X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-d20.mx.aol.com ([205.188.139.136] verified) by logan.com (CommuniGate Pro SMTP 5.2.11) with ESMTP id 3430391 for flyrotary@lancaironline.net; Fri, 16 Jan 2009 19:05:46 -0500 Received: from WRJJRS@aol.com by imo-d20.mx.aol.com (mail_out_v39.1.) id q.c8f.3ba3eb65 (37543) for ; Fri, 16 Jan 2009 19:05:44 -0500 (EST) Received: from smtprly-ma03.mx.aol.com (smtprly-ma03.mx.aol.com [64.12.207.142]) by cia-mb02.mx.aol.com (v121_r5.5) with ESMTP id MAILCIAMB024-5c57497120d257; Fri, 16 Jan 2009 19:05:45 -0500 Received: from MBLK-M19 (mblk-m19.mblk.aol.com [64.12.136.52]) by smtprly-ma03.mx.aol.com (v121_r5.5) with ESMTP id MAILSMTPRLYMA035-5c57497120d257; Fri, 16 Jan 2009 19:05:38 -0500 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: DNA Muffler Date: Fri, 16 Jan 2009 19:05:38 -0500 X-AOL-IP: 66.253.96.219 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: wrjjrs@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CB464E76BF2C9F_458_141F_MBLK-M19.sysops.aol.com" X-Mailer: AOL Webmail 40627-STANDARD Received: from 66.253.96.219 by MBLK-M19.sysops.aol.com (64.12.136.52) with HTTP (WebMailUI); Fri, 16 Jan 2009 19:05:38 -0500 Message-Id: <8CB464E76A7552F-458-9C1@MBLK-M19.sysops.aol.com> X-Spam-Flag:NO ----------MB_8CB464E76BF2C9F_458_141F_MBLK-M19.sysops.aol.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii" Mark, I think the muffler will work OK if it is a was downstream from the exhaust ports. A variant of the idea that would work would be to make the crossmembers from square tubing with one corner turned toward the flow. The resulting hole through the muffler would allow cooling air to pass through the cross tubes, helping to keep them in one piece. Bill Jepson -----Original Message----- From: George Lendich To: Rotary motors in aircraft Sent: Fri, 16 Jan 2009 2:04 pm Subject: [FlyRotary] Re: DNA Muffler ? ----- Original Message ----- From: Mark Steitle To: Rotary motors in aircraft Sent: Saturday, January 17, 2009 12:05 AM Subject: [FlyRotary] DNA Muffler Does anyone on the list?have any?real-life rotary experience with?the DNA Gen II muffler (http://www.dnamufflers.com/DNA/main_DNA.html)?? It is an interesting design in that it has no packing material to burn out.? Instead, it utilizes ladder-rungs, which they call "internal sound diffusers",?which resemble a chain of DNA down through the center of the muffler body, which is made of 304 SS.? Their web site claims that the racers use them with great success.? From speaking with a sales rep, they claim there the rotary crowd uses them too.? I'm considering purchasing one of their FULL THROTTLE COLLECTOR mufflers (P/N 1040), but thought I would check?to see if anyone else has used this style muffler.? This muffler has a 3" inlet/outlet with a 4" body.? So it is compact enough to fit inside?my cowl.? My exhaust header has a 3" swivel joint, so it should be a good fit.? ? Mark S. ? Mark, From my calculations ( and from memory)? 3" is fine, the length and diameter look fine and confirm my own calculations, however their not designed for the rotary specifically, I notice, and I'd be concerned about the thickness of the spiraled internals and believe they would have to be substantial, probably 1/8" to 3/16" thickness material - which makes for a heavy exhaust, but that's the trade-off for having it survive?for a reasonable time. If it were to fail internally, it most certainly block the exhaust gases. ? The trick is to have the correct volume; and restrict the exhaust sound waves from seeing the exit directly without restricting the gas flow. ? Looking back on my notes I'm settled on a 3.5"- 4" exhaust for the 2 rotor and 3" for the single rotor. I've settled on 12" long for the single rotor and 15" long would be fine for the 2 rotor. I've made mine 5" internal and 6" external. So anywhere between the two is fine, just do some of your own calculations to confirm this. ? George ( down under) -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html [Image Removed] ----------MB_8CB464E76BF2C9F_458_141F_MBLK-M19.sysops.aol.com Content-Transfer-Encoding: 7bit Content-Type: text/html; charset="us-ascii" Mark,
I think the muffler will work OK if it is a was downstream from the exhaust ports. A variant of the idea that would work would be to make the crossmembers from square tubing with one corner turned toward the flow. The resulting hole through the muffler would allow cooling air to pass through the cross tubes, helping to keep them in one piece.
Bill Jepson


-----Original Message-----
From: George Lendich <lendich@optusnet.com.au>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Fri, 16 Jan 2009 2:04 pm
Subject: [FlyRotary] Re: DNA Muffler

 
----- Original Message -----
Sent: Saturday, January 17, 2009 12:05 AM
Subject: [FlyRotary] DNA Muffler

Does anyone on the list have any real-life rotary experience with the DNA Gen II muffler (http://www.dnamufflers.com/DNA/main_DNA.html)?  It is an interesting design in that it has no packing material to burn out.  Instead, it utilizes ladder-rungs, which they call "internal sound diffusers", which resemble a chain of DNA down through the center of the muffler body, which is made of 304 SS.  Their web site claims that the racers use them with great success.  From speaking with a sales rep, they claim there the rotary crowd uses them too.  I'm considering purchasing one of their FULL THROTTLE COLLECTOR mufflers (P/N 1040), but thought I would check to see if anyone else has used this style muffler.  This muffler has a 3" inlet/outlet with a 4" body.  So it is compact enough to fit inside my cowl.  My exhaust header has a 3" swivel joint, so it should be a good fit. 
 
Mark S.
 
Mark,
From my calculations ( and from memory)  3" is fine, the length and diameter look fine and confirm my own calculations, however their not designed for the rotary specifically, I notice, and I'd be concerned about the thickness of the spiraled internals and believe they would have to be substantial, probably 1/8" to 3/16" thickness material - which makes for a heavy exhaust, but that's the trade-off for having it survive for a reasonable time. If it were to fail internally, it most certainly block the exhaust gases.
 
The trick is to have the correct volume; and restrict the exhaust sound waves from seeing the exit directly without restricting the gas flow.
 
Looking back on my notes I'm settled on a 3.5"- 4" exhaust for the 2 rotor and 3" for the single rotor. I've settled on 12" long for the single rotor and 15" long would be fine for the 2 rotor. I've made mine 5" internal and 6" external. So anywhere between the two is fine, just do some of your own calculations to confirm this.
 
George ( down under)

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