by Emmett R Smith
In response to a previous posting, on the UP 9000 series 4-12-2 steamers, Practical Pig asks:
“How much better would they run with roller bearings all around? I wonder how expensive these were compared to the normal floating bushings on crankpins? How much were those? They were just some kind of soft babbitt metal, I think. Were roller bearings as much as ten times more expensive at the start of it all?”
First of all, here are a couple of pictures SHOWING the basic idea of it all:
This image from Wikipedia is of an early Timken roller bearing — note the use of grooved rollers. Obviously, this isn’t very exciting to look at…or is it? This tapered bearing race on rollers alone made the mechanical late-modern completely possible, and it is difficult if not impossible to imagine how so many of the gizmoes we take for granted could even have existed without it. It reduced the inertial resistance of huge static weights and masses to a fraction and made the more efficient transmission of power in vehicles, most of all, economically possible. Indeed, I would go further and say that only with antigravity (or at least magnetic levitation!) may we even speak of any sort of historical movement era beyond roller bearings.
Now here is a postmodern descendent from the Wikipedia online archives:
As you can see, the bearing & collar can be mounted on a shaft or journal, cushioned in its supporting “pillow” block. Or the latter can be incorporated in another moving part of the assembly, such as a drive-rod end. The photos below illustrating some roller-bearing applications in steam locomotives during the last steam age (other than on the all-important axle-shafts) are from Atlantic Coast Line Railroad Class R-1 4-8-4’s — the “1800’s” by Hugh Odom, at:
Builder’s Photo (above) of R-1 showing (1) original headlight, (2) original whistle fed with saturated steam from the steam dome, (3) heavy, one-piece forged crosshead and (4) heavy, non-tapered main rods. This photo also shows the ASF wheelsets on the lead truck (indicated by the large hubs with bolts around the perimeter) which were an interesting development of the 1930’s. These wheelsets included both roller bearings and friction bearings on each axle. The friction bearings were intended to serve as a “back-up” in case the “new-fangled” roller bearings should fail.
Late photo (above) of ACL R-1 showing (1) different headlight, (2) larger whistle fed with superheated steam from the superheater header, (3) Timken light-weight crosshead (not seen are Timken light-weight piston and piston rod), and (4) light-weight, tapered main rod with roller bearing wrist pin. This photo unfortunately also shows the not-quite-spic-and-span condition somewhat typical of most ACL steam, especially near the end of steam on the railway.
In closing, I would only note that an excellent online resource for up-to-date steam power information is Mr Odom’s “Ultimate Steam Page,” at:
And finally, the Timken Bearing people are no slouches either!
[Emmett R Smith
[all text-rights reserved & all other rights revert to holders
[2 October 2009]