It seems like roller bearings, especially drive axle bearings, were used only for the larger mainline steam locomotives. Has any railroad run roller bearings on a smaller class of steam, say a 2-8-0 or 4-6-0?

Roller bearings were relatively expensive 'back in the day' and required comparatively careful maintenance (especially if oil-lubricated). Most 'small' steam requirements were handled with hand-me-down power rather than new-build, and it was my understanding that much of the job requirement of the smaller power was not something that beiefited 'enough' from the advantages of roller bearings on locomotives.

There was at least one effort to retrofit rolling-element bearings on a 'tourist' 2-8-0. I have not heard any account that considers it a success, although much of the difficulty appears to have been mistakes in detail design and a poor understanding of what is required for these bearings, particularly on driver axles.

One concern is that, unless the outer race and the cage are made to 'split', the bearings require the drivers to be pressed off, breaking quarter, to service them. Another concern is that, unless the actual journal on the axle is not machined and hardened as the inner race, the bearing will have a larger OD than s typical brass plain bearing, and require a larger axlebox, which may be difficult to accommodate in 'legacy' pedestals or frame construction.

If I remember correctly (and I think there are people on this list with specific reference information) there was an experiment with a grease-lubricated (M-942) bearing on main-rod big ends of a New Zealand Ja (a Cape-gauge 4-8-2 that might be in the power range of interest for this question). This was treated as a package bearing, with an integral inside race, and the rod could be removed laterally for service without needing to press out of the enlarged eye. IIRC it required new mains be forged with enlarged big ends; I don't remember if the crosshead pin end got any special treatment.

Perhaps a more useful application of "rolling element bearings" would be the application of cageless needle bearings to valve gear (as in N&W practice). These are a bit like self-renewing hydrodynamic bearings, with the hardened steel 'rollers' not being held separate from each other to rotate freely. As such, there is less need to machine or harden the pin or eye from what would be involved with the lubricated-bronze-floating-sleeve approach to bearing design.

Years ago, I was involved with a small tourist operation that ran an 0-4-0 saddle tank steam locomotive with roller bearings on the drive axles. They were in a large two piece axle housing which contained the lubricating oil. We did have a bearing failure and had to drop the drivers for repairs. Timken had a bearing on the shelf for the repair.

There are four HK Porter 2 foot gauge 0-4-0T’s at the Youngstown Steel Heritage Museum in Ohio that all have roller bearing axles. They likely represent the smallest steam locomotives factory equipped with roller bearing in the US.

Heisler used roller bearings on their fireless locomotives.

China Rail used roller bearings on their 30" gauge 0-8-0s, along with roller bearing rods.

I've thought of doing this to our tiny 2-6-2, but doubt the benefits outweigh the added costs and maintenance issues if there is a failure. Also would hate to have the brakes off and sneeze. Wind up in the next county!

Retrofitting roller bearings on locomotive driving axles can be extremely difficult, as discovered by the Great Smokey Mountains Railroad, mentioned earlier in the thread. The pedestal openings in the mainframe need to be significantly larger to accommodate the greater diameter of roller bearings and the housings that contain them. The GSMR attempted to use off-the-shelf sealed roller bearings intended for freight cars, which were squeezed into the original driving boxes. They failed after a short time in service and the locomotive was eventually rebuilt into its original configuration.

Not steam, but by 1914, Plymouth gasoline locomotives were all built with roller bearings... which by 1922 or so included locomotives of 7 or 8 tons.. a few years later up to 20 tons.

Plymouth seemed to understand the value of roller bearings, and used them as a sale tool

Having done some serious consideration and research delving into the idea of more sustainable steam, I've concluded that they work well in cannon boxes, they don't work without cannon boxes. Probably the ability of the cannon box to hold the axle and bearings exactly, relative to all parts of the axle / bearing / cannon box, is the key. Cannon boxes don't fit into frames made for standard floating boxes without making the cannon boxes, bearings and axles too small to carry the load required. So, unless designing from new frames out, a successful retrofit is unlikely. Roller bearing pony trucks and rods, however...... haven't studied critical requirements for these, perhaps Overmod can chime in with his perspective?

I recall reading about that, mostly why I was against the idea for the engine itself. Now the tender, if i can find some 3x5 bearings...

One of the reasons for using SKF roller bearings on large locomotives was that cannon boxes were not strictly necessary -- the SKF rollers are 'keg-shaped' and the races curved, so some deflection of the bearing is said to be tolerable in operation. Presumably that is also true for outside-bearing boxes that have some play in the pedestals. If you use tapered roller bearings in driving boxes (e.g. to eliminate the need for wearing hub linersA), you much use them in PAIRS if a cannon-box arrangement is not used

As an adjunct to cannon boxes, some arrangement like Franklin wedges should be used, at the rear pedestal, and a hardened liner applied to the forward pedestal.

I repeat what Chapelon speculated about rod roller bearings -- they require something like .002 tolerance in running, and it's obvious that this is not a fit that will be sustained in typical reciprocating-locomotive running. He therefore speculated (with a sense of misgiving) that the additional accommodation was made by the rods cyclically deflecting... a probable further justification for thin-section rods with spherical bushes...

Wheeling and Lake Erie home built 0-6-0's used Timken roller bearings- when new. 1930's, Brewster, Ohio, shops. Timken was an important online shipper.

It might be an interesting historical study to look at the adoption of roller bearings for industrial and switch-engine power in these years. Timken had actively started promoting the advantages of tapered roller bearings on locomotives (including the construction and touring of locomotive 1111) but from the early 1930s the advantages of internal-combustion locomotives for many small-engine duties became increasingly obvious -- certainly by the era of the early EMD S and N engines. Some railroads (NYC for example) did not prefer using roller bearings on the trailing-truck axles, despite any perceived maintenance or performance advantages. I wonder if the reasons would apply to steel-mill service...

Interesting, also, that so many of the early diesel-electrics were built with plain axle bearings.

A little known fact is that the PRR Altoona Shops installed Timkin roller bearings on the tender trucks of the 1831-era "John Bull" replica in 1940--they are still there today albeit the bearing is a bit worse for the wear.

K.R. Bell