Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.3c2) with ESMTP id 776145 for flyrotary@lancaironline.net; Tue, 08 Mar 2005 20:49:14 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-185-127.carolina.rr.com [24.74.185.127]) by ms-smtp-04-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j291mOCi024576 for ; Tue, 8 Mar 2005 20:48:25 -0500 (EST) Message-ID: <002301c5244a$1941a700$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Anechoic Muffler Date: Tue, 8 Mar 2005 20:48:31 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0020_01C52420.30372180" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0020_01C52420.30372180 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Tom I am in complete agreement with you. I am currently flying with a = muffler design that is: 1. Designed to break up the sonic/transonic shock wave that is so = shattering to the ears 2. Minimize impediment to the lower velocity gas flow. My initial result was inconclusive because it was complicated by the = fact that the discs I had inserted into the muffler to accomplish this = task decided to act like turbine wheels. One of the local airport bums = had mentioned to me after my first test flight that on take off the = exhaust sounded just like a turbine - yeah! Yeah! the poor mans turbine = (rotary) and though no more about it until my next flight - which was to = Florida. But, in any case, the discs spun so fast they caused the = stainless steel metal to deform/flow. I initially had them locked to a = 5/16 SS thread bar with jam nuts on each side. They even caused the jam = nuts to form a flange due to heat and force. All the thread on the rod = has been worn off where the discs were located. The inside of the 3" = muffler clearly showed where the tips of the discs were rubbing on the = walls. But while they did decrease the noise level significantly - they also = reduce the gas flow due to the "windmilling propeller" effect. My = exhaust temp in the one muffler (have two) where this was happening = reflected that by increasing from a nominal 1600F to 1750F. Also the = back pressure was considerable and my engine could not get above 6000 = rpm (I have had it up to 6800 rpm). Well, I was on my way to Lakeland for an RV Flyin in Jan when I = discovered the extent of the problem. At Tracy Crooks we found this out = when I pulled the mufflers apart. I removed 3 of the 5 discs and Tracy = welded a couple of the surviving discs to the 5/16" shaft and I have = flow that way since.=20 I intend to revisit the design with a more robust way of securing the = discs (probably welding) and add the three discs back in to see what = difference it makes. So if you have any ideas you want to discuss off-line as I am certain = most are tired of hearing about the FAW Muffler {:>) Ed Anderson eanderson@carolina.rr.com =20 ----- Original Message -----=20 From: Tom=20 To: Rotary motors in aircraft=20 Sent: Tuesday, March 08, 2005 6:58 PM Subject: [FlyRotary] Re: Anechoic Muffler Just to stir things up... It seems that with exhaust systems, = the exhaust consists of two parts which should be handled differently. = Part 1 is the exhaust gas flow which we want to flow out with little = restriction. Part 2 is the exhaust pulse which we try to attenuate, = breakup, etc. These two are like the difference between wind and = sound-waves. In the past 24 hours or so, I've been wondering about = using anechoic chamber principles to attenuate the pulse. I have a = specific layout in mind which should tend to attenuate the pulses while = not interfering with exhaust gas flow. Anybody hear of such a thing? Tom (looking for project sponsors or a job) -------------------------------------------------------------------------= ----- Celebrate Yahoo!'s 10th Birthday!=20 Yahoo! Netrospective: 100 Moments of the Web ------=_NextPart_000_0020_01C52420.30372180 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Tom
 
I am in complete agreement with = you.  I am=20 currently flying with a muffler design that is:
 
1.  Designed to break up the = sonic/transonic=20 shock wave that is so shattering to the ears
2. Minimize impediment to the lower = velocity gas=20 flow.
 
My initial result was inconclusive = because it=20 was  complicated by the fact that the discs I had inserted into the = muffler=20 to accomplish this task decided to act like turbine wheels. One of = the=20 local airport bums had mentioned to me after my first test flight that=20 on take off the exhaust sounded just like a turbine - yeah! = Yeah! the=20 poor mans turbine (rotary) and though no more about it until my next = flight -=20 which was to Florida. But, in any case, the discs spun so fast = they=20 caused the stainless steel metal to deform/flow.  I initially had = them=20 locked to a 5/16 SS thread bar with jam nuts on each side.  They = even=20 caused the jam nuts to form a flange due to heat and force. All the = thread on=20 the rod has been worn off where the discs were located.  = The inside of the 3" muffler clearly showed where = the tips of=20 the discs were rubbing on the walls.
 
But while they did decrease the noise = level=20 significantly - they also reduce the gas flow due to the "windmilling = propeller"=20 effect.  My exhaust temp in the one muffler (have two) where this = was=20 happening reflected that by increasing from a nominal 1600F to = 1750F.  Also=20 the back pressure was considerable and my engine could not get above = 6000 rpm (I=20 have had it up to 6800 rpm).
 
Well, I was on my way to Lakeland for = an RV Flyin=20 in Jan when I discovered the extent of the problem.  At Tracy = Crooks we=20 found this out when I pulled the mufflers apart.  I removed 3 of = the 5=20 discs and Tracy welded a couple of the surviving discs to the 5/16" = shaft and I=20 have flow that way since. 
 
I intend to revisit the design with a = more robust=20 way of securing the discs (probably welding) and add the three discs = back in to=20 see what difference it makes.
 
So if you have any ideas you want = to discuss=20 off-line as I am certain most are tired of hearing about the FAW = Muffler=20 {:>)
 
Ed Anderson
eanderson@carolina.rr.com
 
  =
----- Original Message -----
From:=20 Tom
Sent: Tuesday, March 08, 2005 = 6:58=20 PM
Subject: [FlyRotary] Re: = Anechoic=20 Muffler

Just to stir things up...     It seems that = with=20 exhaust systems, the exhaust consists of two parts which should be = handled=20 differently.    Part 1 is the exhaust gas flow which = we want=20 to flow out with little restriction.   Part 2 is the = exhaust=20 pulse which we try to attenuate, breakup,=20 etc.     These two are like the difference = between=20 wind and sound-waves.      In the = past 24=20 hours or so, I've been wondering about using anechoic chamber=20 principles to attenuate the pulse.      I have a = specific layout in mind which should tend to attenuate the = pulses while=20 not interfering with exhaust gas flow.     = Anybody hear=20 of such a thing?

Tom (looking for project sponsors or a = job)

Celebrate Yahoo!'s 10th Birthday!
Yahoo! = Netrospective: 100=20 Moments of the Web ------=_NextPart_000_0020_01C52420.30372180--