REFLECTOR: Nose wheel shimmy drag

[Jim Agnew]

Hi Al,

After many years with the nylon washer I can tell you that they work well.  However my washer is about .250 thick and you remove the old composition washer and use it as a template to drill the hole in the nylon washer to accommodate the pin that keeps the washer from rotating on the gear strut and put  the Belleville washer back in.  As far as the machining marks go they will wear off as the new nylon washer seats and will require re-tightening the lock-nut as it seats. In a short time the adjustment will be minimal.  You will probably find that after seating the wear surface is not flat but wears at a small angle.
 
Jim 

James F. Agnew
Jim_Agnew_2 at Yahoo.Com
Tampa, FL
Velocity 173 Elite Aircraft Completed & Flying




________________________________
From: Al Gietzen <ALVentures at cox.net>
To: reflector <reflector at tvbf.org>
Sent: Friday, July 10, 2009 1:12:57 PM
Subject: REFLECTOR: Nose wheel shimmy drag


Just to confirm what some others already know – 
I accepted Jeff’s generous offer of a nylon washer for the nose gear pivot.  He sent me a black, apparently quite hard form of nylon, about .1” thick.  After sanding on flat surface with 600 and 1000 grit to remove machining marks, I installed it yesterday.  I simply put a film of grease on it, and placed between top of the fork and the existing composition washer. I removed one Belleville so the lock nut still does its job.
 
I set the drag to 12# measured at the outer diameter of the tire (this force has worked fine for my plane).  The big difference is that the breakaway force (a.k.a; sticktion) is pretty much negligible.  The movement starts with about 12 ½ #, and continues at 12.  With just the composition washer I typically found the breakaway force to be maybe 3 – 4 # more than that required to maintain movement.
 
This doesn’t solve the issue of difficult steering at low taxi speeds, but should be an improvement. I’ll let you know how it goes after used for awhile; but it seems that Velocitycould certainly consider some type of nylon in place of the composition washer.  Jeff probably has the specs for the nylon he used.
 
Al
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