EMD SW

The EMD SW was one of several closely related switcher locomotive models produced by the Electro-Motive Corporation during the mid-to-late 1930s as part of a broader family of yard and industrial switchers powered by the Winton 201-A diesel engine. The SW designation indicated a switcher unit built on a fabricated, welded underframe constructed by EMC itself, distinguishing it from the SC model, which used a one-piece cast underframe supplied by General Steel Castings of Granite City, Illinois. Both the SW and SC shared the same 600-horsepower rating derived from a straight-eight configuration of the Winton 201-A, with the "S" in the model designation standing for "six hundred." A total of 37 SW units were produced between December 1936 and January 1939, making the welded-frame variant a notable presence in the early diesel switcher market. Customers for the SW came from a broad cross-section of American railroading, ranging from major Class I carriers to smaller industrial and terminal operations. The Chicago, Rock Island and Pacific Railroad was the single largest buyer, taking delivery of 29 units numbered 500 through 528. Other purchasers included the Elgin, Joliet and Eastern Railway with nine units, the Reading Company with six, the Chicago, Burlington and Quincy Railroad with six, and the Lehigh Valley Railroad with six more. Smaller industrial lines such as Great Lakes Steel, Inland Steel, and the Buffalo Creek Railroad also acquired SW units for switching and plant service, reflecting the type's versatility across a wide range of operational environments. The SW's legacy endured well beyond its relatively brief production run. Two examples are known to survive, though neither retains its original Winton engine. One, originally built for the Philadelphia, Bethlehem and New England Railroad as number 206, passed through the Maryland and Pennsylvania Railroad and the Stewartstown Railroad before finding a home on the Allentown and Auburn Railroad in Kutztown, Pennsylvania, where it has operated since 2014. A second survivor, originally Missouri Pacific number 5, was repowered with a Cummins diesel engine and continues to operate on the Thermal Belt Railway as that road's number 1. These surviving examples stand as tangible reminders of EMC's early success in demonstrating the practical advantages of diesel power for switching operations.

The SW was powered by the Winton 201-A engine in a straight-eight configuration, producing 600 horsepower and driving the locomotive through a DC electrical transmission system. The B-B wheel arrangement, with two two-axle trucks, provided adequate tractive effort for the yard switching duties the locomotive was designed to perform. The welded underframe that defined the SW model was fabricated directly by EMC, in contrast to the heavier cast underframe of the SC variant, though both shared identical dimensions and could accept the same running gear. Visually, the SW and SC were distinguished from the higher-powered NW and NC models by a shorter hood and a rounded-edged enclosure positioned ahead of the radiator, which observers sometimes described informally as a satchel shape. The inline eight-cylinder engine also caused the exhaust stacks to be positioned off-center toward the engineer's left side, a distinguishing detail compared to the centrally placed stacks of the V12-powered N-series units. Additional identifying features of the SW and its Winton-engined contemporaries included small louvers located near the top front corners of the hood sides and lifting vents running along the top of the hood, both of which served ventilation purposes and set these early units apart from later EMD switchers equipped with the 567-series engine. The electrical systems on production SW units were sourced from EMC's own designs, a contrast to some of the rarer N-series models that were fitted with equipment from General Electric or Westinghouse during the period when EMC's proprietary electrical components were still being developed and refined.