EMD MP15DC

The EMD MP15DC emerged from Electro-Motive Division's effort to produce a more versatile switcher capable of road service as well as yard work. The design drew directly from an experience gained in 1973, when EMD built sixty specially configured SW1504 locomotives for Mexican railroads. Those units required a slightly elongated frame to accommodate Blomberg B trucks, which had a longer wheelbase than the AAR type A switcher or Flexicoil trucks used on conventional EMD switchers up to that point. Recognizing that the resulting locomotive was genuinely suited for road speeds approaching 60 miles per hour, EMD formalized the concept into a new model line. The designation MP15DC reflected this broader purpose, standing for Multi-Purpose locomotive, 1500 horsepower, DC generator, and production began in 1974. The model was originally marketed simply as the MP15 until the introduction of the alternator-equipped MP15AC in 1975 necessitated distinguishing between the two variants. Production of the MP15DC continued from 1974 through 1987, with approximately 255 units delivered to a range of North American railroads. The locomotive attracted buyers looking for a capable, dual-purpose unit that could handle switching assignments while also being pressed into light road service when needed. Its adoption of Blomberg B trucks, long associated with EMD's mainline road locomotives, gave it better riding qualities and higher speed capability than traditional switchers, broadening its operational appeal. Several Class I railroads as well as regional and short line operators acquired the type during its production run. The MP15DC occupies a meaningful place in the evolution of EMD's switcher and road switcher product lines. It bridged the gap between the conventional yard switcher and the full road switcher, demonstrating that a compact, moderate-horsepower locomotive could serve multiple roles effectively. The subsequent success of the MP15AC, which incorporated more modern electrical equipment, owed much to the market acceptance that the MP15DC had established. Many examples of the type remained in service with various operators well into the twenty-first century, a testament to the durability of the basic design.

The MP15DC was powered by a twelve-cylinder version of EMD's 645E engine, a two-stroke, 45-degree V-configuration prime mover producing 1,500 horsepower at approximately 904 revolutions per minute. The 645 series engine, which EMD introduced in 1966, featured a cylinder bore of nine and one-sixteenth inches and a stroke of ten inches, yielding 645 cubic inches of displacement per cylinder, from which the series took its name. On the MP15DC this engine was aspirated by a Roots-type blower rather than a turbocharger. Power was transmitted to the traction motors through a DC generator, which distinguished the model from the later MP15AC, whose alternator-rectifier arrangement offered improved reliability over the generator-based system. The locomotive rode on Blomberg B trucks with a 108-inch wheelbase, a notably longer stance than the 96-inch wheelbase trucks used on earlier EMD switcher designs, and this contributed directly to the MP15DC's improved tracking at road speeds. The overall length of the MP15DC measured either 47 feet 8 inches or 48 feet 8 inches depending on the specific build date, reflecting minor changes made during its production span. The B-B wheel arrangement, with four powered axles distributed across two two-axle trucks, provided reasonable tractive effort for switching work while the Blomberg trucks enabled the higher speed capability that set it apart from its predecessors. The use of a front-mounted radiator intake with a belt-driven cooling fan was characteristic of the DC variant and followed the convention established on earlier EMD switchers, a configuration that would be revised on the MP15AC in favor of side intakes and electric fans to address cooling reliability concerns.

Models by: Atlas