X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from web46405.mail.sp1.yahoo.com ([68.180.199.194] verified) by logan.com (CommuniGate Pro SMTP 5.3.8) with SMTP id 4389721 for flyrotary@lancaironline.net; Mon, 12 Jul 2010 10:00:49 -0400 Received-SPF: none receiver=logan.com; client-ip=68.180.199.194; envelope-from=dwayneparkinson@yahoo.com Received: (qmail 67775 invoked by uid 60001); 12 Jul 2010 14:00:10 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1278943210; bh=wS6qX6JnR+Oi8LlB0vU1xbk5jm+RPzLOj21Gsw01FLc=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=vY8ZbEcQpV7V9DhFt2/WY+v7XAYOv/Z1Usl++pt0Q0AeBXEgbHXnk5P2PM8Oiz4xlLgjsUI4ET29vZF+SGz+wSB4k0pbYjsVDSvMxQbtdVbTiLRVRZtxS8hBBx2fz8DNcBFAgdnSy4EKK+0KfYVqdzmTS7rrLeYXgH3WOQSjdAs= DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=NlhKFepCPwuGMD9WkpdDmpshSNpyfQHZaXipw80vyo4LSGKTw/OyFi0GYOFRY/P6t00eDxmqguMmZghkcVfKiAvgsu1kmhtHGqMJMzdYWytwq/RuC1ZxYVB5NsP/Deq+0S/csltBCVTSj408eQMMSQpC2LcV99vjnQ+XrN0O0UE=; Message-ID: <119007.66402.qm@web46405.mail.sp1.yahoo.com> X-YMail-OSG: gjACXIgVM1k9DtudSwfrLCZzDmykPscUIULliHAHNLYW30n CqJ4NC.wm3FHOqMTMPKZmEwNvaUlv2XCS1B_WT3GU2abv2yrK2wMAypSoZR8 Iweoglosi._zejG3uSr_FT6YVDz7suBWfXAdiaJ76JQKjwumuJNwqZahRQpz vSxAuH_ISubCWGb9oTnStkNQsN5J8KAUNq5q4wdj7le_VU6AbmuwXI.BcU_F oXAKjSD_7vO6xOumbkL3rk_DFsJqtyyTWz_9S0U0r3a5VqFvCByNWjuVDI.k 0K54zIH1k.6v0wAJAFAZrPcuV5B51r7aEJA-- Received: from [24.177.130.10] by web46405.mail.sp1.yahoo.com via HTTP; Mon, 12 Jul 2010 07:00:09 PDT X-Mailer: YahooMailRC/420.4 YahooMailWebService/0.8.104.274457 References: Date: Mon, 12 Jul 2010 07:00:09 -0700 (PDT) From: Dwayne Parkinson Subject: Re: [FlyRotary] Re: Mufflers To: Rotary motors in aircraft In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-78166758-1278943209=:66402" --0-78166758-1278943209=:66402 Content-Type: text/plain; charset=us-ascii Mark, If' you're up for more experimenting, try a conical "tail pipe" on whatever muffler you have now. The sound waves will behave just as if you held a cone up to your ear. More sound will be coming out of a smaller hole but due to the shape of the cone I believe some of the sound will run into itself and cancel itself out forming a mildly effective second muffler. I haven't tested this so I don't know if this works. If you have a DB meter (which I don't) you can easily test the theory to see if it's worth your time though. Take a tube from the Christmas wrapping paper, cram a kitchen timer or anything else that makes a constant noise in one end and hold your DB meter just outside the other end and then measure the DB of the noise in a straight pipe. If you want to be really clever, record your rotary engine and replay that sound. Now cut sections out of the last 8 or 10" of the tube and form it into a cone. See if there's a DB drop. Play around with different shapes of cones and see if it makes a difference. When I mention this, most people immediately think BACK PRESSURE!!! If you're measuring back-pressure you should see no change. Bernoulli's principle should apply to the exhaust gas and it will merely speed up and exit faster just like it does with the leaf blower attachment on a Shop Vac. There are issues like boundary layers building up and the fact that the muffler pulses aren't a constant pressure, but I believe that shouldn't be an issue based on the fact that there's really no such thing as a true constant pressure and the rotary at any reasonably high RPM will produce a relatively constant flow of exhaust gas. Good luck. Let me know if you try it and how it goes. Thanks, Dwayne ________________________________ From: Mark Steitle To: Rotary motors in aircraft Sent: Fri, July 9, 2010 4:44:19 PM Subject: [FlyRotary] Re: Mufflers Steve, Yes, that would be me, "Mr. Muffler" himself. The Moroso style muffler didn't muffle very well and it kept melting the bolt holding the baffle in place. I finally went with a SS bolt which didn't melt. In an effort to find something that wasn't as noisy, I discarded it for the DNA muffler which wasn't much quieter, but it survived the harsh rotary environment better than anything else I had tried up to that point. I'm now running an inconel 625 tangential muffler, which is the best as for noise attenuation I've used to date. The only problem is that I suspect I'm losing hp due to excess back pressure. But at leaast I can hear to talk on the radio. Its my opinion at this stage of the game that the best muffler is a turbo. At least you achieve a fairly quiet exhaust note, and get some extra hp too. Mark S. On Fri, Jul 9, 2010 at 8:15 AM, Stephen Thomas wrote: I remember some discussion a while back regarding the concept of the Moroso spin muffler. See: > >http://moroso.com/catalog/categorydisplay.asp?CatCode=35054 > >Anyone out there still using it? What were the conclusions of those who tried >it? I know someone made one from scratch. I have a small Burns Stainless >muffler that is totally inadequate in terms of sound attenuation. So, I'm >looking for alternatives and remember a lot of discussion regarding this device. > > >Steve Thomas >________________________________________________________________________ > > > > >-- >Homepage: http://www.flyrotary.com/ >Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html > --0-78166758-1278943209=:66402 Content-Type: text/html; charset=us-ascii
Mark,

