REFLECTOR: wheel shimmy

Chuck Jensen cjensen at dts9000.com
Fri Feb 20 06:08:15 CST 2009


While I haven't tried the dampner, I like the wheel lock for its simplicity, clean look and straightforward functionality.  If a pilot cannot master the act of remembering to engage the nose wheel lock when lined up for TO, then there are probably many flying skills that beyond one's grasp.  

Once engaged, no further effort is required through the entire flight.  Even on landing, if you forget to disengage (a non-critical action), speaking for myself, I'm able to turn off of the runway, down taxiway and back to my tie-down area....all without disengaging the lock.  It's only when making the slow speed, tighter turns in the ramp area is the locked wheel particularly noticeable.  Otherwise, the gentle turns during runway turnoff is more akin to turning a bicycle at higher speeds; you don't really turn the front wheel as much as you influence it.

It appears that the dampner is effective at killing the shimmy, but the loss of full castering is unfortunate and the appearance is, ah hummm, a bit less than stream lined.  Personally, with the old system, I disliked the constant issue of whether the Bellevilles were tensioned properly.  Too tight and taxing and take-off was herky-jerky.  Too loose and taxiing and TO was improved, but I dreaded the moment of truth when the nose touches down.  And because the luxury of a hangar is not available in Knoxville, the dirt blowing across the ramp constantly contaminated the washers, changing their breakout point.

All things considered, simple is better and the nose wheel lock is about as straightforward solution as I can imagine. 

Chuck Jensen



-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of Sid Knox
Sent: Friday, February 20, 2009 2:23 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: wheel shimmy


From: "Al Gietzen" <ALVentures at cox.net>


> So what you are saying is the Sticktion is what we are fighting  right.
> So if we over come this then we would not need toe Hydraulic dampener?
>
> Ron
>
> "Sticktion" is only part of the problem.  I find the sticktion force only
> about 2-3 lbs more that the steady state.  What we want is a freely
> castoring nose wheel that does not shimmy - or as close to that as 
> possible.
>
Here is the graphic of what you are saying... this data was taken some years 
back.  You can see and compare the stiction of the two systems in the 
near-zero Angular Velocity region. (yes, I know now that it should say 
"Belleville").

Sid



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