Nose gear bearing pieces?

[BC0979]

Hello guys. I am doing my initial flight testing and discovered  a few roller bearing pieces on the shelf of my firewall. I believe they are from the flat roller bearing of the nose gear. Anyone else have this issue? The nose gear still Rotates without binding.

 

[IBob]

Nope, that's a new one.

My only suggestion would be to check that you have the components stacked in the right order, as per Ch16 P8/11.

[facthunter]

Parallel rollers are not geometrically correct for thrust applications. Make sure it has a bit of good grease there. Check none are missing. Nev

[fallowdeer]

This bearing doesn’t carry any thrust load, only rotational.  The bungee suspension in this design absorbs thrust loading up until stops are reached.

[facthunter]

Makes no sense from that drawing. It's either thrust or AXIAL. If it had balls it could do both. No funny comments thanx.  Nev

[IBob]

The nose leg is held down by a bungy. In that position (noseleg fully down) the bearing and it's associated washers are taking the downward thrust of the leg.
Once sufficient load comes on the noseleg it telescopes upward and there is no load at all on the bearing. So all the bearing does is provide smooth rotation of the noseleg when taxiing and flying (since the nosewheel is linked to the rudder pedals for steering).

There is little feel to the Savannah rudder pedals when flying, and the rudder is not fully self-centering, probably due to the friction of the bungy. I would guess the bearing was added to avoid further turning friction in the noseleg.

Edited June 9 by IBob

[facthunter]

What stops the rollers falling out? and crud getting in?  Nev

[IBob]

The rollers are not (normally) loose, Facthunter. They have some rudimentary cage.
And nothing stops the crud getting in, but it is in a relatively sheltered spot.
 

[facthunter]

Thanks Bob.  The cage would have to contain them or the end float very controlled. Nev

[BC0979]

There isn't much of a cage for the tiny rollers.

The nose gear tube pushes up and down through the center of this roller cage.

I am flying off a grass field so the nose gear is working hard( lots of up and down). I can hear the nose gear bottoming out as it slams into the top metal plate stop where the two top retention bolts are located. I cannot avoid this hammering,  the field is not perfectly flat.

 

[IBob]

Mine rattles sometimes if taxiing, but I wouldn't describe it as slamming. On takeoff the usual thing is to get the weight off the nosewheel as soon as possible, but without premature rotation.

[facthunter]

Good idea with ALL U/L's. Particularly Jabiru. . Transfer to the rudder early for directional control.  Nev

[BC0979]

 

 

 

Here's my damage assessment. Somehow the SF327-4 top plate(bolted on) allowed the top bearing plate/ring SM003 to move aft which then impacted

the SM002 keeper bracket.

 

 

[BC0979]

As you can see, the bearing is toast

 

 

 

[BC0979]

An both the SF327-4 and the upper bearing ring SM003 are bent

 

[BC0979]

This is a pic of the top of the nose gear tube (lots of grease)where SF327-4 is bolted

So the impact of the nose gear tube retracting from the bungee tension deformed SF327-4 enough to allow the top bearing plate/ring SM003 to slide aft exposing the bearing.

[BC0979]

What if SF327-4 were thicker/stronger, would this prevent this from reoccurring?

 

Why do we use this roller bearing in the first place? It does not seem to be designed for IMPACT loading.

[BC0979]

Here's what the original install looked like as proof that I installed it correctly. LOL

 

[IBob]

Assuming the top of the nose leg is flush and square (we have seen one that wasn't) and that SF327 is bolted down tight to it (with Loctite applied to the bolts) it should not be possible for for SM003 to move sideways. Once it does, you will get the damage shown (also the noises you report).
So I would suggest that is the problem: that for some reason when SF327 in bolted down, it leaves a gap, allowing SM003 to shift sideways.

Check the top of the noseleg is square and flush?

[BC0979]

The top of the nose gear tube is not square to the shelf. The forward is lower than the aft by about 1/8 inch. The other builder hear stated that his nose gear was similar, not square to the shelf. 

The top of the nose gear is not flush with the shelf either. It currently sticks up about 1/16 in the front above the shelf which is SM025.

When all other parts are in place and tightened down, this will preload the nose gear tube.

 

I have a thought that the powder coating may have caused this issue. I had to grind the upper and lower metal supports to get the nose gear to slide up and down. The bearing could have been binding on the nose gear tube as it moved up and down.

Edited June 12 by BC0979

[BC0979]

SM025 installed as per the manual so i thought. In hind sight, the SM025 should be as flat as possible so the two A5 rivets nned to be removed. the foward edge of shelf needs is also contributing to the tilt of the SM025

not good.

[Marty_d]

Interesting,  same basic setup as the Zenith CH701, but there's no bearing in the Zenith. 

[BC0979]

38 minutes ago, Marty_d said:

Interesting,  same basic setup as the Zenith CH701, but there's no bearing in the Zenith. 

I reviewed the parts list for the 701 and it showed just one circular plate at the top to be bolted on. I believe the difference in the two designs is at the lower support. The 701 nose gear rides on the elastomeric centering block whereas the S rides on the upper axial bearing.  Correct me if I am wrong. 

[Marty_d]

Yep that's correct.

I've changed mine from the bungee suspension to the rubber "hockey puck" type - hopefully it works ok.

[BC0979]

I really wanted to use the Zenith pucks or the Viking springs but that would have required me to change ALL support brackets for the nose gear. So I'm stuck with the Bungee