Wheel Bearings Verses Gear Leg failure !!!!!

[PerfTech]

....As most of you know we at Anti-Splat-Aero have been offering our wheel bearing upgrade for the A-model nose wheels now for some time. In the course of doing hundreds of these upgrades to ball bearings we have seen and learned much interesting information. I would like to share some of what we have learned with all of you here on the forums. As most are aware, we developed and market our “Nose Job” product aimed at making the nose gear less vulnerable to failures, hopefully preventing some of the flip-overs and resulting damages. This has been addressed in a few different ways by Vans with the gear and fork change as well as suggesting technique as being one of the main contributing factors in the failures. To some extent this is true, but regardless of how skillfully you land, the wheel will come down at some point and with that it is now out of your hands. The more weight on the wheel, the harder you drop it on or the rougher the surface the more the possibility of a bad outcome for all of the obvious reasons. After viewing all of these wheels, spacers, fork assemblies, axles as well as conducting as many tests as we can conceive of, we want to pass our findings on. We are now convinced that the main contributing cause for the gear failures and subsequent damages lies in the nose wheel bearing set-up. If you adjust the preload on the stock set-up so the wheel turns with an acceptable amount of drag as recommended. When the wheel is subjected to weight or is shock loaded in any way the axle deflects, allowing misalignment of the bearings and causing them to virtually lock-up. Once this begins it just snowballs placing tremendous bending forces on the gear leg (see accompanying video link). This is like landing with a highly effective front brake on and increasing its braking force as the weight is added. The rolling force is converted to a bending force on the gear leg. Approximately ninety percent of the spacers and forks we see show the unmistakable signs of the bearings locking as they are galled and worn into the fork. Some as much as .125" each, (see photographs). This has been observed by many and addressed by pinning or bolting the spacers to the fork to keep them from rotating. At first this looks like a good idea! Unfortunately, this can actually have disastrous affects and will make the gear leg bending action worse if the wheel package is shock loaded or stressed. The aluminum spacers when left free to rotate as the bearings lock, are acting as a safety in essence keeping the wheel from locking and bending the gear leg. If you can imagine the front wheel entering a shallow depression only one or two inches deep at 25 MPH with weight on the wheel. When the wheel impacts the far side of the hole or depression and needs to roll out of the hole freely with no resistance, it locks up instead and this is what actually rolls up the gear leg starting the failure event. We are convinced that the most important thing you can do to lessen the possibility of the gear bending is this wheel bearing modification. I hope this helps clarify some of what seems to be occurring with this nose gear leg. Regards All, Allan....
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VIDEO;
https://cache.nebula.phx3.secureserv...FjNTFkMTI1NWU=
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[gasman]

Originally Posted by PerfTech

....As most of you know we at Anti-Splat-Aero have been offering our wheel bearing upgrade for the A-model nose wheels now for some time. In the course of doing hundreds of these upgrades to ball bearings we have seen and learned much interesting information. I would like to share some of what we have learned with all of you here on the forums.

As most are aware, we developed and market our ?Nose Job? product aimed at making the nose gear less vulnerable to failures, hopefully preventing some of the flip-overs and resulting damages. This has been addressed in a few different ways by Vans with the gear and fork change as well as suggesting technique as being one of the main contributing factors in the failures. To some extent this is true, but regardless of how skillfully you land, the wheel will come down at some point and with that it is now out of your hands. The more weight on the wheel, the harder you drop it on or the rougher the surface the more the possibility of a bad outcome for all of the obvious reasons.

After viewing all of these wheels, spacers, fork assemblies, axles as well as conducting as many tests as we can conceive of, we want to pass our findings on. We are now convinced that one on the main contributing causes for the gear failures and subsequent damages lies in the nose wheel bearing set-up. If you adjust the preload on the stock set-up so the wheel turns with an acceptable amount of drag as recommended. When the wheel is subjected to weight or is shock loaded in any way the axle deflects, allowing misalignment of the bearings and causing them to virtually lock-up. Once this begins it just snowballs placing tremendous bending forces on the gear leg (see accompanying video link). This is like landing with a highly effective front brake on and increasing its braking force as the weight is added. The rolling force is converted to a bending force on the gear leg.

