EMD SDF40-2

The SDF40-2 was not an original EMD design but rather a rebuilt and redesignated variant of the EMD SDP40F, a full-width cowl passenger locomotive originally constructed for Amtrak between 1973 and 1974. Amtrak had ordered all 150 SDP40Fs in two batches to replace its aging inherited fleet of E-units and F-units, and for a time these locomotives served as the backbone of the national passenger railroad's long-distance operations. However, a series of derailments between 1974 and 1976 damaged confidence in the type, prompted several railroads to ban the locomotives from their tracks, and ultimately convinced Amtrak to retire the fleet in favor of the EMD F40PH. Beginning in 1977, Amtrak arranged to trade the majority of its SDP40Fs back to EMD, whose components were reused in new F40PH production. A smaller portion of the fleet, however, was traded to the Atchison, Topeka and Santa Fe Railway rather than returned to EMD. The Santa Fe accepted these former Amtrak units and undertook a significant rebuilding program to make them suitable for heavy freight service. The passenger-specific equipment, including the steam generators and associated water tanks that had been implicated in the derailment controversy, was removed. The rebuilt locomotives emerged from this process carrying the designation SDF40-2, reflecting their rebuilt status and their incorporation of components and features associated with the second-generation SD40-2 freight locomotive family. In freight service on the Santa Fe, the SDF40-2 found a second career far removed from the passenger duties for which its predecessor had been designed. When the Atchison, Topeka and Santa Fe Railway merged with the Burlington Northern Railroad to form the Burlington Northern Santa Fe Railway in 1995, the SDF40-2 fleet passed to the new company. The BNSF continued to operate the locomotives until approximately 2002, when the remaining units were retired. One example has been preserved, the former Amtrak unit numbered 644, which survives as a representative of both the SDP40F passenger era and the subsequent freight rebuilding program that gave the type its final identity as the SDF40-2.

The SDF40-2 traced its mechanical lineage directly to the SDP40F, which was itself built around the EMD 645E3 prime mover producing 3,000 horsepower. The underlying platform also drew on the EMD SD40-2 freight locomotive, sharing its core running gear and electrical systems. The original SDP40F had been configured as a C-C unit riding on two three-axle trucks, and this arrangement carried over into the rebuilt SDF40-2. The most consequential changes made during the Santa Fe's rebuilding program involved stripping out the passenger heating infrastructure, including the two steam generators and the elevated 1,350-gallon water tank that had been positioned above the floor line at the rear of the locomotive. This equipment had added considerable weight to the rear end of the SDP40F and had been theorized as a contributing factor in the lateral instability that plagued the type in Amtrak service. By removing this hardware, the Santa Fe produced a more conventionally balanced six-axle freight unit built on a platform that had already proven reliable in the SD40-2 series. The cowl body, a defining visual characteristic inherited from the FP45 and the original SDP40F, was retained in the rebuilt locomotives, giving the SDF40-2 a distinctive appearance that set it apart from the more common hood-unit freight locomotives of the era.

Models by: Athearn