Digital Rail Artist

  Atlantic Coast Line NW2 605, location, date and photographer unknown. Scanned from a 2 1/4 x 3 1/4 positive owned by Digital Rail Artist. This is a Phase 1a unit built in May, 1942. EMD sold 1,145 of their 1,000 horsepower switchers, built between February, 1939 and December, 1949, when it was replaced by the 1,200 horsepower SW7 . This is a 40-page detailed look at the phases and builder list. Revised to March 20, 2022 at 8:41 a.m., Mountain Standard Time.

The U28C was a bridge model between the 2500 hp U25C and the highly successful U30C. The 2800 hp rating was a bit of a disadvantage compared to Alco's C630 and EMD's SD40, and the model remained in production for just over a year. Within months of the start of production, GE completely re-engineered the Universal Series with a new frame, car body, equipment layout, and in the case of the six-axle units, the new FB-3 floating bolster truck. Here's the link to the .pdf of the phase study and builder's list.

 General Electric created the U25C for a single customer in 1963, the Oroville Dam Constructors. They added the trucks used on the EL-C and E-44 electric units to their successful U25B and created a niche market that served the Burlington, Northern Pacific, Pennsylvania Railroad, Louisville & Nashville, and Atlantic Coast Line. Although it was only in production from 1963 to 1965, there were four distinct phases.  Here is a builder's list and phase guide.  (Revised February 17, 2022, at 18:08 MST)  

  EMD's GP20 was cutting-edge technology in 1959 when the first unit was sold to the Western Pacific.  The builder was loathe to risk the sacrifice of its rock-solid engineering reputation on the altar of unproven technology.  Railroads, however, were having none of it. The horsepower race was well underway. Wealthy customers were already blazing new ground, EMD in tow or not. Union Pacific was happily buying General Electric gas turbines that dwarfed the power of the GP9/GP18. The railroad was also adding turbochargers to their existing GP9 fleet. Southern Pacific and the Denver & Rio Grande Western were importing complex and exotic diesel hydraulics from Germany that had unheard of adhesion and horsepower.   If that wasn't bad enough, General Electric was ready to introduce the 2500 horsepower U25B that had been long under development. Reluctantly, then, EMD introduced the SD24 and the GP20, unfortunately just as a severe recession was getting started.  No one at that mom

  EMD replaced the 1,000 horsepower NW2 with the 1,200 horsepower SW7 in October, 1949. The SW7 continued to be built until it too was replaced by the SW9 in November, 1950. There was some overlap in production, until January, 1951. This was a popular locomotive, and EMD could not keep up with demand. Southern Pacific wanted to place significant orders but had to settle for just four units for the Cotton Belt because of long lead times. Here's the link to the .pdf

 EMD's SW600 was the six-hundred horsepower successor to the SW1. Three new models were introduced in 1954 - the SW600, SW900, and SW1200. EMD built 1,056 of their 1200-horsepower SW1200 model. The SW900, at 900 horsepower, sold reasonably well at 372. The customer base for that model was industry and a few Class I roads with light-duty branch line applications. But the little SW600? Just 15 units for 13 different customers with no repeat orders. Six hundred horsepower units were a niche market by this time. Long gone were the robust sales of the SW1. Customers were few, mostly oil refiners, chemical plants, coal-fired electrical power plants, and rarely, a steel producer.  The only Class I customer was Chicago & North Western, buying just two units. By the time the 645-powered switchers were introduced, EMD could no longer justify including a six-hundred horsepower model because the margins were too low. Here's a link to the .pdf.

Work is largely complete on this study, here's a link to the study as it stands. Proofreading and some added photos and it's done - Revised to March 20, 2022 at 8:30 a.m. Mountain Standard Time