Approximately ninety percent of the spacers and forks we see show the unmistakable signs of the bearings locking as they are galled and worn into the fork. Some as much as .125" each, (see photographs). This has been observed by many and addressed by pinning or bolting the spacers to the fork to keep them from rotating. At first this looks like a good idea! Unfortunately, this can actually have disastrous affects and will make the gear leg bending action worse if the wheel package is shock loaded or stressed. The aluminum spacers when left free to rotate as the bearings lock, are acting as a safety in essence keeping the wheel from locking and bending the gear leg. If you can imagine the front wheel entering a shallow depression only one or two inches deep at 25 MPH with weight on the wheel. When the wheel impacts the far side of the hole or depression and needs to roll out of the hole freely with no resistance, it locks up instead and this is what actually rolls up the gear leg starting the failure event.

We are convinced that the most important thing you can do to lessen the possibility of the gear bending is this wheel bearing modification. I hope this helps clarify some of what seems to be occurring with this nose gear leg. Regards All, Allan....
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VIDEO;
https://cache.nebula.phx3.secureserv...FjNTFkMTI1NWU=
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Nothing new......... This was explained over four years ago..... http://www.vansairforce.com/communit...&postcount=176

[Ricatic]

Originally Posted by gasman

Nothing new......... This was explained over four years ago..... http://www.vansairforce.com/communit...&postcount=176

really...no where near the depth or quality in the explanation from four years ago

Allan has done a great job of demonstrating the real time effects of the oscillations as speed increases...

Thanks Allen...keep up the good work

Regards

[PerfTech]

Originally Posted by gasman

Nothing new......... This was explained over four years ago..... http://www.vansairforce.com/communit...&postcount=176

...Warren, You are correct and your post of four years ago was right on as well. I have only been on this forum for a couple of years and hadn't seen your post. We were trying to clarify the dynamics for people that were unaware of this problem. We were also trying to let them know we offer a relatively quick, inexpensive remedy for this issue with the nose gear. The fact that our modification to the bearing package solves this locking up issue, rolling drag reduction and will never require maintenance makes it a very desirable service for many. To date we have converted over two hundred of these and a few days ago we received our first complaint and though we should share it with the others here on the forum.
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It read as follows;
"Attn Complaint Dept. I wanted to let you all know that after installing my front wheel you modified on my airplane it has subsequently developed a very serious problem that I must say is very annoying. Our hanger floor has a very small, almost undetectable amount of slope for drainage. This has proven to be a problem as the plane rolls out by itself. It is almost like it's possessed and wants to leave. Seems like every time I park and walk away it tries to follow me. I am becoming paranoid now and would suggest you consider giving a free chock with this mod, or at least let a guy know what to expect. Other than this one problem, I love it! Thank You for the great service and products, David P. RV-7A"
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...We hope this is the worst complaint we receive and we sent Dave a pair of complementary chocks. (The squeaking wheel gets the grease) Thanks, Allan...

[zav6a]

Hi Allen

Out of that 200 that you have modifed, I suspect some were of the solid or 2 piece axle design. That is, they have the spacer that bears the load of the torqued axle rather than the bearings.

Have you seen evidence of those spinning too?

[PerfTech]

Originally Posted by zav6a

Hi Allen

Out of that 200 that you have modifed, I suspect some were of the solid or 2 piece axle design. That is, they have the spacer that bears the load of the torqued axle rather than the bearings.

Have you seen evidence of those spinning too?

We have seen some of that type but I only remember one that spun bad. I think is was due to a bearing failure so can't blame the set-up for lack of lubrication. Allan......