What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Tunnel vision---landing gear shimmy

I've been experiencing this issue and even went so far as to order some of the main leg stiffeners to install. As I was working my way through my annual I found my nose wheel was now only taking about 18 pounds of force to rotate versus the 26 lbs Vans recommends in the plans. Those belleville washers definitely smoothed out (I had pre-sanded them a bit too). I also found my nose wheel was under inflated as well. Hopefully that will be the shake I've been feeling.

Just to go back to what Mike started the thread with, be sure to check out the mechanics of the wheels to see if something else is going on.
 
CharlieWaffles said:
I've been experiencing this issue and even went so far as to order some of the main leg stiffeners to install. As I was working my way through my annual I found my nose wheel was now only taking about 18 pounds of force to rotate versus the 26 lbs Vans recommends in the plans. Those belleville washers definitely smoothed out (I had pre-sanded them a bit too). I also found my nose wheel was under inflated as well. Hopefully that will be the shake I've been feeling.

Just to go back to what Mike started the thread with, be sure to check out the mechanics of the wheels to see if something else is going on.
Click to expand...

I had the shake happen twice.

Then I too noticed that the nose wheel torque had dropped to about 10lbs. I tighten it up to about 30lbs. I haven't had a shake incident since.

I also believe that the Planearound spacers on the wheel bracket help tremendously in damping any oscillations over the plan fabricated spacers. If you don't have them installed, I would highly recommend them.
 
CharlieWaffles said:
I've been experiencing this issue and even went so far as to order some of the main leg stiffeners to install. As I was working my way through my annual I found my nose wheel was now only taking about 18 pounds of force to rotate versus the 26 lbs Vans recommends in the plans. Those belleville washers definitely smoothed out (I had pre-sanded them a bit too). I also found my nose wheel was under inflated as well. Hopefully that will be the shake I've been feeling.

Just to go back to what Mike started the thread with, be sure to check out the mechanics of the wheels to see if something else is going on.
Click to expand...

Are you greasing the Belleville washers?
 
The only grease in that area was done via the zerk fitting after assembly. When applied it will ooze out between the washers. So in that way yes, they are greased.
 
CharlieWaffles said:
The only grease in that area was done via the zerk fitting after assembly. When applied it will ooze out between the washers. So in that way yes, they are greased.
Click to expand...

The Bellville washers on my Tiger are specifically called out for a grease application (Aeroshell #6 or equiv.) every 100 hours.

To apply the grease, the nose gear swivel must be removed, the washers cleaned and re-greased, re-assembled and the break out torque adjusted.

Since the system is identical to that on the RVs, it seems like a good maintenance practice.

Does Vans provide any specific maintenance instructions for the Bellville washers?
 
No guidance from Vans that I know of. I think one of the reasons this happens is that there is nothing in the plans about greasing the zerk fitting up there, so most people are setting the breakout with a dry configuration and when its greased later on, the breakout is greatly reduced.
 
I notice a shopping card shimmy today during taxi for take-off. Time to investigate.
 
Just to follow up, after increasing the breakout force on the belleville washers (post greasing), my shimmy is now completely gone. I did not install the main gear stiffners or anything else. So I suspect my problem this whole time was just from the breakout being lowered after greasing.

The plans really should indicate that the setting should be made AFTER greasing the joint.
 
It will likely need to be tightened again, at least once. You may also need to add spacers under the hat on the top of the nose gear shock strut.
 
As a result of reading previous threads, and the classic 15-30kt shimmy on my -10 that is otherwise ready to fly, I checked the torque of the gear leg socket bolt. Right at spec, BUT, I could turn the bolt head with the nut turning right along with it. The stock bolts with plans called for 1 washer plus nut was allowing the nut to bottom on the threads. Installed an additional washer and retorqued. Substantial reduction in shimmy now. I wonder how many -10s do not have adequate torque on that bolt because the nut is just barely bottoming before torque is achieved. It looked like it was fine with torque wrench, until I noticed the bolt wasn't squeezing and could be turned. I also checked the bolt for overall and grip length and it was on spec.
 
Sad to say I learned that lesson about thinking a problem was one thing when it was another in one of my previous homebuilts. A very expensive lesson that left me floating in a life jacket in the middle of a lake. As they say: any landing you walk away from (swim away) is a good one.

Glad you got it down with minimal damage and no injuries.

: Richard Schaller <[email protected]>
Date: March 27, 2016 at 7:57:39 PM MST
To: <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>
Subject: Fwd: Vet This!



Sent from my iPad

Begin forwarded message:
 
Kellym said:
As a result of reading previous threads, and the classic 15-30kt shimmy on my -10 that is otherwise ready to fly, I checked the torque of the gear leg socket bolt. Right at spec, BUT, I could turn the bolt head with the nut turning right along with it. The stock bolts with plans called for 1 washer plus nut was allowing the nut to bottom on the threads. Installed an additional washer and retorqued. Substantial reduction in shimmy now. I wonder how many -10s do not have adequate torque on that bolt because the nut is just barely bottoming before torque is achieved. It looked like it was fine with torque wrench, until I noticed the bolt wasn't squeezing and could be turned. I also checked the bolt for overall and grip length and it was on spec.
Click to expand...

Interesting........

I've not experienced the shimmy in my RV-10, but I have experienced it in others and have always been at a loss to explain the difference.

bob
 
New look at old thread. Going back to the original issue of the wheel pant departure, I would suggest to everyone that they take a second look at the spacing gap between the bottom of the wheel pant and the tire. I had no issues for 225ish hours until it appears that a firmish landing expanded the tire width enough to contact the side of the pant near the outboard rear. We didn't even know we had an issue until pushing back into the hangar and discovering that about a two inch wide chunk of the pant sidewall had ripped upward and was scraping the sidewall of the tire at an angle that was leveraged against the tire rotating backward.

A similar issue could have initiated the destruction/departure of the pant in the OP until jamming under wheel took over.
 
landing gear shimmy

Myron
you are right on. I too had this happen to me, tires were slightly low and the plane with 4 folks aboard must have expanded the tire to the point it ripped the pants. Now I have a finger width gap all around and the no leak tubes from Desser. I have not had any issues since.

Pascal
 
Mike's incident just proves that you dont stop flying the aircraft until it is stopped. Even if you have the best equipment and the best maintenance program out there, things happens. Mike did a good recovering control of his aircraft and preventing much worse from possibly happening, and thats to be commended.
 
You must log in or register to reply here.
Back
Top