Re: HO scale ASF A-3 Ride Control trucks with roller bearings

Daniel A. Mitchell

“Plain Bearing" does indeed seem a better term.

I would suggest “plain bearing" implies only ONE moving part (the “journal") and ONE stationary part (the “bearing”). But such is almost never the case (except ox-carts maybe).

And the term “anti-friction” is confusing in that most all bearings of any type attempt to be anti-friction. The term more usually implies use of some form of ball or roller system between the journal and bearing … here the "inner-race” and “outer race” respectively. Such bearings are clearly multi-part and more complex.

In usual usage a “bearing” consists of several parts including the “journal” (usually the end of an axle of some form). The “bearing” component of this is some (hopefully) low-friction material (bronze, babbitt, teflon) that rests upon (or surrounds) the journal. And, while the “bearing” can consist of just one component and be said to be “solid”, in most cases it is actually several parts, so can’t be said to be solid.

Likewise the term “journal” in a “plain” bearing is the moving (usually rotating) part of the bearing. But in roller or ball bearings the end of the axle usually just carries the inner-race of the bearing, and itself takes no part in the motion of the bearing. Is it still a “journal”? Or is the combination of the axle and inner-race now the journal? In such case it’s no longer “plain” or “solid”.

It’s all quite complicated and confusing, with poor terminology used, and differing from one industry or application to another.

In railroad use the bearings were usually bronze, or bronze with babbitt inserts … until anti-friction bearings (mostly “roller” types) became accepted mostly in the 1960’s.

To further complicate the issue, most bearings use lubrication of some form. This forms a film between the journal and bearing … rather like liquid bearing-balls, that further reduce friction. In most cases, however there is still some physical contact (“bearing”) between the journal and bearing surfaces. However some bearings use pressurized oil to lift the so called “bearing” completely off the journal … so NO "solid” contact remains. In this case the fluid bears the weight … so what’s now the “bearing”?

Similarly consider “air” bearings where compressed air carries the weight. Or magnetic-levitation bearings ...

None of these exotic bearings has much to do with railroads. My point is that the terms “solid" and "anti-friction” are confusing and ill-defined.

Dan Mitchell

On Aug 21, 2018, at 11:43 PM, Tony Thompson <tony@...> wrote:

Dan Mitchell wrote:

Yes, but solid bearings are NOT “solid”. And ball and roller bearings still have friction.

  Gee, those bronze blocks look pretty solid . . . my impression from Railway Age and other professional literature is that the term "plain bearing" was more prevalent than "solid bearing."

Tony Thompson

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