EMD GP15-1

The EMD GP15-1 was introduced in June 1976 as a product of General Motors' Electro-Motive Division, developed as a new-build alternative to the rebuilding programs that many American railroads were undertaking on their aging first-generation road switchers. Rather than offering customers a rebuilt locomotive built around salvaged components, EMD designed the GP15-1 as a relatively low-cost, low-horsepower unit suitable for yard switching and light road assignments. Production continued through March 1982, during which time EMD delivered a total of 310 units to American railroads. The Missouri Pacific Railroad was by far the dominant customer for the GP15-1, purchasing more units than all other buyers combined. Missouri Pacific's units displayed several distinguishing characteristics compared to those delivered to other roads, including grab iron ladders on both sides of the long hood end. The earliest Missouri Pacific units, numbered 1555 through 1574, rode on Blomberg M trucks and featured an 81-inch nose, while units built from December 1976 onward were equipped with Blomberg B trucks and an 88-inch nose. Some Missouri Pacific examples also received a single brake shoe per wheel rather than the standard two-shoe arrangement found on typical Blomberg B trucks. The GP15-1 was the most commercially successful of three GP15 variants produced by EMD, the others being the turbocharged GP15T, of which 28 were built between 1982 and 1983, and the GP15AC, of which 34 were built in late 1982. Union Pacific, which inherited a substantial fleet through its absorption of Missouri Pacific, later rebuilt 22 of its GP15-1 units into GP15N locomotives at the Jenks shop in North Little Rock, Arkansas, fitting them with microprocessor control systems to improve adhesion and extend their operational lifespan. Many GP15-1s have continued to serve in yard and light road assignments well into the twenty-first century.

The GP15-1 is powered by a naturally aspirated 12-cylinder EMD 645E prime mover producing 1,500 horsepower, driving DC traction motors through a conventional DC generator arrangement. The locomotive rides on a B-B wheel arrangement using four-axle Blomberg trucks, with the earliest Missouri Pacific deliveries receiving Blomberg M trucks before standardization on the Blomberg B. One of the most visually distinctive features of the GP15-1 is its radiator section, which closely resembles the radiator arrangement found on the EMD SD40T-2 and SD45T-2 tunnel motors, earning the type the informal nickname "baby tunnel motors" among railroaders and enthusiasts. This design similarity has occasionally led observers to misidentify GP15-1 units as members of the tunnel motor family, despite the GP15-1 being a considerably smaller and less powerful locomotive intended for entirely different service roles. The GP15AC variant differed from the GP15-1 primarily in substituting AR10 AC alternators for the rebuilt D32 DC generators used in the standard model, a change specified by Missouri Pacific to take advantage of more modern electrical technology. Externally, the GP15AC can be distinguished by its straight side sill, a feature shared with the GP15T but absent on the GP15-1. The GP15T variant achieved the same 1,500 horsepower output through a turbocharged 8-cylinder engine rather than the roots-blown 12-cylinder unit, reducing the total cylinder count while maintaining equivalent power output. Only the 25 GP15T units delivered to the Chessie System were built with dynamic braking equipment, making them unique within the broader GP15 family.

Models by: Athearn · Atlas