The EMD DDA40X
was a D-D diesel-electric locomotive
built by the General Motors EMD
division of La Grange, Illinois
for the Union Pacific Railroad
. Nicknamed "Centennial" and "Big Jack", it uses two diesel engines (each providing ), and although recent locomotive designs such as the AC6000CW
have come close, the DDA40X remains the most powerful single-unit diesel locomotive type ever built. It is also the longest single-unit diesel locomotive ever built.
In 1969 Union Pacific began retiring their gas turbine-electric locomotives
, and a more fuel-efficient replacement was needed. Union Pacific had previously ordered EMD DD35s
to replace the turbines, and the DDA40X was a further development of the concept. Forty seven locomotives of this type were built between June 1969 and September 1971, except the first one delivered in April in time to participate in the celebrations of the centennial anniversary of the completion of the Transcontinental Railroad
driving the "Gold Spike Limited" and arriving in Salt Lake City
, on the morning of May 10, 1969. The units were numbered from 6900 to 6946, with 6936
still in service.
The DDA40X is long. The frames were fabricated by an outside contractor, the John Mohr Company of Chicago, since the locomotive frame length exceeded the abilities of EMD's plant. The concept of using more than one prime mover in a single locomotive was not new. The EMD E-series
was one of... Read More