Railroad History

Passenger and Commuter Rail

Railroading Today

Rolling Stock

Infrastructure and Terms

Museums and Tourism

Miscellaneous

About The Site

[?] Subscribe To American-Rails.com

The Alco RSD15, "Alligators"

The Alco RSD15, affectionately known as "Alligators" for their long, low short hood was the final six-axle RS model Alco's US plant in Schenectady, New York would build. It was one of the most powerful models in the Road Switcher (RS) line although sales were very modest and did not top 100 units (however, it did outsell the RSD12 in terms of domestic sales). While the American Locomotive Company (Alco) would offer the RSD15 in either low or high short hoods most were built with the former setup, thus giving them their now well known name. For the lines which purchased Alligators, most employed them in the capacity in which they were intended, heavy freight service. Today, several examples of the RSD15 remain preserved and a few are still operational (all preserved models are original AT&SF units).

Alco actually began production on the RSD15 while its RSD12 line was also still being manufactured. The model began production in 1955 and remained in Alco's catalog until 1960. It was one of just a few of Alco's RS models to receive the upgraded 251B prime mover, which had replaced the 244 model. The six-axle RSD15 came equipped with some serious pulling power at 2,400 horsepower, which was a 25% increase over the RSD12. Unfortunately, it found few buyers although a handful of Class I railroads would purchase the model (Santa Fe, Pennsylvania, Cotton Belt, Southern Pacific, and Duluth Missabe & Iron Range).

The Atchison, Topeka & Santa Fe's RSD15s are of particular note. The AT&SF was not necessarily a loyal Alco customer. However, the railroad did regularly purchase from the builder trying out at least a few of most models that Alco built. Interestingly, despite all of the manufacturer's reliability issues by the time the RSD15 began production in 1955 the Santa Fe was quite impressed with the design. Aside from the earlier RSD7 and Fairbanks Morse's H24-66 "Train Master", the RSD15 offered the greatest horsepower available on the market at that time. This was something the Santa Fe was interested in, as it looked to supply ample horsepower to its heavy freights crossing stiffer areas of its main line in western California, New Mexico, and Arizona.

As such, the railroad wound up purchasing a fleet of 50 RSD15s, which constituted nearly 58% of the total number built. They became famous on the AT&SF system seen throughout all three states in a range of liveries from black and silver to the "Blue Warbonnet" paint scheme. The Santa Fe was apparently pleased with their Alligators as the units remained in regular service on the railroad well through the 1970s. Because the Alco RSD15 was a C-C design it already offered quite impressive tractive effort although as the builder refined its six-axle models the Alligators offered the most in the RS series with a continuous rating of 79,500 pounds. Additionally, as was the case with all of Alco's RS models the design used General Electric's model 752 traction motors and model GT586 main generator (air components, again, came from Westinghouse).

At 66 feet, 7 inches in length the RSD15 was the longest domestic model in the series. The low nose of the Alligators gave them an appearance that would actually become quite common for road switchers (although they were not the first Alco model to receive such a setup). Once again, however, Alco's designs could be easily distinguished, externally, by the notched corners on the carbody. For a total production roster of Alco RSD15s please click here. Also, for technical data please click here. Finally, for more information about the RSD15 and all RS series designs please refer to the chart below.

Please Click Here To Return To The Main Diesel Locomotives Section

RS Series

Model Type	Units Built	Date Built	Horsepower
RS-1	417	1941-1960	1,000
RSD-1	257	1942-1946	1,000
RS-2	469	1946-1950	1,500-1,600
RSC-2	81	1946-1950	1,500-1,600
RS-3	1,370	1950-1956	1,600
RSD-4	36	1951-1952	1,600
RSD-5	204	1952-1955	1,600
RSD-7	29	1954-1956	2,250-2,400
RS-11	426	1956-1964	1,800
RSD-12	161	1956-1963	1,800
RSD-15	87	1955-1960	2,400
RS-27	27	1959-1962	2,400
RS-32	35	1961-1962	2,000
RS-36	40	1962-1963	1,800

For a comprehensive look at the American Locomotive Company and all of the motive power types it built from steam, diesel, to electrics consider the book Alco Locomotives by Brian Solomon. Covering more than 175 pages Mr. Solomon's book details the history of Alco from its esteemed 4-6-4 Hudsons and 4-6-6-4 Challengers to vaunted RS and PA series diesel locomotives. If you have any interest in Alco this book is a must have!

Also consider Mike Schafer's Vintage Diesel Locomotives which looks at virtually all of the classic builders and models from Alco PAs to early EMD Geeps. If you’re interested in classic Alcos, or diesel locomotives in general, this book gives an excellent general history of both. 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.

Share Your Thoughts

Have your say about what you just read! Leave me a comment in the box below. Please note that while I strive to present the information as accurately as possible I am aware that there may be errors. If you have potential corrections the help is greatly appreciated.