EMD BL2

The EMD BL2 emerged in the late 1940s as Electro-Motive Division's attempt to compete in the growing road switcher market without fully abandoning the carbody styling philosophy that had defined its successful F-unit and E-unit locomotives. By that period, rivals including Alco, Baldwin, and Fairbanks-Morse had already introduced true road switcher designs featuring narrow hoods and full-length walkways, locomotives that were proving effective at displacing steam power from branch line and secondary service work. EMD's response was initially the one-off BL1 demonstrator, completed in September 1947, which used a bridge-truss carbody structure derived from the F3 but with the bodywork cut away behind the cab to improve rearward visibility for crews. The designation BL stood for Branch Line, reflecting the intended operational niche for the design. Based on feedback from prospective buyers, EMD refined the concept into the production BL2, which featured a heavier underframe and draft gear along with multiple-unit capability that the BL1 originally lacked. A total of 59 units, counting the single BL1, were built between 1948 and 1949 and sold to a handful of railroads including the Bangor and Aroostook, the Boston and Maine, the Chesapeake and Ohio, the Monon, the Rock Island, and the Western Maryland, among others. Some units were equipped with steam generators for passenger service, identifiable by an exhaust stack positioned between the front windshield panes. Despite EMD's intentions, the BL2 was not a commercial success. Its unusual carbody was costly and labor-intensive to manufacture, the mechanical components were awkward to service, and the design fell into an uncomfortable middle ground between the streamlined carbody unit and the utilitarian road switcher. The locomotive lacked the full-length side walkways that made true road switchers practical for switching operations. Production ended after just 59 units, but the experience was far from wasted. The lessons learned directly informed the development of the GP7, introduced in 1949, which proved enormously successful and established the hood unit as the dominant form of American road locomotive for decades to come. Several BL2s survived into preservation, including examples held by the Kentucky Railway Museum, the Baltimore and Ohio Railroad Museum, and the National Railroad Museum in Green Bay, Wisconsin.

The BL2 was powered by the EMD 567B prime mover, a two-stroke diesel engine that produced 1,500 horsepower and was also used in various other EMD products of the era. Drive was transmitted through a direct current diesel-electric arrangement to a B-B wheel configuration, meaning four powered axles grouped in two two-axle trucks, the same arrangement used in the F-unit carbody locomotives. The locomotive's carbody was constructed using the same bridge-truss method as the F-series rather than the load-bearing underframe typical of a conventional road switcher, which contributed to both its structural complexity and its maintenance difficulties. A Woodward electro-hydraulic governor and notched throttle controlled engine output, matching the setup standardized on the F3 and distinguishing production BL2s from the air-actuated throttle arrangement originally fitted to the BL1 demonstrator. The BL2's bodywork represented a deliberate compromise between the full-width streamlined carbody and the open hood unit, with the rear section of the body tapered and lowered to provide cab crew visibility toward the rear of the locomotive during switching moves. However, this solution created its own problems, as the resulting engine compartment layout made routine maintenance access more difficult than on either a conventional carbody unit or a straightforward hood design. The absence of continuous side walkways, a feature that would become standard on the GP7 and all subsequent EMD road switchers, further limited the locomotive's practical usefulness in switching service, undermining the very operational flexibility the design was intended to provide.