|ALCO S-2 and S-4|
|Grafton and Upton Railroad #1001, an S-4, rests in Hopedale, MA on May 11, 2008.|
|Builder||ALCO and MLW|
|Build date||S-2: August 1940 – June 1950
S-4: June 1949 – August 1957
|Total produced||S-2: 1502
|AAR wheel arr.||B-B|
|Gauge||4 ft 8 1⁄2 in (1,435 mm)|
|Wheel diameter||40 in (1,016 mm)|
|Length||45 ft 5 3⁄4 in (13.86 m)|
|Width||10 ft 0 in (3.05 m)|
|Height||14 ft 6 in (4.42 m)|
|Prime mover||Alco 539T|
|Engine type||Four-stroke diesel|
|Displacement||1,595 cu in (26.14 L) per cylinder
9,572 cu in (156.86 L) total
|Cylinder size||12 in × 13 in (320 mm × 330 mm) 1⁄2|
|Power output||1,000 hp (746 kW)|
The ALCO S2 and S4 were 1,000 horsepower (746 kW) switcher diesel-electric 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.
The S-2 and S-4 are distinguishable externally from the very similar S-1 and S-3 660 hp (492 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 misidentify a unit.
A few S4s are still in service on shortline railroads around the United States. Several more are preserved in US and Canadian railroad museums.
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 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 an 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.
San Francisco Bay Railroad, the short-line railroad for the Port of San Francisco, operates the #23 and #25 Alco S-2's from the San Francisco Belt Line Railroad.
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