X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.122] verified) by logan.com (CommuniGate Pro SMTP 5.2.11) with ESMTP id 3413453 for flyrotary@lancaironline.net; Tue, 06 Jan 2009 15:13:54 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.122; envelope-from=eanderson@carolina.rr.com Received: from computername ([75.191.186.236]) by cdptpa-omta03.mail.rr.com with ESMTP id <20090106201315.DREP13015.cdptpa-omta03.mail.rr.com@computername> for ; Tue, 6 Jan 2009 20:13:15 +0000 From: "Ed Anderson" To: "'Rotary motors in aircraft'" Subject: My Muffler experiments (long) was [FlyRotary] Re: Mistral muffler. Date: Tue, 6 Jan 2009 15:13:21 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0045_01C97011.5073A180" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 Thread-Index: AclwF5Ck00fSf9i7Sw6ssVEVvMhUZQAH5VKw X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 In-Reply-To: Message-Id: <20090106201315.DREP13015.cdptpa-omta03.mail.rr.com@computername> This is a multi-part message in MIME format. ------=_NextPart_000_0045_01C97011.5073A180 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Contrary to intuition - two parallel mufflers actually reduce the sound less than one of the same type. If you have both rotor pulses going through a single muffler you have a dominant high energy frequency (at 6000 rpm) of 200 Hz to filter. If you have a single rotor exhaust port with its separate muffler then the dominant freq for each muffler is now 100Hz rather than 200Hz. The dimensions for two mufflers of equivalent effectiveness would need to be approx twice as large for the 100Hz pulse of which you are required to hang TWO of these twice as larger hummers underneath to get the same effectiveness in sound suppression as using one muffler half the dimensions - or something along those lines. So a single muffler (for sound suppression) appears to be a better way to go - now if you are looking for power instead of sound suppression then the story can be different. Having experimented with several different approaches, the one that seemed to have the most promise was the one in which I placed 3" diameter 1/8" thick Stainless Steel discs. The discs had vanes cut from the outer perimeter down to within 3/8 - 1/2" of the center. Then each vane was bent approx 45 deg to the plane of the disc. These then had a 3/8" dia hole drilled down the center and a rod on which 5 discs were strung and first locked in using jam nuts (don't bother trying) and later welded to the rod. The idea was that the pulse in the exhaust would in effect see (straight on) an almost solid metal disc and bounce back what pulse go through the first disc would find a 2nd and 3rd and 4th etc, where as the exhaust gas would fairly easily flow around the blades and through the discs - relatively unimpeded (so the theory went {:>)). The first one I made I used a 2" dia tube and discs - it was tremendously effective in suppressing the sound - unfortunately it was equally effective in suppressing power. So I concluded I needed a larger tube - so went to the 3" dia tube and six discs. This one I thought was really the solution (and may have been if I had continued development) as it was very effective in suppressing the sound (although not quite as much as the 2" tube) and I got 6000 rpm static. Ah ha! I thought - this is it!!! I have succeeded. So I buckled up and ran the engine up to 6000 rpm and launched. The only unfortunate aspect of the flight is that I never got over 6000 rpm static {:<(. I then cut the number of disc back to 4 and that appear to do the job. However, my next flight was down to Tracy's Crook. I was later told by a witness to my take off that it sound like I had a turbine engine under the cowl (more on that later). In any case, I noticed about 20 minutes into the flight that the EGT on one exhaust was up into the 1700 + range whereas my normal EGT was more like 1550 -1600 max. After landing at Tracy Crooks, I decided to determine what the problem was. It turns out that the discs in one tube had broken loose of their jam nuts and were free wheeling like a turbine blade inside the tube. Not only were the tips of the discs burnished but you could clearly see the polishing effect of their rubbing against the inside of the 3" tube. So that explained the high EGT on the one tube (and the turbine sound reported) the discs were acting like a freewheeling prop and impeding the flow of exhaust gas. So I decided to reduce the number of discs down to 3 and Tracy was nice enough to weld the disc to the rod. Well, that seem to be the answer. I was getting good power and good sound suppression still. However, the discs only stayed welded to the rods for approx 2-3 weeks, and then I began to find pieces of disc back by the end of the tube. The pulse was too powerful and were slowly beating the stuffings out of the SS blades on the discs and they were breaking off and leaving the tube . By that time the expense (and more telling - the work) of six experimentation with mufflers had taken their toll. I decided to have my two tube header modified into one tube - turns out it cost twice to modify the header as two hushpower mufflers. So I just kept my old 10 year old header of stainless steel pipe and put on two hushpower mufflers. Not as quite as my experimental design - but they have lasted. So good luck folks, I'm eagerly awaiting the magic muffler design. Ed Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.dmack.net/mazda/index.html _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mark Steitle Sent: Tuesday, January 06, 2009 10:57 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Mistral muffler. Dennis, Thanks for the suggestion, but I initially felt that the Hushpower 2 was too heavy (10#/ea). I used it anyway out of desperation. So, I really don't want to be dragging two of them around with me everywhere I go if I can help it. I'm ready to give Al's design a try. Mark S. On Tue, Jan 6, 2009 at 9:52 AM, Dennis Haverlah wrote: Mark: Have you thought of splitting the exhaust and running it through two Hushpower's in parallel. If you had room for this I would think it would work. Dennis H. Mark Steitle wrote: Lynn, Thanks, I'll check the Mistral site. At least what I'm running now is durable, not the quietest on the field, but durable. Mark -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_0045_01C97011.5073A180 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Contrary to intuition – two = parallel mufflers actually reduce the sound less than one of the same type.  = If you have both rotor pulses going through a single muffler you have a = dominant high energy frequency (at 6000 rpm) of 200 Hz to filter.  If you have a = single rotor exhaust port with its separate muffler then the dominant freq for = each muffler is now 100Hz rather than 200Hz.  The dimensions for two = mufflers of equivalent effectiveness would need to be approx twice as large for = the 100Hz  pulse of which you are required to hang TWO of these twice as = larger hummers underneath to get the same effectiveness in sound suppression as = using one muffler half the dimensions – or something along those = lines.

