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" <gregory_fuess@yahoo.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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
>
>
>
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