Southern Pacific steam switchers

Like most railroads, Southern Pacific in steam days owned a considerable fleet of switchers, very predominantly of the 0-6-0 wheel arrangement. And as with most of the SP steam locomotive roster, many were built by Baldwin, others by Alco and Lima, but a notable class of relatively modern switchers was built in SP’s own shops, 38 locomotives in switcher class S-12. Many of these survived to the end of steam. I’ve been meaning for some time to summarize the SP fleet as it was in later days.

Like other steam locomotives in the early days, SP switchers originally all had slide-valve cylinders, limiting the boiler pressure and thus the tractive effort which they could use. These older switchers also were frequently equipped with what are often called “slope-back” tenders and inside valve gear. Below is an example from Class S-8, built by Alco-Brooks in 1908 (Wilbur C. Whittaker collection, location unknown). 

But in the summer of 1913, SP began to acquire switchers in new Class S-10 with piston valves, a modern feature in use with SP road locomotives since at least as early as 1900. Engines in the S-10 class were built by Baldwin; following Class S-11 came from Lima. They were succeeded by the SP-built Class S-12 mentioned above, from the summer of 1918 to the summer of 1923, 33 of them built at Sacramento and the other five at Los Angeles General Shops.

Many of the Class S-12 locomotives were equipped with newly-built cylindrical tenders, like the one shown below (Paul Jansen photo at Bayshore, Clark Bauer collection). Long called “sausage tenders” by SP enthusiasts, they were modified after construction with the very tall oil hatch visible here. Note also that the road name lettering is entirely located on the water tank, avoiding the inevitable oil spills on the forward fuel tank.

The earliest versions of this tender design had a 4700-gallon water capacity and were classed accordingly as Class 47-C (C = cylindrical). Soon the design was enlarged to 5200 gallons, Class 52-C (taller and 3 feet longer), for most of the Class S-12 engines. The car shown above is a Class 52-C tender.

Other locomotives of Class S-12, along with those of other classes, were also equipped at times with tenders from older locomotives, suitably modified. By that, I mean changes such as cutting away the projecting sides of the oil bunkers on conventional Vanderbilt tenders for better rearward visibility. The need to do so can be visualized, looking at the Class 70-C tender shown below (behind 4-8-0 no. 2919; Joe Strapac collection).

When one of these 7000-gallon tenders was modified in this way, it looked like the photo below (Gene Deimling collection), and is sometimes called a “clear-vision” tender. (You can click on the image to enlarge it if you wish.) The switcher is from Class S-12. Incidentally, steam locomotive range was entirely a function of tender water capacity, not fuel, so reducing the fuel bunker somewhat did not limit the locomotive.

So if a person were to model a Southern Pacific steam switcher, and do so for the period after World War II, the largest class with piston valves would be the best choice. That class is Class S-12, which has the additional attraction of having been built in the railroad’s own shops.

For much more about SP steam switchers, particularly photographs, the indispensable book is this one by Gene Deimling. It was published by Benchmark Publications, Los Altos, CA, 1987.

In addition, there are other helpful references:

Diebert, Timothy S. and Joseph A. Strapac, Southern Pacific Company Steam Locomotive Compendium, Shade Tree Books, Huntington Beach, CA, 1987.

 Wright, Richard K., Editor, Southern Pacific Company Diagrams of Locomotives and Tenders, Wright Enterprises, Oakhurst, CA 1973.

I am still contemplating a modeling exercise aimed at one of these locomotives, but have been exploring options.

Tony Thompson