MLW RSC-24

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

Only 4 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 1400hp. 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. To spread the weight of the locomotive over the rail surface, MLW designed the RSC-24 using A-1-A A-1-A trucks (2 powered axles, 1 unpowered axle). This resulted in less traction, hence the need to derate the 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 mogul or 10 wheel steam locomotives on light rail branch lines in eastern Canada. One unit was wrecked in an accident on the Gaspe Peninsula, however 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.

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 A-1-A 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.