Nose wheel shimmy

Did you check the "nutcracker" connections?

The upper & lower nutcracker bolts need to be a lot tighter than some mechanics think. They're afraid that "over-tightening" the bolts will lock the nutcracker in one position and prevent it from flexing up and down, but unless specific parts are worn out this is not what happens.

The top & bottom of the nutcracker aren't actually tightening onto the steering column (top) or nosegear (bottom) - it's actually tightening onto a cylindrical steel bearing that passes through these parts. At the top & bottom, the nutcracker, bolt, and bearing should be tightened until they move together as one single piece. This single piece pivots freely as the steel bearing moves inside a phenolic bearing - the phenolic bearings are thin cylindrical brown "shells" that been driven into the steering sleeve (upper connection) and the nosegear (lower connection). 

To make this happen, the steel bearing has spline teeth along the "opening" of its cylindrical shape. These teeth must bite into the metal of the nutcracker when the bolts are tightened.



MAKE SURE THE TEETH AREN'T WORN OUT. They should be sharp enough to bite into metal.

 

MAKE SURE THE NUTCRACKER ISN'T WORN OUT. Age or loose assembly can allow the teeth to chew out a donut-shaped furrow in the nutcracker - where I drew a yellow circle in the photo. If that metal has been worn out then unfortunately that nutcracker part is worn beyond use because when that metal is gone, you can't tighten it properly without binding up the movement. 

 

 

In my experience, my steel bushings were worn out to the point that they had smooth bumps instead of sharp teeth, and the nutcracker metal was worn. I managed to resurrect the nosegear with used nutcracker parts and new steel & phenolic bushings.
 

Nose wheel shimmy is still bad, did the tire pressure 15 pound set, but shimmy is still there? Looks like a whole nose gear rebuild will have to be done unless someone has a better and easier fix? I got one good tip, replace the busing.