REFLECTOR: wheel shimmy

[Rene Dugas]

I'm not a engineer but would an acceptable compromise be a device  
similar to the lock but be a spring loaded ball that fits in a "V"  
notch or groove. Each time the wheel was not centered the verticle  
spring on the ball would dampen the motion but once beyond the notch  
free castoring would exist. Could be light compact and adjustable. A  
screw to ore load the spring would be east too. Ok shoot me down.

Rene' Dugas
Sent from my iPhone 3G

On Feb 20, 2009, at 5:08 AM, "Chuck Jensen" <cjensen at dts9000.com> wrote:

> 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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