REFLECTOR: Shimmy and Nose Gear Pivot Bushings

[Kevin Baker]

Hi All,
Still Building... not flying. Just trying to help.
Did a search online and found this from the RV group for what it's worth.
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http://www.vansairforce.com/community/showthread.php?t=2312


Bob Axsom     Join Date: Mar 2005
Posts: 358

  The previous post is exactly Right

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I have experienced the shimmy, that is actually an understatement. it 
shakes so bad I thought I had blown the nose tire the first time it 
happened. Then I thought I had let the nose down too soon and on my next 
landing I rolled the mains on with nary a squeek and held the nose off 
until it couldn't be held off any more - bang-bang-bang-bang-bang all the 
way until the plane stopped moving. Then it taxied like a pussy cat. I had 
torqued the nose gear and set the breakout force as described in section 10 
to 23 lbs (the book actually says 22 lbs) and I have no holes in the nose 
fairing for an easy way to check the breakout force so checking it is not 
high on my things I like to do list. Off came the fairing and sure enough 
the the breakout force was way down (I don't remember the number if it even 
registered on my coarse fish scale). I retorqued and tested until I had it 
up to 24 lbs. and the problem went away completely! Several months later 
after I had retired and moved to Arkansas it happened again. There was no 
hesitation this time I removed the fairing retorqued the nut and kept 
testing until the breakout force was back up to 24 lbs and there has been 
no recurrence so far. The manual gives a detailed procedure that allows you 
to get rid of some of the "give" in the system but with wear and "settling" 
it probably will recur less and less frequently as the system ages. If it 
happens check and reset it immediatly (or as soon as you get home) and 
check it annually during the condition inspection is my humble 
recommendation. It is a heck of an airplane and nosewheel shimmy is NOT 
something that you "just have to live with." All of the reasons for the 
emergence of tricycle landing gear as the landing gear configuration of 
choice for production airplanes are just as valid for the RV series. The 
tricycle landing gear configuration is harder to build on the RV-6 and I 
assume the RV-7 is the same; the extra big wheeled prong probably makes it 
a little slower; if you lose brakes you also lose taxi steering; etc. etc. 
I went with the tricycle gear strictly because my wife insisted on it and 
during the build process I cussed the unnecessary complications I had to 
deal with because of that choice. Now that I am done with it, having spent 
50 years in aerospace, I wonder at the wisdom of this little lady who knew 
the right choice for us and her elevation above my petty belly aching about 
it. You will not be disapointed if you prefer tricycle gear and build one. 
Don't let the shimmy shake your resolve.
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mrreddick     Join Date: Jan 2005
Location: Hangar/home at Hicks Airfield (T67), Fort Worth, TX
Posts: 53

  Nosewheel Shimmy

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I have to disagree with Mr Baker, they don't ALL shimmy. Mine did when I 
first bought it because the builder didn't have the proper tension torqued 
in on the nosegear nut.
It's a very easy adjustment that took about five minutes using a digital 
fish scale to measure the resistance.
Now, 300 hours later, I NEVER have nosewheel shimmy at any landing speed.