X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail03.syd.optusnet.com.au ([211.29.132.184] verified) by logan.com (CommuniGate Pro SMTP 5.0.4) with ESMTPS id 892277 for flyrotary@lancaironline.net; Thu, 22 Dec 2005 04:46:25 -0500 Received-SPF: none receiver=logan.com; client-ip=211.29.132.184; envelope-from=lendich@optusnet.com.au Received: from george (d58-105-117-19.dsl.nsw.optusnet.com.au [58.105.117.19]) by mail03.syd.optusnet.com.au (8.12.11/8.12.11) with SMTP id jBM9jUoH026723 for ; Thu, 22 Dec 2005 20:45:34 +1100 Message-ID: <001a01c606dc$74af11c0$1375693a@george> From: "george lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Props Date: Thu, 22 Dec 2005 19:45:33 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0017_01C60730.45746B40" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 This is a multi-part message in MIME format. ------=_NextPart_000_0017_01C60730.45746B40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Thanks Ed, I like to reduce things down to the simplest formula, provided one = doesn't lose track of what's relevant. So I guess I should look at this as 100 % theoretically efficient - = whereas we may be looking at only 80 % efficiency ( in real terms), Do = you agree with 80%? However your saying that the lift may give more speed ( MPH, in real = terms) - So are you suggesting that these two (variables) may balance = out? Or should we use a fudge factor, and that could be what? I'm not looking for a finite answer, just close enough to be able to = access the experts opinion, and we all know what an expert is - " A drip = under pressure". George (down under) Yes, George. If we assumed no slip in the prop then theoretically the = formula will give you the pitch of the prop you would need to screw = through the air and achieve your MPH at your RPM input. This is based = simply on the screw principal. I am certainly not a prop expert, but I = also believe that since the prop is a spinning wing (airfoil), that = there is a lift component in the direction of flight which may result = in more speed than the formula could account for. =20 Your second equation can be reduced further from = (Inches/Minute)/(RPM) =3D (Inches/Minute)/(Revs/Minute) =3D inches/Rev Ed A ----- Original Message -----=20 From: Bulent Aliev=20 To: Rotary motors in aircraft=20 Sent: Wednesday, December 21, 2005 7:08 PM Subject: [FlyRotary] Re: Props Don't ask me George. I'm not an engineer or good with mathematics. = Ed A will know better.=20 Buly On Dec 21, 2005, at 6:20 PM, george lendich wrote: Thanks Buly, So, Pitch" =3D MPH x12 x 5280 RPM x 60 I figure 12 (inches in a foot) and 5280 ( feet in a mile) and 60 ( = minute in an hour). So the top line is converted into inches per minute and the bottom = line RPM. So, Pitch " =3D inches per minute RPM Does that look right to you ? George ( down under) Thanks George. my mistake was that i did not convert it to MPH. I was also given the formula for cruise speed: Pitch" x RPM x 60 =3D MPH 12 x 5280 Buly On Dec 21, 2005, at 4:39 PM, george lendich wrote: Buly, Looking at the formula given by members on this list, 2 out of = 3 were spot on with Hoverhawk and the third was close. Examples: 1. Prop Dia x 3.1416x RPM/ 720 - Correct! 2. Prop RPM x Dia x .00436 - Correct ( 3.14/ 720 =3D.00436) 3. 3.14 x 64 {given prop dia} ( 5500/2.17 {given RPM})=3D = 508346/707 - slightly incorrect ( as compared to the other 3 examples, = which include Hoverhawk) i.e 3.14/ 707 =3D .004809 whereas all the others are 3.14/ 720 = =3D .00436. Now that I have that sorted - can someone tell me how to = calculate pitch, easily!! George ( down under) Thanks Perry. This makes me feel much better. Looks like the = formulas given to me were not good. Buly On Dec 19, 2005, at 2:00 PM, Perry Casson wrote: I think your math is off a bit - Here's a online = calculator http:// www.hoverhawk.com/propspd.html I think 6900 puts a 72" prop close to mach 0.9 but I've = never ran mine above 6500 Perry Casson -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net/lists/flyrotary/ Buly atlasyts@bellsouth.net -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net/lists/flyrotary/ -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net/lists/flyrotary/ Bulent "Buly" Aliev = http://home.bellsouth.net/p/s/community.dll?ep=3D16&ext=3D1&groupid=3D164= 323&ck=3D Bulent "Buly" Aliev = http://home.bellsouth.net/p/s/community.dll?ep=3D16&ext=3D1&groupid=3D164= 323&ck=3D ------=_NextPart_000_0017_01C60730.45746B40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Thanks Ed,
I like to reduce things down to the = simplest=20 formula, provided one doesn't lose track of what's = relevant.
So I guess I should look at this as 100 = %=20 theoretically efficient - whereas we may be looking at only 80 % = efficiency ( in=20 real terms), Do you agree with 80%?
However your saying that the = lift may give=20 more speed ( MPH, in real terms) - So are you suggesting that these = two=20 (variables) may balance out?
 