If' you're up for more experimenting, try a conical "tail pipe" on whatever muffler you have now.  The sound waves will behave just as if you held a cone up to your ear.  More sound will be coming out of a smaller hole but due to the shape of the cone I believe some of the sound will run into itself and cancel itself out forming a mildly effective second muffler.  I haven't tested this so I don't know if this works.  If you have a DB meter (which I don't) you can easily test the theory to see if it's worth your time though.  Take a tube from the Christmas wrapping paper, cram a kitchen timer or anything else that makes a constant noise in one end and hold your DB meter just outside the other end and then measure the DB of the noise in a straight pipe.  If you want to be really clever, record your rotary engine and replay that sound.  Now cut sections out of the last 8 or 10" of the tube and form it into a cone.  See if there's a DB drop.  Play around with different shapes of cones and see if it makes a difference.

When I mention this, most people immediately think BACK PRESSURE!!!  If you're measuring back-pressure you should see no change.  Bernoulli's principle should apply to the exhaust gas and it will merely speed up and exit faster just like it does with the leaf blower attachment on a Shop Vac.  There are issues like boundary layers building up and the fact that the muffler pulses aren't a constant pressure, but I believe that shouldn't be an issue based on the fact that there's really no such thing as a true constant pressure and the rotary at any reasonably high RPM will produce a relatively constant flow of exhaust gas.

Good luck.  Let me know if you try it and how it goes.

Thanks,

Dwayne


From: Mark Steitle <msteitle@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Fri, July 9, 2010 4:44:19 PM
Subject: [FlyRotary] Re: Mufflers

Steve, 

Yes, that would be me, "Mr. Muffler" himself.  The Moroso style muffler didn't muffle very well and it kept melting the bolt holding the baffle in place.  I finally went with a SS bolt which didn't melt.  In an effort to find something that wasn't as noisy, I discarded it for the DNA muffler which wasn't much quieter, but it survived the harsh rotary environment better than anything else I had tried up to that point.  I'm now running an inconel 625 tangential muffler, which is the best as for noise attenuation I've used to date.  The only problem is that I suspect I'm losing hp due to excess back pressure.  But at leaast I can hear to talk on the radio.  Its my opinion at this stage of the game that the best muffler is a turbo.  At least you achieve a fairly quiet exhaust note, and get some extra hp too.

Mark S.

On Fri, Jul 9, 2010 at 8:15 AM, Stephen Thomas <glasair2@me.com> wrote:
I remember some discussion a while back regarding the concept of the Moroso spin muffler.  See:

http://moroso.com/catalog/categorydisplay.asp?CatCode=35054

Anyone out there still using it?  What were the conclusions of those who tried it?  I know someone made one from scratch.  I have a small Burns Stainless muffler that is totally inadequate in terms of sound attenuation.  So, I'm looking for alternatives and remember a lot of discussion regarding this device.


Steve Thomas
________________________________________________________________________




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