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Description
The EMD DDA40X was a 6,600 hp (4.9 MW) D-D diesel-electric locomotive built by the General Motors EMD division of La Grange, Illinois for the Union Pacific Railroad. 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, Utah, on the morning of May 10, 1969. The class was therefore nicknamed "Centennial" by the Union Pacific. The units were numbered from 6900 to 6946, with 6936 still in service.
In 1969 Union Pacific began retiring their turbines, and a more fuel-efficient replacement was needed. The DDA40X is 98 ft (30 m) long, and is the longest single-unit diesel locomotive ever built. 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. It remains the most powerful single-unit diesel locomotive type ever built, although recent locomotive designs such as the AC6000CW and SD90MAC have come close. A 4-unit DDA40X lash-up was common for the 1973-1975 period.
The DDA40X uses two diesel engines, each providing 3,300 hp (2.5 MW). The concept of using two prime movers in a single locomotive was not new. The EMD E-series was one of the more popular dual-engine locomotives, and other manufacturers had produced locomotives utilizing up to 4 diesel engines.
The 'X' in the designation stood for Experimental, as the DDA40X locomotives were used as the testbeds for technology that would go into future EMD products. The modular electronic control systems later used on EMD's Dash-2 line of locomotives were first used on the DDA40X. The locomotive was the first to be able to load-test itself using its dynamic braking resistors as an electrical load so that external equipment was not required. The DDA40X used the wide-nosed cab from the FP45 cowl units. This design closely resembled the Canadian comfort cab used on nearly all hood unit diesel locomotives today, but predated it by two decades.
As the DDA40X program was deemed a testbed, a number of experiments were conducted during the service life of these locomotives. One such test included fitting a few of the units with air raid sirens in order to warn trackside personnel when away from grade crossings, but the tests were inconclusive.
Original buyers
| Owner | Quantity |
|---|---|
| Union Pacific Railroad | 47 |
Surviving examples
- 6900 - Kenefick Park, Omaha, Nebraska
- 6901 - Pocatello, Idaho
- 6911 - Mexico Institute of Technology, Mexico City
- 6913 - Museum of the American Railroad, Dallas, Texas
- 6915 - Southern California Chapter, Railway and Locomotive Historical Society, Fairplex, Pomona, California
- 6916 - Ogden, Utah
- 6922 - North Platte, Nebraska
- 6925 - Stored at Chamberlain, South Dakota, on Dakota Southern Railway
- 6930 - Illinois Railway Museum, Union, Illinois. Used as a control cab only, engines and motors are currently non-operational.
- 6936 - Still in service with Union Pacific Heritage Fleet
- 6938 - North Little Rock, Arkansas (Sits in front of Jenks Locomotive Facility)
- 6944 - Museum of Transportation, St. Louis, Missouri
- 6946 - Western Pacific Railroad Museum, Portola, California. The last DDA40X built. This locomotive is fairly complete and on static display.
References
- Union Pacific Railroad Locomotive Department (1979). Locomotive Diagram Book. Union Pacific Railroad Company.
- Union Pacific Railroad Locomotive Department (1994). Locomotive Diagram Book. Union Pacific Railroad Company.
- Strack, Don. Union Pacific's DDA40X Centennial Locomotives. Retrieved on May 11, 2005.
- Hayden, Bob (Ed.) (1980). Model Railroader Cyclopedia-Volume 2: Diesel Locomotives. Kalmbach Books. ISBN 0-89024-547-9.
- WikiAnswers - Traction horsepower