RV-4 Wheel Shimmy

dclay · #1 03-16-2005, 06:53 AM

Greetings all,

Can anyone offer any suggestions on reducing MLG wheel shimmy on my RV-4? The shimmy occurs primarily on landing rollout. I?ve checked all the usual suspects such as loose parts and gear alignment. Any help would be greatly appreciated.

Thanks,
Dave

alame · #2 03-16-2005, 09:35 AM

I would give the tires a close look, doesn't take much to cause a problem, bulges, seperations, out of balance that kinda thing

atreff · #3 03-16-2005, 12:08 PM

I read somewhere that Grumman nose wheel shimmy was cured by static balancing the wheel pants. I think that there is a reference to that fix for RV's in the RV-ator archices as well. I would put a straight edge in a vise, and add weight to the pant until it can be placed on the straight edge in the center of mounting point, and it doesn't feel heavy fore or aft. I don't think I depicted that very well. I hope you get the idea. Then use epoxy and some lead shot and bond into the pant in the appropriate location.

robertahegy · #4 03-16-2005, 04:11 PM

Dittos on the wheel pant balancing idea. Also, I don't know what type of gear the 4 has, but can gear leg stiffeners be put on the legs? I have them on my 7A and have had no problems with gear or wheel shimmy. Too high tire pressure could also be the culprit. Good luck.

Roberta

sf3543 · #5 03-17-2005, 02:29 PM

I had minor shimmy on my RV6 and after several hundred hours, finally added gear leg stiffeners. The shimmy went away.

John_RV4 · #6 03-17-2005, 03:29 PM

Dave,
Try posting in the RV4 specifc topic for better results. Also, there's an RV4 yahoo user's group.

That said, the gear legs are supposed to get wooden dampeners. Many builders don't put them in. Do you know if your plane has them ? I bought an RV4 and plan to add the dampeners. The shimmy doesn't happen all the time and often it takes me by surprise (very annoying).

Good luck.

John

oldsfolks · #7 03-17-2005, 09:17 PM

I had a problem on our first RV-4 back in 1983. As speed decreased on roll out I got an oscillation which felt like a shimmy. The oscillation was fore & aft - NOT side to side.
I put on wood & fibreglas stiffeners and that solved the problem . That RV-4 had short gear legs. Or second RV-4 has long gear legs and I have had no problems with it.
My neighbors RV-6A has a fore & aft oscillation of the nose wheel. I have watched it on landing and it always seems to do it. A gear leg stiffener should solve that problem.
You can shape the stiffeners to streamline shape and no other fairing is needed.

Bob Olds RV-4 , N1191X
Charleston,Arkansas

gmcjetpilot · #8 03-18-2005, 08:51 AM

Quote:

Originally Posted by atreff

I read somewhere that Grumman nose wheel shimmy was cured by static balancing the wheel pants.............Then use epoxy and some lead shot and bond into the pant in the appropriate location.

This can help, as well as the wood gear leg stiffener. Tire pressure can affect the shimmy, but I had the same issue on fast taxi with my RV-4. Gear leg stiffener made it go away and gave it a more solid feel. I would caution sealing the gear leg completely with wood and fiberglass, etc.... If there is a place for moisture enter and remain against the gear leg, you can get corrosion over a long period. Make sure the gear leg is well protected and water can drain or not enter. Cheers George