EMD E-unit

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EMD E-units were a line of passenger train diesel locomotives built by the General Motors Electro-Motive Division (EMD) and its predecessor the Electro-Motive Corporation (EMC). Final assembly for all E-units was in La Grange, Illinois. Production ran from May 1937, to December, 1963. The name E-units refers to the model numbers given to each successive type, which all began with E. The E originally stood for eighteen hundred horsepower (1300 kW), the power of the earliest model, but the letter was kept for later models of higher power.

The predecessors of the E-units were the EMC 1800 hp B-B locomotives built in 1935. These had similar power and mechanical layouts to the E-units, but in boxcab bodies on AAR type B two-axle trucks.

EMC also introduced the TA model in 1937, selling six to the Rock Island. This had similar carbody styling, but otherwise had more in common with UP M-10001, M-10002, and M-10003 through M-10007, in that it was a 1,200 hp (900 kW), single-engined unit on B-B trucks instead of the E-units' A1A-A1A wheel arrangement. It is not part of the E-unit series.

Like many early passenger locomotives, E-units used two engines. Even so, while E-units were used singly for shorter trains, longer trains needed multiple locomotive units; many railroads used triple units. E-units could be purchased with or without driving cabs; units with a cab are called A units or lead units, while cabless units are called B units or booster units. B units did contain simple controls for hostling, but they could not be so controlled on the main line. The locomotive units were linked together with cables which enabled the crew in the lead unit at the front to control the trailing units. Railroads tended to buy either ABA sets (two driving cab-equipped units facing in opposite directions with a booster in between) or ABB sets (a single driving cab with a pair of boosters). The former did not need to be turned to pull in either direction, but B units were cheaper than A units and gave a smoother line to the train.


CB&Q 9911A, an EMD E5, operating at the Illinois Railway Museum, July 18, 2004.

The EA/EB, E1, and E2 were limited production development models, each type selling to a single railroad. Their twin V-12 diesel engine layout, Blomberg A-1-A trucks, and 57 ft 1 in (17.40 m) wheelbase would become the standard for all future E models.

The E3, E4, E5, and E6 were the standard pre-WWII production models, with little difference between them. All had the new 567 engines, for a total of 2,000 hp (1.5 MW). They had the sharply raked “slant nose”, and square windows on the sides. Production would stop in 1942.

The E7 was introduced in 1945, and became the best selling E model. It had the improved 567 “A” engine, and the F style “bulldog nose”.

The E8 and E9 were the final E models. The E8 had 567 “B” engines (2,250 hp (1.68 MW) total), the E9 had the uprated 567 “C” engine (2,400 hp (1.8 MW) total). They both used the same body style, with a grille along the top of the sides the length of the loco, and several “porthole” windows below it.

Model descriptions are as built, EMC/EMD locomotives are often rebuilt to newer standards.[1][2][3]


While there were some cosmetic differences between E-unit models, the major line of development was technological, and largely that of increasing power. The first model, the EA/EB, was rated at 1800 hp (1300 kW), then the E3 was rated at 2,000 hp. The last model, the E9, was rated at 2,400 hp (1800 kW).

Early models (EA/EB through E2) used the Winton 201-A engine that had been purchased by Electro-Motive Corporation, the immediate ancestor of the Electro-Motive Division of General Motors. This engine had been designed for submarine use, and wasn't well suited to the sustained full throttle operation often needed in railroad service. It was not unusual for heavy repairs to be done en route on one engine while the other engine propelled the train at reduced speed. The 201-A engines used in E-units were 900 hp (700 kW) V12s.

The E3 introduced the 567 series diesel engine, which would power all later E units. The 567 was designed for railroad locomotives, a mechanically aspirated two stroke 45 degree V type with 567 cu in (9.29 L) displacement per cylinder, a total of 6,804 cu in (111.50 L) per engine. Two D.C. generators powered four traction motors, two on each truck, in an A1A-A1A arrangement. This truck design was used on all E units and on CB&Q 9908 and MP 7100 power cars. EMC/EMD has built all of its major components since 1939. [4] [5]


All E-units used the same EMD passenger truck design by engineer Martin Blomberg. This was an A1A-A1A truck, with the outer axles powered and the center axle unpowered. Like the well-known two-axle Blomberg B trucks, these trucks had outside spring hangers between the wheels for better cushioning of side-to-side motion. Also like the Blomberg B, there were no drop equalizers between the axles. The success of the design is shown by the few changes to it over the years.


