EMD DDA40X

EMD DD40AX

UP DD40AX #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:
17 ft 1 1⁄2 in (5.22 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 521,980 lb (236,770 kg)
or 260.99 short tons (233.03 long tons; 236.77 t)
Fuel capacity 8,230 US gal (31,200 l; 6,850 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Disposition 1 in service, 46 withdrawn, (13 preserved, 34 scrapped)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 DD40AX 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 DD40AX 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.[1]

Description

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 DD40AX 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 DD40AX 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 DD40AX 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 DD40AX. 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 DD40AX 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.[2]

As the DD40AX program was a test, 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 to warn track-side personnel when away from grade crossings, but the results were inconclusive. Another of the tests included successful modular electrical components. This made for easier diagnosis of electrical problems. These modifications were used in all future locomotive units built by EMD. All DD40AX units included a new load test circuit, allowing units to load test without a track-side load test box. Gearing was 59:18, allowing 80 mph on passenger trains.

By 1974, averaging 22,000 miles a month, most DD40AX units had run over 1,000,000 miles and needed more maintenance. In the early 1980s, this factor, along with other issues including the higher efficiency of newer locomotives such as the SD40-2 and the national recession led to all 45 remaining units into storage. In early 1984 as rail traffic rebounded, Union Pacific brought 25 DD40AX units out of storage and rebuilt them to return to service; 15 unserviceable units were retired in June that year. All DD40AX units were retired by May 1985.[1][3] Number 6936 however is still in service with UP, though mostly in excursion service.

Surviving examples

Thirteen examples survive, including one unit (6936) which is still in service with Union Pacific.

Union Pacific #6936 is the only DDA40X still in service with Union Pacific Railroad, though it is mostly used to haul excursions.
The engineer's control stand.

References

Wikimedia Commons has media related to EMD DD40AX locomotives.
  1. 1 2 Don Strack. "Utah Rails DD40AX page". Utahrails.net. Retrieved 28 January 2015.
  2. ↑ CN Locomotive Cab Layout GR-20c, Commission of Inquiry Hinton Train Collision, December 1986
  3. ↑ "Union Pacific Railroad Roster of Diesel and Turbine Locomotives, 1934-2009". Utahrails.net. Retrieved 2 September 2015.
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