Return-Path: Received: from [65.54.169.162] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2944584 for flyrotary@lancaironline.net; Thu, 22 Jan 2004 18:46:23 -0500 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Thu, 22 Jan 2004 15:46:22 -0800 Received: from 67.25.179.60 by bay3-dav132.bay3.hotmail.com with DAV; Thu, 22 Jan 2004 23:46:22 +0000 X-Originating-IP: [67.25.179.60] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Torsionals Date: Thu, 22 Jan 2004 18:46:20 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00C5_01C3E118.06C62720" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Message-ID: X-OriginalArrivalTime: 22 Jan 2004 23:46:22.0938 (UTC) FILETIME=[F106BBA0:01C3E141] This is a multi-part message in MIME format. ------=_NextPart_000_00C5_01C3E118.06C62720 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable True, my redrive is definitely not tight. As Ed pointed out, it is much = lower in cost to engineer the resonant point lower rather than higher = like Powersport did. It also made field replacement of many of the = parts easy to do because I did not have to worry about the lash buildup = due to splines in the system. We changed the prop shaft on Chuck = Dunlops drive in about 30 minutes when he was here during a fly-in. I = wanted to check out some axial play in his front prop shaft bearing. = Turned out it was normal. The exact resonant point will vary depending on prop weight, length, = and even ignition timing at idle but generally it is around 800 rpm = which is well below idle rpm on my installation. Even when I = intentionally drop engine speed down to the resonant point the "rattle" = is much softer than what I had with the Ross drive. This is due to the = rubber damper and the hydraulic damping of the input shaft. Most of the = noise on the Ross was actually caused by the input shaft slaming back = and forth between bearing in redrive and the crankshaft of engine. =20 Tracy ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Thursday, January 22, 2004 10:39 AM Subject: [FlyRotary] Re: Torsionals Jim; I realize that these are relative terms, but my opinion is that = Tracy's re-drive would not be called "tight" tolerance. There is; what = - =BD back and forth play at the prop tip? As I recall, Tracy had given = this some consideration, and chose to keep the relatively "loose" = tolerance. Al Subject: [FlyRotary] Re: Torsionals Ed, Assuming (key word here) that Tracy's PSRU can be regarded as "tighter tolerances", mightn't rubber bushings effectively "loosen" the = tolerances and get us INto more trouble than they get us OUT of? Just wonderin' .... Jim S. Ed Anderson wrote: > Hi Greg, > > Welcome to the list. > > Torsional vibrations and resonance are a fairly complex topic. .. = In > generally tighter tolerances raises the resonant frequency of an = assembly > and looser tolerances lower it. Tighter tolerances are generally = more > expensive than looser. ...By the way, since the rotary does not = have a > negative torque region in its > power curve this problem is minimal and can generally be handled by = some > simple dampeners such as rubber disks, etc. > > Ed Anderson -- Jim Sower aka Destiny's Plaything ... Crossville, TN; Chapter 5 Long-EZ N83RT, Velocity N4095T >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_00C5_01C3E118.06C62720 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
True, my redrive is definitely not = tight.  As=20 Ed pointed out, it is much lower in cost to engineer the resonant point = lower=20 rather than higher like Powersport did.  It also made field=20 replacement of many of the parts easy to do because I did not have = to worry=20 about the lash buildup due to splines in the system.  We changed = the prop=20 shaft on Chuck Dunlops drive in about 30 minutes when he was here during = a=20 fly-in.  I wanted to check out some axial play in his front = prop shaft=20 bearing.  Turned out it was normal.
 
 The exact resonant point will = vary depending=20 on prop weight, length, and even ignition timing at idle but generally = it is=20 around 800 rpm which is well below idle rpm on my installation.  = Even when=20 I intentionally drop engine speed down to the resonant point the = "rattle" is=20 much softer than what I had with the Ross drive.  This is due to = the rubber=20 damper and the hydraulic damping of the input shaft.  Most of the = noise on=20 the Ross was actually caused by the input shaft slaming back and forth = between=20 bearing in redrive and the crankshaft of engine. 
 
Tracy
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Thursday, January 22, = 2004 10:39=20 AM
Subject: [FlyRotary] Re: = Torsionals

 

Jim;

 

I realize that these = are=20 relative terms, but my opinion is that Tracy=92s re-drive would not be called = =93tight=94=20 tolerance.  There is; what =96 =BD back and forth play at the = prop tip? =20 As I recall, Tracy had given this some consideration, and = chose to=20 keep the relatively =93loose=94 tolerance.

 

Al

 

Subject: [FlyRotary] Re: = Torsionals

 

Ed,

Assuming (key word here) that = Tracy's=20 PSRU can be regarded as "tighter

tolerances", mightn't rubber bushings = effectively=20 "loosen" the tolerances and

get us INto more trouble than they get us = OUT=20 of?

Just wonderin' .... Jim S.

 

Ed Anderson wrote:

 

> Hi Greg,

>

>    Welcome to the=20 list.

>

>  Torsional vibrations and = resonance are a=20 fairly complex topic.  ..  In

> generally tighter tolerances raises the = resonant=20 frequency of an assembly

> and looser tolerances lower it.  = Tighter=20 tolerances are generally more

> expensive than looser.  ...By the = way, since=20 the rotary does not have a

> negative torque region in = its

> power curve this problem is minimal and = can=20 generally be handled by some

> simple dampeners such as rubber disks,=20 etc.

>

> Ed Anderson

 

--

Jim Sower  aka  Destiny's = Plaything=20 ...

Crossville, TN; Chapter 5

Long-EZ N83RT, Velocity = N4095T

 

 

 

>>  Homepage: =20 http://www.flyrotary.com/

>>  Archive:  =20 = http://lancaironline.net/lists/flyrotary/List.html

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