the wraparound portion of the exhast, cut four pieces of material to form a helix, which would wrap around the cylindrical part of the muffler. The muffler would form the bottom of the exhast runner and a strip of metal would be welded onto the top to form the top of the runner.  The drawbacks to this design are that it requires a lot of welding and the exhast runner cross section is square, which might increase the exhast back pressure.  The advantages are that it could be made quite light and that no bending of tubing is involved.
Brian Trubee
Redmond, Wa

I had to read this twice Brian but once it dawned on me it sounds like a great idea.
Can you draw it up and send it to me? If not I will draw something up.

If the mean radius of the runners is 4 inches that will give a runner length
of 25 inches for a 360 degree wrap plus another six inches of straight section
for the needed 31 inches over all tuned length.
The over all diameter would be ten inches for 2 by 2 runners.

The center line of the muffler would be six inches away from the side of the
rotary engine which is about right. The distance from the side of the rotary
engine to the outside of the muffler would be eleven inches. The whole
thing is quite compact for a tuned exhaust system.

This sounds real simple to make.

Cut four circles in steel ten inches in diameter with a six inch hole in
the center. Cut these on a radius and pull them apart to form the
walls of the helix. Find a piece of six inch pipe for the core of the
muffler, weld everything up and you are done.

Paul Lamar
 
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