 

So a single muffler (for sound = suppression) appears to be a better way to go – now if you are looking for = power instead of sound suppression then the story can be = different.

 

Having experimented with several = different approaches, the one that seemed to have the most promise was the one in = which I placed 3” diameter 1/8” thick Stainless Steel discs.  = The discs had vanes cut from the outer perimeter down to within 3/8 – = 1/2” of the center.  Then each vane was bent approx 45 deg to the plane = of the disc.  These then had a 3/8” dia hole drilled down the center = and a rod on which 5 discs were strung and first locked in using jam nuts = (don’t bother trying) and later welded to the rod.

 

The idea was that the pulse in the = exhaust would in effect see (straight on) an almost solid metal disc and bounce = back what pulse go through the first disc would find a 2nd and = 3rd and 4th etc, where as the exhaust gas would fairly easily = flow around the blades and through the discs – relatively unimpeded (so = the theory went {:>)). 

 

The first one I made I used a = 2” dia tube and discs – it was tremendously effective in suppressing the = sound – unfortunately it was equally effective in suppressing power.  So I concluded I needed a larger tube – so went to the 3” dia = tube and six discs.

 

This one I thought was really the = solution (and may have been if I had continued development) as it was very = effective in suppressing the sound (although not quite as much as the 2” tube) and I got = 6000 rpm static.  Ah ha! I thought – this is it!!! I have = succeeded.  So I buckled up and ran the engine up to 6000 rpm and launched.  The = only unfortunate aspect of the flight is that I never got over 6000 rpm static {:<(.  

 

I then cut the number of disc back = to 4 and that appear to do the job.  However, my next flight was down to = Tracy’s Crook.  I was later told by a witness to my take off that it sound = like I had a turbine engine under the cowl (more on that later).  In any = case, I noticed about 20 minutes into the flight that the EGT on one exhaust was = up into the 1700 + range whereas my normal EGT was more like 1550 -1600 = max.  After landing at Tracy Crooks, I decided to determine what the problem = was.

 

It turns out that the discs in one = tube  had broken loose of their jam nuts and were free wheeling like a turbine = blade inside the tube. Not only were the tips of the discs burnished but you = could clearly see the polishing effect of their rubbing against the inside of = the 3” tube.   So that explained the high EGT on the one tube (and = the turbine sound reported) the discs were acting like a freewheeling prop = and impeding the flow of exhaust gas.

 

So I decided to reduce the number = of discs down to 3 and Tracy was nice enough to weld the disc to the rod.  Well, that seem to be = the answer.  I was getting good power and good sound suppression = still.  However, the discs only stayed welded to the rods for approx 2-3 weeks, = and then I began to find pieces of disc back by the end of the tube.  = The pulse was too powerful and were slowly beating the stuffings out of the = SS blades on the discs and they were breaking off and leaving the tube = .

 

By that time the expense (and more = telling - the work) of six experimentation with mufflers had taken their = toll.  I decided to have my two tube header modified into one tube - turns out it cost = twice to modify the header   as two hushpower mufflers. So I just kept = my old 10 year old header of stainless steel pipe and put on two hushpower mufflers.  Not as quite as my experimental design – but they = have lasted.

 

So good luck folks, I’m = eagerly awaiting the magic muffler design.

 

Ed

 

Ed

 

Ed Anderson

Rv-6A N494BW Rotary = Powered

Matthews, NC

eanderson@carolina.rr.com=

http://www.andersonee.com

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

http://www.dmack.net/mazda/index.html<= font size=3D2 face=3DArial>

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mark Steitle
Sent: Tuesday, January = 06, 2009 10:57 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = Mistral muffler.

 

Dennis,

 

Thanks for the suggestion, but I initially felt that the = Hushpower 2 was too heavy (10#/ea).  I used it anyway out of desperation.  = So, I really don't want to be dragging two of them around with me everywhere I go if = I can help it.  I'm ready to give Al's design a = try.

 

Mark = S.

On Tue, Jan 6, 2009 at 9:52 AM, Dennis Haverlah <clouduster@austin.rr.com>= wrote:

Mark:

Have you thought of splitting the exhaust and running it through two Hushpower's in parallel.  If you had room for this I would think it = would work.

Dennis H.

Mark Steitle wrote:

Lynn,
=
Thanks, I'll check the Mistral site.  At least what I'm running now = is durable, not the quietest on the field, but durable.

Mark


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