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We have a project that requires us to use a qty of 4, Ø2" yoke roller bearings mounted two per side on a trolley that roll on a steel track. The maximum total weight that we estimate on the track at any given time while in service will be between 8k to 12k lbs. This will be distrubuted too the 4 rollers which each have a capacity of 8,000 lbs each. So there would about 2k-3k per roller.

We will be using standard yoke roller bearings that have an outer ring hardness at 58-62 Rockwell C or 58-62 Rc. Our Track is hardened to 52-58 Rc. Knowing that the track has a hardness less than that of the bearing, wouldn't it stand to reason that the track will wear out before the bearing? This is unacceptable for this project.

We need a solution so we can make the bearings the wear item on this project. The track would take many man hours to replace , where a bearing would take very little time to replace and cost much less than a new track.

We would need to increase the track hardness to slightly higher than the bearing or lower the hardness of the bearing to make the bearing the wear item instead of the track. The downside to this is that I would sacrifice bearing L10 Life by lowering the hardness of the outer ring.

We would love some help solving this issue if anyone has had any experience with this problem.

****UPDATE 1/14/2020***** Since I posted this question, I have spoken with quite a few other mechanical and manufacturing engineers who specialize in bearing and track design. They all pretty much explained me the same thing that using a a track that is 40-58 Rc will work just fine with a yoke roller that has an outer ring hardness of 58-62 which is the industry standard for that type of bearing. The bearing internal rolling elements and seals will wear out long before the track or the OD of the outer. Being that the track is 52-58 Rc it should endure many yoke roller swap outs over the years with the loads and application this is being used with. I'd like to thank everyone for your time and effort put into helping us come to a conclusion of this issue.

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  • $\begingroup$ Don’t soft things wear hard things? How do soft rubber seals cut grooves in crankshaft seal faces... $\endgroup$ – Solar Mike Jan 13 at 16:38
  • $\begingroup$ @SolarMike with enough time and pressure a lot of soft things can wear a hard one, just like water and stone, enough water dripping on a stone can wear it also. But this is not the answer I'm looking for. I'm looking for an answer from someone with experience in this specific scenario. $\endgroup$ – sgwilliams Jan 13 at 17:19
  • $\begingroup$ The rasilways replace wheels on the trains and track... So you will not limit the wear to one item. $\endgroup$ – Solar Mike Jan 13 at 17:24
  • $\begingroup$ I know that there is a formula that will help determine the proper hardness for each of the items. I no longer have access to that information because the person that used to school me in this is no longer with us. You are right both do eventually wear out, but there is an formula that works very well when used. I'm just hoping that I get lucky and someone with this knowledge will read this post and help me with this. Meanwhile back to the books to try and figure it out myself. $\endgroup$ – sgwilliams Jan 13 at 17:40
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Are you are using the outer race as a "wheel". Sounds like an unusual design , maybe a steel tire should be put over the outer race. The steel tire could easily be any hardness you want. It would be poor judgement to mess with the rolling element bearing hardness. The heat-treatment has been developed over decades. One factor is the residual compressive stresses developed on the surface ( by New Departure years ago) to significantly extend fatigue life. Another is a very small amount of retained austenite ( as I remember it also improves life but I forgot the mechanism ). There are other proprietary factors like double tempering. Improvised heat-treatment will affect these factors , likely adversely. Sounds like a big chance to take because someone thinks there may be excessive wear.

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  • $\begingroup$ This is a Cam Follower / Yoke Roller, full complement, cylindrical needle bearing application. Correct nomenclature is "Outer Ring", the race or raceway is a feature on the outer ring on this type of bearing. This is not an unusual design its been a standard design for generations. And yes double tempered steel helps ensure that the fragile martensite is transformed for improved toughness and ductility. Some steels even require a 3rd temper but not many. Pressing a sleeve onto the OD of the outer ring will work for minimal load but is not advisable for heavy loads such as this application. $\endgroup$ – sgwilliams Jan 14 at 12:50
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You could try pressing the yoke rollers into plastic sleeves, essentially giving the yokes plastic ODs and thus a softer surface. We tried experimenting with this a few years ago at a bearing manufacturer I worked at. Typical materials are Acetal resin and Nylon 6/6.

It's also possible only the bearing races are heat treated, leaving the OD would be softer. I would verify that before going any further.

The hard yoke ODs could also cold work the rails making them slightly harder where they contact, that might be enough on it's own to solve your problem.

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  • $\begingroup$ Plastic will not handle the load so that is not an option. The outer rings are constructed from 52100 bearing steel, thru hardened then tempered back to 58-62 Rc. $\endgroup$ – sgwilliams Jan 13 at 18:33
  • $\begingroup$ Instead of plastics, you could press the yokes into another steel. Or press a ball bearing into either end of a metal sleeve, you get the idea. $\endgroup$ – jko Jan 13 at 18:53

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