Mike,
The
length of the cylindrical section is 24 inches. The conical section is 9
inches long.
The
dome was made from a Kmart mixing bowl. Some of it is less than
0.032 inches thick but has held up so far.
The
cylindrical section was made by a local sheet metal shop with a stove pipe
joint that also has been tack welded in a few places.
I
made the conical section, inside parts, heat shield, and mount from the same
sheet material as the cylindrical section. The joint in the conical
section is similar to the stove pipe joint and is also tack
welded.
Steve
Boese
N613BX,
RV6A, 1986 13B NA, EC2, RD1A
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike
Wills
Sent: Saturday, January 17, 2009 9:13 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: another
Muffler
Quite the opposite
Steve. I think the 3 Kt loss and looks (it actually looks better than most) is
a fair price to payfor a relatively light, easy to construct muffler that
works. My current "muffler" isnt a lot smaller and weighs about the
same.
2) Source for the
dome and cone used in the construction?
----- Original
Message -----
Sent: Friday, January
16, 2009 9:57 AM
Subject: [FlyRotary]
another Muffler
The
following muffler description is provided purely as another data point in
the muffler discussion. I would suspect that not many of you would be
interested in it due to its large size and external mounting. I have
had good service from it so far and it fits somewhat into my loosely
interpreted Navy F6F Hellcat inverted paint scheme as a
bomb.
The
materials of construction are 0.032” thick 304 SS and the design is based on
data in NACA Report 1192. The weight is 9.6 lb and the diameter is
6.25 inches. A SS heat shield is also installed between the muffler
and the fuselage belly. I have about 100 hours on this installation
with no signs of deterioration of the muffler. The engine is NA with
exhaust splitters and is operated normally at density altitudes above 7000
ft which limits max power, although several hours of max power operation at
DA lower than 5000 ft have not damaged this muffler so
far.
I
have been told that from the ground, the primary source of noise for my
plane is the propeller. I have landed with a C172 following me in the
pattern and observers told me that they did not know I was there until I
taxied in since they only heard the C172. I have no quantitative data
on the noise characteristics of my muffler system. Inside the cockpit,
the noise level goes from reasonable to unbearable if the muffler is
removed. This is purely subjective, of course.
Not
shown in the “muffler parts” image are three 1” x 1” angles made from the
same material as the shell that connect the rear of the internal center tube
to the front of the rear cone section. The round flange in the center
of the internal tube is a push fit in the shell and is not fastened directly
to the shell. A down turn also has been added to the outlet of the
rear cone section.
From
data in the “muffler test chart” image, the speed penalty of the muffler is
about 3 kt.
The
“muffler in flight” photo may be of interest in that it shows the heat
distribution in the muffler with the dark areas being hotter. This
image is not current since the lower cowling has been modified and the
engine cooling air outlet is now much smaller than shown in this
photo.
Steve Boese
RV6A, 1986 13B NA, EC2, RD1A
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