X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-qy0-f17.google.com ([209.85.221.17] verified) by logan.com (CommuniGate Pro SMTP 5.2.12) with ESMTP id 3482451 for flyrotary@lancaironline.net; Sun, 08 Feb 2009 06:32:19 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.221.17; envelope-from=msteitle@gmail.com Received: by qyk10 with SMTP id 10so2819042qyk.19 for ; Sun, 08 Feb 2009 03:31:44 -0800 (PST) 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=vSO5KQ4d/hJG3RZ+VlA9G/+y1oWbZJ7yudK3IpNlVX0=; b=GnAsIoPfkC+94WMFg5eJB+dKUy4DyibPV0W0m8PW4PmO6SPwhjDzAC53il0lh25ubg 9QJ5pjpcniQu4FJhfK7T2BuTfA8W0ownOz79iEyJLIqRgDCX5pYtLVVFyBHiYuukvZnb ZegmjVj7yIBp7HDIWZeynLehOUlsP5X+VeHOc= 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=rOL19A/VWn06zo0P0FLyY4e7xsupyDVowNXe8P5VSHWN3aHCJSkluTFbTMmQ4jNe8P 0qLZt1dGmDQRIJLFDkfe2/qeQceI85dKRHRa5FuyXX304GnkeNkqFQxisM3D47p/J1z2 HcwfPumfu9d1f8Cdvuao+Sr1UQyA7blDQMSoc= MIME-Version: 1.0 Received: by 10.214.244.6 with SMTP id r6mr5120361qah.96.1234092704419; Sun, 08 Feb 2009 03:31:44 -0800 (PST) In-Reply-To: References: Date: Sun, 8 Feb 2009 05:31:44 -0600 Message-ID: <5cf132c0902080331l5a964564h304b8a03feb1ebeb@mail.gmail.com> Subject: Re: [FlyRotary] Exhaust question. From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=0015175cded444518404626699d9 --0015175cded444518404626699d9 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Lynn, I have a question regarding exhaust/inlet lengths that I've wanted to ask for quite a while. Q: Do the optimum lengths of 12/24/36/102 hold true only for the 2-rotor engines or does it work for the 3-rotor engines too? Mark S. On Sun, Feb 8, 2009 at 12:51 AM, Lynn Hanover wrote: > The 11"-12" 22"-24" 33"-36" is for primary lengths into a collector. 36" > is about as much as you can fit into a race car. The next primary length > with any data is 102" inches to the collector, and in that case the muffler > is under the rear bumper. Any length that will have 2 full exhaust pulses > inside before the collector is the one of interest. I have read that the > high frequency stuff tends to move along the outer wall of the pipe, so even > a steel pack or glass pack muffler can work for a while, with the really > annoying part of the sounds. > > The 90 degree cut off the pipe is the loudest, any angle of cut away from > 90 will be quieter. You can see this morphing to a fish tail muffler, which > works well. The hammering will disassemble a fish tail unless it has some > blades to support the sides but the long angle cut needs no such > support. Removing heat also quiets the sound. If the headers have no cooling > air supply they will glow orange and heat anything that can "see" the orange > part. A thin wall bit of stainless stood off 1/2" or more, from the pipe > will break the transmission of heat. > > Lynn E. Hanover > > > > Here are some pics from today. I have to safety some wires, hang the prop, > fill the fluids, then I can make some noise. If everything goes well, I can > start her up this week. > > My exhaust questions: You can see in the picture, that I stuck a 150* > piece on the end of the muffler. This isn't permanent, I just put it there > for the radius. I remember Lynn writing something about the exhaust length > should be a multiple of 11 to 12 inches. Is this for 6500 ish rpm? Where > do I start measuring? I measured from the front rotor exhaust port to the > back of the muffler and got 30". > > I can run a short bend and let the exhaust exit out the side of the > cowling, right where it shows in the picture. But I am worried about the > exhaust being too close to the fresh air intake. The other option is to > turn it inboard and down, so it passes over the engine mount tube and exits > out the bottom of the cowling. > > What is the appropriate angle for the end of the pipe as it exits the cowl > so I don't have any back pressure? > > Chris > > > > --0015175cded444518404626699d9 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Lynn,

I have a question regarding exhaust/inlet lengths that I'= ve wanted to ask for quite a while. 

Q:  Do the optimum l= engths of 12/24/36/102 hold true only for the 2-rotor engines or does it wo= rk for the 3-rotor engines too?

Mark S. 

On Sun, Feb 8, 2009 at= 12:51 AM, Lynn Hanover <lehanover@gmail.com> wrote:

The 11"-12"  22"-24" 33"-36" is for p= rimary lengths into a collector. 36" is about as much as you can fit i= nto a race car. The next primary length with any data is 102" inches t= o the collector, and in that case the muffler is under the rear bumper. Any= length that will have 2 full exhaust pulses inside before the collector is= the one of interest. I have read that the high frequency stuff tends to mo= ve along the outer wall of the pipe, so even a steel pack or glass pack muf= fler can work for a while, with the really annoying part of the sounds.

The 90 degree cut off the pipe is the loudest, any angle of cut away fro= m 90 will be quieter. You can see this morphing to a fish tail muffler, whi= ch works well. The hammering will disassemble a fish tail unless it has som= e blades to support the sides but the long angle cut needs no such support.=  Removing heat also quiets the sound. If the headers have no cooling a= ir supply they will glow orange and heat anything that can "see" = the orange part. A thin wall bit of stainless stood off 1/2" or more, = from the pipe will break the transmission of heat. 

Lynn E. Hanover

 

Here are some pics from today.  I have to safety some wires, hang t= he prop, fill the fluids, then I can make some noise.  If everything g= oes well, I can start her up this week.

 My exhaust questions:  You can see in the picture, that I stu= ck a 150* piece on the end of the muffler.  This isn't permanent, = I just put it there for the radius.  I remember Lynn writing something= about the exhaust length should be a multiple of 11 to 12 inches.  Is= this for 6500 ish rpm?  Where do I start measuring?  I measured = from the front rotor exhaust port to the back of the muffler and got 30&quo= t;.

 I can run a short bend and let the exhaust exit out the side of th= e cowling, right where it shows in the picture. But I am worried about the = exhaust being too close to the fresh air intake.  The other option is = to turn it inboard and down, so it passes over the engine mount tube and ex= its out the bottom of the cowling.

What is the appropriate angle for the end of the pipe as it exits the co= wl so I don't have any back pressure? 

 Chris

 



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