Rivet Counter N Scale GE AC4400CW, Kansas City Southern/Gray

Throughout the history of rail transportation, there have been innovations that revolutionized the industry. From Andrew Beard’s patented designs in the late 1800s that resulted in the automatic couplers that are still used today, to the adoption of diesel technology for locomotive propulsion, these seemingly small developments would lead to massive changes in the industry. The adoption of AC traction in the 1990s could arguably be seen as another giant leap forward.

In the early 1900s, diesel-electric locomotives began to appear, initially in the form of “boxcab” design switchers built by the team of ALCO, GE, and Ingersoll-Rand (“ALGEIR”) in 1925. This new propulsion design proved promising. At its most basic definition, a diesel prime mover spins a generator that produces electricity which powers electric traction motors on the axles. Diesel-electric locomotives did not need the extensive and expensive infrastructure of electric or steam locomotives. Maintenance was also far less intensive and expensive compared to the steam locomotives that ruled the rails of the day.

By the late 1930s, the writing was on the wall for steam locomotives. By the end of World War II, railroads in the U.S. started to “dieselize” en masse. Constrained by the production needs for defense materials during the war, many of the longtime steam locomotive builders began to develop diesel-electric designs after peace was declared. The upstart Electro-Motive Division (EMD, by then a division of General Motors) turned heads shortly before the U.S. entered the war with its groundbreaking FT diesel-electric locomotive. Heavy industrial manufacturer General Electric (GE) continued to be involved with railroading, but mostly in a support role, providing electrical components such as traction motors to various builders.

Throughout the 1940s and 1950s, EMD would emerge as the number one builder of diesel locomotives with its successful line of E and F-units, along with GP and SD-series units, which were built by the thousands for railroads all over the country. In 1960, GE was to challenge EMD's dominance with their “Universal” series of locomotives, starting with the U25B. While EMDs continued to outsell these early GE efforts for the next three decades, GE steadily improved its product and increased its market share. In the 1980s, EMD stumbled with quality control issues, most notably with the 50-series. This opened the door for GE going into the 1990s, and they would become the leading locomotive builder in the U.S. thanks to their DASH 8 and DASH 9 series of units. Their next step in locomotive evolution was waiting in the wings.

EMD and GE would soon square off in developing Alternating-Current, or A.C., traction for locomotives. Prior production models from both builders utilized Direct-Current (D.C.) traction motors for propulsion, as was done since the very first diesel-electric locomotives were produced. A.C. traction motors demonstrated significant advantages over their D.C. counterparts by allowing for much greater continuous tractive effort and reduced maintenance. They were also much more resilient than D.C. motors. They were able to endure much higher short-time ratings (the ability of the traction motors to withstand high amperage at low speeds for a set time without incurring damage), giving them extraordinary lugging ability.

A.C. units showed their ability to replace their D.C. predecessors on a 3-to-5 basis, being able to walk away with heavy trains from a dead stop on an upgrade, in scenarios that were nearly impossible with an equivalent number of D.C. units. This wizardry required substantial changes to the locomotive’s electrical system, including a system of electrical inverters to “refine” the current being fed to the traction motors and an extensive microprocessor control system to manage it all. While these changes increased per-unit cost, most railroads found the benefits to be more than worth the expense. With that, EMD would introduce the SD70MAC, and GE the AC4400CW. The AC4400CW was based upon GE’s highly successful Dash 9-44CW design and would become one of the hottest-selling locomotives of the 1990s and beyond.

Initial AC4400CW customers utilized their units in applications best suited for their tremendous lugging ability. Based upon their satisfaction with the DASH 9 fleet and their desire for reliable power to move Powder River Basin coal, the Chicago & North Western (C&NW) was one of the first to purchase the newest A.C. power. Sets of AC4400s, painted in the attractive “Lightning Stripe” variation of their classic green and yellow paint scheme, could be seen all over the Powder River Basin moving seemingly endless strings of coal hoppers or gondolas. 

CSX Transportation (CSXT) was another early customer and ordered a sizable fleet of ACs for service in the Appalachian coal fields. Delivered in the attractive yellow, blue, and gray “YN2” scheme, the new units quickly became crew favorites. The new AC4400CWs handily outperformed older locomotive models in their daunting assignment.

Western giant Southern Pacific (SP) stunned the industry with a massive order of 278 units. All were delivered in their longtime gray and scarlet, but with the Rio Grande Industries-inspired “Speed Lettering” on their flanks. While SP struggled financially throughout the 1980s, by the 1990s they were seemingly on the rebound, ordering large numbers of high-horsepower, 4-axle units over the previous years, for use on high-speed, high-priority intermodal traffic. However, SP’s 6-axle heavy-haul fleet had languished over the years, and the ACs were a much-needed shot in the arm. A.C. power allowed SP to handle growing amounts of bulk traffic (coal, minerals, crude oil, and grain) across the system.

Enticed by the promises of improved train handling and reduced maintenance costs, more and more railroads took notice and joined the A.C. revolution. Eventually, as operating practices evolved, ACs would find themselves in services beyond the heavy-tonnage applications they were originally envisioned for. As piggyback traffic dwindled and heavier double-stack container trains became more prevalent, AC4400s started finding their way onto those trains, where again their performance characteristics proved their value. As older power was retired or cascaded down into more secondary duties, ACs were finding themselves on just about every service on the railroad.

By the time domestic AC4400 production ended in 2004, nearly every Class 1 railroad had ordered examples of AC4400s except for Norfolk Southern (NS). Ever the holdout, NS avoided safety cabs and AC-traction as long as possible. Instead, they would purchase standard-cab DASH 9s as well as large numbers of its safety-cab-equipped version, the C40-9W. Into the 2000s however, NS would eventually acquire AC-traction locomotives and were impressed with their performance. So much so, they would embark on a rebuilding and upgrading program for their older DASH 9 locomotives, dubbing them “AC44C6M” (AC traction, 4,400hp, C for six axles, the number 6 to signify the number of traction motors, and M for “Modified”). They would have their cabs replaced with the latest GE safety cab design, plus new electrical systems, and components upgraded to AC4400 standards.

In recent years, railroads such as Canadian Pacific, CSX, and Union Pacific have embarked on rebuilding programs for their AC4400 fleets. These programs replace worn-out or obsolete components, plus upgrading various systems to improve performance. Examples of competing EMD products have not been as fortunate. Some have already been retired and scrapped. Aside from wreck victims, nearly all AC4400s are still in service. With rebuild and upgrade programs, they will likely be in service for many years.