EMD GP9

The EMD GP9 entered production in 1954 as the successor to the highly successful GP7, extending Electro-Motive Division's General Purpose line of road switcher locomotives. The model proved enormously popular with North American railroads throughout its production run, with EMD ultimately completing more than 4,200 units including cab-less B units, making it one of the most widely purchased diesel locomotive models of its era. Approximately 75 railroads placed orders for the type, ranging from major Class I carriers to smaller regional lines. Among the largest customers were the Chesapeake and Ohio Railway, the Illinois Central Railroad, the Union Pacific Railroad, the Canadian National Railway, and the Pennsylvania Railroad, each of which rostered the type in the hundreds. American production of the GP9 took place at EMD's manufacturing facility in LaGrange, Illinois, and continued until 1959, when domestic output shifted toward the successor GP18 model. However, General Motors Diesel, EMD's Canadian subsidiary, continued building GP9s at its facility to serve Canadian railroad customers until August 1963, when the final example rolled out of the plant. Of the total production run, 646 locomotives were constructed in Canada for Canadian carriers, most notably Canadian National and Canadian Pacific. The GP9's legacy extended well beyond its original production years through an extensive culture of rebuilding and remanufacturing. The Illinois Central converted a portion of its fleet into GP10s by reducing the height of the short hood to improve forward crew visibility, and Conrail later performed similar rebuilds on former Penn Central units. The Southern Pacific and its subsidiary the St. Louis Southwestern Railway rebuilt most of their GP9s into GP9E and GP9R variants between 1970 and 1979. Canadian National undertook a particularly ambitious remanufacturing program beginning in 1981, rebuilding well over 200 units into GP9RM locomotives across four distinct batches extending into the mid-1990s. As of the early 2020s, Canadian National still operated a small number of these remanufactured units, a testament to the fundamental soundness of the original design.

The GP9 was powered by the EMD 567C prime mover, a sixteen-cylinder version of EMD's long-running 567 engine family, producing 1,750 horsepower. This represented an increase of 250 horsepower over the GP7's 567B engine, achieved through refinements to the 567 series rather than a wholesale change in engine architecture. The locomotive rode on a B-B wheel arrangement, meaning two two-axle powered trucks, with all four axles driven by DC traction motors. This configuration gave the GP9 good tractive effort relative to its weight while remaining mechanically straightforward to maintain, a quality that contributed significantly to its commercial appeal. Externally, the GP9 closely resembled its GP7 predecessor, sharing the characteristic long-hood, short-hood body style that defined the General Purpose line. The majority of units were delivered with a high short hood, consistent with prevailing American practice of the period, though the Southern Pacific specified low short hoods on a portion of its order to give crews better forward sightlines. EMD also offered the GP9 in a B-unit configuration without an operating cab, and Union Pacific was the largest customer for this variant, acquiring 125 of the 165 cab-less GP9B units built. A small number of GP9M units were assembled using components salvaged from older EMD F-unit locomotives, resulting in a lower rated output depending on the donor equipment used, either approximately 1,350 or 1,500 horsepower.

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