REFLECTOR: Shimmy and Nose Gear Pivot Bushings

[Ron Brown]

Brian,

I did a Google on "nose wheel shimmy" and got the following article on 
F-15's and a fix for their long standing problem.  See 
http://engineering.wpafb.af.mil/success/F-15_Nose_Wheel_3_08_01.pdf

It involves what looks like a mass weight attached such that the center of 
mass is shifted forward.  Looks like something worth trying assuming there 
is room for the bar when the gear is up - I think there is.

It sure would be nice to be able to reduce the shimmy nut torque to 
something like 5-10 ft lbs instead of the difficult to steer 20 ft lbs.

Ronnie

----- Original Message ----- 
From: "michalk" <michalk at awpi.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Tuesday, November 15, 2005 11:19 AM
Subject: Re: REFLECTOR: Shimmy and Nose Gear Pivot Bushings


>I always wondered why there hasn't been an example where a counterbalance 
>was used?
>
> The problem is that the CG is aft of the pivot point.  If one needs to use 
> ballast anyway, place a counterbalance to get the CG closer to the pivot 
> point.
>
> Might be a problem with RG's, maybe easier with fixed gear.  Get the 
> center of lift to be aft of pivot as well and have self centering 
> nosewheel, with a very light easy to steer friction system.
>
> Ron Brown wrote:
>> I discovered how destructive nose wheel shimmy can be.
>>
>> On a half dozen or so occassions, I have had nose wheel shimmy after 
>> landing.  The last time, I smelled hot epoxy.  After shut down I did some 
>> investigating and found that the right side pivot bushing had worked 
>> loose from its mounting in the keel. It had worn the hole into an egg 
>> shape with most of the wear toward the lower front of the bushing 
>> mounting.
>>
>> I have epoxied a new bushing into place using the Aeropoxy structural 
>> adhesive.
>>
>>> From now on, I am going to keep my bellville washers clean and tighter 
>>> to
>>
>> minimize - or rather prevent nose wheel shimmy.  (sure makes steering 
>> tougher - especially on take off)
>>
>> Has anybody else had this problem?  I am guessing there is a problem in 
>> that there is a new and improved mounting for these bushings.
>>
>> Do I also need to go ahead and plan to replace these with the new 
>> bushings and plates that are shown in the latest on-line plans?
>>
>> Ronnie
>> 173 Elite RG
>>
>>
>>
>> (173 Elite RG).
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