X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from rv-out-0506.google.com ([209.85.198.238] verified) by logan.com (CommuniGate Pro SMTP 5.2.9) with ESMTP id 3272632 for flyrotary@lancaironline.net; Wed, 05 Nov 2008 10:09:38 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.198.238; envelope-from=rwstracy@gmail.com Received: by rv-out-0506.google.com with SMTP id g9so1902467rvb.3 for ; Wed, 05 Nov 2008 07:09:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:sender :to:subject:in-reply-to:mime-version:content-type:references :x-google-sender-auth; bh=8xTpLagqTYgPUvFIAQBXVakS57aNBn6okOOMIhIOmKg=; b=hPQ2Qtt3OG5r7Pd87KYrDDLMrB3T/zJSTRhq0eb8ZHFt720bE53CiQm54i5Kysi7jM Xr5I8y2ObCpl7MYji6HPSwq20BouKcyfID6DIkl+IZ1Cmje6VWm1tjlezZDcYuAlPFP4 UU6Wi2PcaiK+e6VanuBfOtcNjHTcyoU+FReRU= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:sender:to:subject:in-reply-to:mime-version :content-type:references:x-google-sender-auth; b=qkxfi+N2YqE4NJ7sUXbyVh+lFF8HUEEP16Lz7kNNBEhw/9mTjWn8SLJ8DMtf0tBK1C aIjp54bs0W4dNpsouaYlYzVwH3Pdts63TEh/PXgP+oclLyJHZn7hJYCltW2US9TtKPXg l1i4ZTaxmQ9k3Xqao5nw52Fm+R16TQvO6oIjc= Received: by 10.140.128.3 with SMTP id a3mr460026rvd.232.1225897741660; Wed, 05 Nov 2008 07:09:01 -0800 (PST) Received: by 10.141.41.18 with HTTP; Wed, 5 Nov 2008 07:09:01 -0800 (PST) Message-ID: <1b4b137c0811050709u11b01ba5wc3ecb7970424a259@mail.gmail.com> Date: Wed, 5 Nov 2008 10:09:01 -0500 From: "Tracy Crook" Sender: rwstracy@gmail.com To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] single rotor performance In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_4005_22911680.1225897741662" References: X-Google-Sender-Auth: 798260bccf21c5fb ------=_Part_4005_22911680.1225897741662 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Sounds good Richard. But what about RPM delta at full throttle between the two different runner lengths? That is the acid test for HP increase (with a prop load). You are in the best possible position to test different runner lengths with that single runner manifold. I give a lot to see a performance curve plot of different runner lengths in increments of 1" between 8 and 24". I'm surprised you saw a significant difference in MP. Where did you have the tap? If it is in the runner I suspect you may be seeing velocity effects. I know you are aware of the importance of dynamic and static pressure in this situation so I was wondering how you arrived at the total pressure. Also surprised that the long runner did not cause any idle problems when using a carb. With the evaporative cooling in the runner, they sometimes freeze up and condensation of the mixture happens which can cause rough idle. The 2000 rpm idle helps there I guess. Tracy On Wed, Nov 5, 2008 at 9:40 AM, Richard Sohn wrote: > Another step in the right direction. > > In deciding which way to go with the intake for the single rotor, I ran two > tests. The first one with a short 8" long intake runner, and a second one > with a 24" runner. > The results are certainly not surprising, however, I had to check the > possible impact on idle characteristic. > Except for a different idle mixture setting, I was not able to detect a > difference in idle characteristics at 2000RPM. There is no need for lower > idle with a 3.33 : 1 gear ratio. If for any reason I want to go lower with > idle, I would have to increase the fly wheel inertia. With no load on the > engine it idles down to 1300RPM with the 8" runner. > The long runner also resulted in a 1" higher MAP over the short runner. > > The 24" runner as shown in the picture will in the final configuration be > at least 3" longer, because the carb has to com lower than it is now. > > The engine config is 12A rotor and housing using 1 1/2" p-port. > > The HP calculation is based on a bsfc of .5 . This is probably conservative > with EGT at 1700F and mixture ratio at 14.6 . > > Richard Sohn > N2071U > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html > > ------=_Part_4005_22911680.1225897741662 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Sounds good Richard.  But what about RPM delta at full throttle between the two different runner lengths?  That is the acid test for HP increase (with a prop load).  You are in the best possible position to test different runner lengths with that single runner manifold.  I give a lot to see a performance curve plot of different runner lengths in increments of 1" between 8 and 24".

I'm surprised you saw a significant difference in MP.  Where did you have the tap?  If it is in the runner I suspect you may be seeing velocity effects.  I know you are aware of the importance of dynamic and static pressure in this situation so I was wondering how you arrived at the total pressure.

Also surprised that the long runner did not cause any idle problems when using a carb.  With the evaporative cooling in the runner, they sometimes freeze up and condensation of the mixture happens which can cause rough idle.  The 2000 rpm idle helps there I guess.

Tracy

On Wed, Nov 5, 2008 at 9:40 AM, Richard Sohn <res12@fairpoint.net> wrote:
Another step in the right direction.
 
In deciding which way to go with the intake for the single rotor, I ran two tests. The first one with a short 8" long intake runner, and a second one with a 24" runner.
The results are certainly not surprising, however, I had to check the possible impact on idle characteristic.
Except for a different idle mixture setting, I was not able to detect a difference in idle characteristics at 2000RPM. There is no need for lower idle with a 3.33 : 1 gear ratio. If for any reason I want to go lower with idle, I would have to increase the fly wheel inertia. With no load on the engine it idles down to 1300RPM with the 8" runner.
The long runner also resulted in a 1" higher MAP over the short runner.
 
The 24" runner as shown in the picture will in the final configuration be at least 3" longer, because the carb has to com lower than it is now.
 
The engine config is 12A rotor and housing using 1 1/2" p-port.
 
The HP calculation is based on a bsfc of .5 . This is probably conservative with EGT at 1700F and mixture ratio at 14.6 .
 
Richard Sohn
N2071U

--
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