Locomotive Phases - GE AC4400CW
The GE AC4400CW was introduced in 1993 alongside the similar Dash 9-44CW. It marked GE's foray into AC-powered mainline freight locomotives, closely following EMD's successful SD70MAC and eventually outselling it.
The Dash 9-44CW and AC4400CW carried over the general hood and cab styling established with the Dash 8-40CW. Much of the hood and cab remained the same, but the overall length was increased from 70' 8" to 73' 2". The AC4400CW can be told from the Dash 9-44CW chiefly by the large inverter cabinet on the left side behind the cab, together with a longer dynamic brake hood section and a shorter central air intake. Smaller distinctions include the thinner AC traction motor cables, larger traction motors suspended by "dogbone" hangers (in place of supports on the truck frame) and marginally shorter overall hood height over the central air intake.
Both models initially rode on GE's newly introduced high-adhesion "roller-blade" 3-axle truck, which was derived from the high-adhesion design used by MLW on the M-630 and M-636 some 25 years earlier. Compared to the MLW version, GE's design used a longer wheelbase and taller primary springs, but retained the bolsterless rubber pad secondary suspension. The high-adhesion truck differed from GE's earlier "floating-bolster" (FB-3) design in the absence of the bolster and in having all the traction motors oriented in the same direction.
Partway through production, a self-steering truck design was made available for the AC4400CW. The design was more complex than EMD's radial truck (which was used on all SD70M and SD70MAC production) and not all railroads adopted it. CP and CSXT were significant users, while BNSF and UP were not.
While the only major change in appearance was a redesigned inverter cabinet (Phase 2a below) the AC4400CW received a large number of smaller modifications over its production run. Production of the AC4400CW for American railroads ended in December 2004, after which it was replaced by the ES44AC in order to meet Tier II emissions standards. A few orders of the AC4400CW were made in subsequent years by QCM and QNSL in Canada.
These phases are of my own making. Many of the details come from earlier research I did in establishing production variations for the Dash 9-40CW.
Phase 1d through 1f all occurred within a very short time frame, with each phase representing only a few railroad orders and some orders (such as UP 6550-6699) spanning up to three phases. There was a bit of overlap or inconsistency in some of the details (as noted) but I felt the small number of units representing phase 1d through 1f did not warrant further subphases.
|Short hood top grabirons||Single, angled||Double, straight|
|Rear bottom hood intakes||Small, even height||Larger, variable height (taller on doors without latches)|
|Panel under d/b intakes||Rectangular indentation to clear hood door handle||No rectangular indentation|
|Underframe||Revised spacing and height of traction motor cable brackets along underframe (late Phase 1a3)|
|Rear end grabirons||Uneven spacing||Even spacing (appeared on some Phase 1a2 and 1a3 units)|
|Air reservoir notch in fuel tank||Straight||Notch in middle|
|Fuel tank||Suspended from underframe||Welded as part of underframe|
|Corner steps||Zig-zag outer edge, vertical handrail notch, steps attached to stepwell individually||Sloped outer edge, vertical handrail notch, steps attached to stepwell with sheet connecting all steps||No handrail notch, sloped inner edge|
|Handrail behind inverter cabinet||Vertical main rail, additional corner rail above capacitor box (if present)||Jog in main rail above capacitor box (present on all subsequent units)|
|Angled panel behind right-side radiator intake||Yes (angled housing present without hinged panel on last Phase 1c1 units)||No|
|Square panel behind battery boxes||Hinged||Bolted|
|Dynamic brake intake panels||4 raised sections along bottom, hinged front panel (versions with 2 intakes)||Bolted front panel (2 intakes)||Smooth along bottom (1)||Continuous raised ridge along bottom|
|Air reservoir pipes||90-degree connections||Curved pipes (appeared on late Phase 1e1 units)|
|Cab||Small rectangular grill on left side moved rearward|
|Left handrail behind cab||Single rail||Double rail, taller stanchions||(2)|
|Fuel gauge||Wide, recessed gauge housing||Narrow gauge housing (inconsistent in Phase 1e2 and 1f)|
|Right cab subbase intakes||Screen||Louvres (except CP Phase 1f and 1g units)|
|Air reservoir supports||C-shaped||Upside-down U-shaped|
|Bottom of inverter cabinet||3 narrow horizontal panels, bottom edge lower than cab side sill||bottom edge higher than cab side sill||3 rectangular X-panels|
|Top of inverter cabinet||7 narrow vertical panels (1 + 1 + group of 5)||4 rectangular panels (1 + group of 3 panels); lower top edge||3 rectangular panels (1 + 2 large X-panels)|
|Underframe||Revised traction motor cable routing under cab (appeared on late Phase 1g units)|
|Central air intake||At front of auxiliary hood section||Moved rearward|
|Radiator lift rings||Square, with holes for flag holder||Rounded, slanted|
- UP 6625-6634 had unique dynamic brake intake panels between Phase 1e1 and 1e2, which were smooth along the bottom but with two small notches.
- Left handrail behind cab, Phase 2c: Added stanchion immediately behind cab, top rail not attached to cab (except UP 5914-5981)
The Diesel Shop. (2014). General Electric AC-Series Roster. Retrieved January 2017 from https://www.thedieselshop.us/GE_ACseries.HTML
Foster, Gerald. (1996). A Field Guide to Trains. New York, NY: Houghton Mifflin.
Strack, D. (2009). Union Pacific Diesel Locomotives. Retrieved January 2017 from http://utahrails.net/up-diesel-roster/modern-index.php.