Railroad Trains for the Soul: DC2AC Rebuilds
This is the second blog post covering 21st century diesel locomotive rebuilds. As alternating current (AC) traction became more dependable for all Class I railroads, converting a direct current (DC) traction locomotive with AC motors became a practical way to bypass costs of newly manufactured locomotives and to increase reliability for an existing unit. The solution is a rebuild program appropriately named "DC2AC". In 2014, BNSF became the first to modernize a DC unit: a former Santa Fe DASH 9-44CW built by General Electric in the 1990's. Still retaining its number 616, the six-axle DASH 9 was fitted with four AC traction motors that replaced the six DC motors. It was also remanufactured with the A1A truck side frames, which are usually seen on the GE ES44C4 and ET44C4 units on the BNSF roster. This rebuild led to the locomotive's new name: the AC44C4M. Because the DASH 9 was introduced in the same decade as its AC sibling, the AC4400CW, this popular DC traction model is the most suitable candidate for the GE DC2AC program.
In response to the BNSF's AC44C4M modernization, Norfolk Southern developed its plan to convert its own DASH 9 fleet to AC traction. The railroad received the first two prototypes that were rebuilt from the narrow-nose DASH 9-40C locomotives in 2015. Because they were configured to the standard six-motor arrangement, these units are designated as AC44C6M; they also had their standard cabs replaced by the wide nose with comfort cab. Numbered 4000 and 4001, they were painted in a special commemorative scheme with the cab colored blue to represent GE, which initially teamed with American Motive Power, Inc. for them. Some railfans nicknamed these units "Sonic Bonnets". Another four AC44C6M's were also painted in similar schemes (except for the black cab) to commemorate some of the rebuilding done at Norfolk Southern's Roanoke and Juniata Locomotive Shops. By 2018, all of the 125 narrow-nose DASH 9-40C's had been rebuilt, effectively ending the GE standard cab era within the NS roster. The AC44C6M program is still currently in progress as the railroad also began to convert its DASH 9-40CW wide-cabs with AC motors. Prior to modernization, all of the 4,000-horsepower DASH 9's as well as the ES40DC's were upgraded to the standard 4,400-hp rating. It would be interesting if NS plans to reconfigure its DC traction GEVO's to AC technology and call them ES44ACM; after all, the ES44DC is nearly identical to the popular ES44AC.
Additionally, NS introduced a similar GE rebuild program in 2018 by modifying a single DASH 9 wide-cab with six AC motors and other electrical equipment manufactured by a Spanish builder called CAF. The prototype was numbered 8520 and designated as AC44C6CF. Its cab was painted in CAF's company color red as a commemorative scheme, which looks like a "Sonic Bonnet" or in this case a "Knuckles Bonnet". Unfortunately, the one-of-a-kind AC44C6CF was removed from the NS roster in 2020. Although the GE DC2AC program is intended for mainline freight locomotives, Amtrak initiated a scenario to repower the GENESIS fleet with AC traction. In fact, the GE P42DC essentially has the same level of technology as in the DASH 9, making this modernization possible; perhaps these passenger locomotives could be renamed P42ACM. However, they appear to lack the most up-to-date safety features and may not be as fuel-efficient or compliant to the Tier 4 emissions regulations as the upcoming Siemens ALC-42 Charger. By the way, the M in the GE rebuilds stands for "modernization".
Also in 2018, Electro-Motive now joined the DC2AC program with the introduction of Norfolk Southern's SD70ACC (the latter C is short for "converted"), which is a fleet rebuilt from the railroad's SD70 narrow-nose locomotives. Similar to the GE AC44C6M program, the SD70's were reconfigured to AC traction and their comfort cabs were installed, resembling the EMD SD70ACe. The first two rebuilds were numbered from 1800 to 1801 and their cabs were painted yellow, which is the main color of EMD's parent company Caterpillar; these are sometimes nicknamed "Tails Bonnet". Unlike the GE modernization program, not all standard cab SD70's were converted because the rest of them, along with the wide-cab SD70M's, were retired by NS. The latter model could have had a chance of being rebuilt to the SD70ACC since it is internally identical to its narrow-nose sibling. It would also be interesting if the newer SD70M-2's were converted to AC.
While DC2AC has been a successful modernization process, it doesn't mean DC traction is no longer a good thing. For instance, a lot of EMD four-axle General Purpose diesels (some of which were rebuilt) have been demoted to local freight and switching duties on various railroads, but they don't need high levels of tractive effort provided by the AC motors for those relatively small jobs. As mentioned in the last blog post, some of the EMD SD60 and GE DASH 8 diesels were remanufactured but not necessarily converted to AC. Nevertheless, AC traction is still today the standard feature and the only option available on newly built locomotives. In other words, if a railroad chooses to have its fleet 100% AC, then it would practically purge its remaining DC units. Anyway, here’s a brief video of the SD70ACC class unit from Norfolk Southern. Again, please refer to the sources below for photos of the other remanufactured diesels.
Sources