EMD F3

The EMD F3 emerged from General Motors' Electro-Motive Division as the third entry in the celebrated F-unit series of cab unit diesel locomotives, entering production in July 1945 and continuing through February 1949. Its development grew directly out of experience gained with the earlier FT and the short-lived F2. When EMD engineers attempted to upgrade the FT's prime mover output and pair it with a new D12 main generator, early demonstration locomotives revealed problems with that generator arrangement. Rather than delay production, EMD introduced the F2 as a stopgap, reverting to the D4 generator from the FT and accepting a reduced output of 1,350 horsepower. Once the D12's difficulties were resolved, full F3 production got underway in November 1946 at EMD's La Grange, Illinois facility, and the model quickly became a commercial success. By the close of production, EMD had delivered 1,106 cab-equipped A units and 694 cabless booster B units to forty-nine domestic railroads. The F3 played a meaningful role in accelerating dieselization across the American railroad network during the late 1940s. Practical demonstrations of the type's efficiency were persuasive to railroad management still weighing the transition away from steam. The Missouri-Kansas-Texas Railroad, for instance, conducted rigorous comparative trials pitting EMD's demonstrator against its own 2-8-2 steam locomotives before committing to an order of 21 F3s, and the road achieved complete dieselization by 1952. The three largest purchasers were the Union Pacific Railroad with 179 units, the Southern Railway with 178, and the Southern Pacific Railroad with 160, while the Pennsylvania Railroad, the Chicago Burlington and Quincy, and the Atchison Topeka and Santa Fe Railway were also among the prominent buyers. The F3's later service life extended well beyond its original freight and passenger assignments. Between 1978 and 1979, the Illinois Central Gulf Railroad rebuilt eighteen F3s, along with one F7, for commuter rail use, fitting them with separate head-end power generators and redesigning their carbodies in the process. These rebuilt machines, designated FP10 and numbered in the 1100 and 1150 series, went on to serve commuters under the MBTA from 1979 through 1991 and subsequently operated on Metro-North Railroad until modern Brookville BL20GH locomotives arrived in 2008. A number of unmodified F3s have also been preserved at museums and tourist railroads, including the Steamtown National Historic Site, the Danbury Railway Museum, and the Alberta Railway Museum.

The F3 was powered by a 16-cylinder version of EMD's 567B series diesel engine, a two-stroke, mechanically aspirated design arranged in a 45-degree V configuration with 567 cubic inches of displacement per cylinder, yielding a combined displacement of approximately 9,072 cubic inches. Running at 800 rpm, this prime mover produced 1,500 horsepower, an improvement over the 1,350 horsepower of its predecessor. Power was transferred through a D12 direct current generator to four nose-suspended traction motors, with two motors carried on each Blomberg B truck in a B-B wheel arrangement. The locomotive could be geared for either freight or passenger service, and with passenger gearing it was capable of a maximum speed of approximately 102 miles per hour. Toward the end of the production run, some examples received the heavier-duty D27 traction motors and associated electrical cabling that would become standard on the subsequent F7; EMD's engineering staff informally referred to these late units as the F5, though that designation never achieved official status. The carbody of the F3 A unit underwent visible changes across its production life, and historians have grouped these variations into four distinct phases. The earliest Phase I units closely resembled the F2 and featured three portholes along the carbody sides together with characteristic wire mesh grilles along the upper edge. Phase II reduced the porthole count to two and added wire mesh panels between them, while Phase III removed that intermediate mesh. The final Phase IV substituted a stainless steel grille for the upper wire mesh that had characterized earlier examples, and it was primarily these late units that EMD's engineers occasionally labeled F5. Final assembly of all variants took place at the La Grange, Illinois plant, with the total cab unit production reaching 1,111 units according to some tallies, making the F3 one of the most numerically significant locomotives of the early diesel era.

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