Shimmy Help

[Flybuddy2]

I've read all of the shimmy posts and have a couple of questions:

1) tire pressure--my experience in various diff steering nosewheel aircraft (RVs, Grummans, Velocity) has been lower tire pressure seemed to lessen nosewheel shimmy BUT most posts here advocate higher tire pressures. Anyone have experience with higher pressure reducing shimmy?

2) I've noticed shims and stiffeners mentioned--how would those work or are they for mains only??

3) putting lead in forward portion of nosewheel fairing--anyone do that and how much weight used??

I've been fighting a marginal shimmy for a while. I've changed tires/tubes and balanced--have the Matco setup, have 36 lbs breakout force, played with pressures, pulled the downtube, put in a larger bolt and retorqued, etc, etc. I'm running out of things to try--any info appreciated...thx

[RV6airplanePilot]

and that was beneficial. They are mounted in the middle. The nose pant geometry is much different. i don't see a benefit to balancing the nose pant. I reduced the nose tire pressure fairly low; on a normal landing the spin force on touch down ripped the valve stem. I keep the nose tire pressure on the high side now. I like the optional axel, too. I have a belly cam that shows all 3 wheels. I can never tell without looking which wheel is actually the offender. Since I balanced the main pants and bought the better quality nose tire (Matco I think) I have had no problems. Most of the Shin tires are not very round, too egg shaped for me.

Dale
RV6a 1555 hrs

[bird]

You might want to try putting that wheel in the back just below the rudder.

sorry couldn't resist

bird

[Walt]

Just fixed one like that yesterday, I replaced the tire/tube, balanced the assy, replaced the disc spring washers and reset the breakout force.. all is wonderful again and owner is a happy camper .

[Flybuddy2]

Originally Posted by Walt

Just fixed one like that yesterday, I replaced the tire/tube, balanced the assy, replaced the disc spring washers and reset the breakout force.. all is wonderful again and owner is a happy camper .

Might be time for new washers---what did you set the breakout force at??
I saw one post a while back where someone had it in the 40s, my next door neighbor has a 6A and he doesn't check it, he just keeps tightening till it stops shimmying. I've got 36 and his is tighter than mine. I wonder at what point it will not self align in the air?

[L.Adamson]

Originally Posted by Flybuddy2

Might be time for new washers---what did you set the breakout force at??
I saw one post a while back where someone had it in the 40s, my next door neighbor has a 6A and he doesn't check it, he just keeps tightening till it stops shimmying. I've got 36 and his is tighter than mine. I wonder at what point it will not self align in the air?

Plans called for 22 lbs. side force, with a fish scale pulling at the axle location. Mine was around 25 lbs. If it doesn't self align, it will act somewhat like a rudder.

L.Adamson

[gasman]

Be sure and have someone witness the wheel that is shimmying. You might find that it is not the nose wheel.

[Vlad]

Need opinion too. Couple weeks ago I was at unfamiliar airport and slipped hard to lose altitude. After touch down I hold the nose up then relaxed a bit and as soon as it touched the runway the vibration started. Next second I lifted the nosewheel again and after it lowered itself at slow speed the vibration repeated but was lighter and then went away fast. Somebody happened watched and he said it was visible. Never experienced that again, checked nosegear attach points everything by the book. What it could be? Cocked nosewheel on touchdown after forward slip?

[L.Adamson]

Originally Posted by Vlad

Need opinion too. Couple weeks ago I was at unfamiliar airport and slipped hard to lose altitude. After touch down I hold the nose up then relaxed a bit and as soon as it touched the runway the vibration started. Next second I lifted the nosewheel again and after it lowered itself at slow speed the vibration repeated but was lighter and then went away fast. Somebody happened watched and he said it was visible. Never experienced that again, checked nosegear attach points everything by the book. What it could be? Cocked nosewheel on touchdown after forward slip?

Quite a number of RVs have experienced minor shimmy while still on the rollout, or severe shimmy on landing, if the nosewheel comes down too quick. Severe shimmy feels like a flat tire. Seems like the best answer is to keep the nose as light as possible during the rollout...........in addition to breakout force, balance, etc.

L.Adamson

[Vlad]

Thanks Larry. Looks like it's the case and I experienced it only once after more than 100 landings.