X-Virus-Scanned: clean according to Sophos on Logan.com
Return-Path: <ceengland@bellsouth.net>
Received: from imf18aec.mail.bellsouth.net ([205.152.59.66] verified)
  by logan.com (CommuniGate Pro SMTP 5.1.9)
  with ESMTP id 2086421 for flyrotary@lancaironline.net; Tue, 05 Jun 2007 22:46:27 -0400
Received-SPF: pass
 receiver=logan.com; client-ip=205.152.59.66; envelope-from=ceengland@bellsouth.net
Received: from ibm61aec.bellsouth.net ([216.76.224.196])
          by imf18aec.mail.bellsouth.net with ESMTP
          id <20070606024550.JXLP11571.imf18aec.mail.bellsouth.net@ibm61aec.bellsouth.net>
          for <flyrotary@lancaironline.net>; Tue, 5 Jun 2007 22:45:50 -0400
Received: from [216.76.224.196] by ibm61aec.bellsouth.net with ESMTP
          id <20070606024549.PXQC25479.ibm61aec.bellsouth.net@[216.76.224.196]>
          for <flyrotary@lancaironline.net>; Tue, 5 Jun 2007 22:45:49 -0400
Message-ID: <46661FDB.8040404@bellsouth.net>
Date: Tue, 05 Jun 2007 21:45:47 -0500
From: Charlie England <ceengland@bellsouth.net>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.2) Gecko/20070222 SeaMonkey/1.1.1
MIME-Version: 1.0
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Single rotor video
References: <list-2086368@logan.com>
In-Reply-To: <list-2086368@logan.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

Russell Duffy wrote:
> Greetings,
>  
> Thanks for all the comments, but I do think some of you are getting a 
> bit ahead of me on this :-)  The following are mostly random thoughts.
>  
> The phenomenon is really amazing to me, but until more combinations are 
> tested, I'm not sure if it's even a problem.  My gut feeling is that it 
> happens to some extent with any flexible prop, and requires some 
> instability in thrust to set it off.  Low rpms and changing speeds seem 
> to set it off for sure.  IVO props are more flexible, and have an even 
> worse problem, but the only caution is to allow 5" clearance at the tips 
> of the IVO so it won't hit anything.  Even with that clearance, my old 
> IVO on the Kolb hit the back of the fuselage cage on startup one 
> day.  They flex a LOT. 
>  
> Common sense would dictate that too much of this flexing is clearly not 
> good, and a line will have to be drawn before prop, or engine damage is 
> done, but who can say where that line needs to be without a ton of 
> testing?    
>  
> A single rotor Mazda (without a flywheel) has to be about the worst 
> case, because it's got a big powerful combustion chamber.  Rotax had 
> plenty of single cylinder engines, but at most, they were half the size 
> of the single Mazda chamber.  By the time any "normal" engine gets to 
> the displacement of the single rotor Mazda, it's got at least two 
> cylinders to help smooth things out.  Clearly, what we need is a 2 or 3 
> rotor engine that's sized to make an easy 100 HP. 
>  
> My goal will be to re-video the current configuration, perhaps with a 
> yardstick or some other markings in the picture for scale.  I'll zoom it 
> more to get just the engine and prop, for more detail.  I might even use 
> the real video camera instead of my Cannon PowerShot 3 :-)  I'll video 
> set rpms from about 2000 to maybe 5000, depending on how brave I feel 
> about my trailer stand.  Not sure when this will happen, as I'll be out 
> of town for a few days getting dual in a similar gyro (nice try Lynn <g>).  
>  
> I smell fajitas, and my beer is empty.  Gotta go :-) 
>  
> Rusty
>  
> 
Might be worthwhile to put the trailer on blocks (yes, I'm from 
Mississippi) and tie it down if you want realistic info. It wouldn't be 
too surprising to find that you're getting the same kind of low 
frequency resonance effect you get in a V-8 car letting it 'lug' in hi 
gear, where it lurches with each power pulse as all the drive train 
components wind up & unwind.

Charlie