I removed my Hushpower the other day to re-do the heat shielding around
 it.
It's submerged and does not get enough cooling air around it. I used an
aluminum heat shield and some woven ceramic insulation  with aluminized
mylar, I don't know what that particular heat shielding is called, but,
 the
aluminum burned through and the mylar melted. So, I'm doing a re-design
where I have double stainless steel heat shielding with forced air going
through the air space. Backing that up will be a layer of fiberfrax.

But, back to the Hushpower. When I pulled it off, I shook it and it
 sounds
like a baby rattle. So, I'm going to use a bore scope and see what's
 what
with it. Hmmm....

Brian Trubee

Good idea Brian. Harbor Frieght has a cheap bore scope.

I like the outer case design. I would cut it open and gut it
and then weld it backup.


Paul Lamar

 Paul,

 I tried one of these and it couldn't handle the heat.  Packing melted
 within
 the first hour.  (Maybe Brian could cut it open, stuff it full of SS
 shavings, and weld it back together.  The outer shell is made of 304 SS,
 but
 the perforated cone appears to be made of mild carbon steel.  It melted
 and disintegrated after about 25 hrs.

 Mark

 I am not sure I would put anything in it but shavings might
 be small enough to be spited out :)

 For the new guys this is what can happen if your cheap automotive
 muffler fails. This one caused a crash. The pilot lived fortunately.

 Rotary mufflers are best from Inconel if weight is important but
 .064 thick SS 321 is OK too for a 30% muffler weight increase trade off.

 Paul Lamar

 Paul,

 What material was the baffle made of?  The Hushpower II has a cone-shaped
 baffle.

 Mark

 Looked like mild steel to me.

 Here are some fail safe ideas.


 Paul Lamar

 Brian,


 You might look into Aerogel insulation as it is the lightest and most
 efficient stuff out there. Mylar is basically plastic. Fiberfax might
 trap moisture.

 Doug in Japan

 Here are some pictures of Brian's muffler installation for the new guys.

 Paul Lamar


 So Doug, I looked up Aerogel, it sounds like it could be effective,
 but is there a source that sells it in form that is usable and
 affordable for my application? I don't think I'd worry about Fiberfrax
 absorbing moisture too much- not where it would be situated and with
 the conditions it would see. But I'm willing to look at anything that
 you think might be better.
 The heat of the exhaust is the only thing that really makes me a bit
 nervous about my plane.

 Brian Trubee



You might have another look at my muffler that I published on this web
site. It is quiet!

chris smale

I think I lost it Chris.
Can you send it again?

Paul Lamar

Has anyone had expeience good or bad ceramically coating exhaust pipes and
the inside and outside of a muffler. Our SS muffler has a spiral innards.
Bob Izett. West. Aust.