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.