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Mike,
No worries, just thought that revisiting some of
the basics might help someone.
On the reflective type mufflers the trick is
to reflect the sound waves ( which converts them to heat as they scrub the
exhaust walls) - while maintaining free exhaust passage.
I don't know if Bill's and my design as well as we
think it will, but it does cover those criteria simply using cone shaped
deflectors in the area of exit of the exhaust. The trick is to not allow a
'direct line of sight' for the sound waves to follow to the
exit.
We also cover heat issues by introducing cool air
via the centre of the exhaust and into the space between the exhaust and outer
skin. The outer skin also acting as a heat shield.
The process also incorporates exhaust
augmentation from the centre cool air when there is sufficient incoming air
velocity and using the velocity of the exhaust itself to draw cool air through
the outer skin.
Please remember this is not just my design but a
collaborative attempt with a well respected engineer. Mind you it's
not super light either, maybe using inconel but I haven't looked that
that.
I'm still working on my single before I can prove
or disprove the design - in the mean time I'm still building my
shed.
George ( down under)
George,
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.
Mike
----- Original Message -----
Sent: Sunday, October 04, 2009 11:38
PM
Subject: [FlyRotary] Re: engine runup
video
Mike,
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.
George ( down under)
----- Original Message -----
Sent: Monday, October 05, 2009 11:45
AM
Subject: [FlyRotary] Re: engine runup
video
That link didnt work for me
George.
Mike
----- Original Message -----
Sent: Sunday, October 04, 2009 3:45
PM
Subject: [FlyRotary] Re: engine
runup video
Mike,
Here's a good site for general info on
mufflers, mine and Bill Jepson design is around deflection.
George ( down under)
----- 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.
Mike Wills
RV-4
N144MW
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