X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao101.cox.net ([68.230.241.45] verified) by logan.com (CommuniGate Pro SMTP 5.3.3) with ESMTP id 4151023 for flyrotary@lancaironline.net; Wed, 03 Mar 2010 14:06:27 -0500 Received-SPF: none receiver=logan.com; client-ip=68.230.241.45; envelope-from=alventures@cox.net Received: from fed1rmimpo02.cox.net ([70.169.32.72]) by fed1rmmtao101.cox.net (InterMail vM.8.00.01.00 201-2244-105-20090324) with ESMTP id <20100303190551.XLZR4995.fed1rmmtao101.cox.net@fed1rmimpo02.cox.net> for ; Wed, 3 Mar 2010 14:05:51 -0500 Received: from BigAl ([72.192.128.205]) by fed1rmimpo02.cox.net with bizsmtp id oj5r1d00J4S1t5C04j5rMQ; Wed, 03 Mar 2010 14:05:51 -0500 X-VR-Score: 0.00 X-Authority-Analysis: v=1.1 cv=zS9SgV63hfBKgCfMNmcWTXDxxMKGbBeTgNVRdCpsi3s= c=1 sm=1 a=Vegc0WxVmH5BHtpNDyThtA==:17 a=wy6nB6qx8L52d_v7w8YA:9 a=XobfO6NplCjkp-8jMFvi_BMuWZcA:4 a=qH6noaKk5WQhQfB0Le8A:9 a=RHWg5-nqtkMcEjDafpQA:7 a=956BUy9nwwRWbWypx9Sr69TfUKIA:4 a=Vegc0WxVmH5BHtpNDyThtA==:117 X-CM-Score: 0.00 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: single rotor Date: Wed, 3 Mar 2010 11:06:02 -0800 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0008_01CABAC1.83249E30" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6856 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Importance: Normal Thread-Index: Acq69bDVbx5xexzvSEmXvU3aGvGR+wADcuEg In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0008_01CABAC1.83249E30 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Looking at the two sizes of the engine, it takes 1.6 times as much horsepower to develop 1.18 times as much static thrust! Somehow this = does not compute for me..I always doubt the performance figures in a sales presentation and when they don't make sense to me...??? =20 Bill B (hoping this generates an educational experience for me :>) =20 =20 We're talking about the amount of force exerted by the prop with the = plane (motor) standing still. So, it seems to make sense to me that the power needed to accelerate the = air to generate the thrust would go as the cube root; and the cube root of = 1.6 is very close 1.18. =20 To move the amount of air it takes to generate the thrust certainly does take horsepower. Very much the same as the power it takes to drive the = pump (or generator) on a dyno. So I don't know how Tracy was interpreting = the question. =20 Al ------=_NextPart_000_0008_01CABAC1.83249E30 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Looking at the two sizes of the engine, it = takes 1.6 times as much horsepower to develop 1.18 times as much static = thrust!  Somehow this does not compute for me….I always doubt the = performance figures in a sales presentation and when they don’t make sense to me…..???

 

Bill B (hoping this generates an educational experience for me  :>) 

 

We’re talking about the = amount of force exerted by the prop with the plane (motor) standing = still.

So, it seems to make sense to me = that the power needed to accelerate the air to generate the thrust would go = as the cube root; and the cube root of 1.6 is very close 1.18.

 

To move the amount of air it = takes to generate the thrust certainly does take horsepower.  Very much the = same as the power = it takes to drive the pump (or generator) on a dyno.  So I don’t know = how Tracy was = interpreting the question.

 

Al

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