My shimmy woes
Learn to keep the nose off on take off and landing and you will have an aircraft for a long time without damage.
I have a bit of a different situation here. My first 6A landing on the initial test flight, got the shimmy. I let the nose down too quick. From then on I made it a point to keep the nosewheel light. I control it throughout the takeoff and landing roll.
The next 98 hours went with no shimmy, but I was noticing that our runway was getting more bumpy, most likely due to heat. Since the 6A sit's nose high, it's closer to a flying attitude than the 7 or 9A's, which are at a flat attitude.
By keeping the nose very light on the landing, each bump would cause the nose to spring up. Then it happened; the nose came down and the front wheel went into an oscillation that felt like the tire had just gone flat. I think it's a side to side movement, rather than fore and aft, but not positive. This would not stop until the plane was near fully stopped. This same phenomenon has been described in previous threads.
I checked the tire ( no scrub marks) and added a bit of air. Went to another airport with a smooth runway for some touch and goes, and all was fine. But landing at this airport again, I got the same oscillating shimmy. And as before, it won't stop until nearly all the way stopped for the taxiway.
At that point, I took it up again, and decided to "plant" the nosewheel on the runway. And what I mean here, is to ride the stick, so that the nosewheel isn't allowed to pop upwards on the bumps. But I'm still keeping it as light as possible. This technique is now working fine. For smooth runways, I keep the nosewheel off, and bumpy ones get special attention. I've also set the fork nut at 26 lbs side force with the fish scale. 22 lbs. is the recommendation. However from previous postings on the subject, it seems that a bit more torque helps.
L.Adamson --- RV6A