The EMD SD7

The Electro-Motive Division's (EMD) SD7 (“SD” stood for Special Duty) was essentially the very same thing as a GP7 except that it sported a C-C truck arrangement as opposed to the Geep’s B-B setup (meaning the SD had six axles instead of four). For EMD, railroads at the time were simply not interested in six-axle locomotives despite their added benefits. Even similar designs being offered by the American Locomotive Company (Alco), Baldwin and Fairbanks Morse all sold poorly. Still, EMD would continue to offer six-axle variants of popular General Purpose (GP) line until sales finally began to take off with the SD40 of 1966. It is somewhat surprising that despite less than 200 SD7s built a few still remain in regular freight service. Additionally, units officially preserved include Central of Georgia #201 at the Virginia Museum of Transportation and EMD's first SD7, demonstrators #990 at the Illinois Railway Museum.

One last standpoint of the SD7 was that while competitors offered six-axle models based from the same frame of a four-axle, EMD designed its very own frame for the SDs, which at 60 feet was about five feet longer than the GP7 (to provide adequate space for the C-C trucks). The SD7's two additional axles allowed it to produce far more tractive effort than the GP7. Using GM's model D47 traction motor (the GP7 utilized the D27B) the SD7 could produce 75,000 pounds of continuous tractive effort while the GP7 produce roughly half that amount, 40,000 pounds. Additionally, it offered a starting effort 90,800 pounds compared to the GP7's 65,000 pounds. This also meant that the SD7 could start a train much more quickly than its four-axle counterpart.

EMD also constructed two demonstrators, #990 and #991 with the former going to SP and the latter to the B&O. Despite their relative poor sales numbers, several SD7s remain in service on shortlines, more than a half-century since they first left EMD's shops in La Grange, Illinois (a true testament to the reliability of EMD's first generation diesels). Interestingly, SP kept their SD7s in service through the end with the UP merger in 1996. Places you can still find SD7s include the Dakota Southern, Tate & Lyle grain elevator in Mattoon, Illinois, Cargill's grain elevator in Litchfield, Minnesota, Peavy grain elevator in Jamestown, North Dakota, Portland & Western Railroad, and a few others are stored away on sidings, some since forgotten. For technical data regarding the EMD SD7 please click here. Also, for information about EMD's SD series please refer to the chart below.

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Electro-Motive Division's "Special Duty" Road Switchers

You might want to also consider the book EMD Locomotives from author Brian Solomon. Solomon's book highlights the history of EMD from its earliest beginnings in the 1920s, to its phenomenal successes in the mid-20th century, and finally its decline into second spot behind General Electric in the late 20th century and eventual sale by General Motors in 2005. The book features 176 pages of EMD history and is filled with excellent photography and illustrations. If you're interested in perhaps purchasing either (or both) of these books please visit the links below which will take you to ordering information through Amazon.com, the trusted online shopping network.

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