Friction Bearing Re-Babbit or replacement

6-ET · **Posted:** Tue Nov 20, 2018 2:05 am

FredNystrom wrote:

And in passing, don't think that roller bearings are pure rollers, either, because many types of rolling-contact bearings have plenty of sliding friction, tapered rollers being one of the worst offenders. IMHO, what seals the deal for roller axle bearings on rail vehicles is that they have a secure environment maintained by effective and reliable seals; and because they are cartridge assemblies, the environment stays secure (usually) until they're swapped out. (In addition, the much smaller static friction, compared to plain bearings, saves lots of fuel.) In stark contrast is the plain axle box with a non-secure hinged lid and a simple, ill-fitting rear seal that often wears out and is difficult to replace. As a result, this very dirty environment is the cause of most failures, in my opinion.

Interesting. A couple of questions:
1.) Could you expand a little on why tapered roller bearings have a lot of sliding friction?
2.) Was grit entering through the rear seal a major cause of hot boxes?

David H. Hamley · **Joined:** Tue Aug 24, 2004 3:07 pm **Posts:** 705

I always thought "solid bearing" was the better descriptive term.

jayrod · **Posted:** Tue Nov 20, 2018 10:53 am

I agree with Dave & David. You'll want to closely examine the journal for any kind of damage and address it or you may still be in the same pickle with a new brass/Babbitt.

On the bearing term controversy, we just call them brass bearings as opposed to rollers. Nobody misunderstands. I've gotten more quizzical looks using "plain" bearing.

Kelly Anderson · **Posted:** Tue Nov 20, 2018 11:01 am

6-ET wrote:

1.) Could you expand a little on why tapered roller bearings have a lot of sliding friction?

Here is a shot of an SKF self-aligning bearing with the outer race swiveled out of position. The barrel shaped rollers are held in position by the brass cage, and so have friction against it in operation.

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20180625_145001.jpg [ 297.59 KiB | Viewed 2142 times ]

Here is another of the same type of bearing. Note the wear and mushrooming on the brass cage of this one. Lots of wear, friction and heat in this bearing's history.

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bearing A.jpg [ 306.79 KiB | Viewed 2142 times ]

Also, due to the shape of these rollers, their outer ends are traveling slower than the fat center portion of each roller. Something has to slide against something. The same thing is happening with tapered rollers. Per a Timken manual, normal operating temperatures (after break in is over) for their bearings are up to 50 degrees higher than the ambient temperature, i.e. on an 85 degree day, a Timken bearing can be too hot to touch and still be considered normal. Heat comes from friction.

Friction Bearing Re-Babbit or replacement

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