The EMD SD70 is a series of diesel-electric locomotives produced by Electro-Motive Diesel in response to the GE Dash 9-44CW. Production commenced in late 1992 and since then over 4,000 units have been produced; most of these are the SD70M and SD70MAC models. All locomotives of this series are hood units with C-C trucks.
Prior to the SD70ACe and SD70M-2 models, all SD70 models were delivered with the self-steering HTCR radial truck. The radial truck allows the axles to steer in curves which reduces wear on the wheels and railhead. With the introduction of the SD70ACe and SD70M-2 models, EMD introduced a new bolsterless non-radial HTSC truck as the standard truck for these models in an effort to reduce costs. The HTCR-4 radial truck is still an option.
The SD70 uses the smaller standard cab or spartan cab, common on older 60 Series locomotives, instead of the larger, more modern comfort cab. This makes it hard to distinguish from the nearly-identical SD60, the only difference being the use of the HTCR radial truck instead of the HT-C truck mounted under the SD60. The main spotting feature is the difference in length between the two models – the SD60′s 71 feet, 2 inches vs. the SD70′s 72 feet, 4 inches. The SD70 also rides higher as its frame is approximately 1⁄2 inch (13 mm) higher than the SD60′s. This model is equipped with direct current (DC) traction motors, which simplifies the locomotive’s electrical system by obviating the need for computer-controlled inverters (as are required for alternating current (AC) power). It is equipped with the 4,000 horsepower (3,000 kW), 16-cylinder EMD 710 prime mover. One hundred and twenty-two examples of this model locomotive were produced for Norfolk Southern Railway (NS), Conrail (CR), Illinois Central Railroad (IC) and Southern Peru Copper Corporation (SPCC). Conrail’s assets were split between Norfolk Southern (PRR) and CSX Transportation in 1999, and all 24 of Conrail’s SD70 units went to NS. Other than the CR paint scheme these units were built to NS specifications and numbered (2557 – 2580) in series with their SD70′s.
Production of the standard cab at EMD’s London, Ontario plant ended in 1994. The 24 Conrail SD70s were assembled from kits at Conrail’s (later NS’s) Juniata Shops in Altoona, Pennsylvania, and the IC and SPCC SD70s were assembled from kits at Super Steel Schenectady. All SD70s are still in service with Norfolk Southern and Canadian National (CN), which merged Illinois Central in 1999.
The SD70M has a wide nose and a large comfort cab (officially known as the “North American Safety Cab”), allowing crew members to ride more comfortably inside of the locomotive than the older standard cab designs. There are two versions of this cab on SD70Ms: the Phase I cab, which was first introduced on the SD60M, and is standard on the SD80MAC and SD90MACs, and the Phase II cab, which is a boxier design similar to the original three-piece windscreen on the SD60M, which is shared with the Phase II SD90MAC, SD89MAC, and SD80ACe. The Phase II cab has a two-piece windscreen like the Phase I windscreen but the design of the nose is more boxy, with a taller square midsection for more headroom.
The SD70M is equipped with D90TR DC traction motors and the 710G3B prime mover. They are capable of generating 109,000 lbf (480 kN) of continuous tractive effort. From mid-2000, the SD70M was produced with SD45-style flared radiators allowing for the larger radiator cores needed for split-cooling. Split-cooling is a feature that separates the coolant circuit for the prime mover and the circuit for the air pumps and turbocharger. There are two versions of this radiator: the older version has two large radiator panels on each side, and the newer version has four square panels on each side. This modification was made in response to the enactment of the United States Environmental Protection Agency’s (EPA) Tier I environmental regulations.
Production of the SD70M ceased in late 2004 as production of the SD70M-2 model began (the EPA’s Tier II regulations went into effect on 1 January 2005). 1,646 examples of the SD70M model were produced. Purchasers included CSX, New York Susquehanna & Western (NYSW; part of EMDX order no. 946531), Norfolk Southern and Southern Pacific (SP; now part of the Union Pacific Railroad), but the vast majority were purchased by Union Pacific.