Hey Ed, can you make a sketch? … I can’t quite picture your
concept just from text.
Jeff
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson
Sent: Tuesday, October 06, 2009 6:30 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Absorbtion muffler [FlyRotary] Re: engine runup
video
Good luck, Mike, on the absorption muffler with a rotary. I
have tried a number of different approaches including mufflers with ceramic
packing that can withstand 2000F+. The heat is no problem, the problem is
the exhaust shock wave pulverizes the ceramic/fiberglass/stainless steel/etc
into small pieces in a relative short time. Its true they were good in
suppressing sound while they lasted, but two weeks – 1 month was about the
limit.
I still dream of doing a remake of a muffler design I came up with
which had 3” 1/8” stainless steel discs (about 4-5) in a 36” tube. The
disc were slotted and “blades” bent until the disc looked a bit like a
fan. The blades were bent at an approx 45 deg angle. If you looked
down the tube with the disc in it all you saw was solid metal – however the
blades provide room for exhaust gas to flow around them. The theory was
the shock wave would see basically a solid disc and reflect some/most of its
energy back and forth between discs, whereas the gas could more or less
freely flow around and through the blades.
The concept worked well in that my hangar neighbors were all
remarking how quite the engine sounded and I could still get a static rpm
of 6000.
The problem was I am not a welder and while I had the disc clamped
with Jam nuts to a SS thread rod through their center – it was not sufficient
to keep the exhaust from loosening the nuts and causing the discs to spin like
a turbine wheel. IF I could have welded the tips of the blades to the
tube then it may have been viable. But, not a welder and got tire of
messing with exhaust so I hung two Hushpower mufflers and went flying.
Ed
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills
Sent: Tuesday, October 06, 2009 12:58 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: engine runup video
Thanks.
Read through it yesterday. Nothing too earth shattering here. What the article
really didnt discuss and what I think is the major problem we face in
aircraft which is less of a problem in a car is the need to get sufficient
muffler volume. Finding space for a muffler that actually has sufficient volume
to do any good on an airplane is problematic.
Havent
yet seen the muffler that relies on "reflective" (aka passive
cancellation) that really works. Tried a variety of them on various cars over
the years, and of course the homebrewed "spiral flow" muffler on my
airplane currently. Still waiting for someone to come up with one that actually
works and will fit on my airplane.
Meanwhile
I am intrigued by the absorptive design which I posted here the other day. Its
the only thing I've seen that actually provides plenty of volume, appears to be
capable of both muffling and lasting, and wont look too terrible. I'm thinking
about trying to throw together something cheap and easy to try out before
committing a bunch of time and effort.
-----
Original Message -----
Sent: Sunday, October 04,
2009 11:38 PM
Subject: [FlyRotary] Re:
engine runup video
The
address is right, but it didn't work when I tried it also.
What
I did was use up to Miscellaneous on the address and clicked on exhaust etc on
the LHS of the screen - OK.
-----
Original Message -----
Sent: Monday, October 05,
2009 11:45 AM
Subject: [FlyRotary] Re:
engine runup video
That
link didnt work for me George.
-----
Original Message -----
Sent: Sunday, October 04,
2009 3:45 PM
Subject: [FlyRotary] Re:
engine runup video
Here's
a good site for general info on mufflers, mine and Bill Jepson design is around
deflection.
-----
Original Message -----
Sent: Monday, October 05,
2009 2:34 AM
Subject: [FlyRotary] engine
runup video
For
anyone who hasnt had that first engine run and is looking for some motivation.
A buddy visited the hangar a few weeks ago and shot some video of an engine
runup. He posted it to his website and you can find it here:
This
was shot right after I re-installed my original muffler after the aborted DNA
muffler test. Noticeable in the video is the big staging bog. I had this tuned
out about 15 minutes after he shot the video.