CRI&P's EMC AB6 No. 751 in suburban commuter service at Joliet, IL, October 16, 1966.
(Roger Puta, courtesy Marty Bernard, Public domain, via Wikimedia Commons)
EMC AB6 DIESEL ELECTRIC LOCOMOTIVE
The EMC AB6 was a type of diesel locomotive built exclusively for the Chicago, Rock Island and Pacific Railroad (the "Rock Island Line") by the Electro-Motive Corporation and delivered in June 1940. Two examples were built, numbered No. 750 and No. 751. They were built for the Rocky Mountain Rocket passenger train, which travelled as a unified train from Chicago, Illinois, to Limon, Colorado, which then divided. One section went to Colorado Springs, Colorado, and the other to Denver, Colorado. The Rock Island desired a locomotive that could look like an integrated part of the train during the Chicago-Limon portion of the route, and could then be operated independently to take three cars to Colorado Springs. A regular, cab-equipped A-unit could have been purchased, but that would have ruined the streamlined look of the train, so the RI had EMC build a flat-fronted locomotive based on an E-series E6B (B unit) but with an operating cab, headlight, pilot, and other features to enable it to operate as an independent locomotive.
Since the small three- and four-car trains the units would have to haul independently were very light, the AB6 pair were built with only one 1,000 hp EMC 567 V12 engine, and a baggage compartment where the second engine would have been. Later, with increasing trainloads, the baggage compartment was replaced with a second engine.
In 1965, the units had their steam generators replaced with head-end power and were reassigned to push-pull suburban service in the Chicago area. In this form, they lasted until the mid-1970s and were eventually scrapped.
AB6 751 in later Rock Island livery and in suburban service, 1960's. (www.railcards.com, Fair use, 17 U.S.C. § 107, via W. Lenheim Collection)
The Rock Island's AB6 No. 751 in a different paint scheme, now used in commuter service, Chicago, 1970. Photo by Ken Christ. (Audio-Visual Designs, Earlton, NY, Public domain, W. Lenheim Collection)
Type and origin
Power type Diesel-electric
Builder Electro-Motive Corporation (EMC)
Build date 1940
Total produced 2
Specifications
Configuration:
• AAR
New: A1A-3
Later: A1A-A1A
Gauge: 4 ft 8+1⁄2 in (1,435 mm) standard gauge
Prime mover: EMD 567, x 1 off, later x 2
Engine type: V12 Two-stroke diesel
Cylinders: 12
Performance figures
Power output New: 1,000 hp (750 kW)
Power Output Later: 2,000 hp (1,491 kW)
Career
Operators: Rock Island
Numbers: 750 and 751
Delivered: June 1940
Retired: mid-1970s
Disposition: Both scrapped 1973–74