Giant turbine and diesel locomotives followed Union Pacific’s famous Big Boys

Alone among U.S. railroads, UP had a substantial fleet of turbine-powered locomotives. Following a 21-month test of General Electric’s experimental 4,500-hp gas-turbine-electric locomotive No. 101 (renumbered UP 50), the road ordered 10 similar units. GE delivered UP Nos. 51–60 during 1952–53. The turbines’ voracious appetite for fuel prompted the road to pair them with tenders from retired steam locomotives in 1956. These “standard” turbines were retired during 1962–64. Here, No. 58 stands at Council Bluffs in April 1962.

Carl Hehl, A. J. Wolff collection

In 1954, UP followed the “standard” turbines with 15 similar “veranda” types, so called because of their open side walkways, visible on No. 64 working east out of Green River, Wyo., with a 4-8-4 in September 1958. UP retired Nos. 61–75 during 1963–64.

Henry R. Griffiths Jr.

UP’s third, final, and largest (in both power and quantity) group of turbines arrived from GE between 1958 and ’61. Numbered 1–30, the two-unit (three, counting tender) monsters packed 8,500 hp. The turbine prime mover was in the B unit; the A unit housed auxiliaries. The howling yellow giants were retired in 1968–69.

Union Pacific

UP’s quest for very-high-horsepower locomotives included diesel-electrics as well. In 1963–64, EMD built 27 DD35s (Nos. 72B–98B) for the road, which were essentially two 2,500-hp GP35s under one roof (but without an operating cab) riding on two four-axle trucks. Fifteen cab-equipped DD35As followed in 1965. (Overland Route partner Southern Pacific also sampled the cabless DD35, getting 3.) All of the double 35s were retired by the end of 1981. Here, DD35A No. 83 and three SD40-2s pull west out of Cheyenne in October 1978.

A.J. Wolff

General Electric got into the double-diesel game with the 5,000-hp U50. Built on the B+B-B+B running gear from retired standard and veranda turbines, the U50 was the equivalent of two U25Bs. GE constructed UP Nos. 31–53 (plus 3 for SP) during 1963–65. All 23 UP units were off the roster by April 1977. In this view, UP 31 towers over a U25B on a test run at Omaha in October 1963.

Lou Schmitz, A. J. Wolff collection

Alco’s entry in the high-high-horsepower sweepstakes was the Century 855, built in mid-1964 around two 2,750-hp engines and riding on ex-turbine trucks. Only three were built, all for UP: C855s 60 and 61 and C855B 60B. Alco bragged that the three-unit set constituted the most powerful diesel locomotive ever built. Nevertheless, they had short lives, being scrapped in early 1972.

Carl Hehl, A. J. Wolff collection

The unquestioned stars of UP’s big-diesel era were the 47 6,600-hp DDA40X units built by EMD between April 1969 and September 1971. With the first arriving a month before the 100th anniversary of the Golden Spike, and the class numbered in the 6900 series, the units became known as Centennials. The “X” in the model designation indicated the presence of a number of experimental features, notably a new modular electronics system that presaged the Dash 2 line. The 6900s also constituted North America’s first fleet of “wide-nose” units. The last regular run of a Centennial was in May 1985, but a remarkable 13 have been preserved, including No. 6936, which is part of UP’s fleet of heritage locomotives.

A.J. Wolff

The final act in Union Pacific’s double-diesel drama was a dud. The 40 U50Cs (Nos. 5000–5039) of October 1969–November ’71 had the same odd cab design and 5,000-hp rating as the U50, but rode on three-axle trucks from retired 8,500-hp turbines. The 221-ton U50Cs were the heaviest C-C diesels ever built, which caused stress fractures in their frames and trucks, and their aluminum wiring was prone to catch fire. All were out of service by the end of 1976.

A.J. Wolff