X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.3) with ESMTP id 871591 for flyrotary@lancaironline.net; Sun, 11 Dec 2005 14:38:00 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.101; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-025-165.carolina.res.rr.com [24.74.25.165]) by ms-smtp-02-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id jBBJbC4p026754 for ; Sun, 11 Dec 2005 14:37:12 -0500 (EST) Message-ID: <000e01c5fe8a$4d868290$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Elippse Propeller Date: Sun, 11 Dec 2005 14:37:20 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000B_01C5FE60.646B5B40" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_000B_01C5FE60.646B5B40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Could be, Barry I start to lose track when loads change, rpm changes and fuel = consumption stays the same {:>). Burning the same fuel would certainly = imply producing the same HP (all other factors being constant). I have = recorded dozens of flights MP fuel flow and rpm, so should be able to = check back and find some apple and apple comparisons. You are right rpm is not the entire story as your example points out. = That is why its essentially useless to try and program the EC2 without a = prop load. RPM,airflow (manifold pressure) and fuel flow generally = tell the story (that's assuming you have the air flow/manifold pressure = to combust the fuel flow). ED ----- Original Message -----=20 From: Barry Gardner=20 To: Rotary motors in aircraft=20 Sent: Sunday, December 11, 2005 10:42 AM Subject: [FlyRotary] Re: Elippse Propeller Ed, If you're burning the same amount of fuel and the efficiency of your = engine hasn't changed (i.e., BSFC constant), doesn't that just mean that = you're producing the same horsepower at the higher RPM? That could be a = consistent finding if your manifold pressure is lower than it used to be = when you were running lower revs.=20 RPM isn't the whole story. For instance, one could race a car engine = in neutral at high RPMs but produce very little horsepower. It's the = reason that a dyno needs to put a load on the engine in order to = generate a meaningful horsepower/torque curve. Your advantage in running the higher RPMs is that you are in the = higher output part of your horsepower/torque curve when you are in = rev-limited situations like climbing or takeoff. And theoretically, if = allowed by your prop pitch, you could generate higher maximum horsepower = because you could get to the upper revs (e.g., 8500 or so) if you wanted = it, subject to the limit of your prop tip speed going supersonic. Barry Gardner Wheaton, IL Ed Anderson wrote:=20 Hi Todd, Actually, No - not anything significant. Although I now cruise at = 5600 rpm vice 5200 rpm with the 2.17 the fuel burn is identical. I = think the 2.85 puts less load on the engine permitting it to turn faster = at the same fuel burn. Just a theory. Ed ----- Original Message -----=20 From: Todd Bartrim=20 To: Rotary motors in aircraft=20 Sent: Sunday, December 11, 2005 3:06 AM Subject: [FlyRotary] Re: Elippse Propeller Hi Ed; I know that it has been stated in the past, but refresh my = memory. Have you observed any fuel consumption change from the 2.17 to = the 2.85???? Todd (tough game tonight, so too tired to check the archives) Also looking at the power difference at the two different rpms, = I calculate 160 at 5200 and 180HP at 6000, whether that is accurate = absolute power it shows a possible 12.5% increase. The disc area carved = out by the 74" prop is approx 18% more although its speed is approx 13% = less. So I think more area, more HP and more pitch appears to add up in = my case to considerably better low speed performance. The top speed = appears not to have changed, still a shade under 200 MPH around 197MPH = for both props. -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ ------=_NextPart_000_000B_01C5FE60.646B5B40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Could be, Barry
 
I start to lose track when loads change, rpm = changes and=20 fuel consumption stays the same {:>).  Burning the same fuel = would=20 certainly imply producing the same HP (all other factors being = constant). =20 I have recorded dozens of flights MP fuel flow and rpm, so should be = able to=20 check back and find some apple and apple comparisons.
 
You are right rpm is not the entire story as = your example=20 points out.  That is why its essentially useless to try and program = the EC2=20 without a prop load.   RPM,airflow (manifold pressure) =  and fuel=20 flow generally tell the story (that's assuming you have the air = flow/manifold=20 pressure to combust the fuel flow).
 
ED
----- Original Message -----
From:=20 Barry=20 Gardner
Sent: Sunday, December 11, 2005 = 10:42=20 AM
Subject: [FlyRotary] Re: = Elippse=20 Propeller

Ed,

If you're burning the same amount of fuel = and the=20 efficiency of your engine hasn't changed (i.e., BSFC constant), = doesn't that=20 just mean that you're producing the same horsepower at the higher RPM? = That=20 could be a consistent finding if your manifold pressure is lower than = it used=20 to be when you were running lower revs.

RPM isn't the whole = story. For=20 instance, one could race a car engine in neutral at high RPMs but = produce very=20 little horsepower. It's the reason that a dyno needs to put a load on = the=20 engine in order to generate a meaningful horsepower/torque = curve.

Your=20 advantage in running the higher RPMs is that you are in the higher = output part=20 of your horsepower/torque curve when you are in rev-limited situations = like=20 climbing or takeoff. And theoretically, if allowed by your prop pitch, = you=20 could generate higher maximum horsepower because you could get to the = upper=20 revs (e.g., 8500 or so) if you wanted it, subject to the limit of your = prop=20 tip speed going supersonic.

Barry Gardner
Wheaton,=20 IL



Ed Anderson wrote:=20
Hi Todd,
 
Actually, No - not anything = significant. =20 Although I now cruise at 5600 rpm vice 5200 rpm with the 2.17 the = fuel burn=20 is identical.  I think the 2.85 puts less load on the engine = permitting=20 it to turn faster at the same fuel burn.  Just a = theory.
 
Ed
-----=20 Original Message ----- From:=20 Todd=20 Bartrim To:=20 Rotary motors in = aircraft=20 Sent:=20 Sunday, December 11, 2005 3:06 AM Subject:=20 [FlyRotary] Re: Elippse Propeller

Hi Ed;
    I know that it has been stated in the = past, but=20 refresh my memory. Have you observed any fuel consumption change = from the=20 2.17 to the 2.85????
Todd    (tough game tonight, so too tired = to check=20 the archives)
 
Also looking at the power difference at = the two=20 different rpms, I calculate 160 at 5200 and 180HP at 6000, = whether that=20 is  accurate absolute power it shows a possible 12.5%=20 increase.  The disc area carved out by the 74" prop is = approx=20 18% more although its speed is approx 13% less.  So I=20 think more area, more HP and more pitch appears to add up = in my=20 case to considerably better low speed performance.  The top = speed=20 appears not to have changed, still a shade under 200 MPH around = 197MPH=20 for both props.
 

--

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