REFLECTOR: Shimmy and Nose Gear Pivot Bushings

[Wayne]

I actually balanced mine with the lead weight in the front of the wheel pant 
. I think I remember holding  the fork horizontal and balanced it like an 
aileron The moment arm was short and it took about 17 lbs of lead. It 
sucked.
Wayne
----- Original Message ----- 
From: "Ron Brown" <romott at adelphia.net>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Friday, November 18, 2005 9:14 AM
Subject: Re: REFLECTOR: Shimmy and Nose Gear Pivot Bushings


> I'm pretty certain the rod projects forward - to counterbalance the weight 
> behind the pivot that the fork, wheel and tire has.
>
> Any body who hasn't installed their nose wheel and tire - could you weigh 
> the wheel and tire to give me an idea of how much mass needs to be placed 
> out front.
>
> I'm guessing that nose wheel shimmy is similar to control surface flutter. 
> The likelihood of shimmy would be reduced/eliminated by having the 
> counterbalance equal or heavier than the tire and wheel.
>
> Ronnie
>
> ----- Original Message ----- 
> From: "Chuck Jensen" <cjensen at dts9000.com>
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Sent: Friday, November 18, 2005 8:16 AM
> Subject: RE: REFLECTOR: Shimmy and Nose Gear Pivot Bushings
>
>
> Ronnie,
>
> The photo wasn't a detailed as one would like but I'm estimating that's
> a $50,000 to $75,000 military mod.  Of course, if the bolts that hold it
> on weren't bought at Home Depot, then it's probably more.
>
> Alex had a good question about whether it's a trailing or leading mass,
> though it may not make a difference.  If trailing works, and if a 6" rod
> with a 2-3 pound mass of lead on the end of it would do the trick,
> wouldn't that be great.  If it's out front, a person would have to do
> some measuring and calculation for dog house clearance, but in the
> trailing position, it would look better and have lots of clearance.
>
> Do we have any guinea pigs in the house?
>
> Chuck
>
>
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Ron Brown
> Sent: Thursday, November 17, 2005 6:13 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).
>>> _______________________________________________
>>> To change your email address, visit
>>> http://www.tvbf.org/mailman/listinfo/reflector
>>>
>>> Visit the gallery!  www.tvbf.org/gallery
>>> user:pw = tvbf:jamaicangoose
>>> Check new archives: www.tvbf.org/pipermail
>>> Check old archives:
> http://www.tvbf.org/archives/velocity/maillist.html
>>
>> _______________________________________________
>> To change your email address, visit
>> http://www.tvbf.org/mailman/listinfo/reflector
>>
>> Visit the gallery!  www.tvbf.org/gallery
>> user:pw = tvbf:jamaicangoose
>> Check new archives: www.tvbf.org/pipermail
>> Check old archives:
> http://www.tvbf.org/archives/velocity/maillist.html
>>
>
> _______________________________________________
> To change your email address, visit
> http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
> _______________________________________________
> To change your email address, visit 
> http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  www.tvbf.org/gallery
> user:pw =vbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
> _______________________________________________
> To change your email address, visit 
> http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>