I made one of those with a house jack tube for the center tube out of carbon steel. The tube was 1/8" wall. I drilled a bunch of 1/2" holes near the front and 5/32" holes near the end. It worked pretty well, but lasted only 9 weekends before the center tube melted loose. External tube in .062" stayed just fine. You can do a lot of heat, or a lot of pounding, but not both. Nothing flat will survive.

 

Lynn E. Hanover 

 

Hi Thomas,

Thanks for the photo.

The exhaust pulse from the rotary is just incredible powerful.  Any flat
surface perpendicular to the pulse (such as the end of you muffler), appears
to be doomed to fatigue failure from the pounding of the pulse.

I once squished the tips of 2" dia SS steel tubes together and drilled
holes to make a "fishtail" sound suppressor.  After a 30 min flight, I came
back to find chunks of the SS tube missing where the pulse had hammer and
fatigued the tips during that short flight.

Rather than a flat surface, a cone or angle surface which deflects some of
the pulse energy appears to be required for longer term survival.

Better luck on your next choice

Ed