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The Alco S2

The Alco S2 was the second model of switcher the company produced although it was constructed at the same time as the earlier S1. One of the significant differences between the two models was the increased horsepower of the S2, which was a 40% increase over the previous design. The model had a ten year production run and railroads apparently liked the increased power as the S2 went on to being Alco's best selling small switcher. While the large Class I systems tended to purchase the most S2s numerous smaller lines and industries also found the locomotive quite useful. Today, the S2 is one of the most preserved Alco models in existence and can be found throughout the country many of which are still operational. Additionally, a handful of these locomotives still find a place on shortline rosters who find the units easy to maintain, rugged, with a knack to pull just about anything.

Like its S1 sister, the Alco S2 was first produced in 1940 featuring an end-cab design using McIntosh & Seymore's 539 diesel engine. However, unlike the S1 the S2 was more powerful and came equipped with a 1,000 horsepower rating. With this increased power the S2 was more suitable for a wide range of duties from yard and switching services to freight operations (normally on branch and secondary lines). The adept little switcher and its ability to seriously pull (an Alco trademark with all of its diesels) made it a favorite amongst industries as well because it could lug around heavy cuts of cars while also being able to negotiate the sharp curves and tight clearances found in these settings.

The Alco S2, like the S1, was born out of the company's long history (even by 1940) of studying and developing small diesel locomotives that dated back to 1918. Their first true diesel line came with the HH (High Hood) series that began in 1931. These switchers were developed in conjunction with McIntosh & Seymore and Westinghouse, the former providing the prime mover and the latter air components and a revolutionary cab design (the "Visibility Cab") that enabled crews maximum visibility. With the help of famed industrial designer Otto Kuhler, Alco gave the High Hood models (which included the HH300, HH600, HH660, HH900, and HH1000) a clean look with beveled edges to the hood and cab.

When Alco released the S series in 1940 it carried over many of the Kuhler design recommendations. As mentioned above the builder also carried over the McIntosh & Seymour prime mover and also continued to work with General Electric (which provided traction motors and generators) and Westinghouse (which provided air components such as brakes and compressors). Easily the most popular design of the S series the S2 sold more than 1,500 units to various Class Is, shortlines, and industries by the time production had ended in June, 1950. Of note, the company's Montreal Locomotive Works branch also sold a number of S2s. Several Canadian lines including the Canadian National, Canadian Pacific, Alma & Janquiere, Ontario Northland as well as industry Aluminum Company of Canada all purchased the MLW version of the S2.

In total, MLW built 114 examples of the model for these companies. The S2 was also the last in the S series to be equipped with Alco's Blunt trucks, as all future designs used the more standard AAR type 1 or type 2 trucks. The S2 also offered some serious tractive effort, another reason it sold very well. For weighing only about 115 tons the locomotive could produce 69,000 pounds of starting tractive effort and around 30,000 pounds continuous.

The S2 was the same length as the S1 and one of the few noticeable differences was the size of the radiator grill, which was smaller on the S1, as well as the smoke stack (the S2 featured a flared stack at its bottom while the S1's stack was more conical). These were not all of the slight design differences of the two but some of the more noticeable. For a total production roster of Alco S2s please click here. Also, for technical data on the unit please click here. Finally, for more information about the S2 and all S series designs please refer to the chart below.

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Model Type	Units Built	Date Built	Horsepower
S-1	550	1940-1950	600
S-2	1,502	1940-1950	1,000
S-3	292	1950-1957	660
S-4	782	1950-1961	1,000
S-5	7 (Built for B&M)	1954	800
S-6	126	1955-1960	900
T-6	57	1958-1969	1,000

For a comprehensive look at the American Locomotive Company and all of the motive power types it built from steam, diesel, to electrics consider the book Alco Locomotives by Brian Solomon. Covering more than 175 pages Mr. Solomon's book details the history of Alco from its esteemed 4-6-4 Hudsons and 4-6-6-4 Challengers to vaunted RS and PA series diesel locomotives. If you have any interest in Alco this book is a must have!

Also consider Mike Schafer's Vintage Diesel Locomotives which looks at virtually all of the classic builders and models from Alco PAs to early EMD Geeps. If you’re interested in classic Alcos, or diesel locomotives in general, this book gives an excellent general history of both. If you're interested in perhaps purchasing either (or both) of these books please visit the links below which will take you to ordering information through Amazon.com, the trusted online shopping network.

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