Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 552357 for flyrotary@lancaironline.net; Wed, 01 Dec 2004 08:47:01 -0500 Received-SPF: none receiver=logan.com; client-ip=24.25.9.100; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-069-132-109-019.carolina.rr.com [69.132.109.19]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id iB1DkRKk007209 for ; Wed, 1 Dec 2004 08:46:28 -0500 (EST) Message-ID: <001501c4d7ac$30b19e30$2502a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" Subject: Reactive vs Absorbtion Mufflers for the Rotary engine Date: Wed, 1 Dec 2004 08:46:42 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0012_01C4D782.47A718B0" 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_0012_01C4D782.47A718B0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable One thing I forgot to mention about the muffler design. It is referred = to as a "reactive" type muffler as contrasted to an "absorbtion" type = muffler. From my research it appears that "absorption" type mufflers = (packed with fiberglass,steelwool, ceramic wool, etc) appear to be most = effective in filtering out exhaust frequencies around 1000Hz and above. = The reactive (sometimes referred to as sound canceling) muffler is more = effective at the lower frequencies such as 50-400Hz. Since at 6000 rpm the dominate frequency of the exhaust is the frequency = of the exhaust pulse at 200 Hz (combined ports) or 100Hz (separate = ports), I decided that the reactive approach would produce better = results. Besides, I had tried the absorption approach earlier using a ceramic = wool absorption material. While it did soften the high frequency = metallic sounds of the exhaust, it really did not decrease the overall = volume very much. Besides that - while the ceramic wool survived the = heat of the exhaust - the force of the exhaust pulses soon pulverize it = into dust. The spintech muffler is in the reactive muffler category. FWIW Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com ------=_NextPart_000_0012_01C4D782.47A718B0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
One thing I forgot to mention about the = muffler=20 design.  It is referred to as a "reactive" type muffler as = contrasted to an=20 "absorbtion" type muffler.  From my research it appears that = "absorption"=20 type mufflers (packed with fiberglass,steelwool, ceramic wool, = etc) appear=20 to be most effective in filtering out exhaust frequencies around = 1000Hz and=20 above.  The reactive (sometimes referred to as sound canceling) = muffler is=20 more effective at the lower frequencies such as 50-400Hz.
 
Since at 6000 rpm the dominate = frequency of the=20 exhaust is the frequency of the exhaust pulse at 200 Hz (combined = ports) or=20 100Hz (separate ports), I decided that the reactive approach would = produce=20 better results.
 
  Besides, I had tried the=20 absorption approach earlier using a ceramic wool absorption=20 material.  While it did soften the high frequency metallic = sounds of=20 the exhaust, it really did not decrease the overall volume very = much. =20 Besides that - while the ceramic wool survived the heat of the exhaust - = the=20 force of the exhaust pulses soon pulverize it into dust.
 
The spintech muffler is in the reactive = muffler=20 category.
 
FWIW
 
Ed
 
 
Ed Anderson
Rv-6A N494BW Rotary=20 Powered
Matthews, NC
eanderson@carolina.rr.com
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