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Al,
If you go through the archives, you'll find lots of examples of
failed muffler designs. Many by your's truly. I think I've tried every
concoction known to man and the Swiss. They all worked... for a while.
Actually, the many variations of the Swiss muffler I tried had the
best exhaust note by far. None lasted more than an hour, some less than a
few minutes. Heat wasn't so much the problem since I had found many
materials good to 2200F but none could stand the pounding.
http://www.piteraq.dk/flight/muffler.html
My best overall design (see attached) is a 2" tube, full of holes
inside a 5" tube. All made of 16ga SS, all welded together. Needless to
say, the flange is more like 3/16" - 1/4" SS. The inside end of the 2" tube
is welded to the end cap of the 5" tube. That blocks off the one end of the
2" tube and secures it from movement. The exhaust end of the 2" tube is
welded through a 2" hole in the other 5" end cap. Rather than drilling the
2" tube full of round holes, we cut slots with a saw. Then take a big flat
blade screwdriver, stick it in the slot and bend it over. This creates an
oblong hole. (Much easier than drilling into SS. This is what will go on
the Volmer.
The sound is quite acceptable, it fits inside the cowl and Jim M.'s
version lasted the life of the aircraft... 600+ hours.
Neil
PS: Are you considering Rough River?
-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Al Wick
Sent: Saturday, June 07, 2008 4:57 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Mistral Crash Analysis
C'mon guys. You do this every time there's a crash. Instantly go into
rationalization mode. It's unhealthy. Greatly increases risk builders won't
take action. Increases risk you won't research it thoroughly.
A healthy response would be:" Here's another example of how our engines
produce unusually destructive exhaust temperature and pulses. We have a rich
history of broken exhaust components. We need to be very thorough when
designing and building exhaust."
I designed my own muffler. It had two inlets, two outlets. So if (when) my
muffler failed, it could never block both pipes. I also put loose safety
wire around my pipes, because on a pusher loosing pipe wipes out prop. So
basically, I assume stuff will fail, then design it to control the way it
fails. I've heard of rotary guys doing same type of thing. This is a good
time to share those key items.
On your car, they deliberately design products to fail a certain way. They
will make a component weak, so it fails first. They do that with wheels and
hubs. So when the muffler fails, little pieces come apart, not big sections?
You guys do a great job of sharing successes, design and construction
details. This is another opportunity.
-al wick
<No doubt you are on the money, Rusty. When folks are already predisposed
to bad mouth the rotary - this will only be more ammunition. "See! even
with umpteen million dollars you can't get one to fly" {:>). But, I
serious doubt it will effect many who have researched the rotary and come to
understand its benefits - as for the rest, who cares {:>)
>
I'm certain it was a relief to Mistral that the culprit was not one of
their engine components.
Whew! a close one for sure.
Hi Ed,
Unfortunately, I bet the majority of people will only hear "Mistral
rotary", "lost power", and "crash" :-(
Rusty (RV-3 taking forever.)
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