X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.122] verified) by logan.com (CommuniGate Pro SMTP 5.3.9) with ESMTP id 4498854 for flyrotary@lancaironline.net; Fri, 08 Oct 2010 17:18:30 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.122; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=1.1 cv=UAZ0ep3suvkVn+xl78ZyFqEJZfCyw4fsauT9kMdOA88= c=1 sm=0 a=-FbNrU69mQEA:10 a=rPkcCx1H5rrOSfN0dPC7kw==:17 a=arxwEM4EAAAA:8 a=r1ClD_H3AAAA:8 a=GMhzFt1iOFsePrJbvuoA:9 a=-EwH1CdkpOpVAiU1jx9Dgamf9J0A:4 a=pILNOxqGKmIA:10 a=oxNrwmvGM2bocBam:21 a=9BzUBH0TkH7BO5zZ:21 a=E93lBu2AAAAA:8 a=8UDeC92688M9dMyUTi8A:9 a=9gOJ-XnJMN-WVdWPTDgA:7 a=PF2Rmg47xHgTYrQ86tRM9qYIkU8A:4 a=hO30gm18fF0A:10 a=MpuOTR30KwMA:10 a=FOUTPhXFUAcA:10 a=zgjei8Deq7QA:10 a=NWVoK91CQyQA:10 a=rPkcCx1H5rrOSfN0dPC7kw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.167.5 Received: from [174.110.167.5] ([174.110.167.5:58055] helo=EdPC) by cdptpa-oedge04.mail.rr.com (envelope-from ) (ecelerity 2.2.2.39 r()) with ESMTP id F8/7C-03860-18A8FAC4; Fri, 08 Oct 2010 21:17:53 +0000 Message-ID: <63EBC023F4424491B7446DD1F5560426@EdPC> From: "Ed Anderson" To: "Rotary motors in aircraft" Subject: Rule of Thumb Prop Diameter? Date: Fri, 8 Oct 2010 17:17:45 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0037_01CB670C.B9589590" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_0037_01CB670C.B9589590 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Fixed pitch With this (fixed) propeller the blades are fixed and cannot move = (except rotate), thus propeller blade angle is fixed (but the blade = angle changes from the root to the tip as explained above). It can be = seen that there is also one RPM / airspeed combination where the = propeller is operating at its optimum angle of attack and produces its = maximum thrust. On all other airspeeds (or conditions of flight) there = is less thrust available from the propeller. In other words, its = effective angle of attack depends on RPM and airspeed. some rule of thumb equations for relating HP and prop diameter, I found = cruising the internet. Two-blade: d =3D 22 x fourth root of (HP) Three-blade: d =3D 18 x fourth root of (HP) Using these two relationships (no ideal how valid the relationship - for = one thing no indication of the effect of chord which we have found to be = considerable) here are some of the blade dimensions that result 2 blade=20 =20 3 blade=20 HP D inches=20 D inches=20 150 76.99=20 62.99=20 160 78.24=20 64.02=20 170 79.44=20 65=20 180 80.58=20 65.93=20 190 81.68=20 66.83=20 200 82.73=20 67.69=20 210 83.75=20 68.52=20 220 84.73=20 69.32=20 230 85.68=20 70.1=20 Edward L. Anderson Anderson Electronic Enterprises LLC 305 Reefton Road Weddington, NC 28104 http://www.andersonee.com http://www.eicommander.com ------=_NextPart_000_0037_01CB670C.B9589590 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
 

Fixed pitch

With this (fixed)  propeller the = blades=20 are fixed and cannot move (except rotate), thus propeller blade=20 angle is fixed (but the blade angle changes from the root to the tip as=20 explained above). It can be seen that there is also one RPM / = airspeed=20 combination where the propeller is=20 operating at its optimum angle of attack and produces its maximum thrust. On = all other=20 airspeeds (or conditions of flight) there is less thrust = available from=20 the propeller. In=20 other words, its effective angle of attack depends on RPM and=20 airspeed.

some rule of thumb equations for relating HP and = prop=20 diameter, I found cruising the internet.
 
Two-blade:      d =3D = 22 x fourth=20 root of (HP)
Three-blade:    d =3D 18 x fourth root of = (HP)
Using these two relationships (no ideal = how valid the=20 relationship - for one thing no indication of the effect of chord which = we have=20 found to be considerable) here are some of the blade dimensions = that result=20
2 blade

3 blade
HP D inches
D inches
150 76.99
62.99
160 78.24
64.02
170 79.44
65
180 80.58
65.93
190 81.68
66.83
200 82.73
67.69
210 83.75
68.52
220 84.73
69.32
230 85.68
70.1
 
Edward L. Anderson
Anderson Electronic = Enterprises=20 LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com
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