Ian & Irene Beadle wrote:

Does anybody have drawings of a succesfull muffler yet? I put two

straight through 'hot dogs' after my expansion chamber, dropped the noise to
the just tolerable level. I need something a bit better and lighter.

Ian Beadle W. Australia.
beadles@webace.com.au

This is Tracy's latest muffler design. Are you still flying with it Tracy?
BTW Ian got any pictures of your airplane you can send us?

Paul Lamar

Yes.  I did add another pair of deflectors 90 degrees from the first pair
and slightly down stream.  Dropped the sound level a bit more but nothing
like the difference when I put in the first set.

More muffler findings:

A few days ago I flew down to pick Bruce Turrentine up in Clearwater where
he was checking out the damage on Bill Hughs 13B  (long story)  When I took
him back to catch a 757 home, one of my exhaust collector pipes started
contacting the engine mount directly bolted to the airframe on my way back
to Shady Bend.  The amount of vibration (and noise) transmitted to the
airframe from this light contact was unbelievable.  Since I didn't know the
actual cause at the time, I thought something had come loose on the
flywheel/damper assembly causing a severe imballance.  Anyway, it ended up
showing me how important the exhaust system supports were to isolating noise
& vibration from the airframe.  In addition to re-routing the collector pipe
to give more clearance, I improved the exhaust system mounts and the plane
is quieter than ever.  Surprisingly, the sound level instrument reading in
the cockpit only went down 1 - 2 DB compared to readings prior to the
collector problem.  I took off my head set to better evaluate the noise and
realized that much of the noise in the cockpit is now wind noise.  Air at
180 mph can make an amazing amount of racket.   Need to work on closing some
small gaps around the canopy.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

 
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