The GE U50 and U50C were 5,000 hp (3,700 kW) diesel locomotives built by GE Transportation Systems. They were twin-engined locomotives, combining two 2,500 hp (1,850 kW) diesel engines. The two models were similar in layout, cab appearance and power, but differed in many ways.

U50

The U50 rode on four two-axle trucks, grouped in pairs linked by span bolsters, giving a wheel arrangement of B+B-B+B. The trucks and bolsters were re-used from scrapped UP gas turbine locomotives built by GE during the 1950s. The U50 was built in response to the Union Pacific Railroad's requirement, issued in the early 1960s, for a 15,000 hp (11,100 kW) 3-unit locomotive. The design was effectively two U25B locomotives on a single frame; each diesel engine and generator powered only the two trucks at the same end. Three were delivered to the UP in October 1963, and three to the Southern Pacific Railroad in May and June 1964. Other locomotives built to this requirement were the EMD DD35 and the ALCO Century 855.

The Southern Pacific kept the three but did not order any more. They were kept on the roster until the late 1970s, but were often sidelined. Original numbers were #8500-8502; they were later renumbered #9950-9952.

The Union Pacific was more satisfied with their three, and ordered 20 more. A batch of 12 were delivered between July and September 1964, while a final eight were built May through August 1965. They were numbered #31-53.

Most were withdrawn from service in 1973 and 1974 and traded-in to GE for more modern high-powered units, although three survived in service until 1977.

The U50 is sometimes inaccurately referred to as the U50D, a back-formation from the U50C name given to the six-axle units. The name is incorrect and was never used by the manufacturer nor the railroad. The U50 did not ride on D trucks in any case.

U50C

The U50C was an evolution of the U50 design produced between November 1969 and November 1971 solely for the Union Pacific; 40 locomotives were constructed. The U50C used a pair of three-axle trucks instead of the four two-axle trucks used by the U50. Again, these were reused trucks, this time from the later, three-unit GE turbine locomotives.

Development of the U50C was to the same UP specification that produced the EMD DDA40X "Centennial" units—a requirement for a high power locomotive for the railroad's high-speed freight trains. The span-bolster B-B+B-B design was not suited to this service; furthermore, the requirement for power at speed rather than low-speed hauling meant that six driven axles would be sufficient.

The design needed extensive weight saving not to overload six axles instead of eight. GE replaced the 16-cylinder engines of the U50 with more advanced 12-cylinder engines, which were lighter and shorter. The engines were reversed in orientation compared to the U50, placing the radiator sections at the middle of the locomotive instead of the ends. The shorter overall length required a wider radiator section design, similar to that used on the U33B /C locomotives.

The U50C was not a very successful design. The extreme weight saving measures taken to make the locomotive able to use six axles rather than eight caused numerous problems, especially in the electrical wiring; aluminum wires instead of the regular copper had been used, which proved prone to overheating. The U50Cs suffered from many serious electrical fires as well as lesser failures; the UP rewired one unit with copper experimentally and considered having a contractor replace the wiring on all of them, but decided that the units' other problems were too serious. The trucks suffered from cracks in the cast frames; the engines were prone to low oil pressure; the cooling water leaked; the dynamic brake grids were prone to failure too.

A business downturn in 1976 proved the end of the U50C in service; all were withdrawn, although many were stored in serviceable condition. No return to service occurred, though five were loaned as stationary power generators during a coal miners' strike in early 1978. All were sold for scrap during 1977-1978.

References

• Komanesky, John et al. General Electric U50 Roster. Retrieved January 14, 2005.
• Percy, Richard A. Southern Pacific U50. Retrieved January 14, 2005.
• Strack, Don. A History of Union Pacific Dieselization, 1934-1982, Part 4. Retrieved January 14, 2005.
• Strack, Don. All-Time UP Diesel Roster. Retrieved January 14, 2005.
• Strack, Don. Union Pacific GE Dash 8 Locomotives. Retrieved January 14, 2005. Mentions earlier UP GE purchases also.