I had Les Palmers do that on first flight and the wheel pants just 
dicetagrated. He added a couple of washers and used a tighter spring, never 
happened again and I have had that plane at 100 mph on the runway, Down wind 
engine out.

--- On Sat, 4/25/09, Mark Langford <n5...@hiwaay.net> wrote:

From: Mark Langford <n5...@hiwaay.net>
Subject: Re: KR> RE: KR nose wheel shimmy
To: "KRnet" <kr...@mylist.net>
List-Post: krnet@list.krnet.org
Date: Saturday, April 25, 2009, 5:52 AM

Mark W wrote:

> If the caster angle and wheel & tire balance are right, you
shouldn't have
> this problem... think GM/Ford/Chrysler front end alignment... not shopping
> cart. I've yet to see a Corvette experience 'shimmy' at speeds
exceeding
> anything a KR would land at.

I would have to disagree with that.  You can have a perfectly balanced 
wheel/tire, but external forces such as which way the wheel is pointed at 
touchdown, or even which way the wind is blowing, can get the shimmy 
started.  That's a side to side phenomenon, not a "perpendicular to
the 
axis" thing.  But it's really a matter of insufficient damping, which
is the 
real cure for a shimmy like that, regardless of what got it started.

There's an aerodynamic effect (it has a name but it's been 10 years
since I 
read about it) which describes how this oscillation happens to aero 
controls, or even stop signs in a high wind...similar to flutter.  Damping 
is the key to fixing it, not balance.  Stop signs have no damping, just a 
metal post which acts a spring to help perpetuate it.  Diehl accounts for 
damping through washers or something, and as mentioned, there's an 
adjustment/cure.  If that were my plane I'd have that nose gear off and be 
checking for cracks and wallowed out attachment points though....


Mark Langford
N56ML "at" hiwaay.net
website at http://www.N56ML.com



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