X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from EXHUB003-2.exch003intermedia.net ([207.5.74.29] verified) by logan.com (CommuniGate Pro SMTP 5.2.11) with ESMTPS id 3413471 for flyrotary@lancaironline.net; Tue, 06 Jan 2009 15:21:32 -0500 Received-SPF: none receiver=logan.com; client-ip=207.5.74.29; envelope-from=jwhaley@datacast.com Received: from EXVMBX003-5.exch003intermedia.net ([207.5.74.45]) by EXHUB003-2.exch003intermedia.net ([207.5.74.29]) with mapi; Tue, 6 Jan 2009 12:20:57 -0800 From: Jeff Whaley To: Rotary motors in aircraft Date: Tue, 6 Jan 2009 12:20:59 -0800 Subject: RE: [FlyRotary] My Muffler experiments (long) was [FlyRotary] Re: Mistral muffler. Thread-Topic: [FlyRotary] My Muffler experiments (long) was [FlyRotary] Re: Mistral muffler. Thread-Index: AclwO26L2qvR0rW4RVm/7x3KEbMJ/QAAL+nw Message-ID: References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/alternative; boundary="_000_C03ABB0A7362B84BB53D544B3C305E0ED1361D1D2BEXVMBX0035exc_" MIME-Version: 1.0 --_000_C03ABB0A7362B84BB53D544B3C305E0ED1361D1D2BEXVMBX0035exc_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hi Ed, does that mean you have 2 Hush Powers in series? Jeff From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Beh= alf Of Ed Anderson Sent: Tuesday, January 06, 2009 3:13 PM To: Rotary motors in aircraft Subject: [FlyRotary] My Muffler experiments (long) was [FlyRotary] Re: Mist= ral muffler. Contrary to intuition - two parallel mufflers actually reduce the sound les= s 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 separat= e muffler then the dominant freq for each muffler is now 100Hz rather than = 200Hz. The dimensions for two mufflers of equivalent effectiveness would n= eed to be approx twice as large for the 100Hz pulse of which you are requi= red to hang TWO of these twice as larger hummers underneath to get the same= effectiveness in sound suppression as using one muffler half the dimension= s - or something along those lines. So a single muffler (for sound suppression) appears to be a better way to g= o - 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" thi= ck 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 4= 5 deg to the plane of the disc. These then had a 3/8" dia hole drilled dow= n the center and a rod on which 5 discs were strung and first locked in usi= ng 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 firs= t 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 un= impeded (so the theory went {:>)). The first one I made I used a 2" dia tube and discs - it was tremendously e= ffective in suppressing the sound - unfortunately it was equally effective = in suppressing power. So I concluded I needed a larger tube - so went to t= he 3" dia tube and six discs. This one I thought was really the solution (and may have been if I had cont= inued development) as it was very effective in suppressing the sound (altho= ugh 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 engi= ne 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. How= ever, my next flight was down to Tracy's Crook. I was later told by a witn= ess 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 fl= ight that the EGT on one exhaust was up into the 1700 + range whereas my no= rmal EGT was more like 1550 -1600 max. After landing at Tracy Crooks, I de= cided 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 ef= fect of their rubbing against the inside of the 3" tube. So that explaine= d the high EGT on the one tube (and the turbine sound reported) the discs w= ere 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 eno= ugh 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 on= ly 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 an= d were slowly beating the stuffings out of the SS blades on the discs and t= hey were breaking off and leaving the tube . By that time the expense (and more telling - the work) of six experimentati= on with mufflers had taken their toll. I decided to have my two tube heade= r modified into one tube - turns out it cost twice to modify the header a= s two hushpower mufflers. So I just kept my old 10 year old header of stain= less steel pipe and put on two hushpower mufflers. Not as quite as my expe= rimental 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 Beh= alf 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 to= o 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 he= lp 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 Hushpo= wer'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 dura= ble, 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 --_000_C03ABB0A7362B84BB53D544B3C305E0ED1361D1D2BEXVMBX0035exc_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Hi Ed, does that mean you have 2 Hush Powers in series?=

Jeff

 

From: Rotary motors= in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anders= on
Sent: Tuesday, January 06, 2009 3:13 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] My Muffler experiments (long) was [FlyRotary] R= e: Mistral muffler.

 

Contrary to intuition – two parallel mufflers actually re= duce the sound less than one of the same type.  If you have both rotor pulses g= oing 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 wit= h 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  pu= lse 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 bet= ter way to go – now if you are looking for power instead of sound suppres= sion 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” diam= eter 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 e= ach vane was bent approx 45 deg to the plane of the disc.  These then had a 3/8R= 21; dia hole drilled down the center and a rod on which 5 discs were strung and fir= st locked in using jam nuts (don’t bother trying) and later welded to th= e 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 thro= ugh the first disc would find a 2nd and 3rd and 4th<= /sup> etc, where as the exhaust gas would fairly easily flow around the blades an= d through the discs – relatively unimpeded (so the theory went {:>))= . 

 

The first one I made I used a 2” dia tube and discs ̵= 1; it was tremendously effective in suppressing the sound – unfortunately it wa= s 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 i= f I had continued development) as it was very effective in suppressing the soun= d (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 o= f 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 t= he 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 landi= ng 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.&= nbsp;  So that explained the high EGT on the one tube (and the turbine sound repor= ted) the discs were acting like a freewheeling prop and impeding the flow of exh= aust 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.&nb= sp; 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 .<= /o:p>

 

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 muffle= r design.

 

Ed

 

Ed

 

Ed Anderson

Rv-6A N494BW Rotary Powered

Matthews, NC

eanderson@carolina.rr.com

http://www.andersonee.c= om

http://members.cox.net/rogersda/rotary/configs.htm#N494BW<= /o:p>

http://www.d= mack.net/mazda/index.html

From: Rotary motors= in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mark Stei= tle
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 t= he Hushpower 2 was too heavy (10#/ea).  I used it anyway out of desperati= on.  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> w= rote:

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 wo= uld 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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