EMD GP7

The EMD GP7 entered production in October 1949 and represented a significant turning point in American locomotive design. It was the first road locomotive from Electro-Motive Division to employ a hood unit configuration rather than the enclosed car-body style that had characterized earlier EMD products such as the F-series cab units. EMD had previously attempted to enter the road switcher market with the BL2, which sold only 58 units during its brief production run, proving that railroads were not satisfied with that design. The GP7 addressed the shortcomings of the BL2 by adopting a simpler, more practical structure built on a welded steel frame. This approach reduced construction costs, simplified maintenance, and gave operating crews far better visibility in both directions, making the locomotive suitable for switching duties as well as mainline road service. Competitors including ALCO, Fairbanks-Morse, and Baldwin had already established themselves in the road switcher market, but the GP7 quickly overtook them in sales. Production continued through May 1954, during which time EMD built approximately 2,729 to 2,734 units depending on how certain rebuilt and reassigned serial numbers are counted. The vast majority served American railroads, with around 112 units delivered to Canadian operators and a small number going to Mexican lines. Demand was so strong that EMD opened a second assembly facility in Cleveland, Ohio to keep pace with orders. Five units were completed without full control cabs and designated GP7B, all of them built for the Atchison, Topeka and Santa Fe Railway in early 1953. The GP7 was succeeded in EMD's catalog by the GP9, which appeared in 1954 and incorporated refinements addressing some of the GP7's known structural weaknesses, including a tendency for the frame to bow and sag under sustained heavy service conditions. The GP7 established the GP series, which became one of the most enduring and prolific locomotive families in North American railroad history. The designation stood for General Purpose, reflecting the locomotive's intended versatility across different operating environments. Decades after their construction, many GP7s remained active on shortline railroads and in industrial service. Several Class I railroads extended the working lives of their fleets through substantial rebuild programs. Illinois Central's Paducah Shops transformed their GP7s into units designated GP8, fitting upgraded 567BC prime movers and four-stack exhaust systems among other improvements, and later offered similar rebuilding services to other railroads. Canadian Pacific rebuilt its GP7 fleet in the early 1980s as GP7u units for yard service, upgrading the prime movers with 645-series power assemblies. Missouri Pacific similarly upgraded their units with 567BC engines and revised exhaust arrangements, achieving power outputs of approximately 1,600 horsepower.

The GP7 was powered by the EMD 567B prime mover, a 16-cylinder two-stroke diesel engine producing 1,500 horsepower. This engine drove a direct current generator supplying power to four traction motors arranged in two two-axle trucks, giving the locomotive a B-B wheel arrangement. The use of an unstressed hood body mounted atop a rigid welded steel frame distinguished the GP7 structurally from the earlier car-body designs, where the outer shell contributed to the locomotive's structural integrity. The frame itself was fabricated from flat, formed, and rolled structural steel members combined with steel forgings, all welded into a single assembly. The locomotive was offered with a range of options that allowed railroads to tailor individual units to their specific operational needs, including the choice of which end to designate as the front, the installation of dynamic brakes, and the addition of a steam generator in the short hood for passenger train heating service. When a steam generator was fitted, the standard fuel tank was divided to carry both diesel fuel and boiler water. One distinctive option available on units without dynamic brakes involved relocating the two large air reservoir tanks from their standard position beneath the frame to the roof of the locomotive, above the prime mover. These roof-mounted tanks earned the informal nickname torpedo tubes among railroad workers. This arrangement freed up space beneath the locomotive for enlarged fuel and water tanks, with some roads opting for fuel capacities of up to 2,200 US gallons in freight service configurations. Visually, GP7s can be distinguished from the later GP9 primarily by the presence of three sets of ventilation grilles beneath the cab and two pairs of grilles at the end of the long hood, though some late production GP7s were built with bodywork essentially identical to early GP9 examples, complicating identification. Over 100 units produced from March 1953 onward were equipped from the factory with 567BC or 567C engines rather than the standard 567B, further adding to the variety within the production run.

Models by: Athearn · Atlas · Walthers