----- Original Message -----
Sent: Thursday, January 08, 2009 9:09
AM
Subject: [FlyRotary] Muffler design
In these two, from Paul Lamar's web site, it looks to me like there was a
cooling sleeve around the muffler.
If so, a great idea. I don't see an outlet for the cooling air unless it
is coaxial with the exhaust gas outlet, and that would also be a good idea.
It looks like Mistral did this one, but in the crash report it was stated
that a third party supplier had produced a test muffler that failed and
blocked the exhaust outlet.
The front and rear sections of the main tube should be slip jointed in
some manor to account for expansion.
The overlap could extend over the whole distance between the head pipe
spacing.
While a cooling sleeve could have extended the life dramatically it would
not affect internal temperatures to any great extent.
In that regard, the perf tube head pipes seem way too thin even in
Inconel. Those would be between dull red
(no problem) and bright orange (big problem). Even Inonel cannot survive
high stress at extreme temperatures, in a thin section. I bought header sets
from Indy cars that were discarded after only three heat cycles, because they
can crack after that and cost a race.
The end cap on the perf tubes probably should have been a very thick
piece. I would have made the perf tubes .160" wall or more to assure long
life.
The mounting flanges could have been thinner. I use only a bit of 100% GE
tub and tile caulk silicone to seal the headers to the engine. Never leaks.
Never blows out. If there is no thick stainless gasket installed, it cannot
fail. Unless there is a huge amount of back pressure, this junction will be
below one bar, and a leak will allow air to enter the header pipe, and cause a
crackleing sound on closed throttle. There is no magic here. The aluminum
housing is just not very hot just away from the port. The silicone does not
decompose ofter long term use, and is a pain to scrape off. Do safety wire the
nuts.
If this design was not what they arrived at, or were not happy with,
perhaps the power loss was too great. But it looks like a winner with the
thicker pieces, to me. A cooling sleeve would solve a lot of cowel heating
problems.
If the design had all of the pieces internally sized so as to fit
through the down pipe with room to spare, then even a failure would dispose of
the spent piece with a smaller likelyhood of power loss.
Lynn E. Hanover
--
Homepage: http://www.flyrotary.com/
Archive and
UnSub:
http://mail.lancaironline.net:81/lists/flyrotary/List.html