Bill Jepson wrote:

Paul, here is the basic support layout using the rod. To construct this
setup the inner tube and the tailpipe would have to have a seam in front
of or behind the 120° fin supports. I would slot the tube and make them
go all the way through. (listening ED?) and then fusion weld flush to
the outside of each pipe. I am not sure how small we could make the main
tube OD's. The rod shown here is .5 in diameter. The fins are .75 long
(axially)  This should work since the front support is inside the air
tube and the tailpipe support is after the air mix. The rear fins could
be twisted or not.

 So everone knows, I figured the muffler inside the cowl. In a pusher a
scat tube could get close to the front. in a tractor I figured a clean
1.5 in diameter hole with a rigid exit in front of the can. for those
who don't have any room it could be outside and would work real well,
just draggy. For the outside system the tailpipe could be straight which
would work better.
I really hope we have a good system here. Bill Jepson

The big thing is you have to assume the muffler and the inner tube
will expand at a different rate. Anything fastened to the inner
tube at the hot end might crack.

Paul Lamar

Paul,
I did some research some time ago on a muffler which had an external vortex
flow used in the racing industry, but it had a fibreglass stuffed inner
tube - it was supposed to be working very well.

The chap did tell me that they experimented very extensively with the angle
of the spiral and that there were significant differences with different
angles.

He wouldn't tell me what angle he settled on but he said it worked much
better at that particular angle.

So that may need to be a consideration!

George (down under)

 
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