Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2942724 for flyrotary@lancaironline.net; Wed, 21 Jan 2004 20:26:15 -0500 Received: from edward (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i0M1Q8KZ020449 for ; Wed, 21 Jan 2004 20:26:09 -0500 (EST) Message-ID: <009e01c3e086$bb721040$2402a8c0@edward> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Torsionals Date: Wed, 21 Jan 2004 20:26:16 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit 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 X-Virus-Scanned: Symantec AntiVirus Scan Engine Hi Greg, Welcome to the list. Torsional vibrations and resonance are a fairly complex topic. Any rotating assembly has physical characteristics that together with the parameters of force driving it determine whether there is a problem. Since any rotating assembly has a torsional resonance frequency, the secret is to design the system such that the resonant frequency is NOT in you operating frequency (RPM). There appears to be two basic design approaches in achieving this. In generally tighter tolerances raises the resonant frequency of an assembly and looser tolerances lower it. Tighter tolerances are generally more expensive than looser. Both design approaches work so long as it keeps the resonance frequency out of your operating range. But, before I expose even more of my ignorance on the topic here is a site that has some good discussions about PSRUs. http://www.epi-eng.com/GBX_TOC.htm#CONTENTS 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 RV-6A N494BW Rotary Powered Matthews, NC ----- Original Message ----- From: "Greg Fuess" To: "Rotary motors in aircraft" Sent: Wednesday, January 21, 2004 6:55 PM Subject: [FlyRotary] Torsionals > Hello Fellow Rotary Enthusiasts, > > As a new member of this list, and to rotaries in general, have any of you > guys considered torsional vibrations with regards to the rotary, PSRU and > propeller combinations? > > There is a lot of discussion about this on another site, and since I am > considering the rotary, thought I would go to the source. > > Appreciate any feedback or direction to information. > > Regards, > > Greg Fuess > > > > >> Homepage: http://www.flyrotary.com/ > >> Archive: http://lancaironline.net/lists/flyrotary/List.html >