> I was involved in the Exhaust industry for a number of years including
> designing the odd muffler.
>
> What Paul says is true, however the one thing not mentioned is just
> how
> bad this style of design is
> it will allow exhaust gas flow that's about it, this is what is
> nicknamed a "back pressure" it is
> unbelievably bad in gas flow which = HP which means increased fuel
> consumption by quite a bit,
> My suggestion is do not use this style design at all. It is one of the
> worst designs there is.
>
> It will shut things up but , it will run a lot hotter, create
> excessive
> back pressure, increase fuel
> consumption & reduce horsepower just to name a few things all of which
> you really do not want!
> Sorry. I just had to stress this.
>
> Try another style. While not the best option it will work somewhat
> better if you use the can with out the tube
> in the middle try to improve the tube curve into it, and use the pipe
> out it bigger the better within limits in the
> same place, while not the most efficient it is better than with the
> perforated tube in the middle it will also last a while
> and yes use at least 2 or more support straps to stabilize it and to
> ensure if it breaks it stays right there you
> will hear it if it breaks.
>
> Regards David
Hi David,
So it happens I'm involved in the aircraft exhaust systems industry
for the last 6 months. Got to inspect and certify hundreds of
different systems. >From all of these only one was welded on the
inside of the flange. I don't know why, but all of them are welded on
the outside? Just a fact.
Regarding the back pressure: Flew with straight out pipes for 2
hours, than with my new muffler. Did not notice any loss of power?
The straight pipes were unacceptable for noise reasons, and they were
activating my headset microphone in flight. There are trade offs for
everything, and I'm happy with this one. For my PP engine I may go
with a better? design.
Thanks for your input.
Buly
A lot of piston aircraft engines don't have the same
problem we have. The pipes comes straight down from the cylinders
to the muffler. The bending loads, if any, are low. There are
four or more pipes supporting the weight of the muffler in tension
and not bending under the engine. Our mufflers are cantilevered
off the side of the engine. In the case of professionally made AC
mufflers systems the parts may be heat treated to minimize the
effects of welding.
Paul Lamar
Paul & Bluey,
I've been reading about the exhaust header cracking and thinking
about my motorcycle riding/repairing days and wondering if the method of
attachment used on motorcycle headers could be applied to the rotary...?
The motorcycle headers use diamond-shaped flanges that capture the
header tubes (which have a rolled flange) to bolt the header to the
motor. I found a picture on the Web that illustrates what I'm thinking
about. On my Hondas, the flange incorporated fins and acted as
heat-sinks to draw the heat from the joint.
Jack Beale
Everett Hatch used something similar.
Did you see it on this web site?:
http://www.rotaryeng.net/exhaust.html
Paul Lamar
P,
Er... no, I don't think I saw Everett's work, but I should have...!
That type of "header" should solve the cracking problem completely.
How many hours has he accumulated on this set-up...?
Jack Beale
Unfortunately Everett passed away less than a year after I took
that picture about 8 or 10 years ago. Evidence that this
is not a new problem.
BTW I forgot to mention above our exhaust systems run a lot
hotter than air cooled aircraft engine mufflers.
Paul Lamar ...No rotor no motor.
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