BHP Billiton’s Electro-Motive Division SD40 and SD40-2 locomotives

This small group of locomotives only operated for ten years in Australia. However, they were obtained at a critical time during a mining boom and most went straight into service as trailing units, despite being up to forty years old at the time.

Background

In the early 1960s the three surviving North American locomotive manufacturers were engaged in a horsepower race, as North American railroads became interested in more powerful locomotives to reduce the number of locomotives required on their increasingly long and heavy trains. One technical problem limiting locomotive power was that the design of direct current (DC) generators, used effectively, limited the power of the locomotive to about 2500 h.p.

This was overcome by using three-phase alternating current (AC) alternators in conjunction with solid-state rectifiers, Alco using