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Jeff's RV-6 Site

Balancing the Wheel Pants

Gear leg shimmy in RVs is a well documented, yet elusive phenomenon. Some planes have it, others are immune. One of the most common fixes is the addition of wooden stiffeners to the gear legs. This process is covered in detail in the build manuals. I built and test flew my plane without the stiffeners, and added them during the test period. I had some luck with reducing, but not eliminating the shimmy. Over the last year, I learned to live with it, and avoided it by keeping the tire pressure low (28 psi or so.)

On the advice of one of the local old-timers, I decided to balance my wheel pants. He swears by it, and claims to have completely eliminated gear shimmy in his own airplane (a 40 year old, one-off fiberglass design) so I decided to try it. The theory is that the pants are very unbalanced fore and aft, which tends to exacerbate any shimmying motion which might develop.

The results have been impressive. Since balancing the pants, I have yet to experience any detectable gear shimmy, with tire pressures up to 35 psi.

The process is pretty straight forward, and similar in concept to balancing a tire. The wheel pants are suspended at the balance point (the axle) and weight is added to the light end until it isn't light anymore.

This picture shows the basic ingredients for balancing wheel pants. The metal pipe is leftover elevator pushrod material; any old dowel rod will do. Some epoxy and dixie cups, a roll of tape and some lead shot. I used #8 bird shot, you could use old sinkers or anything similar.

The pipe is secured to the wheel pant at the axle point, just forward of the split in the wheel pants. A dixie cup is taped to the front, slightly offset to get as close as possible to the position the lead will be in once you glue it into the nose of the wheel pant. The whole shebang is then balanced between two tables, sawhorses, etc. You will find that it is very tail-heavy. That's where the lead comes in.

Just add lead to the dixie cup until the tail is no longer heavy and the pant balances on the axle point. I didn't bother to weigh the lead, but I would guestimate half a pound or so. Remove the cup of lead, mix up a small batch of epoxy and mix it up with the lead (remove a pinch of lead to make up for the weight of the epoxy. This is not an exact science.) Stand the front half of the wheel pant on it's nose (supported obviously) and pour the lead in. I added a patch of fiberglass over the whole thing to help hold it in place.

Let it dry overnight. Screw it all back together and go fly. I think you will be surprised at the results.