Main gear bearing fail

After landing our 12 smoothly on a concrete runway and using the brakes the right wheel of the LG suddenly blocked completely and we were very lucky to be at low speed which prevented a ground loop.
Scrary moment.
After removing the wheel the main ring of the outside bearing appeared to be split which made the rollers move out and jam. This also ruined the race on the outside.
We recently checked the play on the 100 h and the nut was tightened as per Matco instructions.
I cannot see how this side if the bearing gets any side loads causing this or was it just a monday morning bearing?

We had to replace the complete wheel by one of another friendly builder just to get home. Of course these things happen far away on a long 4 h flight.

Will order new bearings but sofar cannot get the race from the hub. No instructions in the manual for this.

Anybody experienced this failure before or a clue how this can happen?

Was there any scoring or discoloration from overheating that might suggest the bearing wasn't operating properly? Was there any noise coming from it when you towed the plane on the ground?

Well, THAT picture is more helpful! It looks discolored, which might mean the rollers weren't turning. How long since the bearing was packed? Did you use heavy duty grease?

I would love to know WHAT grease you used as well. Matco recommends a specific grease (it took me several weeks to obtain the proper grease for mine), but comments on the forum indicates most just ignore that and use any ol grease they choose.

There is absolutely no discoloring. It must be the lighting when i took the photo.

I used special Molycote heavy duty ball bearing grease also used on simular bearings in motor cycle wheels.
The grease Matco advises is not available in Europe.
On the other hand i cannot see this as a critical factor.

I did not mean to insinuate that the grease you used caused it, but if more failures happen, knowing the grease used each time might be of some value. The "proper" Matco grease is not like any other wheel bearing grease I have previously seen or used.

Hotscam said:

There is absolutely no discoloring. It must be the lighting when i took the photo.

I used special Molycote heavy duty ball bearing grease also used on simular bearings in motor cycle wheels.
The grease Matco advises is not available in Europe.
On the other hand i cannot see this as a critical factor.

Click to expand...

The Vans MM calls for Aeroshell 22 (yellow) (Page 1-11.) That is also called out in the Matco Manual (page 29.) Matco has a list of approved greases, with several in addition to Aeroshell 22.

Bob Bogash
N737G
Completed her 50th flight on Monday!

The grease can break down under heavy load and elevated temperature. I use automotive axle grease. I don't know if motorcycle axle grease is comparable. Did you find any contamination in the bearing race?

What did the actual bearing rollers look like? What happened to them?

The rollers look perfect but because of the rim which broke off that holds them they came down the taper and jammed against the race which does not look perfect.
The roller cage also in good shape.

The greases advised are difficult to get here: just very large quantities.
If it is so critical Matco should supply the right grease with their wheels.

On the other hand a good motorcycle or automotive axle grease should do the job as well I would say.
It seems like the only difference is the extreme temperature range which you require at 30000 feet.
Will continue the search for one of these greases , but it does not give me the feeling I now know the cause of the failure.

If it isn't a defective bearing, I would tend to believe it was set up too tight ,the type of grease used can be debated til cows come home ,much like religion and politics..........Tomcatrv4

So, have you inspected the rest of the bearings for any damage?? The other wheel has the same time and miles on it, so if it is an operational issue it should be common on all 4 bearings.

Considering the size and hours on the 12 fleet, and the fact that this is the first time I have heard of this problem, I suspect it is more than likely that this is a one time event, possibly due to a material or manufacturing failure of the bearing itself.

Let me start by saying I'm not a metallurgist. Someone knowledgeable may glean some information from the face of the separation line like a pre-existing flaw. If you are close to a university with a metallurgy program they might give it to their students as a project to examine for free.

Bad wheel bearing

Sorry you had the wheel bearing problem. There are multiple causes that can have this end effect. Grease, impact, defective bearing, improper mounting, improper bearing fits on other components, just too many to guess from this side of the pond. I work with bearings everyday and if the outer race is still stuck in the wheel I can help. There is a trick to getting it out with out harming the rest of the wheel. It might have spun in the bearing bore of the wheel which will be bad. To remove the outer race down in a bore, just mask everything off and use a welder and run a small bead on the inside of the bad race. Do it all the way around and fast and ugly is fine. After doing this just let it cool on it's own and turn the wheel upside down and it should fall out. What happens is the race will expand when you heat it up but it will shrink back smaller than it was. Old trick that works.
Good luck.
DWC7A
RV7A still under construction.

Grove Brakes Wheels Bearings

Thinking about using Grove 51-201 Brakes, Wheels and Bearings on my 12 and a grove parking break valve.

Any Pros or Cons

Any Help would be appreciate
Thanks

Thanks for all the Ideas.
Ordered new bearings and complete hub wirh races from Matco.
They blame the grease and advice to replace the complete hub

Good tip DWC7A; will try that n the old hub.

Just for information here, this is the way Matco wants us to do it. Most of us who have been greasing and adjusting bearings our whole life, find this almost disturbing - but correct for our bearings.

