EMD SD70

The EMD SD70 entered production in late 1992 as the base model of a new locomotive family intended to succeed the SD60 series. Electro-Motive Diesel developed the SD70 line as a response to evolving railroad operational demands and tightening emissions regulations, and the platform ultimately proved far more expansive than its humble origins suggested. While only 122 examples of the base SD70 model were constructed between 1992 and 2004, the broader SD70 family spawned numerous variants that collectively account for thousands of units in service across North America and beyond. The original SD70 found buyers in a small but notable group of railroads. Norfolk Southern was the primary customer, with Illinois Central and Conrail also purchasing units. The 24 locomotives ordered by Conrail were assembled from component kits at Conrail's Juniata Shops facility in Altoona, Pennsylvania, rather than at EMD's main plant in London, Ontario. When Conrail was divided between Norfolk Southern and CSX in 1999, all 24 of the Conrail SD70s passed to Norfolk Southern, where they were renumbered into the existing NS SD70 roster. Illinois Central's units eventually came under Canadian National ownership following that railroad's merger with Illinois Central in 1999. Production of the standard cab configuration at the London, Ontario facility concluded in 1999, marking the end of the base SD70's production run for domestic North American customers. The SD70 family as a whole holds considerable significance in modern railroad history. The SD70MAC variant, introduced in 1993, became central to the widespread adoption of AC traction technology on American freight railroads, competing directly against General Electric's AC4400CW. Later, the SD70ACe carried the platform into the era of stricter EPA emissions compliance. Norfolk Southern took the unusual step of beginning a conversion program in February 2017 to repower and rebuild its DC-equipped SD70s into AC units fitted with wide-nose cabs, a modification that would reclassify the converted locomotives as SD70ACCs, demonstrating the fundamental soundness of the original platform decades after it first entered service.

The base SD70 is a C-C road switcher powered by the 16-cylinder EMD 710G3B prime mover producing 4,000 horsepower. It employs direct current traction motors, which kept the electrical architecture relatively straightforward compared to the AC-motored variants that would follow. The locomotive rides on EMD's new HTCR bolsterless radial truck, which replaced the older HTC truck used on the SD60 series. This radial steering design was intended to reduce wheel and rail wear by allowing the axles to better align with curves. The SD70 measures 72 feet 4 inches in overall length, approximately two inches longer than the SD60, and its frame sits roughly half an inch higher than that of its predecessor. EMD's broader SD70 platform introduced a range of engineering refinements as successive variants were developed. From late 2001, the SD70M variant was produced with flared radiators derived from the SD45 design, accommodating the larger radiator cores required by a split-cooling system that separates the coolant circuits for the prime mover from those serving the turbocharger and air pumps. This modification was driven largely by compliance requirements under the EPA's Tier 1 emissions standards. The HTCR truck remained the standard fitment through 2002, after which the less costly non-radial HTSC truck became standard on newer variants, though the radial design continued to be offered as an option for purchasers who preferred it.

Models by: Athearn · Walthers