X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.4) with ESMTP id 889172 for flyrotary@lancaironline.net; Mon, 19 Dec 2005 20:26:13 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.100; 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-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id jBK1PMWe020474 for ; Mon, 19 Dec 2005 20:25:22 -0500 (EST) Message-ID: <000f01c60504$40566650$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Props Date: Mon, 19 Dec 2005 20:25:23 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000C_01C604DA.572A7620" 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_000C_01C604DA.572A7620 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Bully, the formula's correct. However, you must put in the rpm of the = prop - not the engine which in our case means we need to simply divide = whatever answer you got with the formula by 2.17 I get 772 ft/sec for a 64" dia prop with engine turning at 6000 rpm with = a 2.17 So formula for us should be tip speed =3D (Dia" *3.1416* = rpm/(12*60))/2.17 or whatever your gear ratio is. Ed ----- Original Message -----=20 From: Bulent Aliev=20 To: Rotary motors in aircraft=20 Sent: Monday, December 19, 2005 6:44 PM Subject: [FlyRotary] Re: Props Thanks Dave. it makes me feel better now that I know I was wrong. My = problem now is: I can spin my "monster prop" (static) up-to 4000RPM and = 50" MP I don't think I can get much more in motion and may not get = enough rpm for flight. I'll see first how much difference it will make = on fast taxi. John Slade also will bring his Performance prop one day, = so we can compare them. BTW the prop tip speed formula given to me was: Prop D" x 3.1416 x RPM divided by 720 Buly On Dec 19, 2005, at 6:06 PM, David Leonard wrote: Oh, BTW Bully. You will also note that at 6000 RPM the prop is = doing 2750 which a lot of certified props will turn, even if 74"long. Also, short prop are not necessarily less efficient, its just that = the speed of peak efficiency is shifted to a higher airspeed, and = probably that peak is a little more narrow. Dave Leonard =20 On 12/19/05, Buly wrote:=20 Yesterday somebody gave me the formulas to calculate the prop tip speed. I did some calculations and looks like us with the 2.17 redrives are kind of painted in the corner. Hope I'm wrong, but if = I want to keep the tips from going supersonic, I have to cut down = the prop to 64" or keep the engine below 5500 RPM. The choice is = either=20 inefficient prop and adequate power, or efficient long prop and = not getting all the power from the engine? Am I wrong? Buly atlasyts@bellsouth.net -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net/lists/flyrotary/ --=20 Dave Leonard Turbo Rotary RV-6 N4VY http://members.aol.com/_ht_a/rotaryroster/index.html http://members.aol.com/_ht_a/vp4skydoc/index.html Bulent Aliev atlasyts@bellsouth.net = http://home.bellsouth.net/p/s/community.dll?ep=3D16&ext=3D1&groupid=3D164= 323&ck=3D ------=_NextPart_000_000C_01C604DA.572A7620 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Bully, the formula's correct.  However, you = must put=20 in the rpm of the prop - not the engine which in our case means we = need=20 to  simply divide whatever answer you got with the formula by=20 2.17
 
I get 772 ft/sec for a 64" dia prop with engine = turning at=20 6000 rpm with a 2.17
 
So formula for us should be tip speed =3D (Dia" = *3.1416*=20 rpm/(12*60))/2.17 or whatever your gear ratio is.
 
Ed
----- Original Message -----
From:=20 Bulent=20 Aliev
Sent: Monday, December 19, 2005 = 6:44=20 PM
Subject: [FlyRotary] Re: = Props

Thanks Dave. it makes me feel better now that I know I = was=20 wrong. My problem now is: I can spin my "monster prop" (static) up-to = 4000RPM=20 and 50" MP I don't think I can get much more in motion and may not get = enough=20 rpm for flight. I'll see first how much difference it will make on = fast taxi.=20 John Slade also will bring his Performance prop one day, so we can = compare=20 them.
BTW the prop tip speed formula given to me was:
Prop D" x 3.1416 x RPM divided by 720
Buly

On Dec 19, 2005, at 6:06 PM, David Leonard wrote:
Oh, BTW Bully.  You will also note that at 6000 RPM the = prop is=20 doing 2750 which a lot of certified props will turn, even if = 74"long.
 
Also, short prop are not necessarily less efficient, its just = that the=20 speed of peak efficiency is shifted to a higher airspeed, and = probably that=20 peak is a little more narrow.
 
Dave Leonard

 
On 12/19/05, Buly=20 <atlasyts@bellsouth.net>=20 wrote:=20
Yesterday=20 somebody gave me the formulas to calculate the prop tip
speed. = I did=20 some calculations and looks like us with the 2.17
redrives are = kind of=20 painted in the corner. Hope I'm wrong, but if I
want to keep = the tips=20 from going supersonic, I have to cut down the
prop to 64" or = keep the=20 engine below 5500 RPM. The choice is either
inefficient prop = and=20 adequate power, or efficient long prop and not
getting all the = power=20 from the engine? Am I wrong?
Buly
atlasyts@bellsouth.net

=


--
Homepage:  http://www.flyrotary.com/
Archi= ve=20 and UnSub:   http://mail.lanca= ironline.net/lists/flyrotary/


--
Dave Leonard
Turbo Rotary RV-6 N4VY
http://memb= ers.aol.com/_ht_a/rotaryroster/index.html
http://members= .aol.com/_ht_a/vp4skydoc/index.html

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

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