The ALCO S-1 and S-3 were 660 horsepower (490kW)diesel-electricswitcher locomotives produced by ALCO and their Canadian subsidiary Montreal Locomotive Works (MLW). The two locomotives differed only in trucks, with the S-1 using ALCO's own Blunt trucks, and the S-3 using AAR type A switcher trucks. The S-1 was built between April 1940 and June 1950, with a total of 543 completed, while the S-3 was constructed between February 1950 and November 1953 (MLW until 1957) with total sales of 300. A modified version, the S-10, was built by MLW only; 13 were built between January and June 1958.
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The S-1 and S-3 are distinguishable externally from the very similar S-2 and S-41,000 horsepower (750kW) switchers in that they have a smaller exhaust stack with a round base and a smaller 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 smaller stack is due to the lack of turbocharging.
The S-10 is not externally distinguishable from later Canadian-built S-3 locomotives; it differed mostly in electrical equipment.
The S-1 and S-3 models were sold to an extensive list of railroads and industrial operators, as detailed below. Major owners of the S-1 included the New York Central Railroad (NYC), with 71 locomotives; the New Haven with 65 locomotives; the L&N with 45 locomotives; the C&NW, with 29 locomotives; and the Pennsylvania Railroad (PRR) with 27 locomotives. Major customers for the S-3 included the CP, with 101; the CN, with 49; the NYC, with 43 locomotives; the B&M, with 16; and the PRR, with 13. The MLW S-10 was sold only to the CP.
The totals below include export orders and MLW-built locomotives.
S-1
ALCO constructed approximately 535 S-1s for the US market between 1940 and 1950.[1][3]
MLW constructed 13 S-10s in 1958, all for the Canadian Pacific Railway, numbered 6601–6613.[3] These units were essentially similar to late-built S3s, though with minor updates to the electrical gear.
S-11
In 1959, MLW built a final order of 660 horsepower switchers for the Canadian Pacific, as model S-11, numbered 6614–6623. The internal machinery of these units was essentially the same as that of the S-10, but the car body was radically redesigned, with the radiator on the front end of the hood instead of on the sides.[4]
Ex-Canadian Pacific MLW S-3 No. 6568 on display at the Saskatchewan Railway Museum
Numerous S-1 and S-3 locomotives remain in use, and several are preserved: