View source for EMD E-unit

{{Short description|American diesel-passenger locomotive}}
{{redirect|E-unit|the Execution unit of a CPU|Execution unit}}
{{more footnotes|date=July 2016}}
{{use mdy dates|date=March 2022}}
[[File:Southern Pacific Shasta Daylight circa 1949.JPG|thumb|300px|[[Southern Pacific]] [[EMD E7]]s on the [[Shasta Daylight]] in 1949]]
'''EMD E-units''' were a line of [[passenger train]] [[streamliner]] [[diesel locomotive]]s built by the [[Electro-Motive Diesel|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 (1800&nbsp;hp = 1300&nbsp;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 [[EMC TA|TA]] model in 1937, selling six to the [[Chicago, Rock Island and Pacific Railroad|Rock Island]].  This had similar carbody styling, but otherwise had more in common with [[Union Pacific Railroad|UP]] [[M-10001]], [[M-10002]], and [[M-10003 to M-10006]], in that it was a 1,200&nbsp;hp (900&nbsp;kW), single-engined unit on [[AAR wheel arrangement#B-B|B-B]] trucks instead of the E-units' [[AAR wheel arrangement#A1A-A1A|A1A-A1A]] [[wheel arrangement]].  It is not part of the E-unit series.

The [[EMD F-unit]]s followed the basic B-B truck design of the TA model, but with a V-16 EMD 567 [[prime mover (locomotive)|prime mover]] generating 1350&nbsp;hp as introduced in 1939.

E-units standardized the two engine configuration for passenger locomotives to maximize power and, while the less-reliable Winton Diesel prime movers were in use, faced a less severe loss of power should one of the engines become disabled. 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 cabs; units with a cab are called [[A unit]]s or lead units, while cabless units are called [[B unit]]s or booster units. B units did contain [[hostler]] controls, 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 to control the trailing units.  Railroads tended to buy either ABA sets (two cab-equipped units facing in opposite directions with a booster in between) or ABB sets (a single cab with a pair of boosters).  The former did not need to be turned to pull in either direction, but B units were less expensive than A units and gave a smoother line to the train.

As locomotives of EMC's own standardized design produced in-house, expandable to meet various power requirements, the E-units marked the arrival of Diesel power benefiting from [[economies of scale]] and were adequate for full-sized consists, a significant threshold in the viability of Diesel motive power as a replacement for steam in passenger service.

== Development ==
[[Image:EMD E5 at IRM.jpg|thumb|300px|[[Chicago, Burlington and Quincy Railroad|CB&Q]] 9911A, an [[EMD E5]], operating at the [[Illinois Railway Museum]], July 18, 2004.]]
The [[EMC EA/EB|EA/EB]], [[EMC E1|E1]], and [[EMC E2|E2]] models were powered by twin 900&nbsp;hp Winton 201A V-12 engines in each power unit. They were standardized mechanically and in overall design.  Union Pacific's E2 cab unit was distinguished from the slant-nosed EA and E1 units by its bulbous nose, round porthole style windows, and stainless steel ornamentation on the pilot and nose.  The "E" designation originated to denote the locomotive units' '''E'''ighteen hundred horsepower, as opposed to the '''T'''welve hundred horsepower "T" units but was later used to refer to all [[Carbody unit|carbody]] constructed twin-engine mainline passenger locomotives units produced by EMC.  Their twin V-12 diesel engine layout, Blomberg A-1-A trucks, and {{convert|57|ft|1|in|m|2|abbr=on}} wheelbase would become the standard for all future E models. EMC/EMD has built all of its major components since 1939.

The [[EMC E3|E3]], [[EMC E4|E4]], [[EMD E5|E5]], and [[EMD E6|E6]] had the new GM-EMC 567 purpose-designed locomotive engines, for a total of {{convert|2000|hp|MW|abbr=on|lk=in}}. They had the sharply raked "slant nose", and square windows on the sides (with the exception of [[Union Pacific]] orders with porthole style windows). Production stopped in 1942.  The E5 designation was used for [[Chicago, Burlington and Quincy Railroad|Chicago Burlington and Quincy's]] [[stainless steel]] clad locomotives in keeping with their ''[[Pioneer Zephyr|Zephyr]]'' theme.

