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breakout force on nosewheel fork

david.perl

david.perl

Well Known Member
Ive set the nose wheel fork breakout force at 22 pounds using a spring balance as recommended. It feels really stiff and i can just turn the fork by hand. I thought the nosewhell was supposed to castor easily.

Is this correct or is my spring balance giving odd readings or am i just getting weak with age?
 
It is not a shoping cart, you don't want it flopping around in the air. it should be a little difficult to swing.
 
Nose wheel breakout force

I just changed out my nose wheel last week and used a fish scale to measure
the force it takes to move the fork. 22 lbs works good and it will feel a bit stiff to
move.
 
Agreed, the nose wheel should be stiff. I have even bumped up the breakout force to 24 lbs which has worked well on my 9A. Of course, I do not know how accurate my fish scale is, but it has worked well. Good luck.

Steve
Catto 3 blade prop
380 plus hours
 
a data point

....and just to make you feel better, I just increased mine from about 10 to 22, and it made ZERO difference on how much shimmy I have on roll-out.
I'd speculate, and only speculate, that the tire pressure, CG (nose load) and runway surface have much to do with the initiation and magnitude of any oscillation....not a scientific test, but some of us find that touching the brakes will instantly stop a shimmy. ( load, speed etc all change momentarily)...
go figure.
 
I notice the shimmy only when letting the airplane decelerate without braking. AS it slowly passes through some speed range the shimmy starts and only stops when the speed gets really slow.

I'd like to see some good video of the nosewheel during the shimmy for analysis. Antisplat has one but the video quality is not adequate for a good analysis. I think they are on a path, but would like to look myself. Anyone have a camera they can set up on their wingtip and induce the shimmy during taxi? A 60 hz frame rate would be good.
 
flyboy1963 said:
....and just to make you feel better, I just increased mine from about 10 to 22, and it made ZERO difference on how much shimmy I have on roll-out.
I'd speculate, and only speculate, that the tire pressure, CG (nose load) and runway surface have much to do with the initiation and magnitude of any oscillation....not a scientific test, but some of us find that touching the brakes will instantly stop a shimmy. ( load, speed etc all change momentarily)...
go figure.
Click to expand...

This sounds like main gear shimmy - do you have verification from someone outside that it is indeed the nose gear that is shimmying?

For others who are not setting the breakout force per plans - you do so at your own peril. If the nose gear should get into a divergent shimmy, it could bend the nose gear under. When the tire is at a significant angle to the direction of travel, it puts a lot of rearward force on the nose gear strut.
 
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