X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao102.cox.net ([68.230.241.44] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3645749 for flyrotary@lancaironline.net; Mon, 18 May 2009 12:46:21 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.44; envelope-from=alventures@cox.net Received: from fed1rmimpo03.cox.net ([70.169.32.75]) by fed1rmmtao102.cox.net (InterMail vM.7.08.02.01 201-2186-121-102-20070209) with ESMTP id <20090518164546.DUGA20976.fed1rmmtao102.cox.net@fed1rmimpo03.cox.net> for ; Mon, 18 May 2009 12:45:46 -0400 Received: from BigAl ([72.192.135.181]) by fed1rmimpo03.cox.net with bizsmtp id t4ll1b00a3uzsQg044ll7D; Mon, 18 May 2009 12:45:46 -0400 X-Authority-Analysis: v=1.0 c=1 a=Ia-xEzejAAAA:8 a=Hl1Gy0H5AAAA:8 a=UretUmmEAAAA:8 a=21HoqxOMAAAA:8 a=7g1VtSJxAAAA:8 a=3WSAOAI0q-RICMZGuZgA:9 a=LsEVbFDdPuWVUddhLgQA:7 a=jK9AQPYg52OY8B9UYVr18lZXtcIA:4 a=EzXvWhQp4_cA:10 a=iVkDmfvjeKcA:10 a=Oxi3NFFUgcgA:10 a=DR22w9f7iA0o7Uen:21 a=BDLthyVIAuGJTGSM:21 a=Hij4lPL86Cx2rXUgZ1IA:9 a=E0ECFhyAthshhb_EORkA:7 a=ETG_YxMPhpaGuVYVU52TAjnTfCAA:4 a=OoyQGewizjs1ECBo:21 a=4V7NIKoGAHR0j6JC:21 X-CM-Score: 0.00 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: 20b Exhaust Date: Mon, 18 May 2009 09:47:34 -0800 Message-ID: <6C987B5D8B754413B99BE3711DDEAB92@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0006_01C9D79D.AB90CA40" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6838 Importance: Normal Thread-Index: AcnXitVA8or/IRE/T1a7fl7SqB5fPgAVJWkg In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_0006_01C9D79D.AB90CA40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable George; =20 I did some similar calculations, but I =96 as Joe is doing =96 have a = tangential manifold muffler which significantly spreads the pulses. So I did some = sort of velocity calculations and chose 2 =BE=94 for its outlet. A bit = further downstream I have secondary muffler, I guess it could be called a pulse dampener; which quiets things down another half dozen DBs, or so. For convenience I kept the same outlet dia., but probably have reduced a bit more for a couple more DB with little effect on back pressure since the length from there is very short. =20 FWIW, Al G =20 =20 -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of George Lendich Sent: Sunday, May 17, 2009 10:41 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: 20b Exhaust =20 Tracy,=20 The reason I ask is that I like to keep the muffler outlet the same area size or a little bigger than the exhaust outlet in the rotor housing = which is usually about 2" dia. =20 I do understand the 2 and 3 rotors are staged and the exhaust and the exhaust (shock) waves are in sequence, but I like to keep the volume of = the muffler and muffler exit to the total of the rotor exits i.e. 3x Pi.r squared (3x Pi 1 x 1) =3D 9.2 sq" or Radius of 1.71" =3D Dia of 3.42". =20 I thought 2.25 may have a little too much back pressure, as the rotary doesn't like back pressure. =20 Probably to do this exercise properly would be to calculate the volume = of the heated and expanded exhaust gases and calculate the timing of the = pulses to see how a particular sized muffler and exit size coped with the speed = and volume of flow. It would be an interesting exercise. George (down under) Too soon to say really. I have not even had time to assemble the = builders log to get ready for the DAR. Lack of engine power is definitely not = what is keeping this thing grounded though : ) Tracy On Sun, May 17, 2009 at 6:01 PM, George Lendich wrote: Tracy,=20 Any significant back pressure to speak of? George (down under) ----- Original Message -----=20 From: Tracy Crook =20 To: Rotary motors in aircraft =20 Sent: Monday, May 18, 2009 12:11 AM Subject: [FlyRotary] Re: 20b Exhaust =20 In general, the bigger the exit pipe, the louder the exhaust will be. I used 2.25" which I think is about the minimum for a 20B. Tracy On Sat, May 16, 2009 at 9:28 AM, wrote: I have fabricated my exhaust manifold/tangential muffler for my 20b. = All I have left is to fit and weld the exhaust pipe. I would like opinions on = the size the exhaust pipe should be. This is in a pusher application = (Velocity) with a relatively short run from the muffler to the exit point. Similar installation to Al G. Thanks, Joe -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html =20 =20 ------=_NextPart_000_0006_01C9D79D.AB90CA40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

George;

 

I did some similar calculations, = but I – as Joe is doing – have a tangential manifold muffler which = significantly spreads the pulses. So I did some sort of velocity calculations and = chose 2 =BE” for its outlet. A bit further downstream I have secondary muffler, I = guess it could be called a pulse dampener; which quiets things down another half = dozen DBs, or so.=A0 For convenience I kept the same outlet dia., but probably have reduced a bit more for a = couple more DB with little effect on back pressure since the length from there = is very short.

 

FWIW,

Al G

 

 

-----Original = Message-----
From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of George Lendich
Sent: Sunday, May 17, = 2009 10:41 PM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: = 20b Exhaust

 

 Tracy, =

The reason I ask is that I = like to keep the muffler outlet the same area size or a little bigger than the = exhaust outlet in the rotor housing which is usually about 2" = dia.

 

I do understand the 2 and 3 = rotors are staged and the exhaust and the exhaust (shock) waves = are in sequence, but I like to keep the volume of the muffler and muffler exit = to the total of the rotor exits i.e. 3x Pi.r squared (3x Pi 1 x 1) =3D 9.2 = sq" or Radius of 1.71" =3D Dia of 3.42".

 

I thought 2.25 may have a = little too much back pressure, as the rotary doesn't like back = pressure.

 

Probably to do this = exercise properly would be to calculate the volume of the heated and expanded = exhaust gases and calculate the timing of the pulses to see how a particular = sized muffler and exit size coped with the speed and volume of flow. It would = be an interesting exercise.

George (down = under)

=

Too soon to say really.  I have not even had time to assemble the = builders log to get ready for the DAR. Lack of engine power is definitely not what is keeping this thing grounded though : )

Tracy

On Sun, May 17, 2009 at 6:01 PM, George = Lendich <lendich@aanet.com.au> = wrote:

Tracy,

Any significant back = pressure to speak of?

George (down = under)

=

----- Original Message = -----

From: Tracy Crook

To:<= /font> Rotary motors in aircraft =

Sent: Monday, May 18, 2009 12:11 AM

Subject: [FlyRotary] Re: 20b Exhaust

 

In general, the bigger the exit pipe, the louder the exhaust will be.  = I used 2.25" which I think is about the minimum for a 20B.

Tracy

On Sat, May 16, 2009 at 9:28 AM, <jewen@comporium.net> wrote:

I have fabricated my exhaust = manifold/tangential muffler for my 20b.  All I have left is to fit and weld the exhaust = pipe.  I would like opinions on the size the exhaust pipe should be. =  This is in a pusher application (Velocity) with a relatively short run from = the muffler to the exit point.  Similar installation to Al G.

Thanks,
Joe


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