X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-bw0-f163.google.com ([209.85.218.163] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3645778 for flyrotary@lancaironline.net; Mon, 18 May 2009 13:01:53 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.218.163; envelope-from=msteitle@gmail.com Received: by bwz7 with SMTP id 7so3612868bwz.19 for ; Mon, 18 May 2009 10:01:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=4y7bBoc9IO8oWnSQrmneiGK6T3eRIqz2kHVdulkM4bE=; b=mPvtUCum1cBSN3EAn6C2BmzKToR3tG8tjSwgFASb0RQCgYasHpMwEYVxf0NiwILsHO O2hQNX25etXIPDmMeBZreLVLk4GIfRZhdGSYwqZcGlH5bklC8OAefi8pOdmirL1IHk85 9Nw6nHcu/QYwIHs7hy9btYluS7EjGw9lEOlxQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=Rr0a/lcDJO6CH2mzkNhPwn43EidU4CAOk0umvNyfakBdNLNawlLM0oNyXgn2hRnJtX GTBckNnC6XlpelbmkWPeSLJP5kI7B8oJquD+DQnRItuqzV291LQV6DODSSqpI4t+gVM1 n1t8qm/l2KwaKiUPJukXr96OQIOGumokbFzJQ= MIME-Version: 1.0 Received: by 10.204.31.71 with SMTP id x7mr6951295bkc.2.1242666073611; Mon, 18 May 2009 10:01:13 -0700 (PDT) In-Reply-To: References: Date: Mon, 18 May 2009 12:01:13 -0500 Message-ID: <5cf132c0905181001s12062e3eu56fa3441e19d790a@mail.gmail.com> Subject: Re: [FlyRotary] Re: 20b Exhaust From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=001485f7c55ce4600a046a32bd64 --001485f7c55ce4600a046a32bd64 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit My latest exhaust system uses a DNA muffler which has a 3" inlet and 3" outlet. When I first ran it, I was disappointed at how unacceptably loud it was. Then I remembered Tracy's statement about most guys using too large of an exit. So, I reduced the outlet to 2". Sure enough, it reduced the noise level significantly and there was no detectable loss of power. I'm still running it with the 2" exit. Mark S. On Mon, May 18, 2009 at 10:14 AM, Tracy Crook wrote: > Your mathematics are sound George and using that approach will certainly > keep back pressure to a minimum. But I think it is doomed to be noisy. > That's just my understanding about how mufflers generally work and I could > be wrong. > During a test of mufflers at a rotary fly-in some years back I was amazed > at how effective the muffler became and how small the power loss was when we > installed a 1" diameter muffler outlet pipe on the test stand engine > (13B). 1" is admittedly too small but we learn by going to extremes > sometimes. > > Tracy > > On Mon, May 18, 2009 at 2:40 AM, George Lendich wrote: > >> 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) = 9.2 sq" or Radius of 1.71" = 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 wrote: >> >>> Tracy, >>> Any significant back pressure to speak of? >>> George (down under) >>> >>> ----- Original Message ----- >>> *From:* Tracy Crook >>> *To:* 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, 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 >>>> >>> >>> >> > --001485f7c55ce4600a046a32bd64 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
My latest exhaust system uses a=A0DNA muffler which has a 3" inle= t and 3" outlet.=A0 When I first ran it, I was disappointed at how una= cceptably loud it was.=A0 Then I remembered Tracy's statement about mos= t guys=A0using too large=A0of an exit.=A0 So,=A0I reduced the outlet to 2&q= uot;.=A0 Sure enough, it reduced the noise level significantly and there wa= s no=A0detectable=A0loss of power.=A0=A0I'm still running it with the 2= " exit.=A0
=A0
Mark S.=A0

On Mon, May 18, 2009 at 10:14 AM, Tracy Crook <tracy@rotar= yaviation.com> wrote:
Your mathematics are sound Georg= e and using that approach will certainly keep back pressure to a minimum. B= ut I think it is doomed to be noisy.=A0 That's just my understanding ab= out how mufflers generally work and I could be wrong.
=A0During a test of mufflers at a rotary fly-in some years back I was amaze= d at how effective the muffler became and how small the power loss was when= we installed a 1" diameter muffler outlet pipe on the test stand engi= ne=A0 (13B).=A0 1" is admittedly too small but we learn by going to ex= tremes sometimes.

Tracy

On Mon, May 18, 2009 at 2:40 AM, George Lendich = <lendich@aanet.com.au> wrote:
=A0Tracy,
The reason I ask is that I like to kee= p 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.
=A0
I do understand the 2 and 3 rotors are= staged and the exhaust and the exhaust (shock)=A0waves are=A0in 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 R= adius of 1.71" =3D Dia of 3.42".
=A0
I thought 2.25 may have a little too m= uch back pressure, as the rotary doesn't like back pressure.
=A0
Probably to do this exercise properly = would be to calculate the volume of the heated and expanded exhaust gases a= nd 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 inte= resting exercise.
George (down under)
Too soon to say re= ally.=A0 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 t= hing 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 -----
To: 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.=A0 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@compo= rium.net> wrote:
I have fabricated my= exhaust manifold/tangential muffler for my 20b. =A0All I have left is to f= it and weld the exhaust pipe. =A0I would like opinions on the size the exha= ust pipe should be. =A0This is in a pusher application (Velocity) with a re= latively short run from the muffler to the exit point. =A0Similar installat= ion to Al G.

Thanks,
Joe


--
Homepage: =A0http://www.flyrotary.= com/
Archive and UnSub: =A0 http://mail.lancaironline.= net:81/lists/flyrotary/List.html




--001485f7c55ce4600a046a32bd64--