The EA and E1 had sloping noses with recessed headlights, while the E2 had a more bulbous "bulldog" nose. Models E3 through E6 had a sloping nose but with a protruding headlight, while models E7 through E9 used a less sloped (closer to vertical) style like the freight F-units. A patent of 1937 signed by several EMC engineers defined the styling.[6]

Many older E-units were updated to newer styles. The E8 introduced the one-piece stamped Farr stainless-steel side grilles that made a continuous band from front to rear just below the roof, but these were often retrofitted to earlier units. Side windows were half-rounded on the EA/EB, square on the E1, round on the E2, square on most E3 through E7 units, and rounded portholes again on the E8 and E9, but again many railroads updated older locomotives.

The E5 units were unique, produced for the Chicago, Burlington and Quincy Railroad in all stainless steel with fluted lower carbody sides, to match the railroad's Zephyr passenger trains. Models E3 through E9 used the EMD model 567 engine, named after its engine displacement in cubic inches per cylinder. Although similar in some ways to the earlier Winton design, the 567 model had been developed by EMD specifically for locomotive use, and exhibited excellent performance and reliability in high speed passenger train service. The 567 had a greater displacement per cylinder than the 201-A and ran at a higher maximum rpm, elements which when combined gave greater engine output. The 12V-567 V12 model used in the E3 through E6 developed 1000 hp (750 kW). The E7 model used the 12V-567A rated at 1000 hp (750 kW). The E8 used the more advanced 567B unit, with improved exhaust manifolds and other enhancements to give 1,125 hp each. More development resulted in the 1200 hp (900 kW) 567C engine used in the E9.

Other changes[edit]

Other improvements occurred independently of the change in engine design. The E8, for example, was the first model to incorporate electric cooling fans, and offer dynamic braking as an option.


Model designation Build year Total produced AAR wheel arrangement Prime mover Power output Image
EA/EB 1937–1938 012 6 A units,
6 B units[nb 1]
A1A-A1A Winton 201-A 1,800 hp
(1,300 kW)
Capitol Limited EMD EA and Tom Thumb 1937.jpg
E1 1937–1938 011 8 A units,
3 B units[nb 2]
A1A-A1A Winton 201-A 1,800 hp
(1,300 kW)
Golden Gate Santa Fe train.JPG
E2 1937 006 2 A units,
4 B units[nb 3]
A1A-A1A Winton 201-A 1,800 hp
(1,300 kW)
City of Los Angeles 1944.JPG
E3 1938–1940 019 17 A units,
2 B units[nb 4]
A1A-A1A EMD 567 2,000 hp
(1,490 kW)
Atlantic Coast Line 501.jpg
E4 1938 019 14 A units,
5 B units[nb 5]
A1A-A1A EMD 567 2,000 hp
(1,490 kW)
Arrival of the Orange Blossom Special train- Plant City, Florida.jpg
E5 1940–1941 016 11 A units,
5 B units[nb 6]
A1A-A1A EMD 567 2,000 hp
(1,490 kW)
EMD E5 at IRM.jpg
E6 1939–1942 117 91 A units,
26 B units
A1A-A1A EMD 567 2,000 hp
(1,490 kW)
Rock Island locomotive 630.jpg
E7 1945–1949 510 428 A units,
82 B units
A1A-A1A EMD 567A 2,000 hp
(1,490 kW)
Afternoon Hiawatha 1956.JPG
E8 1949–1954 496 450 A units,
46 B units
A1A-A1A EMD 567B 2,250 hp
(1,678 kW)
Rock Island locomotive 652.jpg
E9 1954–1964 144 100 A units,
44 B units
A1A-A1A EMD 567C 2,400 hp
(1,790 kW)
19950813 10 UP Clinton, Iowa (5368209041).jpg


  1. ^ For the Baltimore and Ohio Railroad.
  2. ^ For the Atchison, Topeka and Santa Fe Railway.
  3. ^ In 2 ABB sets. For the jointly owned and run Union Pacific Railroad, Chicago and North Western Railway, and Southern Pacific trains City of San Francisco and City of Los Angeles.
  4. ^ For the Atchison, Topeka and Santa Fe Railway (1 A, 1 B), Atlantic Coast Line Railroad (2 A), Chicago, Rock Island and Pacific Railroad (2 A), Florida East Coast Railroad (2 A), Kansas City Southern Railroad (2 A, + ex EMC demonstrator A), Chicago and North Western Railway (4 A), Missouri Pacific Railroad (2 A), and Union Pacific Railroad (1 A, 1 B).
  5. ^ For the Seaboard Air Line.
  6. ^ For the Chicago, Burlington and Quincy Railroad.


