X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost01.isp.att.net ([204.127.217.101] verified) by logan.com (CommuniGate Pro SMTP 5.3.8) with ESMTP id 4439956 for flyrotary@lancaironline.net; Sun, 22 Aug 2010 13:24:02 -0400 Received-SPF: none receiver=logan.com; client-ip=204.127.217.101; envelope-from=bbradburry@bellsouth.net Received: from desktop (adsl-85-109-27.mco.bellsouth.net[98.85.109.27]) by isp.att.net (frfwmhc01) with SMTP id <20100822172323H0100dndrce>; Sun, 22 Aug 2010 17:23:23 +0000 X-Originating-IP: [98.85.109.27] From: "Bill Bradburry" To: "'Rotary motors in aircraft'" References: In-Reply-To: Subject: RE: [FlyRotary] Re: Prop orientation with TDC Date: Sun, 22 Aug 2010 13:23:23 -0400 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0016_01CB41FD.32D98A80" X-Mailer: Microsoft Office Outlook 11 Thread-Index: ActCDuISaVdvvacTRHSz8cUbyfM3dgAD2X/Q X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6001.18049 This is a multi-part message in MIME format. ------=_NextPart_000_0016_01CB41FD.32D98A80 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Can some of you more "experienced" folks tell me..does the prop windmill after the engine quits, or does it stop rotating? Bill B _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Lehanover@aol.com Sent: Sunday, August 22, 2010 11:29 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Prop orientation with TDC In a message dated 8/22/2010 10:28:20 A.M. Eastern Standard Time, blake.lewis@gmail.com writes: On Sat, Aug 21, 2010 at 7:34 AM, Jeff Whaley wrote: > What is the Rotaries best prop orientation at the prop flange relative to TDC? > The Lycomings are typically entering the compression stroke at 11-10 o'clock and 5-4 o'clock. > The 13B goes through 3 compression strokes per e-shaft revolution - does this predicate a 3-bladed prop is the ideal match? > Jeff The orientation idea comes from the older 4 cylinder airplane engines that had to be hand started. So the position of the blade made a difference in that the person starting the engine needed a good body position to start out. It was also a good idea, because in the event of an engine stoppage, that very same position had the prop near horizontal, and that kept a blade from digging in on landing. In the rotary powered craft, the engine will be at TDC twice per crank shaft rotation (for a two rotor) so, 2 times the reduction ratio tells you how many times it gets to TDC per propeller revolution. 3 times for a 3 rotor, and 4 times for a 4 rotor. A 2 rotor with a 2.78:1 reduction unit will see TDC 2 X 2.78 = 5.56 or about every 65 degrees of prop rotation. This suggests that hand propping might be more difficult because of the mechanical disadvantage of the reduction unit, and should the engine fire, the length of time available to remove your hand might be very short, should the very next rotor face fire as well. Lynn E. Hanover ------=_NextPart_000_0016_01CB41FD.32D98A80 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Can some of you more = “experienced” folks tell me..does the prop windmill after the engine quits, or does it = stop rotating?

 

Bill B

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Lehanover@aol.com
Sent: Sunday, August 22, = 2010 11:29 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = Prop orientation with TDC

 

In a message dated 8/22/2010 = 10:28:20 A.M. Eastern Standard Time, blake.lewis@gmail.com = writes:

On Sat, Aug 21, 2010 at 7:34 AM, = Jeff Whaley <jwhaley@datacast.com> wrote:
> What is the Rotaries best prop orientation at the prop flange = relative to TDC?
> The Lycomings are typically entering the compression stroke at = 11-10 o'clock and 5-4 o'clock.
> The 13B goes through 3 compression strokes per e-shaft revolution - = does this predicate a 3-bladed prop is the ideal match?
> Jeff

The orientation idea comes from = the older 4 cylinder airplane engines that had to be hand started. So the position = of the blade made a difference in that the person starting the engine needed a = good body position to start out. It was also a good idea, because in the = event of an engine stoppage, that very same position had the prop near horizontal, = and that kept a blade from digging in on landing.

 

=

In the rotary powered craft, the = engine will be at TDC twice per crank shaft rotation (for a two rotor) so, 2 = times the reduction ratio tells you how many times it gets to TDC per propeller revolution. 3 times for a 3 rotor, and 4 times for a 4 rotor. =

 

=

A 2 rotor with a 2.78:1 reduction = unit will see TDC 2 X 2.78 =3D 5.56 or about every 65 degrees of prop = rotation. 

 

=

This suggests that hand propping = might be more difficult because of the mechanical disadvantage of the reduction = unit, and should the engine fire, the length of time available to remove your = hand might be very short, should the very next rotor face fire as well. =

 

=

Lynn E. = Hanover 

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