EMD FP7

The EMD FP7 emerged in June 1949 as Electro-Motive Division's purpose-built answer to the practical challenges of diesel-powered passenger service. Although EMD's E-units had established a strong record in passenger operations, their A1A-A1A wheel arrangement posed difficulties on steep grades and in mountainous territory. Meanwhile, the F3 and its successors were proving capable freight locomotives, but adapting them cleanly to passenger service was complicated by the limited space available for the steam generators and associated water supplies needed to heat passenger cars. Rather than rely on the makeshift solutions some railroads had devised on their own, EMD formalized the concept by stretching the standard F7 carbody by four feet, creating a dedicated passenger variant with substantially greater water storage capacity. Production continued through December 1953, and over that span a total of 378 cab-equipped A units were completed, all of them lead units, as no cabless B-unit version of the FP7 was ever offered for sale. Assembly took place primarily at EMD's facility in La Grange, Illinois, though locomotives destined for Canadian railroads were completed at General Motors Diesel's plant in London, Ontario. Among the largest purchasers were the Louisville and Nashville Railroad with 45 units, the Atlantic Coast Line Railroad with 44, the Pennsylvania Railroad with 40, the Canadian Pacific Railway with 35 built by GMD, and the Milwaukee Road with 32. The Ontario Northland Railway also received 22 Canadian-built examples. These locomotives saw widespread service across the continent on named passenger trains, and some operators such as Southern Pacific and Canadian Pacific added rooftop icicle breakers to protect dome car windows from ice formations in tunnel-heavy mountain routes. The FP7's legacy rests both on its own service record and on its role as the foundation for the subsequent FP9, which carried the same stretched-carbody concept forward with the more powerful 567C prime mover. As dieselization of North American passenger service reached completion through the 1950s, the FP7 was a common and reliable presence in passenger consists. When Amtrak assumed intercity passenger operations in 1971, some FP7s continued in service for a time, and numerous examples survived into the preservation era. Specimens representing several original owners, including the Western Pacific, Milwaukee Road, Southern Railway, and Canadian Pacific, are maintained at museums and heritage railroads across the United States and Canada.

The FP7 was powered by the EMD 567B prime mover, with later production units upgraded to the 567C variant, both delivering 1,500 horsepower through a direct-current electric transmission system to a B-B wheel arrangement, with each of the four axles individually driven by a traction motor. The defining structural feature distinguishing the FP7 from a standard F7A was the addition of approximately four feet of carbody length inserted just behind the first body-side porthole, a modification that created room for expanded water tankage to supply the steam generator used in heating passenger equipment. This additional length is visually apparent in the greater spacing between the forward porthole and the first carbody filter grille, and the corresponding space beneath the frame was sometimes occupied by a distinctive barrel-shaped transverse water tank. Dynamic brake equipment was available as an option, and the fan diameter for this system changed over the production run, starting at 36 inches on early units and increasing to 48 inches on later examples. Over the course of production, detail variations accumulated across the roster, including differences in carbody louver arrangements, side grille styling, and certain features specific to Canadian-built units. Standard F7B booster units were sometimes paired with FP7 A units in service, as the B units, lacking cabs, could accommodate additional water and steam generator capacity without the spatial constraints of a control cab. The FP7 measured longer than the standard 50-foot F7A, and while visually similar to other F-unit variants, this extra length and the associated mechanical provisions for passenger heating set it apart as a mechanically distinct model rather than simply a modified freight locomotive.

Models by: Athearn