DDA40X - MagnumMacKivler/RLCPT2 GitHub Wiki
Two DDA40X locomotives, along with a GP20 B unit pull a hotshot trailer and container train in Sept. 1973. Photo credit Kevin Cavanaugh
The DDA40X was a dual engine locomotive exclusively made for Union Pacific by Electromotive Division. The Do-Do (4-4 wheeled), cab equipped (termed with an "A") 40 series (which meant it was equipped with a turbocharged V16 645E3 engine) e x perimental locomotive was made for UP between 1969 and 1971. The locomotive experimented with modular electronics that were later used in the "Dash 2" locomotive line (such as the SD38-2 and GP40-2), and also uniquely increased the horsepower to 3300 for each engine (not used for Dash 2 locomotives.)
These locomotives, made in time for the 100 year anniversary of the 1869 completion of the Transcontinental Railroad, were nicknamed "Centennials" among railfans.
47 examples were made; 34 were scrapped (some for their cabs by Morrison Knudsen passenger GP40 rebuilds), 13 were preserved in museums (with a unit for parts actually being donated in as recent as 2024), with a noteable one in preservation being UP 6936: Union Pacific originally had this unit as a part of their Heritage Fleet for officer car specials/PR trains, and parked it around 2016 because of purported engine issues.
6936 was then donated in 2022 to the Railroading Heritage of Midwest America msueum (Known for having the UP challenger, UP 5511, and BNSF B40-8W 537) in a special equipment move along with the Challenger 3985 and other UP equipment out to their Silvis Illinois (Former National Railway Equipment and Rock Island engine shops). RRHA has since gotten the engine back to operating condition as of mid 2023.
A newly repaired UP 6936 runs sans UP wings outside of the Silvis shops on August 19th of 2023. Photo credit Cate Kratville-Wrinn.
PT-Specific Information
| General Info | - |
|---|---|
| Prime Mover | 2x EMD 16-645E3 |
| Horsepower | 6600 HP (1) |
| Truck Type | EMD "Flexicoil" D |
| Axles | 8 |
| Traction Motors | 8 |
| Minimum Weight | 519,000 lbs ⚠ |
| Maximum Weight | 563,000 lbs ⚠ |
| Model Base Speed | 65 MPH |
| Top Speed | 65, 70, 76, 82, or 90 MPH (2) |
| Electrical System | - |
|---|---|
| Generator Max Current | 6000 |
| Max Traction Motor (TM) Current | 1500 |
| Max Continuous TM Current | 1050 |
| Traction Motor Type | DC |
| Factor of Adhesion | 25% |
| Transition Mode | Automatic |
| Transition Groups | 1 |
| Transition Shunts | 1 |
| Generator Transition | No |
| Traction Control | APR with sanding |
| Dynamic Braking (DB) Mode (if used) | Mechanical Blowers |
| DB Max Current | 700 |
| DB Max Continuous Current | 700 |
| Blended Braking | No |
| Miscellaneous | - |
|---|---|
| Head-End Power (HEP) | No |
| HEP Power Consumption | N/A |
| HEP Standby/Run Mode | N/A |
| Load Ramp Speed | 2 Amps/Tick |
| TM Overload Protection | No |
| Starter Mode | Manual Primer, Manual Start |
| Air Brake Schedule | 26L |
| Compressor CFM | 254 (WBO @ 900 RPM) |
| Main Reservoir Volume | 50.7 Cubic Feet ⚠ |
###Notes:
(1): The first three units were delivered as 7000 horsepower; these were later derated to 6600 horsepower and all future units were built as such.
(2): Union Pacific DDA40X engines were geared for 90 MPH for faster trains, however they likely were geared down as they entered normal freight service.
⚠: Not verified or educated guess