X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from smtp1.av-mx.com ([137.118.16.57] verified) by logan.com (CommuniGate Pro SMTP 5.2.9) with ESMTP id 3273058 for flyrotary@lancaironline.net; Wed, 05 Nov 2008 14:17:21 -0500 Received-SPF: pass receiver=logan.com; client-ip=137.118.16.57; envelope-from=res12@fairpoint.net Received: from main (dblt-74-209-35-248.gtcom.net [74.209.35.248]) (Authenticated sender: res12@fairpoint.net) by smtp1.av-mx.com (Postfix) with ESMTP id BA520290500 for ; Wed, 5 Nov 2008 14:16:46 -0500 (EST) Message-ID: From: "Richard Sohn" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: single rotor performance Date: Wed, 5 Nov 2008 13:17:01 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00A9_01C93F48.C9AD9000" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5512 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_00A9_01C93F48.C9AD9000 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I think there are a few things that need clarification.=20 The lower RPM runs were not WOT! I just recorded those on the way up to = WOT, all at the same prop pitch. Meaning the only significant data point = is at 6000RPM, which I consider about static. For that reason, the power = level at those lower RPM are more reflecting the prop power demand than = anything else. As to the RPM difference, It may have been 100 or 150 RPM higher on the = long runner than on the short one(tach reading a bit iffy). There is = some thing else I ran into. All previous tests I ran with the prop = showed some intermittent prop noise, seemingly influenced by the wind = condition at testing time. This noise is very stady with the long = runner. It is acoustically so strong you think it is going to blow your = brains out. I could barely stand it until the fuel flow meter = stabilized.=20 I have observed that phenomenon with the same type or prop on the SOOB = at static runups. It seems that the increased power produced with the = long runner is consumed by a sudden drag increase in the prop. This prop = may just not be suitable for that kind of tests.=20 I will do further tests with different prop pitch, where the noise issue = is one thing I want to find out more. I may have to look for another prop. The MP is measured at the same location in both cases, about 1" from the = rotor housing. The pressure is picked up through a .035 hole. I guess I = should have said "MP" and not "MAP", sorry for that. Generally I am not very inclined to do a lot more basic performance = tests since the engine is already producing way more power than my test = bed needs for flying.=20 But that may change as I get further down the road.=20 Richard Sohn N2071U ----- Original Message -----=20 From: Tracy Crook=20 To: Rotary motors in aircraft=20 Sent: Wednesday, November 05, 2008 9:09 AM Subject: [FlyRotary] Re: single rotor performance 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.=20 The results are certainly not surprising, however, I had to check = the possible impact on idle characteristic.=20 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.=20 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.=20 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 -------------------------------------------------------------------------= ----- No virus found in this incoming message. Checked by AVG - http://www.avg.com=20 Version: 8.0.175 / Virus Database: 270.8.6/1769 - Release Date: = 11/5/2008 7:17 AM ------=_NextPart_000_00A9_01C93F48.C9AD9000 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
I think there are a few things that = need=20 clarification.
 
The lower RPM runs were not WOT! I just = recorded=20 those on the way up to WOT, all at the same prop pitch. Meaning the only = significant data point is at 6000RPM, which I consider about static. For = that=20 reason, the power level at those lower RPM are more reflecting the prop = power=20 demand than anything else.
 
As to the RPM difference, It may have = been 100 or=20 150 RPM higher on the long runner than on the short one(tach = reading a bit=20 iffy). There is some thing else I ran into. All previous tests I ran = with the=20 prop showed some intermittent prop noise, seemingly influenced by the = wind=20 condition at testing time. This noise is very stady with the long = runner. It is=20 acoustically so strong you think it is going to blow your brains out. I = could=20 barely stand it until the fuel flow meter stabilized.
I have observed that phenomenon with = the same type=20 or prop on the SOOB at static runups. It seems that the increased power = produced=20 with the long runner is consumed by a sudden drag increase in the prop. = This=20 prop may just not be suitable for that kind of tests.
I will do further tests with different = prop=20 pitch, where the noise issue is one thing I want to find out=20 more.
I may have to look for another = prop.
 
The MP is measured at the same location = in both=20 cases, about 1" from the rotor housing. The pressure is picked up = through a .035=20 hole. I guess I should have said "MP" and not "MAP", sorry for=20 that.
 
 
Generally I am not very inclined to do = a lot more=20 basic performance tests since the engine is already producing way more = power=20 than my test bed needs for flying.
But that may change as I get further = down the road.=20
 
Richard Sohn
N2071U
 
----- Original Message -----
From:=20 Tracy=20 Crook
Sent: Wednesday, November 05, = 2008 9:09=20 AM
Subject: [FlyRotary] Re: single = rotor=20 performance

Sounds good Richard.  But what about RPM delta at full = throttle=20 between the two different runner lengths?  That is the acid test = for HP=20 increase (with a prop load).  You are in the best possible = position to=20 test different runner lengths with that single runner manifold.  = I give a=20 lot to see a performance curve plot of different runner lengths in = increments=20 of 1" between 8 and 24".


I'm surprised you saw a significant difference = in=20 MP.  Where did you have the tap?  If it is in the runner I = suspect=20 you may be seeing velocity effects.  I know you are aware of the=20 importance of dynamic and static pressure in this situation so I was = wondering=20 how you arrived at the total pressure.

Also surprised that the = long=20 runner did not cause any idle problems when using a carb.  With = the=20 evaporative cooling in the runner, they sometimes freeze up and = condensation=20 of the mixture happens which can cause rough idle.  The 2000 rpm = idle=20 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=20 direction.
 
In deciding which way to go with = the intake for=20 the single rotor, I ran two tests. The first one with a short 8" = long intake=20 runner, and a second one with a 24" runner.
The results are certainly not = surprising,=20 however, I had to check the possible impact on idle characteristic.=20
Except for a different idle mixture = setting, I=20 was not able to detect a difference in idle characteristics at = 2000RPM.=20 There is no need for lower idle with a 3.33 : 1 gear ratio. If for = any=20 reason I want to go lower with idle, I would have to increase the = fly wheel=20 inertia. With no load on the engine it idles down to 1300RPM with = the 8"=20 runner.
The long runner also resulted in a = 1" higher=20 MAP over the short runner.
 
The 24" runner as shown in the = picture will in=20 the final configuration be at least 3" longer, because the carb has = to com=20 lower than it is now.
 
The engine config is 12A rotor and = housing=20 using 1 1/2" p-port.
 
The HP calculation is based on a = bsfc of .5 .=20 This is probably conservative with EGT at 1700F and mixture ratio at = 14.6=20 .
 
Richard=20 = Sohn
N2071U

--
Homepage: =  http://www.flyrotary.com/
Archive and UnSub: =   http://mail.lancaironline.net:81/lists/flyrotary/List.htm= l



No virus found in this incoming message.
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