Here is another way to keep stress off of the flanges. A slip joint
just
outboard of the header flange. The tabs should have heavy springs
pulling
the
two halves together. For aircraft use, an additional hole in each tab
inboard
of the springs will allow for a 4130 strap to connect the inboard
holes.
Holes in the ends of each strap align with these holes in the tabs. AC
bolts
with jet nuts go through the straps and tabs and are just torqued to
just
short of tight. The pipes can move around during operation.
This is used on race cars around the world. Another method is to have
the
tabs long enough to pass each other, and a hole through both tabs
lines
them
up, and a single bolt does the same thing. My muffler weighs 10
pounds. I
wouldn't dare hang it on the engine. Failure of a tube would be
immediate.
I
did that already. I also hammered a SuperFlow muffler to pieces. I
also
melted the end off of a steel bodied steelpack muffler. I also melted
a
piece
of tunnel sheet aluminum and overheated a Halon fire bottle. It went
off
during the race and scared the bejesus out of the driver. I also
melted
the
outside of a tube bend and boiled the fuel out of the carb, even with
a
shield in between. The header tubes squirm around during operation.
They
don't move far but have a great amount of force. The tubes have to be
free
to
move. The muffler weight and even the header weight cannot be hung on
the
engine. They are running bright orange at 50 degrees lean of peak EGT.
Even
stainless looses some strength at 1,700 degrees.
Lynn
Lynn;
What alloy do you guys use? SS (like 321) will fail much more easily at
1700 than inconel; especially if under any stress loads. It gets
inter-granular stress corrosion and loses it strength.
Al
I like 321 for its excellent weldability. *If* you have an expert welder &
proper equipment, Inconel is probably better. I lack both of these items.
FWIW, Keeping the stress off the flange joint is a much easier and less
expensive answer. Lynn's advice above sounds very good to me. I'm going to
use this method on my 20B RV-8 installation. Short header pipes and
flexible couplers have worked well for 1300+ hours on my RV-4 (using .035
wall 321 SS for pipes)
Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com
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