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Nose wheel bearings pitting

V

Vlad

Well Known Member
After removing nose wheel I decided to repack the bearings. After thorough washing I found out that one of the bearings has severe pitting on almost all rollers.
I am wondering what are the causes? Manufacturing defects, foreign particles in grease I used or a plain side-load while turning? Only one assembly is pitted the other one is perfect. The ring in the disc is perfect not a scratch. Any insight appreciated.














All assemblies are original with over 1,500 hours flight time on them.



Edit; flight time doesn't mean much for the bearings they survived 2,182 landings some of them not pretty...
 
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I have read that there are 2 primary causes of taper wheel bearing failures. Over torqueing the axle, even slightly or severly under torqueing. The other is contamination in the grease, typically introduced during field repacking.

It happened to me with my car when I was a young lad. Yep over torqued it just a bit. Lasted only 500 miles afterwards.

It takes huge loads to over load these bearings in use. Almost never the cause.

Go with sealed bearings and you eliminate one of the causes. That's what automakers did.
 
brg.

Vlad, Go for the ball bearing upgrade. There are plenty of issue's with that fork and no spacer between the inner races. The ball bearing setup works very well with one less chance to lock up the front wheel and do a digger. Ron
 
RVDan said:
I have read that there are 2 primary causes of taper wheel bearing failures. Over torqueing the axle, even slightly or severly under torqueing. The other is contamination in the grease, typically introduced during field repacking.


....
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Thanks Dan it might be the cause. What puzzles me it's on one side only.





868RM said:
Vlad, Go for the ball bearing upgrade. There are plenty of issue's with that fork and no spacer between the inner races. The ball bearing setup works very well with one less chance to lock up the front wheel and do a digger. Ron
Click to expand...

LifeofReiley said:
One answer... Call Allan and get the upgrade and be done. :)
Click to expand...


Surely some day I will. I already got new bearings. :)
 
Bearing Cups

Vlad, don't forget to check the bearing cups in the wheels to make sure they are not damaged, might have to replace the one that bearing came out of.
 
bhester said:
Vlad, don't forget to check the bearing cups in the wheels to make sure they are not damaged, might have to replace the one that bearing came out of.
Click to expand...

You should always replace the race when you replace the bearing.

Grove and Beringer both offer tubeless sealed bearing front wheel replacements for the the RV, highly recommended.
 
Another vote here for the Grove nose wheel/axle system. Once you see it, you'll wonder why anyone installs the standard RVMatco style.
 
scoring

Vlad, Is there any signs of scoring between the spacers and the wheel fork? Also, what seems to be the correct torque on the axle bolt nut (bearing preload) when one is doing final assembly, changes a lot when the fork twists during loads. One reason a spacer with good dia. is very important. It stiffens the fork a lot. Ron
 
You got some water in there. The pitting is a dead give-away. It can happen on the mains just as easy, so a bearing upgrade is not the answer.
 
Wash the bearings?

The proper maintenance of a wheel bearing is to wipe the bearing completely free of all material with a clean DRY shop towel, and pack the bearing with new properly rated grease. This means to force out the old grease and replace it with new clean grease. You can do this by hand (like us old timers do) or use a bearing packing tool.

Check out tips here.

NEVER put solvent on a bearing.

Residual solvent washes the surface of the bearing and can cause the damage you are seeing.

CC
 
Did You Re-Oil the Felt Seal?

That seal is the primary barrier to water or moisture entering the bearing. Forget to oil one side and you're opening a channel. No problems on mine so far, but I have less than 1000 hours on the Hobbs. On the other hand, I'm still learning how to change/maintain tires.
Terry, CFI
RV9A N323TP
 
Alaska?

Vlad, it looks like some "Alaska" hitch hiked in your nose wheel bearings.

comfortcat said:
... wipe the bearing completely free of all material ... and pack the bearing with new properly rated grease. NEVER put solvent on a bearing.
Click to expand...

Just my experience - each A&P who has participated in my condition inspection has had me clean the bearing completely with a solvent (or used a washing station). We do a thorough inspection to make sure the bearing run free and have no foreign matter. Then we pack by hand until the grease presses out.
 
Vlad,
I don?t claim to be a taper-roller bearing expert, but I do have experience with the design and maintenance of landing gear wheels used on wide-body aircraft (brand A and brand B). The photos depict classic spalling (fatigue and subsequent loss of the metal). Trouble shooting bearings is frequently tricky. Yes, water ingress and corrosion could be a contributor as well as loss of pre-load or very high pre-load (axle nut too loose or too tight) and / or loss of lubrication. However, my ?guess? is the bearing cone & rollers are simply at the end of their fatigue lives. I don?t see corrosion elsewhere and I suspect you would have reported if the bearing was dry of grease.

I?d replace both lcone and the cup inside the wheel hub (both sides since the other side may be ready to give up), pack with Aeroshell 22 or Mobile 28 (be sure to squeeze grease into the roller cage ? yes, a bearing packer works great for this, but you can do it with your hands just as well), tighten the axle nut while slowly turning the wheel until you feel some resistance, then back off the nut about a ?flat or two?. There should be absolutely no wiggle of the wheel of any kind on the axle.

