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


I heard of one guy on the other rotary list who has a hushpower with 250 hours on his renesis powered plane, it crapped out it's innards and is slightly louder, but otherwise fine. It did not have any obstructions like the Mistrial muffler incident when it's guts came out. I noted that the Renesis has a slightly attenuated exhaust because of the side porting. I have a 13 BREW, which has no exhaust splitters in the exhaust ports, and so is harder on mufflers. I did see this- and might have a go with;this:

http://www.stainlessworks.net/cart/product_info.php?cPath=24_185&products_id=507

Brian Trubee