Re: Solid Bearings vs. Roller Bearings



What is the date of that volume?

Specific to the "over-35" claim - the early roller bearings were also oil filled - an appeasement to the old concept that oil immersion in bearings was critically important - but the oil also increased the drag forces, especially at higher speeds. Modern RB's are nearly dry and have small quantities of grease in them for the races that maintain roller position - but not on the bearing surfaces, which are best left dry and clean. Oil is long gone from RB's.

Timken and the PRR experimented with 100 hopper cars that were RB equipped in the 1930 time frame, and found that the "friction" at higher speeds was about the same (but much lower at low speeds, and longer trains could be started with RB's compared to friction bearings). That was even after the PRR insisted in using a higher viscosity oil during the RB tests than Timken preferred in the tapered roller bearings (a design more like some of today's passenger cars - the bearings were inboard of the wheels - there was no outboard truck frame on these test cars.)

The latest roller bearings have considerably less drag, at all speeds, compared to "plain"/"solid"/ "friction"/"journal" bearings, but much of the reduction in friction at higher speeds occurred late, and after, the era of this list.

Equipment reliability was a huge savings, but an ASME book on RR equipment development indicated that once plain bearings developed better oil distribution geometries, and sealed bearing cup caps in the 1950's, the incidence of hot boxes began to reduce dramatically, but that level was still well above the failure rate for tapered roller bearings. Note that the savings were from both reduced accidents and delays due to HB setouts - which benefited the operating RR, not the car owner, hence some of the resistance to RB deployment (much more expensive.) The setout rate was remarkably high prior to the early 50's.

I have a co-worker who grew up in Portage, PA, right along the PRR mainline, and he recalls playing ice hockey on a frozen creek adjacent to the main line as a child. There was a siding at that location that often had coal hoppers on it, and as young kids they did not think anything of taking the oil soaked rags out of the bearings and using them to start a fire to stay warm.... He had no idea - 40 years later he was buying the new DODX flat cars for the M1 Abrams tank when he learned about hot box failures.


Which recalls another cost of plain bearings - I think some on this list have posted links to photos of RR car men in hump yards checking bearing oil level as cars were humped. There were so many different forms of savings by going to RB's.

But MUCH higher reliability was the main mechanical benefit.  There are many posts on this topic from a few years back that include such data, IIRC.

Dave Evans

---In STMFC@..., <thecitrusbelt@...> wrote :

I found this statement in Volume 72 of the Proceedings Of The American Railway Engineering Association:


"There is no appreciable difference between solid bearings and roller bearings above 35 mph, but other mechanical considerations heavily favor the use of all roller bearings."


I believe I have seen this same statement elsewhere.


So what other mechanical considerations favor the use of all roller bearings?




Bob Chaparro

Hemet, CA

Join { to automatically receive all group messages.