Eliminating Landing Gear Shimmy - Gear Leg Stiffeners

 
 
After completing the 40 hour flyoff period I noticed that under certain circumstances the plane showed a mild landing gear shimmy when slowing from landing to taxi speed. The problem wasn't consistent, but occurred more frequently when the plane was heavily loaded. The shimmy began at approximately 25 mph while braking and quit by changing the brake pressure (either more or less) and slowing to about 15 mph. It wasn't really a problem, but it was a bit annoying and I wanted to eliminate it.

Researching the phenomenon of gear shimmy, I believe the cause was a combination of factors. First, the gear leg will resonate at some natural frequency, and this is where the shimmy occurs. Changing the natural frequency will change the point of the shimmy. This can be accomplished by stiffening the gear leg with a vibration-dampening wood strip. Second, the force that exited the vibration can be reduced or eliminated. This force is typically the wobble from an imbalanced wheel assembly. Balancing the wheel greatly reduces the force driving the vibration into the leg.

The RV crowd solves the shimmy problem by gluing and fiberglassing a tapered wood strip to the backside of the gear leg. I followed the standard instructions slightly modifying the dimensions to suit the Sonex gear leg.

RV Gear Leg Stiffener Instructions (PDF)


NOTE:  photos link to full size image

 

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Updated: 1 Sep 14