ALCO S-2 and S-4

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ALCO S-2 and S-4
Power type Diesel-electric
Builder ALCO and MLW
Build date S-2: April 1940 – June 1950
S-4: August 1950 – January 1961
Total production S-2: 1502
S-4: 797
AAR wheel arr. B-B
Gauge 4 ft 8½ in (1435 mm)
Power output 1000 hp (750 kW)

The ALCO S2 and S4 were 1000 hp (750 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. The S-2 was built between April 1940 and June 1950, with a total of 1502 completed, while the S-4 was constructed between August 1950 and January 1961 (MLW until 1957) with total sales of 797. A modified version, the S-7, was built by MLW only; 29 were built between June and August 1957.

[edit] 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.

[edit] References


 v • d • e Diesel-electric locomotives built by ALCO
Switchers: HH series, S-1, S-2, S-3, S-4, S-5, S-6, T-6, SB-8/SSB-9
RS series: RS-1, RS-2, RS-3, RS-11, RS-27, RS-32, RS-36
RSC series: RSC-2, RSC-3
RSD series: RSD-1, RSD-4, RSD-5, RSD-7, RSD-12, RSD-15
Cab units: DL-103b, DL-105, DL-107, DL-109, DL-110, DL-203, FA, FB, PA, PB
Century series: C415, C420, C424, C425, C430, C628, C630, C636, C855
Diesel-hydraulics: DH643
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