I'm a bit late to the party as I don't regularly check this thread. But in catching up I note "Mem160" asked about friction bearings. One of the responses included the following:
Technically all bearings are friction bearings .... Roller and plain. Plain bearings are often referred to as friction bearings informally but it is technically not correct.
Correct that all bearings involve some degree of friction. However regarding the statement that it is not technically correct to use the term "friction bearing", I would add the words "in an engineering or textbook context." In a railroad context, it IS appropriate and correct because that is the term the industry uses and has used for at least 60 years. For example, the Field Manual for the AAR Interchange Rules, Rule 90, notes "Friction (plain) journal bearings" as prohibited in interchange. That's the 1996 version as it was the first one I put my hands on but it may well read the same today.
Furthermore, get out your November 1954 issue of TRAINS magazine (you DO have a copy, right?
). On page 4 is an ad from Timken, promoting roller bearings of course. Included is the phrase "...and cars with friction bearings".
So while the term may be scientifically inappropriate, when used in a railroad context I would submit it is entirely appropriate.
The issue with failure of a plain bearing is that hardly any railroad, and probably no Class 1's have the tools or materials to repair one when something happens hence the general ban in standard AAR interchange.
To "tools and material" I would suggest we add "knowledge". Sadly few carmen today would have any idea what they were looking at if they encountered one, just as few of today's engineers would have a clue if confronted with the backhead of a steam locomotive. Times change!