Mailing List lml@lancaironline.net Message #31918
From: <Sky2high@aol.com>
Sender: <marv@lancaironline.net>
Subject: Re: [LML] Re: LNC2 elevator hinges
Date: Fri, 16 Sep 2005 22:18:36 -0400
To: <lml@lancaironline.net>
In a message dated 9/16/2005 8:51:10 P.M. Central Standard Time, marv@lancaironline.net writes:
Excessive wear is the very nature of aluminum in a hinge environment.  The
  wear is not on the pin, but rather on the inside diameter of the hinge
  itself.  Aluminum is a relatively soft material and it corrodes easily.
  Logically as the aluminum wears away on the inside diameter that houses the
  pin, you would conclude that the slop would increase over time.  Flutter is
  caused by unbalanced control surfaces.  I don't think loose pins would
  necessarily lead to flutter, but perhaps, if there is a minor imbalance,
  movement allowed between the control surface and airframe via a sloppy
  fitting hinge could move you closer to destructive flutter.
John,
 
The issue of hinge looseness is not about flutter per se.  It doesn't take much looseness in the LNC2 aileron hinges to be reflected in the "lash" in what should be a very tight system.  With tight hinges, if one clamps one aileron and moves the other, one would see 1/8 to 1/4 inch of movement, a measure of the lash inherent in any system consisting of 2 times several push-rods with bearing rod ends, bell cranks with bearing pivots and hinges that are another pivot point.  With loose hinges alone (my airplane, prior pins) that lash could be 1/2" to 5/8", depending on how much force is applied.  One compensation for any lash is to rig the ailerons a bit high so as to put a wee air load on both, thus eliminating sloppy movement that could be potentially excited by airframe vibration.  For me, another assist is the use of a servo driven spring trim system which also places a small tension on the aileron control system.
 
I am not experiencing "flutter" at the outboard elevator hinges, but a peculiar movement that excites the horizontal stab.
 
If carbhinges would have been available when I was building the wings (Um, 1991-92) I would have considered them although my education took flight only after flight.  I would not consider installing them now, after the paint has dried.  I would rather like to investigate my minor "problem."
 
 
Scott Krueger AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)



Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster