View source for EMD DDA40X

{{Short description|Model of diesel–electric locomotive}}
{{more footnotes needed|date=August 2008}}
{{use mdy dates|date=March 2022}}
{{Infobox locomotive
| name = EMD DDA40X
| powertype = [[diesel locomotive#Diesel–electric|Diesel–electric]]
| image = The king of the monsters- DDA40X - there largest diesel locomotives ever. Riverside, CA March 1979.jpg
| caption = Union Pacific 6933 (with another DDA40X and a [[EMD GP30|GP30]]) hauls a TOFC train through Riverside, California in March 1979
| gauge = {{track gauge|ussg}}
| builder = [[Electro-Motive Diesel|General Motors Electro-Motive Division]] (EMD)
| aarwheels = [[AAR wheel arrangement#D-D|D-D]]
| uicclass = Do'Do'
| operator = [[Union Pacific Railroad|Union Pacific]]
| totalproduction = 47
| builddate = April 1969 – September 1971
| fleetnumbers = 6900 – 6946
| disposition = 12 in museums (1 operational), 1 pending disposition, 34 scrapped
| nicknames = "Centennial"
| length = {{convert|98|ft|5|in|m|2|abbr=on}}
| deliverydate = 6900-6924 April – December 1969<br />6925-6946 June 1970 – September 1971
| wheelbase = Between truck centers: {{convert|65|ft|m|2|abbr=on}}<br />[[Bogie|Truck]] wheelbase:<br /> {{convert|20|ft|1+1/2|in|m|2|abbr=on}}
| width = {{convert|10|ft|4|in|abbr=on}}
| height = cab roof: {{convert|14|ft|11+3/8|in|m|2|abbr=on}}<br />overall: {{convert|16|ft|4|in|m|abbr=on}}
| locoweight = {{convert|545,000|lb|kg|abbr=on}}<br />or {{convert|260.99|ST|LT t|abbr=on}}
| primemover = 2 × [[Electro-Motive Diesel|EMD]] [[EMD 645|16-645]]
| enginetype = [[V16 engine|V16]] [[diesel engine|diesel]]
| cylindercount = 16
| aspiration = [[Turbocharger|turbocharged]]
| poweroutput = {{convert|6600|hp|kW|-1|abbr=on}}
| maxspeed = {{convert|80-90|mph|kph|0|abbr=on|lk=in}}
| tractiveeffort = starting: {{convert|113940|lbf|kN|abbr=on}} @25% continuous: {{convert|103000|lbf|kN|abbr=on}} @12 mph
| fuelcap = {{convert|8,280|USgal|abbr=on}}
| safety = Leslie Supertyfon model S5TRRO or S3LR horns, US&S Type 'EL' Cab Signals (6936 equipped with US&S MicroCab ATC & CCS)
}}

The '''EMD DDA40X''' is a 6,600&nbsp;hp (4,943&nbsp;kW) [[AAR wheel arrangement#D-D|D-D locomotive]], built by [[Electro-Motive Diesel|EMD]] from 1969 to 1971 exclusively for the [[Union Pacific Railroad]].<ref name=":2" /> It is the most powerful [[diesel locomotive#Diesel–electric|diesel–electric locomotive]] model ever built on a single frame, having two 16-645E3A [[Diesel engine|diesel]] [[prime mover (locomotive)|prime movers]].<ref name=":0">{{Cite book |title=The field guide to trains : locomotives and rolling stock |last=Solomon |first=Brian |isbn=9780760349977 |location=Minneapolis, Minnesota |page=189 |chapter=EMD DDA40X |date=15 June 2016 |oclc=928614280 |chapter-url=https://books.google.com/books?id=tigVDAAAQBAJ&pg=PA189}}</ref> Union Pacific has marked '''DD40X''' on the cab exteriors, while EMD literature inconsistently refers to this model as either '''DD-40X''' or '''DDA40X'''.<ref>{{Cite web |url=https://www.up.com/aboutup/special_trains/diesel-electric/index.htm |title=Diesel–Electric Locomotives }}</ref>

UP's DDA40X locomotives were the culmination of the company's experiments with extremely powerful locomotives that began with its [[Union Pacific GTELs|gas turbine–electric locomotives]] and [[DD35]]s.<ref name=":1">{{Cite book|last=Schafer|first=Mike|title=Vintage diesel locomotives|date=1998|publisher=Motorbooks International|isbn=0-7603-0507-2|location=Osceola, WI|pages=40|oclc=38738930}}</ref> For manufacturer EMD, the construction of the world's most powerful single frame locomotive was a sign of the company's dominance of the North American diesel locomotive market, with only [[GE Transportation]] an equal competitor. The DDA40X also pioneered a number of new technologies that would go on to be incorporated in future EMD designs.

Ultimately, UP did not continue with exceptionally powerful locomotives like the DDA40X built on single frames, instead moving toward [[distributed power]] using smaller locomotives closer to 4,000&nbsp;hp. All DDA40X locomotives were retired between 1984 and 1986; several of them survive. Union Pacific 6936 operated as a member of the [[Union Pacific Heritage Fleet]] until 2022, when it was announced it would be donated to the Railroading Heritage of Midwest America museum.<ref name=":2">{{Cite web |title=Centennial DDA40X |url=http://www.up.com/up/heritage/fleet/centennial/index.htm |access-date=2021-07-30 |website=UP.com }}</ref><ref>{{cite web |url=https://railfan.com/up-donates-two-steam-locomotives-to-non-profit-challenger-to-run-again/ |title=UP Donates Two Steam Locomotives to Non-Profit; 'Challenger' to Run Again |last=Franz |first=Justin |date=April 28, 2022 |website=railfan.com |publisher=White River Productions |access-date=April 28, 2022 }}</ref>

==History==
<!-- [[Union Pacific Centennial]] redirects here. -->
In 1969, Union Pacific was retiring the last of their [[Union Pacific GTELs|gas turbine–electric locomotives]]. Beginning in 1963, Union Pacific had ordered [[EMD DD35]]s and [[EMD DD35A|DD35A]]s to replace the turbines, and the DDA40X was a further development from this design.<ref name=":1" />

The first DDA40X, UP 6900, was delivered in April 1969, in time for the centenary celebration of the [[first transcontinental railroad]]'s completion, driving the "Gold Spike Limited"; it arrived in [[Salt Lake City]], Utah, on the morning of May 10. In honor of this, the class was nicknamed '''Centennials'''<ref name=":1" /> and the choice of locomotive numbers in the 6900s was made for the same reason.<ref name=":2" /> Forty-six more were built between June 1969 and September 1971, numbered from 6901 to 6946.

[[File:UP Mixed Power, Feather River Canyon, 1984 - 2 Photos (26480806933).jpg|thumb|left|upright=1.2|DDA40X 6943, behind [[GE C30-7]] 2400, demonstrating its comparative length on the [[Keddie Wye]] of the [[Feather River Route]] in 1984]]

The DDA40X is {{convert|98|ft|m|abbr=on}} long. The frames were fabricated by the John Mohr Company of Chicago, because they were too large for EMD's factory. The use of more than one prime mover in a single locomotive was not new; the [[EMD E-unit|E-series]] were popular dual-engine locomotives, and Baldwin had produced (but not sold) a locomotive with four diesel engines.

The ''X'' in the model number stood for ''experimental'', as DDA40X Centennials were testbeds for technology that would go into future EMD products. UP frequently used these locomotives to haul heavy freights. Each unit successfully ran about {{convert|2000000|mi|spell=in}} before they were retired from revenue service in 1985. The modular electronic control systems later used in [[EMD Dash-2]] models were first used on the DDA40X and the 4,200&nbsp;hp [[EMD SD45X|SD45X]]. All DDA40X units included a new load test circuit, whose [[dynamic braking]] resistors allowed units to load test without a track-side load test box. Gearing was 59:18, allowing {{cvt|80|mph}} on freight trains.

The DDA40X has a [[Cab (locomotive)|wide nose]] akin to those on the [[EMD F45|F45]] and [[EMD FP45|FP45]] [[cowl unit]]s. These cabs were superficially similar to the Canadian [[comfort cab]] introduced by Canadian National in 1973, though without the structural reinforcements of the Canadian design.<ref>CN Locomotive Cab Layout GR-20c, Commission of Inquiry Hinton Train Collision, December 1986</ref>

Other experiments were conducted during the service life of these locomotives. A few of the units were fitted with Federal Signal Thunderbolt air raid sirens to warn track-side personnel when away from grade crossings, but the results were inconclusive.<ref>{{Citation |last=Edmund |title=UP_6918_TB-1003 |date=2018-09-04 |url=https://www.flickr.com/photos/gmpullman/42670106420/ |access-date=2022-12-02}}</ref><ref>{{Citation |last=Edmund |title=UP_DDA40X_TB-1003 |date=2008-12-15 |url=https://www.flickr.com/photos/gmpullman/43760748844/ |access-date=2022-12-02}}</ref> Another test included the modular electrical components, which was successful. This made for easier diagnosis of electrical problems. These modifications were used in all future locomotives built by EMD.

Despite their excellent performance and relatively good efficiency, these units were costly to maintain, which ultimately prompted Union Pacific to begin placing them into storage in the early 1980s. But in early 1984, as rail traffic rebounded, Union Pacific brought 25 units out of storage and rebuilt them to return to service.<ref name=Strack>{{cite web|author=Strack, Don|title=Union Pacific DDA40X Centennial Locomotives|url=http://utahrails.net/articles/up-dda40x.php|accessdate=7 April 2011}}</ref><ref>{{Cite web |title=EMD DDA40X Centennial |url=https://www.trains.com/ctr/railroads/locomotives/emd-dda40x-centennial/ |access-date=2022-12-17 |website=Trains |language=en-US}}</ref> All locomotives were finally retired by 1986. Twelve DDA40X units are preserved by various museums, while another unit survives as a source of spare parts for other locomotives. [[Union Pacific 6936|UP 6936]], the sole operating unit, was owned by Union Pacific and was used in excursion service until 2016. In 2022, this locomotive was donated by Union Pacific to the Railroading Heritage of Midwest America, which returned the locomotive to operation.<ref name="RRHMA">{{cite web|last=Glischinski|first=Steve|date=April 28, 2022|title=Railroading Heritage of Midwest America, Union Pacific agree to donation of Challenger, other locomotives, cars|url=https://www.trains.com/trn/news-reviews/news-wire/railroading-heritage-of-midwest-america-union-pacific-agree-to-donation-of-challenger-other-locomotives-cars/|work=Trains|publisher=Kalmbach Publishing|access-date=April 28, 2022|archive-url=https://web.archive.org/web/20220428191606/https://www.trains.com/trn/news-reviews/news-wire/railroading-heritage-of-midwest-america-union-pacific-agree-to-donation-of-challenger-other-locomotives-cars/|archive-date=April 28, 2022}}</ref> 6936 was operated by the museum for the first time in August 2023.<ref>{{Cite web |last=Franz |first=Justin |date=2023-09-06 |title=Union Pacific 'Centennial' Restored to Service in Illinois |url=https://railfan.com/union-pacific-centennial-restored-to-service-in-illinois/ |access-date=2023-09-06 |website=Railfan & Railroad Magazine |language=en-CA}}</ref>

== Accidents and incidents ==

* On April 6, 1974, 6903 and 6924 were heading downhill on [[Cajon Pass]] with a freight train when the train rear ended an [[Atchison, Topeka and Santa Fe Railway|ATSF]] freight train on Sullivan's Curve. 6903 was written off from the roster and scrapped in [[Lake Point, Utah]] due to heavy damage, while 6924 was repaired and returned to service.
* In June 1978, 6940 was wrecked in Peru, Wyoming. The unit was later repaired and put back into service.
* On August 28, 1978, 6921 and 6937 were wrecked at [[Point of Rocks, Wyoming]] and severely damaged. The remains of 6921 were moved to [[Salt Lake City|Salt Lake City, Utah]] for parts and later scrapped in [[Ogden, Utah|Ogden]] in 1979, while 6937 was repaired and returned to service that same year.
* On the evening of November 28, 1980, 6909 derailed in a yard at [[Commerce, California]] while it was being switched with other locomotives. The locomotive's weight turned over the rail in a curve, causing the whole unit to derail on both ends. The unit was rerailed the next morning and later repaired but was later put into storage.
* On November 30, 2000, 6936 collided with a dump truck at a railroad crossing in [[Livonia, Louisiana]], killing the dump truck driver and a railroad employee riding in the nose section. The unit was later repaired at [[North Little Rock, Arkansas]] with a reinforced nose.<ref>{{Cite web |title=Wreck damaged UP 6936 sitting in North Little Rock, Ark, December 7, 2000 |url=https://www.trainweb.us/arkansastrains/railroad/up6936/P0001809.htm |access-date=2025-09-30 |website=www.trainweb.us}}</ref>

==Surviving examples==
[[File:20240629 12 UP 6936 @ Silvis Shops open house.jpg|thumb|right|[[Union Pacific 6936]] at the Railroading Heritage of Midwest America in Silvis, Illinois]]
[[File:Union Pacific DD40AX -6944 at the National Museum of Transportation in Kirkwood, Missouri.jpg|thumb|Union Pacific Railroad DD40AX #6944 at the [[National Museum of Transportation]] in [[Kirkwood, Missouri]].]]
Thirteen DDA40Xs survive today. The following list details the surviving locomotives and their current owners.
* 6900{{dash}}[[Kenefick Park]], [[Omaha, Nebraska]]. The first DDA40X built, it was moved to its current location on April 15, 2005.
* 6901{{dash}}Ross Park, [[Pocatello, Idaho]].
* 6911{{dash}}[[Mexico Museum of Technology]], [[Mexico City]].
* 6913{{dash}}[[Museum of the American Railroad]], [[Frisco, Texas]].
* 6915{{dash}}[[RailGiants Train Museum]], [[Fairplex]], [[Pomona, California]].
* [[UP 6916|6916]]{{dash}}[[Union Station (Ogden, Utah)|Utah State Railroad Museum]], [[Ogden, Utah]].
* 6922{{dash}}[[Cody Park]], [[North Platte, Nebraska]].
* 6925{{dash}}Stored at [[Ringneck and Western Railroad, LLC]]’s rail yard located in [[Kimball, South Dakota]], having been used as a parts source and for fuel storage. It was owned by the [[Nebraska Railroad Museum]], until October 2022, when it was sold to a private owner in Kansas City.<ref>{{Cite web |last=Franz |first=Justin |date=2022-10-24 |title=Struggling Nebraska Museum Sells UP Centennial |url=https://railfan.com/struggling-nebraska-museum-sells-up-centennial/ |access-date=2022-11-15 |website=Railfan & Railroad Magazine |language=en-CA}}</ref>
* 6930{{dash}}[[Illinois Railway Museum]], [[Union, Illinois]]. Originally donated to Smoky Hill Railway & Historical Society (Kansas City area); traded and moved to the IRM in 1991. To be restored to operating condition.<ref>{{Cite web |title=Illinois Railway Museum to restore ‘Centennial’ diesel to operation |url=https://www.trains.com/trn/railroads/heritage-rail/preservation/illinois-railway-museum-to-restore-centennial-diesel-to-operation/ |access-date=2025-09-18 |website=Trains |language=en-US}}</ref><ref>{{Cite web |last=Franz |first=Justin |date=2025-10-02 |title=IRM Launches Effort to Restore ‘Centennial’ |url=https://railfan.com/irm-launches-effort-to-restore-centennial/ |access-date=2025-10-02 |website=Railfan & Railroad Magazine |language=en-CA}}</ref>
* [[Union Pacific 6936|6936]]{{dash}}Railroading Heritage of Midwest America, [[Silvis, Illinois]]. Previously operated as part of the [[Union Pacific Heritage Fleet#Rolling stock acquisition by RRHMA|UP Heritage Fleet]] until 2016. Operational.
* 6938{{dash}}[[North Little Rock, Arkansas]]. Sits in front of Jenks Locomotive Facility.
* 6944{{dash}}[[National Museum of Transportation]], [[St. Louis, Missouri]]. No. 6944 was sent to [[Altoona, Pennsylvania]] in July, 2014 for cosmetic restoration, which was completed in May, 2015. The locomotive returned to St. Louis in June, 2015.
* 6946{{dash}}[[Western Pacific Railroad Museum]], [[Portola, California]]. The last DDA40X built, it is fairly complete and on static display.

== In popular culture ==
A [[Rail transport modelling|scale model]] of DDA40X No. 6915 was featured in the 1995 music video for the song "Big Train" by [[Mike Watt]], directed by [[Spike Jonze]], and it was part of Watt's 1995 studio album ''[[Ball-Hog or Tugboat?]]''.<ref name=":3">{{Cite magazine |last=Keefe |first=Kevin P. |date=July 1995 |title=Railroad News - A Centennial's day in court |url=https://www.trains.com/trn/magazine/archive-access/trains-july-1995/ |url-access=limited |access-date=December 12, 2024 |magazine=Trains |publisher=Kalmbach Publishing |page=17 |volume=55 |issue=7}}</ref> In the video, No. 6915 was driven by Mike Watt as a drunk engineer, who threw bombs off of the locomotive and used it to run over pedestrians.<ref name=":3" /><ref name=":4">{{Cite news |date=April 28, 1995 |title=U-Pac Tunnelvision |url=https://www.newspapers.com/article/the-tennessean-union-pacific-tunnelvisio/160776596/ |access-date=December 12, 2024 |work=The Tennessean |page=69}}</ref> Union Pacific was agitated by the use of No. 6915 in the video, since an estimated 529 trespassers had been run over and killed by American trains throughout the previous year.<ref name=":3" /> In April 1995, the railroad successfully sued the video's producers, [[MTV]], [[Sony Music]], and Satellite Films, for copyright infringement.<ref name=":3" /><ref name=":4" />

==See also==
* [[EMD DD35]]
* [[EMD DD35A]]
* [[EMD DDM45]]

==References==
{{reflist}}

== Further reading ==
* 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.
* {{Cite book|editor=Hayden, Bob|title=Model Railroader Cyclopedia-Volume 2: Diesel Locomotives|publisher=Kalmbach Books|year=1980|isbn=0-89024-547-9}}

==External links==
{{Commons category|EMD DDA40X locomotives}}
* [https://web.archive.org/web/20160420165301/http://rgusrail.com/album/nekenefick/up_6900_16.jpg EMD DDA40X Dimensions]
* [https://www.steamlocomotive.com/centennials/ Union Pacific Centennials (DDA40X)]
* [https://www.youtube.com/watch?v=kj6LXplMorg Union Pacific DDA40X Centennial 6922 October 20 1984]

{{EMD SDs}}
{{UP Giants}}

{{DEFAULTSORT:Emd Dda40x}}
[[Category:Diesel–electric locomotives of the United States]]
[[Category:Electro-Motive Division locomotives|DDA40X]]
[[Category:D-D locomotives]]
[[Category:Union Pacific Railroad locomotives]]
[[Category:Railway locomotives introduced in 1969]]
[[Category:Freight locomotives]]
[[Category:Standard-gauge locomotives of the United States]]