REFLECTOR: Shimmy and Nose Gear Pivot Bushings

[Brian Michalk]

It should be leading, since shifting the CG forward would be more stable.

Alex Balic wrote:
> Good find Ron! Now is that damper leading or trailing? Hard to tell from
> the picture, and no description......
> 
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Ron Brown
> Sent: Thursday, November 17, 2005 5:13 PM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Shimmy and Nose Gear Pivot Bushings
> 
> 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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