The EMD SD24, "The First, Second-Generation, Six-Axle Power"

The Electro-Motive Division's SD24 began the company's entry into the manufacturing of second-generation diesel locomotives. Interestingly, while the model offered new features it kept many of the standard features of the early first-generation Special Duty locomotives like the SD7, SD9, and SD18. It had yet to feature the new Spartan Cab design and stuck with the tapered nose of the SD18. All of this would, change, however, when EMD released the SD28 in 1965. In any even, the locomotive saw modest sales although just a handful of railroads would buy it with most orders taken by the Atchison, Topeka & Santa Fe Railway (the Santa Fe). The SD24 was also the only six-axle model to have cabless B units built. Today, none are known to still be in use for freight service although regional Pan Am Railways keeps two rebuilt as SD26s stored. Also, two others are known to be preserved, Chicago, Burlington & Quincy #504 is completely restored at the Illinois Railway Museum while the National Railroad Museum has CB&Q #510 partially restored.

The SD24's primary purpose was that the extra two axles produced more traction (which allowed the locomotive to handle stiffer grades), allowed for better weight distribution (which was a big plus on light rail and bridges unable to support heavy loads, found on many branch lines) and its Flexicoil trucks allowed for ease of maintenance on its center traction motor. Another significant difference with the SD24's internal components was its use of General Motors model D47 traction motors, as opposed to the GP30's model D57. Up to that time the SD24 offered the most tractive effort of any of EMD's six-axle models; 97,500 pounds starting and 72,300 pounds continuous.

Of course, turbocharging was nothing new and certainly not pioneered by EMD. The American Locomotive Company had been turbocharging its road switchers since the 1940s and was so good at it that typically Alco models were very fuel efficient while offering comparable, if not better, horsepower ratings than the competition. While the SD24 was not as successful as its early sisters it did pave the way for future second-generation six-axle models that would become legendary for their durability and reliability like the SD40, SD40-2, SD45, and others.

While the SD24 was offered with an optional steam boiler no railroads ever purchased it with the option. Additionally, only Kennecott Copper's one unit, #904, did not feature multiple-unit capability (MU). Railroads to purchase the locomotive included the Santa Fe (80, numbered 900–979), Burlington (16, numbered 500–515), Southern/Cincinnati, New Orleans & Texas Pacific/New Orleans Northeastern (48, numbered 2502–2524, 6305–6325, and 6950–6953), and Union Pacific who purchased the only B units (30 As numbered, 400–429 and 45 Bs, 400B–448B). Additionally, EMD's four demonstrators went to UP. For technical data regarding the EMD SD24 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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