Nose Gear hypothesis.

frankh · #1 03-16-2009, 01:00 PM

Morning all,

It has long been a theory of mine that for/aft oscillation of the nose gear is caused by the NG bearings being set too tight..This possibly even leading to NG collapse.

With the old style nose gear brackets its a real PITA to set the bearing tension because you have to do it with the wheelpant in place..Not easy. Add to this that you have to remove loosen the spindle bolt to flex the wheelpant to inflate the tire (tyre) then this is all leading to way too much of a chore...One day I might cut a hole in the pant to access the valve.

Now I have staked my wheel spacers so there is no reason to have the spindle set too tight and have never had the oscillations.

needless to say I just went through this whole procedure and for the first time I believe I can feel the oscillations.Uh ha!

So I need to re-adjust the spindle torque..Not a big deal but it would be a whole lot better if the wheelpant did not have to be in situ while the spindle bolt was tightened.

The new style of wheelpant bracket solves this issue.

So I was wondering if anyone has notched the old style wheelpant bracket to enable it to be slipped on after the spindle torque is set.

is there enoough meat on the rear bracket to be able to do this??

Frank

IowaRV9Dreamer · #2 03-16-2009, 01:56 PM

Frank - I can't help you directly, but I am watching the NG discussions with extreme interest. My engineering background has me convinced that the fore/aft oscillation is a very bad thing, and some of it may be caused by excess rolling friction in the NG system. It is my understanding that the friction can come from 2 places: the rubber seals on the bearings (this is supposed to be there), and the friction due to excessive preloading from the axle attachment.

Have you considered converting to the new Matco single piece axle ($43)?

It supposedly allows setting of the bearing preload independently from the wheel attach bolt torque. The idea is to avoid excess drag due to the compression of the bearings between the nose gear forks. The bearings are installed and preloaded off the fork, and then the assembly is attached to the fork.

I talked to them today and they are quite helpful about their product. I would love to hear from someone who had the dreaded fore/aft oscillation and found that this solves the problem. I'm trying to decide between this solution and a Grove wheel.

frankh · #3 03-16-2009, 02:17 PM

Yes my engineering background tells me the same thing!

As I have never experienced it before and the feeling of the oscillation (seems about the correct frequency) only happened right after I pumped up the front tire then I can only conclude its a function of tire pressure or bearing preload.

I'll look into the axle solution..if $43 takes the issue away then that is a no brainer.

Frank

frankh · #4 03-16-2009, 02:37 PM

I just looked at the Matco website and it sure looks like this is the answer.

I already have a holes in my forks but it lloks like I could use one of my existing holes and drill/tap a new thread in the matco axle as there is no way my existing holes will be in the right place.

Thanks

Frank

frankh · #5 03-16-2009, 03:02 PM

The New axle head is solid and may therefore be drilled and tapped to suit the existing holes in the fork.

Looks like the way to go as it will be much easier to set the preload on the bench without the wheelpant in the way.

Frank

339A · #6 03-16-2009, 03:47 PM

Frank,

I just installed the new Matco Axle this past weekend. I needed a new nose wheel tire also, so I used the "new" one from Desser made by Aero Classic. Looks like a mini Flight Custom in 8 Ply.

The installation is straight forward, they would have you drill a hole in the fork to lock the axle but after reviewing it, once you torque the axle bolt down there is no way the axle can rotate (you'll understand when you do it). It was easier to set the preload with the wheel on the plane, nose in the air. You can adjust the bearing preload by turning the big threaded end in about 1/8 inch increments. Verify the seals aren't moving, then install the locking bolt for that.

As for landing.... is it any better? What I noticed the most was on wheel touchdown (around 40 mph for me) it was really smooth, way better. There was always this little downward jerk as the tire spins up that seems to be gone. I still have a shimmy during the slow down but I don't know if it's related to the nose wheel or the mains.

Quite happy with it and for the price, well worth it.

frankh · #7 03-16-2009, 04:03 PM

I think you have the wheelpant bracket that can be installed after the wheel..I have the old style brackets..in other words the wheelpant is covering the wheel as your trying to set the preload.

This makes it much harder i think and I suspect I over tightened this time around..i will back it off this evening but I will look forward to setting the preload on the bench..and more to the point without the darn wheelpant covering the wheel..

Cheers

Frank

kentb · #8 03-16-2009, 05:39 PM

I looked at Matco information about their parts.
Do I understand this correctly that the Vans two bearings and axle/bearing holder would be replaced by the solid axle?

Kent

339A · #9 03-16-2009, 06:06 PM

Hi Kent,

Quote:

I looked at Matco information about their parts.
Do I understand this correctly that the Vans two bearings and axle/bearing holder would be replaced by the solid axle?

What the new axle does is replace the axle/bearing holder or "mushrooms" as I call them, from the original design. The Bearings are reused.

Before I took my wheel off, I tested it's spinability with the old setup. It did not spin freely at all. It took a fair amount of force to pull it through. With the new setup it moves very easy/smooth. I have the bearings loaded to the minimum that is required to keep the seal from moving. All this is in Matco's instructions that come with the axle.

I'm curious how much the new tire has helped with this? There is a lot of rubber on the new tire. The original one had 535 landings in 510 hours of service.

hevansrv7a · #10 03-16-2009, 06:07 PM

Quote:

Originally Posted by kentb

I looked at Matco information about their parts.
Do I understand this correctly that the Vans two bearings and axle/bearing holder would be replaced by the solid axle?

Kent

The Matco assembly looks a little like a dumbell. One end screws onto the center cylinder so that it's two larger diameter, flatter cylinders at the ends of a longer, smaller diameter cylinder. Because of the screw on part, the total length and thus the length between the inside surfaces of the two end cylinders is adjustable.

The two "pucks" get replaced, but not the actual bearings. You adjust the Matco assembly to get the correct pressure on the bearing, lock into place with a set screw and then put the axle bolt through the assembly and the fork. The entire assembly fits inside the fork. When you tighten the nut on the axle bolt you snug the fork to the assembly, but that no longer has any effect on the pressure on the bearings. I hope this helps.