Or should we use a fudge factor, and = that could be=20 what?
 
I'm not looking for a finite = answer, just=20 close enough to be able to access the experts opinion, and we all know = what an=20 expert is - " A drip under pressure".
 
George (down under)
Yes, George.  If we assumed no slip in = the prop=20 then theoretically the formula will give you the pitch of the prop you = would=20 need to screw through the air and achieve your MPH at your RPM = input. =20 This is based simply on the screw principal.  I am certainly not = a prop=20 expert, but I also believe that since the prop is  a spinning = wing=20 (airfoil), that there is a lift component  in the direction of = flight=20 which may result in more speed than the formula could account = for.  =20
 
Your second equation can be reduced further = from  =20 (Inches/Minute)/(RPM) =3D (Inches/Minute)/(Revs/Minute) =3D=20 inches/Rev
 
Ed A
 
 
----- Original Message -----
From:=20 Bulent=20 Aliev
To: Rotary motors in = aircraft=20
Sent: Wednesday, December 21, = 2005 7:08=20 PM
Subject: [FlyRotary] Re: = Props

Don't ask me George. I'm not an engineer or good with = mathematics. Ed A will know better.=20
Buly
On Dec 21, 2005, at 6:20 PM, george lendich wrote:
Thanks=20 Buly,
So, Pitch"  =3D = MPH=20 x12 x 5280
           =       =20  RPM x 60
I figure 12 (inches = in a foot)=20 and 5280 ( feet in a mile) and 60 ( minute in an=20 hour).
So the top line is = converted=20 into inches per minute and the bottom line = RPM.
 
So, Pitch " =3D = inches=20 per minute
           =         =20 RPM
 
Does that = look right to=20 you ?
George ( down=20 under)
 
 
Thanks George. my mistake was that i did not convert it to = MPH.
I was also given the formula for cruise speed:

Pitch" x = RPM x=20 60  =3D MPH
       12 x 5280

Buly
On Dec 21, 2005, at 4:39 PM, george lendich wrote:

Buly,
Looking = at the=20 formula given by members on this list, 2 out of 3 were=20 spot
on with = Hoverhawk=20 and the third was close.
Examples:
1. Prop = Dia x=20 3.1416x RPM/ 720 - Correct!
2. Prop = RPM x Dia x=20 .00436 - Correct ( 3.14/ 720 =3D.00436)
3. 3.14 = x 64 {given=20 prop dia} ( 5500/2.17 {given RPM})=3D 508346/707 = -
slightly incorrect=20 ( as compared to the other 3 examples, which = include
Hoverhawk)
i.e = 3.14/ 707 =3D=20 .004809 whereas all the others are 3.14/ 720 =3D = .00436.
Now = that I have=20 that sorted - can someone tell me how to calculate = pitch,
easily!!
George = ( down=20 under)
Thanks Perry.=20 This makes me feel much better. Looks like the = formulas
given = to me were=20 not good.
Buly
On = Dec 19, 2005,=20 at 2:00 PM, Perry Casson wrote:
I = think your=20 math is off a bit - Here's a online calculator=20 http://
www.hoverhawk.com/propspd.html
I = think 6900=20 puts a 72" prop close to  mach = 0.9 but=20 I've never ran
mine = above=20 6500
Perry=20 Casson
--
Homepage:  http://www.flyrotary.com/
Archive and=20 UnSub:  =20 http://mail.lancaironline.net/lists/flyrotary/
Buly
atlasyts@bellsouth.net
--
Homepage:  http://www.flyrotary.com/
Archive and=20 UnSub:  =20 http://mail.lancaironline.net/lists/flyrotary/
--
Homepage:  http://www.flyrotary.com/
Archive = and UnSub:=20   http://mail.lancaironline.net/lists/flyrotary/

Bulent "Buly" Aliev

http://home.bellsouth.net/p/s/community.dll?ep=3D16&ext=3D= 1&groupid=3D164323&ck=3D


Bulent "Buly" Aliev

http://home.bellsouth.net/p/s/community.dl= l?ep=3D16&ext=3D1&groupid=3D164323&ck=3D

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