SD24
Generated by GPT-5-miniExpansion Funnel Raw 88 → Dedup 0 → NER 0 → Enqueued 0
| SD24 | |
|---|---|
| Name | SD24 |
| Manufacturer | Electro-Motive Division |
| Production | 1958–1963 |
| Class | Locomotive |
| Power output | 2400 hp |
SD24 The SD24 is a diesel-electric locomotive model produced by Electro-Motive Division for North American railroads in the late 1950s and early 1960s. It combined a EMD 16-cylinder 567D3A prime mover with six-axle A1A-A1A-style or C-C trucks to provide high tractive effort for heavy freight service on routes operated by railroads such as the Atchison, Topeka and Santa Fe Railway, Union Pacific Railroad, and Santa Fe Railway. The design influenced subsequent models from General Motors's Electro-Motive Division and saw use across the United States, Canada, and select international buyers.
Overview
The SD24 was marketed as a high-horsepower six-axle road locomotive variant of EMD's four-axle GP20 and six-axle SD18 series, intended for heavy-haul assignments for carriers including Northern Pacific Railway, Great Northern Railway, and Chicago and North Western Transportation Company. Its 2400 horsepower rating positioned it alongside contemporaries from manufacturers such as Alco and Baldwin Locomotive Works, while competing with later designs from General Electric. The model shared many components with the EMD F-series and E- and F-unit lineage, allowing parts commonality across fleets of Pennsylvania Railroad, New York Central Railroad, and Southern Pacific Railroad locomotives.
History
Development of the SD24 emerged during the postwar dieselization era when Class I railroads like Canadian National Railway and Canadian Pacific Railway sought higher-traction six-axle units for mountain and heavy manifest service. The SD24 followed testing protocols used for prototypes at locations such as Altoona Works and performance trials on the Transcontinental Railroad corridors between Chicago and Los Angeles. Orders were placed by regional and national carriers including Rock Island, Missouri–Kansas–Texas Railroad, and Baltimore and Ohio Railroad. Rebuild programs involving shops like Illinois Central Railroad's facilities and contractors such as National Railway Equipment later extended the service life of several units, paralleling rebuilds seen for SD40 and SD45 classes.
Geography and Route
SD24 units operated on mainlines spanning the Interstate 80 freight corridors, mountain routes over the Rocky Mountains, and the Cascade Range corridors of Washington (state). They were deployed on heavy coal drifts to and from terminals near Powder River Basin mines and on mixed freight trains through hubs like Chicago, Illinois, St. Louis, Missouri, and Los Angeles, California. In Canada, units ran on routes linking Montreal, Toronto, and Vancouver via corridors paralleling the Canadian Pacific Railway and Canadian National Railway transcontinental networks.
Technical Specifications and Design
The SD24 used the EMD 567 series engine, a 16-cylinder two-stroke diesel also applied in GP20 and SD18 units, driving a generator and traction motors built by EMD. The C-C truck arrangement provided six driven axles with traction motors similar to those on SD35 and SD40 classes, offering high continuous tractive effort suited for tonnage moves on grades such as those at Raton Pass and Sherman Hill. The carbody incorporated electrical systems referencing standards later formalized by Association of American Railroads and featured air braking systems compatible with Westinghouse Electric Company equipment. Some units received dynamic braking packages like those found on SD28 rebuilds and were retrofitted with multiple unit (MU) control gear used in consists with F7 and GP9 units.
Operations and Services
Operators deployed SD24s in manifest freight, unit coal trains, and occasional heavy reefers or intermodal lash-ups on routes served by Southern Railway (U.S.), Seaboard Air Line Railroad, and Missouri Pacific Railroad. Crews trained under union oversight from organizations such as the Brotherhood of Locomotive Engineers and Brotherhood of Locomotive Firemen and Enginemen to run SD24 consists alongside EMD GP and EMD SD series motive power. Maintenance cycles were handled at home shops including Altoona Works, Paducah Shops, and private contractors like General Railway Signal-certified facilities. During their service life, SD24s participated in seasonal surges for grain movements to ports at New Orleans, Seattle, and Philadelphia.
Safety and Incidents
SD24 units were subject to the same regulatory frameworks enforced by agencies such as the Interstate Commerce Commission and later safety oversight associated with Federal Railroad Administration mandates. Notable incidents involving six-axle EMD road switchers occurred on mountain grades and at interlocking locations like Crescent Junction and Horseshoe Curve; investigations often involved organizations such as the National Transportation Safety Board and railroad legal departments from Union Pacific and Kansas City Southern Railway. Lessons learned influenced subsequent design changes adopted in models like the SD40 and operational rules administered by dispatch centers in St. Paul, Minnesota and Atlanta, Georgia.
Cultural and Economic Impact
SD24s contributed to freight capacity increases that supported industrial corridors serving companies such as U.S. Steel, Anheuser-Busch, and Boeing. Their presence influenced late-20th-century railroading depictions in media produced by studios in Hollywood, model railroading catalogs by firms like Athearn and Williams Models, and preservation efforts at museums including the National Railroad Museum and California State Railroad Museum. Secondary markets and leasing firms such as Locomotive Leasing Company traded refurbished units, while historical societies in cities like Portland, Oregon and Spokane, Washington documented their operational histories.