Matco's website http://matco.veracart.com/pdf/GeneralizedTechR2.pdf? says the following:
"The axle nut should be tightened until all play is out of the assembly. Rotate the wheel back and forth while tightening the nut to help seat the bearing. When all play is out of the assembly, and the wheel rotates freely, tighten to the next castle slot and insert the cotter pin. The rubber seal on the tapered roller bearings will remain stationary while the wheel rotates around it. If the seal is spinning on the axle, the nut should be tightened further until the seal stops spinning with the wheel."
"IMPORTANT NOTE ABOUT AXLE NUT TORQUE ON WHEELS WITH TAPERED
ROLLER BEARINGS
Your MATCG mfg wheel is equipped with Timken tapered roller bearings with integrated grease seals on the bearing cone to ensure the longest possible life. The torqueing procedure for bearings with these type seals is different than for tapered roller bearings without them, A common torqueing technique for bearings without seals is to tighten the axle nut until the wheel stops spinning freely and then back off to the nearest locking feature. THIS TECHNEQUE WILL NOT WORK ON A BEARING WITH AN INTEGRATED SEAL. The reason for a different torqueing technique is that the grease seal produces some drag and makes the wheel feel somewhat stiff when rotated.
Reducing the axle nut torque until the wheel spins freely will allow the grease seal and the bearing cone to improperly rotate with the wheel (the cone must not rotate relative to the axle). The higher rolling drag is completely normal for this bearing and allows for longer bearing life since the seal will keep most contaminants out. Timken specification state, for example, that the two 1.25 inch tapered roller bearing used on the WE51 will produce between 18-26 inch pounds of torque (drag) when properly installed. Alight coating of grease on the seal will help reduce the drag on initial installation. "The drag will also reduce after the bearings have been installed and the seal relaxes in the bore. It is important that the axle nut torque be sufficient to keep the seal from rotating with the wheel."

Hotscam said:

On the other hand a good motorcycle or automotive axle grease should do the job as well I would say.

Click to expand...

I wouldn't expect that a good motorcycle or automotive axle grease would be anything like Aeroshell 22

Dave and Trina,

I'm curious as to why you think automotive axle grease wouldn't work. I use it because the environment is identical during the duty cycle. Am I missing something?

Rich

I have pondered the reasons as well. Here is my feelings, not supported by any real facts other than those stated:
That tiny wheel during landing goes from zero to ultra fast bearing spin almost instantly, unlike automotive or motorcycles (that have a far larger tire resulting in far slower bearing speed). Until there is some heat generated, the stiff ol automotive wheel bearing grease does not do much.
The Matco recommended grease, is almost a liquid already, and would obviously afford full lubrication to the bearing, just because it is so thin.

the recommended Aeroshall grease

is most certainly not almost a liquid. I do my annual in Nov in a 65 deg hangar and that stuff is THICK!

Wayne

Don,

My first home built was a WAR FW190 with go kart wheels. I used to touch down at 80 KIAS in wheel landings which was Vso (yeah, scary airplane!). My tire tread lasted about a year, but the axle grease and bearings did just fine with auto axle grease from Auto Zone. I think I'll stick with it. BTW there was something really scary about using go kart tires with "Do Not Exceed 45 MPH" on them! I guess God protects drunks and this here idiot!

Rich

Grease is grease? uh no

In 1972 I was a resident rep on the east coast for my company for the development of a control fin actuator for a missile. There was a very heavy load requirement on the output that had to be satisfied in the qualification test program. This was a small company with a very special responsible engineer who was very experienced and very intently focused on his design. Anyway, this actuator would not pass the test for satisfying that output load requirement. I don't remember how many times the company rebuilt the actuator to a new refined configuration and we repeated the test over a period of weeks. The test scenario was always the same, the tremendous load was applied to the output shaft simulating the air loads on the control fin in a high speed low altitude environment. We would see it start cycling from one extreme to the other looking good then well into the test period, smoke and sound was quickly followed by seizure meaning another failure. Then Don specified yet another kind of grease and after the rebuild we settled in for another test expecting yet another failure. It started out the same as always, looking good. It was getting near the failure point in the test period around 9 0'clock at night as I recall, and the monitoring went into hight intensity mode. It passed the previous endurance record and was still going, spirits started picking up with each second as it went further into unexplored territory. It not only made it to the end of the required period, it showed no sign that it was anywhere near a failure. That specific grease was an essential part of the design and a version of that test became a part of the production acceptance test procedure. When we built our RV-6A I was very careful to buy and apply the exact lubricants specified even tough they were some times hard to locate (even in the USA) and the minimum volume was larger than I would ever use in a lifetime. Those lubricants are itemized on my annual condition check list and nearing 1,000 hours of operation I have never had a lubrication failure.

Since your manufacturer is claiming the failure was due to the lubrication, I think it is likely the cause as well but compliance with the installation procedure is critical too. I wish you luck with the new one, I can only imagine how you felt when this happened to your airplane. However it performs when you get everything restored it would be a very good thing to come back to this thread and post your experience.

Bob Axsom

Interesting Wayne. I had to look back at invoices, what I wound up with was called "Mobil Grease 28", which I believe was one of those authorized by Matco. I never saw it below about 76 degrees, where it was far from even close to "thick". Which one are you using?

yankee-flyer said:

is most certainly not almost a liquid. I do my annual in Nov in a 65 deg hangar and that stuff is THICK!

Wayne

Click to expand...

Mobil 28 is my grease of choice for almost everything, including wheel bearings.

RFSchaller said:

Dave and Trina,
I'm curious as to why you think automotive axle grease wouldn't work. I use it because the environment is identical during the duty cycle. Am I missing something?
Rich

Click to expand...

I don't know. That would be something that you would have to take up with Matco. They are the ones that specified a very specific grease and they know their reasons for doing so.
A $3 tube of auto grease is not in anyway the same as the $12 tube of AeroShell 22

Can't argue the fact that OEM should know best. But I'm happy with my operating experience. That's why they call it experimental!