EMD DDA40X

EMD DDA40X

UP DDA40X #6922 at Cody Park; North Platte, Nebraska.

Type and origin Power type Diesel-electric Builder General Motors Electro-Motive Division (EMD) Build date April 1969 – September 1971 Total produced 47

Specifications AAR wheel arr. D-D Gauge 4 ft 8 1⁄2 in (1,435 mm) Wheelbase Between truck centers: 65 ft (19.81 m) Truck wheelbase: 20 ft 1 1⁄2 in (6.13 m) Length 98 ft 5 in (30.00 m) Width 10 ft 4 in (3.15 m)) Height cab roof: 14 ft 11 3⁄8 in (4.56 m) overall: 16 ft 4 in (4.98 m) Loco weight 545,000 lb (247,000 kg) or 260.99 short tons (233.03 long tons; 236.77 t) Fuel capacity 8,280 US gal (31,300 l; 6,890 imp gal) Prime mover 2 × EMD 645E3A Engine type V16 diesel Aspiration turbocharged Cylinders 16 Safety systems Leslie Supertyfon model S5TRRO or S3LR horns, US&S Type 'EL' Cab Signals (#6936 equipped with US&S MicroCab ATC & CCS)

Performance figures Power output 6,600 hp (4,920 kW) Tractive effort starting: 113,940 lbf (506.8 kN) @25% continuous: 103,000 lbf (460 kN) @12 mph

Career Operators Union Pacific Numbers 6900 – 6946 Nicknames "Centennial", "Big Jack" Delivered 6900-6924 April – December 1969 6925-6946 June 1970 – September 1971 Disposition 1 in service, 46 withdrawn, (13 preserved, 34 scrapped)

The DDA40X is a 6,600 hp (4.92 MW) D-D diesel-electric built by the General Motors EMD division of La Grange, Illinois for the Union Pacific Railroad. Nicknamed "Centennial" and "Big Jack", the DDA40X uses two diesel engines (each 3,300 hp (2.46 MW)) and is the most powerful single-unit diesel locomotive ever built, although more recent locomotive designs such as the GE AC6000CW and EMD SD90MAC have come close. It is also the longest single-unit diesel locomotive ever built.

In 1969 Union Pacific was retiring the later gas turbine-electric locomotives. Union Pacific had ordered EMD DD35s and DD35As to replace the turbines, and the DDA40X was a further development. Forty seven 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 units were numbered from 6900 to 6946, with 6936 still in service.

The DDA40X is 98 ft (30 m) long. The frames were fabricated by an outside contractor, the John Mohr Company of Chicago, since the frame length exceeded the abilities of EMD's plant. Using more than one prime mover in a single locomotive was not new; the E-series were popular dual-engine locomotives, and Baldwin had produced (but not sold) a locomotive with four 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 and the 4200 HP SD45X. The locomotives were 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 was superficially similar to the Canadian comfort cab introduced by Canadian National soon afterwards in 1973, but it lacked the structural reinforcements introduced in the CN design that were carried over to future wide-nosed cabs.