EMD GP39

The EMD GP39 was a diesel-electric road switcher produced by General Motors' Electro-Motive Division between June 1969 and July 1970. Only 23 units were constructed during this brief production run, making the GP39 one of the less commercially successful entries in EMD's GP family of locomotives. The model emerged as a turbocharged variant of the GP38, occupying a middle position in EMD's product lineup by offering more power than the naturally aspirated GP38 while using fewer cylinders than the larger GP40. The production roster was heavily concentrated among a small number of buyers. Twenty of the 23 units went to the Chesapeake and Ohio Railway, with the remaining three split between Kennecott Copper, which received two specially configured units, and the Atlanta and St. Andrews Bay Railroad, which took delivery of a single locomotive. Despite its modest commercial reception, the concept behind the GP39 would later be revisited by EMD when the builder introduced the GP39-2 in 1974 as part of its second-generation dash-2 series. Burlington Northern Railway later applied the GP39 designation to rebuilt locomotives derived from GP30 and GP35 units, though these were internal rebuilds rather than factory-built GP39s. A small number of related variants also emerged from the original production period, including the GP39X, a higher-powered 2,600 horsepower variant built in limited numbers for the Southern Railway, and the GP39DC, two units of which were constructed for Kennecott Copper using a DC main generator configuration.

The GP39 was powered by a turbocharged EMD 645E3 prime mover configured with 12 cylinders, producing 2,300 horsepower and driving the locomotive through a DC traction system. The use of a turbocharger to boost output from the 645 engine series distinguished the GP39 from the GP38, which relied on a naturally aspirated version of the same engine family. The locomotive rode on a B-B wheel arrangement, meaning two two-axle trucks, each axle equipped with a DC traction motor. The GP39DC variant, of which two examples were built for Kennecott Copper in June 1970, differed from the standard production model by substituting a conventional DC main generator in place of the alternator found on regular GP39 units. This made the GP39DC better suited to the specific operational requirements of Kennecott's mining railroad environment. These two units were later transferred to the Copper Basin Railway, where they were renumbered 401 and 402. Apart from the generator arrangement, the GP39DC was mechanically consistent with the standard model.