The EA/EB, E1, E2, E4, and E5 model names reflected EMC's early convention of assigning a model name for each individual customer order.  EMC started to change that convention with the multiple-customer E3 model and the new naming convention was fully incorporated with the E6 model.

The [[EMD E7|E7]] was introduced in 1945, and became the best selling E model. It had the improved 567 "A" engine, and the [[EMD F-unit|F]] style "bulldog nose".

The [[EMD E8|E8]] and [[EMD E9|E9]] were the final E models. The E8 had 12-V567B engines ({{convert|2250|hp|MW|abbr=on}} total), while the E9 had uprated 12V-567C engines ({{convert|2400|hp|MW|abbr=on}} 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 originally built; EMC/EMD locomotives are often rebuilt to newer standards.<ref>{{cite book|last=Dorin|first=Patrick C.|title=Chicago and NorthWestern Power |year=1972|publisher=Superior Publishing|isbn=0-87564-715-4|pages=128–133}}</ref><ref>{{cite book|last=Pinkpank|first=Jerry A|title=The Second Diesel Spotter's Guide|year=1973|publisher=Kalmbach Books|isbn=0-89024-026-4|pages=13, 26, 118–124}}</ref><ref>{{cite book|editor-first=David|editor-last=Ross|title=The Encyclopedia of Trains and Locomotives|year=2003|publisher=Barnes and Noble|isbn=978-0-7607-9679-5|pages=273–274}}</ref>

== Engines ==
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&nbsp;hp (1300&nbsp;kW), then the E3 was rated at 2,000&nbsp;hp. The last model, the E9, was rated at 2,400&nbsp;hp (1800&nbsp;kW).

Early models (EA/EB through E2) used the [[Winton Motor Carriage Company|Winton]] 201-A engine that had been developed in the early 1930s by the partnership of [[General Motors]] and Winton.  While this engine represented a breakthrough in [[power-to-weight ratio]]s and output flexibility for Diesel engines, it was a compromise between marine and locomotive requirements 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&nbsp;hp (700&nbsp;kW) [[V12 engine|V12]]s.  Experience with the 201-A, which was the first two-stroke Diesel engine in operational use, was invaluable in the development of the next-generation Diesel engine, the [[EMD 567]], a purpose-designed engine that achieved a factor-of-five improvement in piston life for locomotive use.<ref name= "Kettering">{{cite journal|author= Kettering, E. W.|title= History and Development of the 567 Series General Motors Locomotive Engine|volume= Proceedings of the American Society of Mechanical Engineers, November 29, 1951}}</ref>

The E3 introduced the 567 series engine, which would power all later E units, the 567 being a [[Roots-type supercharger|mechanically aspirated]] [[Two-stroke diesel engine|two stroke]] 45 degree V-type with {{convert|567|cuin|L|abbr=on}} displacement per cylinder, a total of {{convert|6804|cuin|L|abbr=on}} per engine. Models E3 through E9 used the EMD model 567 engine, named after its [[engine displacement]] in [[cubic inch]]es per cylinder.  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 [[Revolutions per minute|rpm]], elements which when combined gave greater engine output.  The 12V-567 [[V12 engine|V12]] model used in the E3 through E6 developed 1000&nbsp;hp (750&nbsp;kW). The E7 model used the 12V-567A rated at 1000&nbsp;hp (750&nbsp;kW).  The E8 used the more advanced 567B unit, with improved exhaust manifolds and other enhancements to give 1,125&nbsp;hp each.  More development resulted in the 1200&nbsp;hp (900&nbsp;kW) 567C engine used in the E9.

== Trucks ==
All E-units used the same EMD passenger [[bogie|truck]] design by engineer [[Martin Blomberg]]. This was an [[AAR wheel arrangement#A1A-A1A|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. Two [[direct current]] [[electric generator|generator]]s powered four [[traction motor]]s, 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. The success of the design is shown by the few changes to it over the years.

