X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from rv-out-0506.google.com ([209.85.198.238] verified) by logan.com (CommuniGate Pro SMTP 5.2.11) with ESMTP id 3413606 for flyrotary@lancaironline.net; Tue, 06 Jan 2009 15:56:14 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.198.238; envelope-from=msteitle@gmail.com Received: by rv-out-0506.google.com with SMTP id f6so9986978rvb.7 for ; Tue, 06 Jan 2009 12:55:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:in-reply-to:mime-version:content-type:references; bh=raoJ4LtWPHBS0rlAKsmiKp9lTOwpSZhJ2yraHjGi0nc=; b=ab9POySSz3ZkmkgQjXSmXQWx4jP+Z2cDwo7VPDxfB0pjBZWYecPYl28oUGFjDJhVOh E76jgbDGJR12K3qCwLng+4z3Hw4Jp+a+X2ch9T2scJTnARHOcZIneqdhyZkBmuN+fOIk Gkmz06Ryax9RGwr+glJq5BdCwmde8TaiiiKCA= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version :content-type:references; b=G7F071RKHDHzAVPwFZAR8SF3HTAT1iNfXT0HI1Qyecj93xkg4VVjJf6ocPHXNfr2G2 HrJkrJ+uKI5r5I/nblMZcTVh1dhJkpBCeyrCtygt4Sm59fw0Dkro2Tppda8csqOOKU+p 1FP1VbrMbuVFGffGxSObluQWvKCNHMXIVudSc= Received: by 10.141.106.14 with SMTP id i14mr11113375rvm.143.1231275338148; Tue, 06 Jan 2009 12:55:38 -0800 (PST) Received: by 10.140.166.4 with HTTP; Tue, 6 Jan 2009 12:55:38 -0800 (PST) Message-ID: <5cf132c0901061255m2ebc7da0oce5fdb10d54384c8@mail.gmail.com> Date: Tue, 6 Jan 2009 14:55:38 -0600 From: "Mark Steitle" To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] My Muffler experiments (long) was [FlyRotary] Re: Mistral muffler. In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_133854_32735714.1231275338136" References: ------=_Part_133854_32735714.1231275338136 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Ed, As I understand your design, the discs were bolted to the threaded rod on the bench and then slid up into the pipe. From your description, I picture the discs being shaped like butterflies. If that's correct, then the "wings" would have a huge amount of leverage compared to the centers where they are bolted to the threaded rod. Seems that if you were to weld the outer edges to the 3" tube, then they couldn't flex or spin. Sounds like you have more work to do here. Mark S. On Tue, Jan 6, 2009 at 2:13 PM, Ed Anderson wrot= e: > Contrary to intuition =96 two parallel mufflers actually reduce the soun= d > less than one of the same type. If you have both rotor pulses going thro= ugh > 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 separ= ate > 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 t= he > same effectiveness in sound suppression as using one muffler half the > dimensions =96 or something along those lines. > > > > So a single muffler (for sound suppression) appears to be a better way to > go =96 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 seeme= d > 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 =96 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 ro= d. > > > > 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 =96 > relatively unimpeded (so the theory went {:>)). > > > > The first one I made I used a 2" dia tube and discs =96 it was tremendous= ly > effective in suppressing the sound =96 unfortunately it was equally effec= tive > in suppressing power. So I concluded I needed a larger tube =96 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. A= h > ha! I thought =96 this is it!!! I have succeeded. So I buckled up and ra= n 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 th= e > 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 m= y > 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 nu= ts > and were free wheeling like a turbine blade inside the tube. Not only wer= e > 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) t= he > discs were acting like a freewheeling prop and impeding the flow of exhau= st > 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 di= scs > 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 power= ful > and were slowly beating the stuffings out of the SS blades on the discs a= nd > 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 modif= y > 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 =96 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] *O= n > 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 > > > ------=_Part_133854_32735714.1231275338136 Content-Type: text/html; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
Ed,
 
As I understand your design, the discs were bolted to the threaded rod=  on the bench and then slid up into the pipe.  From your descript= ion, I picture the discs being shaped like butterflies.  If that's= correct, then the "wings" would have a huge amount of leverage c= ompared to the centers where they are bolted to the threaded rod. = ; Seems that if you were to weld the outer edges to the 3" tube, then = they couldn't flex or spin.  Sounds like you have more work to do = here. 
 
Mark S.

On Tue, Jan 6, 2009 at 2:13 PM, Ed Anderson <eanderson@ca= rolina.rr.com> wrote:

Contrary to intuition =96 two paral= lel 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 d= ominant high energy frequency (at 6000 rpm) of 200 Hz to filter.  If y= ou have a single rotor exhaust port with its separate muffler then the domi= nant freq for each muffler is now 100Hz rather than 200Hz.  The dimens= ions for two mufflers of equivalent effectiveness would need to be approx t= wice as large for the 100Hz  pulse of which you are required to hang T= WO of these twice as larger hummers underneath to get the same effectivenes= s in sound suppression as using one muffler half the dimensions =96 or some= thing along those lines.

 

So a single muffler (for sound supp= ression) appears to be a better way to go =96 now if you are looking for po= wer instead of sound suppression then the story can be different.

 

Having experimented with several di= fferent approaches, the one that seemed to have the most promise was the on= e 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 =96 1/2" o= f the center.  Then each vane was bent approx 45 deg to the plane of t= he 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 bo= unce back what pulse go through the first disc would find a 2nd = and 3rd and 4th etc, where as the exhaust gas would f= airly easily flow around the blades and through the discs =96 relatively un= impeded (so the theory went {:>)). 

 

The first one I made I used a 2" di= a tube and discs =96 it was tremendously effective in suppressing the sound= =96 unfortunately it was equally effective in suppressing power.  So = I concluded I needed a larger tube =96 so went to the 3" dia tube and six d= iscs.

 

This one I thought was really the s= olution (and may have been if I had continued development) as it was very e= ffective in suppressing the sound (although not quite as much as the 2" tub= e) and I got 6000 rpm static.  Ah ha! I thought =96 this is it!!! I ha= ve succeeded.  So I buckled up and ran the engine up to 6000 rpm and l= aunched.  The only unfortunate aspect of the flight is that I never go= t 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 i= t sound like I had a turbine engine under the cowl (more on that later).&nb= sp; 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 li= ke 1550 -1600 max.  After landing at Tracy Crooks, I decided to determ= ine 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 burnish= ed 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 th= e one tube (and the turbine sound reported) the discs were acting like a fr= eewheeling prop and impeding the flow of exhaust gas.

 

So I decided to reduce the number o= f discs down to 3 and Tracy was nice enough to weld the disc to the rod.&nb= sp; Well, that seem to be the answer.  I was getting good power and go= od 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 b= eating the stuffings out of the SS blades on the discs and they were breaki= ng off and leaving the tube .

 

By that time the expense (and more = telling - the work) of six experimentation with mufflers had taken their to= ll.  I decided to have my two tube header modified into one tube - tur= ns out it cost twice to modify the header   as two hushpower muff= lers. 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= =96 but they have lasted.

 

So good luck folks, I'm eagerly awa= iting the magic muffler design.

 

Ed

 

Ed

 

From: Rota= ry 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.

= Mark S.

clouduster@austin.rr.com> w= rote:

= Mark:

Have you thought of splitting = the exhaust and running it through two Hushpower's in parallel.  I= f 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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