Rock Island No. 751 at Joliet, Illinois in October 1966
  • AB6 - Two B units built with a flat-fronted driving cab for the Chicago, Rock Island and Pacific Railroad. These were used to take one portion of a train to a side destination while the rest of the train continued onward.
  • AA - half an E6, with a single 1,000 hp (750 kW) engine and a baggage compartment where the rear engine would have been. One unit built for Missouri Pacific.
  • CNW E9BS Crandall cab - E9 B units converted to A units by the Chicago and North Western Railway, with a squarish cab built in the railroad's own shop in Oelwein.

Surviving E-units[edit]

A number of E-units survive, a good number in running order. Several railroads retain a set to haul passenger specials, management inspection specials, and the like. Others survive in museums or on short lines. The Southeastern Railway Museum in Duluth, Georgia has Southern Railway #6901, an E8 that powered the Southern Crescent.



  1. ^ Dorin, Patrick C. (1972). Chicago and NorthWestern Power. Superior Publishing. pp. 128–133. ISBN 0-87564-715-4. 
  2. ^ Pinkpank, Jerry A (1973). The Second Diesel Spotter’s Guide. Kalmbach Books. pp. 13, 26, 118–124. ISBN 0-89024-026-4. 
  3. ^ Ross, David, ed. (2003). The Encyclopedia of Trains and Locomotives. Barnes and Noble. pp. 273–274. ISBN 978-0-7607-9679-5. 
  4. ^ "EMD 567C Engine Manual". rr-fallenflags.org. 
  5. ^ "EMD’s 567, History and Development". utahrails.net. 
  6. ^ "Patent Number: US0D0106919". patimg1.uspto.gov. Retrieved 2010-10-18. 


  • Lamb, J. Parker (2007). Evolution of the American Diesel Locomotive. Railroads Past and Present. Bloomington, IN, USA: Indiana University Press. ISBN 9780253348630. 
  • Marre, Louis A. (1995). Diesel Locomotives: The First 50 Years: A Guide to Diesels Built Before 1972. Railroad Reference Series (Book 10). Waukesha, WI, USA: Kalmbach Publishing. ISBN 0890242585. 
  • Pinkepank, Jerry A. (1973). The Second Diesel Spotter’s Guide. Milwaukee, WI: Kalmbach Publishing Company. ISBN 0-89024-026-4. 
  • Schafer, Mike (1998). Vintage Diesel Locomotives. Enthusiast Color Series. Osceola, WI, USA: MBI Publishing. ISBN 0760305072. 
  • Solomon, Brian (2000). The American Diesel Locomotive. Osceola, WI, USA: MBI Publishing. pp. 53–56, 63, 65, 67, 68, 70. ISBN 0760306664. 
  • Solomon, Brian (2006). EMD Locomotives. St. Paul, MN: Voyageur Press. ISBN 978-0-7603-2396-0. 
  • Solomon, Brian (2010). Vintage Diesel Power. Minneapolis, MN, USA: MBI Publishing. ISBN 9780760337950. 
  • Solomon, Brian (2011). Electro-Motive E-Units and F-Units: The Illustrated History of North America's Favorite Locomotives. Minneapolis, MN, USA: Voyageur Press. ISBN 9780760340073. 
  • Solomon, Brian (2012). North American Locomotives: A Railroad-by-Railroad Photohistory. Minneapolis, MN, USA: Voyageur Press. ISBN 9780760343708. 
  • Wilson, Jeff (2002). E Units: Electro-Motive's Classic Streamliners. Classic Trains / Golden Years of Railroading series. Waukesha, WI, USA: Kalmbach Publishing. ISBN 0890246068. 

External links[edit]