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Type and origin
Power type Diesel-electric
Builder Montreal Locomotive Works
Serial number 82589–82592
Model RSC-24, Specification DL-814
Build date March to April 1959
Total produced 4
AAR wheel arr. A1A-A1A
UIC class A1A'A1A'
Gauge 4 ft 8 12 in (1,435 mm) standard gauge
Prime mover ALCO 244
Engine type V12 Four-stroke diesel
Displacement 8,016 cu in (131.36 L)
Generator DC generator
Traction motors DC traction motors
Cylinders 12
Cylinder size 9 in × 10.5 in (229 mm × 267 mm)
Transmission Electric
Performance figures
Power output 1,400 hp (1,040 kW)
Operators Canadian National Railway
Class MR-14a
Numbers 1800–1803
Retired Mid-1970s

The MLW RSC-24 was a type of diesel-electric locomotive built by Montreal Locomotive Works for use on Canadian National Railway (CN).

Only four RSC-24's were built – all in 1959 — and were numbered 1800–1803 by CN. The locomotives were conceived by MLW as a way to use the 12-cylinder 244 diesel engines removed from 4 MLW FPA-2s which were receiving the more-capable Alco 251 engine (making them similar to the MLW FPA-4 locomotive).

The model 244 diesel engine used in the RSC-24 program saw their horsepower derated to 1,400 hp (1,040 kW). In order to make the locomotive suitable for weight-restricted light rail branch lines, MLW built the locomotives using a switcher frame as a start, resulting in the "squashed" appearance of a road switcher. This was largely the result of a very short rear hood housing the electrical cabinet, whereas electrical cabinets were normally located in the long hood on most road switcher designs. In order to make the locomotive suitable for weight-restricted light rail branch lines, MLW spread the weight over the rail surface using A1A-A1A trucks (2 powered axles, 1 unpowered axle) which were manufactured by Dominion Foundries and Steel (DOFASCO); this same truck was also adopted for the MLW RSC-13. This resulted in less traction, hence the need to de-rate the engine horsepower to avoid wheel slippage.

The RSC-24 was a one-of-a-kind diesel locomotive design, and CN used these unique units to replace 2-6-0 or 4-6-0 steam locomotives on light rail branch lines in eastern Canada. In May 1969, 1802 was wrecked in a head-on collision at Pointe-à-la-Garde, Quebec. The remaining three units found their way to the South Shore of Nova Scotia toward the end of their career by the late 1960s, and their domain extended throughout CN's former Halifax and Southwestern Railway system.

The troublesome model 244 diesel engine plagued the units throughout their lifespan, and they were retired in the mid-1970s, when CN also scrapped its MLW RSC-13 fleet; the A1A trucks of the RSC-13 and RSC-24 fleets were used by CN to retruck several dozen MLW RS-18s to become MLW RSC-14s.

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