EMD SW series

EMD SW series
Name	EMD SW series
Powertype	Diesel-electric
Builder	Electro-Motive Division
Builddate	1939–1958
Totalproduction	1,000+ (various models)
Primemover	EMD 567 and 567A/B/C variants
Poweroutput	600–1,000 hp
Operator	North American railroads, industrial operators, export customers

EMD SW series

Introduction

The EMD SW series are a family of switcher diesel-electric locomotives built by Electro-Motive Division of General Motors for use by railroad and industrial operators across United States, Canada, Mexico, and export markets including Argentina and Australia. Designed during the late 1930s and produced through the 1950s, the SW series succeeded earlier EMD switcher types and competed with switchers from ALCO, Baldwin Locomotive Works, and Fairbanks-Morse, becoming a staple on classification yard and industrial siding operations. Their use by major carriers such as the Atchison, Topeka and Santa Fe Railway, Pennsylvania Railroad, Union Pacific Railroad, Southern Pacific Railroad, and New York Central Railroad solidified EMD's dominance in diesel switching power during the transition from steam.

Design and Development

EMD developed the SW series from experience with early diesel switchers including the EMD NW1 and the experimental EMD 567 powered demonstrators; design goals emphasized compact dimensions, reliable EMD 567 two-stroke V-type engines, and modular electrical components used in contemporaneous road locomotives. Influences included wartime production constraints under World War II procurement and lessons from competitors such as ALCO S-1, Baldwin VO-1000, and GE 44-ton units; collaboration with suppliers in the Chicago region and engineering at EMD's La Grange, Illinois plant produced a standardized carbody and truck design. Development cycles incorporated feedback from major customers including Pennsylvania Railroad and New York Central Railroad, while innovations in traction motor design drew on work at Westinghouse and General Electric laboratories.

Models and Variants

The series includes models designated by horsepower and internal changes, such as the early SW1 (600 hp) and later SW7 (1,200 hp predecessor concepts) family members, plus transitional units using the EMD 567B and 567C blocks found in SW9 (1,200 hp equivalent) and SW1200 (1,200 hp) designs; related switchers from the era include the NW2 and TR series ordered by Atchison, Topeka and Santa Fe Railway and Chicago and North Western Transportation Company. Variants include cab modifications for industrial use, long-hood conversions for Baltimore and Ohio Railroad and Southern Railway switching patterns, and export versions adapted for narrow-gauge operations in Argentina and industrial sidings in Australia. Rebuilds and renumberings were common among operators such as Conrail, Canadian National Railway, Kansas City Southern, and various shortline railroad companies.

Production and Operators

Production at EMD's La Grange and earlier McCook facilities yielded over a thousand units delivered to Class I railroads like Union Pacific Railroad, Santa Fe, Penn Central, and Southern Pacific Railroad, industrial firms including U.S. Steel and Bethlehem Steel, and public agencies such as New York City Transit Authority for yard and shop duties. Export orders and secondhand sales extended service lives into fleets owned by Ferrocarriles Argentinos and private mining companies in Chile and Mexico; units were also acquired by commuter agencies and industrial switching contractors during the dieselization era that saw rapid retirements of steam switchers across North America. Leasing and rebuild programs by firms in Illinois and Ohio redistributed many units to short line railroad and preservation groups.

Technical Specifications

The SW series typically used the EMD 567 series two-stroke diesel engine in V6 or V8 configurations, driving a main generator and four traction motors mounted on two-axle trucks; ratings ranged from about 600 to 1,200 horsepower depending on model and upgrade, with prime movers and electrical systems sharing parts commonality with road units supplied to Union Pacific and Pennsylvania Railroad. Dimensions, weight, and tractive effort varied by submodel and frame, with trucks derived from designs used on contemporary EMD F-unit and GP series locomotives; braking systems, control gear, and dynamic features were influenced by regulatory standards in Interstate Commerce Commission filings and operating practices at large carriers. Fuel capacity and cooling systems were tailored for yard duty and industrial short-haul assignments favored by operators such as Northern Pacific Railway and Illinois Central Railroad.

Service History and Preservation

SW series locomotives served extensively in switching, yarding, and industrial roles, participating in the postwar dieselization that reshaped operations on lines owned by New York Central Railroad, Chicago, Burlington and Quincy Railroad, Milwaukee Road, and others; several units were rebuilt into road slug or transfer configurations for Conrail and Southern Pacific Railroad. Preservation efforts by museums and heritage railways, including collections at institutions in Illinois, Pennsylvania, California, and Ontario, have kept multiple SW units operational for excursion and display service, with volunteers and restoration shops replicating original paint schemes from railroads like Santa Fe and Pennsylvania Railroad. Remaining examples appear in industrial use, tourist operations, and static exhibits, often documented in publications and rosters maintained by historical societies focused on rail transportation and locomotive preservation.

Category:Electro-Motive Division locomotives Category:Diesel-electric locomotives of the United States