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 RSD12

The Alco RSD12 was one of the final C-C, six-axle designs produced in the Road Switcher (RS) series. The RSD12 sold relatively well for the American Locomotive Company (Alco) considering most RS series six-axle models were lucky to have more than 50 orders. The model was essentially an extension of the RS11, which was Alco's attempt to compete with EMD's four-axle GP9. Unfortunately, once again the builder was late to the game releasing a competing model as EMD's SD9 (the six axle version of its GP9) had already been in production for two years. As such, despite railroads continued reluctance to purchase six-axle locomotives in large numbers EMD was able to sell three times more SD9s compared to the RSD12. Today, there are at least three RSD12s preserved although it is unknown whether any are currently operational.

With the woefully unsuccessful RSD7, which Alco attempted as a competitor to Fairbanks Morse's H24-66 "Train Master" the Schenectady builder switched directions back to a more traditional model with the RSD12. The Alco RSD12 began production in the spring of 1956, after the short two-year production run of the RSD7, and was nearly the only RS model to use Alco's newer 251B model prime mover, which produced 1,800 horspower in the RSD12 (the same as the RS11). Production on the RSD12 lasted until 1963 and while the design would sell more than 150 units, it didn't have many US buyers. Only Class I railroads Pennsylvania, Southern Pacific, C&O, and Nickel Plate purchased the RSD12 (the mining railroad Lake Superior & Ishpeming also bough a few).

The RSD12 offered the highest continuous tractive effort of any Alco diesel locomotive up to that time, 78,500 pounds that included dynamic braking. In comparison, EMD's SD9 offered just 75,000 pounds. The high tractive effort of the model was actually an Alco trademark, as its locomotives (even at the time) had gained quite a reputation for pulling more tonnage far above what the builder had rated (and many railroads used this to their advantage employing their Alco's in heavy-haul service). Despite the fact that General Electric was just a few years away from releasing its own line of diesels (partly due to the fact that they were losing faith in Alco remaining a serious competitor to EMD). As such, the RSD12 still used traction motors and generators built by GE.

The Alco RSD12 was one of the builder's first to offer a low, short nose although only the Southern Pacific ultimately purchased the model with such a setup. In general, Alco's six axle models were meant to provide a sizable increase in traction and be used on light branch/secondary lines allowing the locomotive's weight to be distributed more evenly over additional axles. While most of the Class Is which purchased the RSD12 would retire their fleets within ten years or so, these unique beasts were beloved by the Lake Superior & Ishpeming for their amazing ability to pull juts about anything. After receiving their batch of four from Alco between 1956 and 1963, purchased six of the Santa Fe's later RSD15s ("Alligators"). All of these locomotives remain in service on the LS&I's roster today. For a total production roster of Alco RSD12s please click here. Also, for technical information on the model please click here. Finally, for more information about the RSD12 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.