ALCO S-2 and S-4

The ALCO S2 and S4 were 1,000 horsepower (746 kW) switcher diesel locomotives produced by ALCO and Canadian licensee Montreal Locomotive Works (MLW).  Basically, the two locomotives differed only in trucks, with the S-2 using ALCO's own Blunt trucks, and the S-4 riding on standard AAR type A switcher trucks. Both were powered by ALCO 539 turbocharged, 6 cylinder diesels. The S-2 was built between August 1940 and June 1950, with a total of 1502 completed, while the S-4 was constructed between June 1949 and August 1957 (MLW until 1957) with total sales of 797. Canadian production of the S-4 started more than a year before U S production of the S-4. ALCO did not start building the S-4 until August 1950. A modified version, the S-7, was built by MLW only; 29 were built between June and August 1957.

Identification

The S-2 and S-4 are distinguishable externally from the very similar S-1 and S-3 660 hp (490 kW) switchers in that they have a larger exhaust stack with an oblong base and a larger radiator shutter area on the nose sides.  The S-1/S-3 radiator shutter area is taller than it is wide, while the S-2/S-4 radiator area is wider.  The larger stack is due to turbocharging. The carbody and cab of late S-2s are nearly indistinguishable from those of S-4s. Hence, a truck swap can cause many to mis-identify a unit.

Survivors

A few S4s are still in service on shortline railroads around the United States.  Several more are preserved in US and Canadian railroad museums.

SP1474 is in operation, in rotation, at the Orange Empire Railway Museum in Perris, CA, pulling a tourist train on weekends.

Western Pacific 563, one of 2 S4s purchased by that railroad, is today preserved at the Western Pacific Railroad Museum at Portola, California.

New York, Susquehanna and Western Railway S2 #206 sits cosmetically restored at Maywood Station in Maywood, New Jersey. ^[1]

The Cooperstown and Charlotte Valley Railroad operates a pair of restored ex-Canadian National units. S4 #3051 and S7 #3052 are both in regular tourist passenger and maintenance of way service between Milford and Cooperstown, NY.

Muskogee, Oklahoma at the Three Rivers Museum a S-2 #63-138 sits outside in the back of the Midland Valley Station.

The Houston Railroad Museum in Houston, Texas have two S-2's; Ex Santa Fe, #2350 and Ex Houston Belt and Terminal, #14.

Louisville & Nashville rebuilt many of their Alco switchers with 12-567 EMD prime movers in an effort to standardize their switching fleet.  One of these, S4 (or S4m as rebuilt) #2326 survives at Gerdau Ameristeel in Cartersville, GA.  Ameristeel recently donated the locomotive to the Southeastern Railway Museum at Duluth, GA.

The Oil Creek and Titusville Railroad operates S-2s #75 and #85 on its tourist/freight railroad.

The Virginia & Truckee Railroad acquired an S-4 from PPL Montana in 2010. The locomotive is in operable condition & slowly being repainted to the railroad's diesel colors.

Class III railroad Toledo, Lake Erie, and Western uses 3 ALCO S-2 locomotives, most commonly used, #5109 on passenger service. One S-2 is used as a parts locomotive, along with a Ex-Penn Central S-2 as a parts locomotive as well. Currently as of October 2011, TLEW isn't running due to vandalism of at least $75,000 of its equipment.

The North Alabama Railroad Museum in Huntsville, Alabama runs an S-2 in regular tourist excursions. It is Mercury & Chase #484. The engine is currently temporarily out of service due to repairs. 

References

• Pinkepank, Jerry A. (1973). The Second Diesel Spotter's Guide. Kalmbach Publishing Co., Milwaukee, WI. ISBN 0-89024-026-4. 
• Toppan, Andrew et al. Alco/MLW S-2 Roster. Retrieved on December 29, 2005.
• Toppan, Andrew et al. Alco/MLW S-4 Roster. Retrieved on December 29, 2005.
• Steinbrenner, Richard T. (2003). The American Locomotive Company: A Centennial Remembrance. On Track Publishers LLC, New Brunswick, NJ. ISBN 0-911122-07-9.