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From: "Al Wick" <alwick@juno.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-2958036@logan.com>
In-Reply-To: <list-2958036@logan.com>
Subject: Re: [FlyRotary] Muffler failed designs.
Date: Sun, 8 Jun 2008 10:32:48 -0700
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You got 600 hours from that design? That's phenomenal. I'd call that a huge 
success. I'd add second outlet, so when it fails, it can't clog outlet. 
Every week, I play around with frequency response and resonating. That tells 
me to play close attention to length of perf tube inside muffler. Basically 
that tube turns into sine wave shape while running. So if you are successful 
with 2.1" long tube internally, you might find 2.3" long tube would resonate 
and fatigue at the weld point. If you had two outlets, I'd make them 
different lengths internally.

I don't think I'll make rough river. My plane just sitting there for months 
now. Haven't completed my install.

-al


> 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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--------------------------------------------------------------------------------


> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub: 
> http://mail.lancaironline.net:81/lists/flyrotary/List.html
>
-Al Wick
Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and cam 
timing.
Artificial intelligence in cockpit, N9032U 240+ hours from Portland, Oregon
Glass panel design, Subaru install, Prop construct, Risk assessment info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html 

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