Yes, you are correct, Mike.  Typical Glass pack style.

 

Certainly not against anyone trying out something different and the one you describe is certainly different – it could do the job, but just wanted to pass on my experience.

 

Ed

 

 

----- Original Message -----

From: Ed Anderson

To: Rotary motors in aircraft

Sent: Tuesday, October 06, 2009 3:29 AM

Subject: [FlyRotary] Absorbtion muffler [FlyRotary] Re: engine runup video

 

Good luck, Mike, on the absorption muffler with a rotary.  I have tried a number of different approaches including mufflers with ceramic packing that can withstand 2000F+.  The heat is no problem, the problem is the exhaust shock wave pulverizes the ceramic/fiberglass/stainless steel/etc into small pieces in a relative short time.  Its true they were good in suppressing sound while they lasted, but two weeks – 1 month was about the limit.

 

I still dream of doing a remake of a muffler design I came up with which had 3” 1/8” stainless steel discs (about 4-5) in a 36” tube.  The disc were slotted and “blades” bent until the disc looked a bit like a fan.  The blades were bent at an approx 45 deg angle.  If you looked down the tube with the disc in it all you saw was solid metal – however the blades provide room for exhaust gas to flow around them.  The theory was the shock wave would see basically a solid disc and reflect some/most of its energy back and forth between discs,  whereas the gas could more or less freely flow around and through the blades.

 

The concept worked well in that my hangar neighbors were all remarking how quite the engine sounded and I could still get a  static rpm of 6000.

 

The problem was I am not a welder and while I had the disc clamped with Jam nuts to a SS thread rod through their center – it was not sufficient to keep the exhaust from loosening the nuts and causing the discs to spin like a turbine wheel.  IF I could have welded the tips of the blades to the tube then it may have been viable.  But, not a welder and got tire of messing with exhaust so I hung two Hushpower mufflers and went flying.

 

Ed

 

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.rotaryaviation.com/Rotorhead%20Truth.htm

---

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills
Sent: Tuesday, October 06, 2009 12:58 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: engine runup video

 

George,

 

Thanks. Read through it yesterday. Nothing too earth shattering here. What the article really didnt discuss and what I think is the major problem we face in aircraft which is less of a problem in a car is the need to get sufficient muffler volume. Finding space for a muffler that actually has sufficient volume to do any good on an airplane is problematic.

 

Havent yet seen the muffler that relies on "reflective" (aka passive cancellation) that really works. Tried a variety of them on various cars over the years, and of course the homebrewed "spiral flow" muffler on my airplane currently. Still waiting for someone to come up with one that actually works and will fit on my airplane.

 

Meanwhile I am intrigued by the absorptive design which I posted here the other day. Its the only thing I've seen that actually provides plenty of volume, appears to be capable of both muffling and lasting, and wont look too terrible. I'm thinking about trying to throw together something cheap and easy to try out before committing a bunch of time and effort.

 

Mike

 

 

----- Original Message -----

From: George Lendich

To: Rotary motors in aircraft

Sent: Sunday, October 04, 2009 11:38 PM

Subject: [FlyRotary] Re: engine runup video

 

Mike,

The address is right, but it didn't work when I tried it also.

What I did was use up to Miscellaneous on the address and clicked on exhaust etc on the LHS of the screen - OK.

George ( down under)

----- Original Message -----

From: Mike Wills

To: Rotary motors in aircraft

Sent: Monday, October 05, 2009 11:45 AM

Subject: [FlyRotary] Re: engine runup video

 

That link didnt work for me George.

 

Mike

----- Original Message -----

From: George Lendich

To: Rotary motors in aircraft

Sent: Sunday, October 04, 2009 3:45 PM

Subject: [FlyRotary] Re: engine runup video

 

Mike,

Here's a good site for general info on mufflers, mine and Bill Jepson design is around deflection.

www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.html

George ( down under)

----- Original Message -----

From: Mike Wills

To: Rotary motors in aircraft

Sent: Monday, October 05, 2009 2:34 AM

Subject: [FlyRotary] engine runup video

 

For anyone who hasnt had that first engine run and is looking for some motivation. A buddy visited the hangar a few weeks ago and shot some video of an engine runup. He posted it to his website and you can find it here:

 

http://www.stinsonvoyager.com/images/MikeWills13bEngineRun.wmv

 

This was shot right after I re-installed my original muffler after the aborted DNA muffler test. Noticeable in the video is the big staging bog. I had this tuned out about 15 minutes after he shot the video.

 

Mike Wills

RV-4 N144MW

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