Here's my new muffler parts. Inside pipe is 321 stainless, .035", outside
 tube is
  .030 304 stainless. There is another 17" of inside tube for a total of
 52" of inside
  tube.
  Brian Trubee

  Looks good Brian. The inside pipe is pretty thin but if it fails there is
 unlikely to
  be a loss of power.

  Paul Lamar

  Brian,
  Are you sure you have enough holes in the inner pipe?

  Mark

  Are you joking? :) It's open on the far end.

  Paul Lamar

 Yeah, so is a straight pipe, but it wouldn't quiet the rotary roar at all.

 Mark

 In theory this would. If one lowers the pressure and reduces the
 temperature in a
 pipe the velocity will be reduced. The noise comes from the sudden
 expansion of hot,
 high velocity, high pressure gases at the end of the pipe.

 A gun silencer works in the same way.


 "Boyle's law (sometimes referred to as the Boyle–Mariotte law) states that
 the
 absolute pressure and volume of a given mass of confined gas are inversely
 proportional, if the temperature remains unchanged within a closed system.
 Thus, it
 states that the product of pressure and volume is a constant for a given
 mass of
 confined gas as long as the temperature is constant. The law was named
 after chemist
 and physicist Robert Boyle, who published the original law in 1662."

 http://en.wikipedia.org/wiki/Boyle%27s_law

 It is not just a good idea it is the LAW!!  (Of Physics :))

 Of course there is some optimum size for the holes.

 The whole idea here is the keep the frontal area down to minimize the
 aerodynamic
 drag and use the slip stream to help cool the pipe. The configuration is
 somewhat
 like a jet engine in that you are heating the gas in the outer pipe so in
 theory a
 bit of thrust is created off setting the drag. One pound of thrust at 300
 feet per
 second (200 MPH) is 300 foot pound per second or 300/550 or .545 HP.

 Paul Lamar


 Paul,

As you know, one test is worth a thousand theories.  Take some Db readings
and we'll see how well it works.  My threshold for mufflers is if it
overwhelms the ANR, its too loud.  ;-)

Mark

I don't know if Brian has a db meter. I have one and I have some data on that. The
average rotary 30 feet away off a wing tip is about 100 db plus or minus 2 or 3. A
lot of that is prop noise so it is rather difficult to separate the engine noise from
the prop noise. Have you measured yours? Maybe a better way is use a computer to
record it and then do a Fourier analysis AKA spectrum analyzer. My Linux music player
program has that option.

Paul Lamar

-- 
The Rotary Engine News Letter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
You Tube key word PaulLamar2
Copyright 1998-2012 All world wide rights reserved.