Re: Truck bearings: Solid vs. RB


-- In STMFC@..., Anthony Thompson <thompson@...> wrote:

Dave Evans wrote:
The Mechanical Engineer's definition of "journal" is that portion of
the shaft that rotates within a bearing, AND the relative motion
between the two is sliding. There is NO sliding motion in a roller
bearing, so a roller bearing does not have a "journal".
I urge you to check any Car Builders Cyc in the period of this
list. The definitions for railroad use are quite clear.

Tony Thompson Editor, Signature Press, Berkeley, CA


A fair point. My 1940 Car builders cyc is actually rather schizophrenic on this - if we want to adopt a clear naming convention based on the prototype of our era - I believe the term is "We're hosed"

In the cyc's definition of terms, there are two entries - one for Journal Bearings, and one for Roller bearings. There are also a WHOLE bunch of entries for "Journal xxx", but no "journal roller bearing", or "roller journal bearing". The definition of journal is the part of an axle or shaft on which the journal bearing rests.

The confusion is that the definition of Journal bearing includes rollers and balls (and then a reference to see roller bearings), along with the "traditional" journal bearing components.

Looking through the vendor documents, you can sense the source of the confusion. All of the roller bearing vendors used the term journal in their adds, but generally in reference to the "journal" not the bearing itself.

ASF promoted a roller bearing on the interior of the wheel that was supported by a fixed axle (good in curves since it will allow the wheels to rotate at different speeds.) Only the term roller bearing is used here - no journals.

Hyatt refers to the bearings as roller bearings only, although they were contained in a "journal box" and the "journal" part of the axle was where the bearing was pressed on. But their roller bearings are not referred to as journal bearings.

Timken uses the term roller bearing, or Timken bearing, but not journal bearing. They do stress the importance of a good journal box - mainly to maintain the oil supply - a feature no longer used today (just thin grease today, and only in select areas) (More on this later)

SKF seems to be the most confused - spherical bearings, spherical journal bearings, and even spherical roller journal bearing. Ughh..

Based on how the definitions and the ads are written, I would surmise that the industry knew it was confronting at least 50 years of long established journal bearing practice, and was caught between trying to promote a new and hopefully better technology while at the same time avoiding the perception that roller bearings were a major change that would obsolete equipment and the maintenance workforce (or require significant re-training).

Hence the conundrum.

But I would note that the terms "friction bearing", "plain" bearing and "solid" bearing do not appear in the cyclopedia. Anti-friction bearing does appear in some of the ads to describe roller bearings.

So while the prototype in the era may have been confused with the new technology and its terminology, we will either need to remain similarly confused, or adopt some form of standard convention.

As a mechanical engineer, I will stick with journal bearings (not to be confused with Journals, journal boxes, etc), and roller bearings. Plain, solid and friction are out for me. YMMV.

Dave Evans

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