As far as inspections, you can use solvent to clear rollers / cones, MIL-PRF-680 Type II is the usual spec for solvents, but the key here is use low-pressure air to purge the solvent (don?t spin the bearing with air, however) then inspect and repack the bearings immediately. Replace any bearing that has any ding or deformation or loss of material - or one that has hit the floor. Stains can be OK if they are still smooth. The steel used in bearings is very susceptible to corrosion (even in mildly humid environments), so don?t let more than a few minutes go by from cleaning to inspection to re-packing. Or course, keep out the dirt / grime.

The prior comments about ball-bearings are interesting. Somebody might (and probably will) correct me on this, but I can?t think of a single ?modern- aircraft wheel application that uses ball bearings in place of roller bearings. Roller bearings do a great job resisting side loads inherent in aircraft wheel applications and tolerate the rapid spin-up upon touchdown, but maybe somebody has made a better mousetrap will a ball bearing setup.
Good Luck?
 
Vlad,

If you need hangar space - once you're new parts arrive - and can temporarily repack you're existing bearings for the flight, you're welcome to use my shop and even over-night if you wish.
 
n601sc said:
Vlad,
I don?t claim to be a taper-roller bearing expert, but I do have experience with the design and maintenance of landing gear wheels used on wide-body aircraft (brand A and brand B). The photos depict classic spalling (fatigue and subsequent loss of the metal). Trouble shooting bearings is frequently tricky. Yes, water ingress and corrosion could be a contributor as well as loss of pre-load or very high pre-load (axle nut too loose or too tight) and / or loss of lubrication. However, my ?guess? is the bearing cone & rollers are simply at the end of their fatigue lives. I don?t see corrosion elsewhere and I suspect you would have reported if the bearing was dry of grease.

I?d replace both lcone and the cup inside the wheel hub (both sides since the other side may be ready to give up), pack with Aeroshell 22 or Mobile 28 (be sure to squeeze grease into the roller cage ? yes, a bearing packer works great for this, but you can do it with your hands just as well), tighten the axle nut while slowly turning the wheel until you feel some resistance, then back off the nut about a ?flat or two?. There should be absolutely no wiggle of the wheel of any kind on the axle.

As far as inspections, you can use solvent to clear rollers / cones, MIL-PRF-680 Type II is the usual spec for solvents, but the key here is use low-pressure air to purge the solvent (don?t spin the bearing with air, however) then inspect and repack the bearings immediately. Replace any bearing that has any ding or deformation or loss of material - or one that has hit the floor. Stains can be OK if they are still smooth. The steel used in bearings is very susceptible to corrosion (even in mildly humid environments), so don?t let more than a few minutes go by from cleaning to inspection to re-packing. Or course, keep out the dirt / grime.

The prior comments about ball-bearings are interesting. Somebody might (and probably will) correct me on this, but I can?t think of a single ?modern- aircraft wheel application that uses ball bearings in place of roller bearings. Roller bearings do a great job resisting side loads inherent in aircraft wheel applications and tolerate the rapid spin-up upon touchdown, but maybe somebody has made a better mousetrap will a ball bearing setup.
Good Luck?
Click to expand...

My 8K lb cummins 4X4 truck has done 300,000 miles with those ball bearing type wheel bearings with all kinds of side loading and thrashing.
 
Vlad said:
After removing nose wheel I decided to repack the bearings. After thorough washing I found out that one of the bearings has severe pitting on almost all rollers.
I am wondering what are the causes? Manufacturing defects, foreign particles in grease I used or a plain side-load while turning? Only one assembly is pitted the other one is perfect. The ring in the disc is perfect not a scratch. Any insight appreciated.

All assemblies are original with over 1,500 hours flight time on them.

Edit; flight time doesn't mean much for the bearings they survived 2,182 landings some of them not pretty...
Click to expand...

Interesting that we found the exact same problem on a plane in for inspection today. The bearings were full of grease. Plane has 1,100 hrs (RV-10). The bearing races are very nice still, so just the bearings are ruined. Got some new bearings ordered in the interest of time and will get it going next week. The main wheel bearings are fine. Just the nose wheel is badly pitted.
 
pa38112 said:
You got some water in there. The pitting is a dead give-away. It can happen on the mains just as easy, so a bearing upgrade is not the answer.
Click to expand...

...Actually our bearing upgrade will stop this as they are permanently lubricated with water proof grease and will never require service, Our main bearings are double sealed, water proof, incorporate dust / debris deflectors and are designed to, and can be run submerged. It doesn't get much better than this. These will never require service as well. We do recommend replacing these every 50,000 flight hours, or 100,000 landings whichever occurs first just to feel secure.Thanks for your support over these past years, and Happy Holidays to all from Allan & Staff at Anti-Splat-Aero..:D:D:D
 
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