== Styling ==
The EA and E1 had sloping noses with recessed headlights, while the E2 had a more bulbous [[Bulldog nose|"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 [[EMD F-units|F-units]]. A patent of 1937 signed by several EMC engineers defined the styling.<ref>{{cite web |url=http://patimg1.uspto.gov/.piw?Docid=D0106919&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect2%3DPTO1%2526Sect2%3DHITOFF%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsearch-bool.html%2526r%3D1%2526f%3DG%2526l%3D50%2526d%3DPALL%2526S1%3DD106919.PN.%2526OS%3DPN%2FD106919%2526RS%3DPN%2FD106919&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page |title=Patent Number: US0D0106919 |publisher=patimg1.uspto.gov |access-date=2010-10-18 |archive-date=January 3, 2017 |archive-url=https://web.archive.org/web/20170103085441/http://patimg1.uspto.gov/.piw?Docid=D0106919&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect2%3DPTO1%2526Sect2%3DHITOFF%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsearch-bool.html%2526r%3D1%2526f%3DG%2526l%3D50%2526d%3DPALL%2526S1%3DD106919.PN.%2526OS%3DPN%2FD106919%2526RS%3DPN%2FD106919&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page |url-status=dead }}</ref>

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.

== Other changes ==
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.

==Models==
{|class="wikitable sortable"
!Model designation!!Build year!!Total produced!![[AAR wheel arrangement]]!![[Prime mover (locomotive)|Prime mover]]!![[Horsepower|Power output]]!!class="unsortable"|Image
|- align="center"
|[[EMC EA/EB|EA/EB]] 
|1937–1938
|<span style="display:none">012</span> 6 A units,<br/> 6 B units{{#tag:ref|For the [[Baltimore and Ohio Railroad]].|group="nb"}}
|[[AAR wheel arrangement#A1A-A1A|A1A-A1A]]
|[[Winton 201-A]] 
|1,800&nbsp;hp<br />(1,300&nbsp;kW)
|[[File:Capitol Limited EMD EA and Tom Thumb 1937.jpg|100px]]
|- align="center"
|[[EMC E1|E1]] 
|1937–1938 
|<span style="display:none">011</span> 8 A units,<br/> 3 B units{{#tag:ref|For the [[Atchison, Topeka and Santa Fe Railway]].|group="nb"}}
|[[AAR wheel arrangement#A1A-A1A|A1A-A1A]]
|[[Winton 201-A]] 
|1,800&nbsp;hp<br />(1,300&nbsp;kW)
|[[File:Golden Gate Santa Fe train.JPG|100px]]
|- align="center"
|[[EMC E2|E2]] 
|1937 
|<span style="display:none">006</span> 2 A units,<br/> 4 B units{{#tag:ref|In 2 ABB sets. For the jointly owned and run [[Union Pacific Railroad]], [[Chicago and North Western Railway]], and [[Southern Pacific Transportation Company|Southern Pacific]] trains ''City of San Francisco'' and ''City of Los Angeles''.|group="nb"}}
|[[AAR wheel arrangement#A1A-A1A|A1A-A1A]]
|[[Winton 201-A]] 
|1,800&nbsp;hp<br />(1,300&nbsp;kW)
|[[File:City of Los Angeles 1944.JPG|100px]]
|- align="center"
|[[EMC E3|E3]] 
|1938–1940
|<span style="display:none">019</span> 17 A units,<br/>2 B units{{#tag:ref|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).|group="nb"}}
|[[AAR wheel arrangement#A1A-A1A|A1A-A1A]]
|[[EMD 567]] 
|2,000&nbsp;hp<br />(1,490&nbsp;kW) 
|[[File:Atlantic Coast Line 501.jpg|100px]]
|- align="center"
|[[EMC E4|E4]]
||1938-1939
||<span style="display:none">019</span> 14 A units,<br/>5 B units{{#tag:ref|For the [[Seaboard Air Line]].|group="nb"}}
|[[AAR wheel arrangement#A1A-A1A|A1A-A1A]]
||[[EMD 567]]
|2,000&nbsp;hp<br />(1,490&nbsp;kW)
|| [[File:Arrival of the Orange Blossom Special train- Plant City, Florida.jpg|100px]]
|- align="center"
|[[EMD E5|E5]] 
|1940–1941 
|<span style="display:none">016</span> 11 A units,<br/>5 B units{{#tag:ref|For the [[Chicago, Burlington and Quincy Railroad]].|group="nb"}}
|[[AAR wheel arrangement#A1A-A1A|A1A-A1A]]
|[[EMD 567]] 
|2,000&nbsp;hp<br />(1,490&nbsp;kW)
|[[File:EMD E5 at IRM.jpg|100px]]
|- align="center"
|[[EMD E6|E6]]
||1939–1942
||<span style="display:none">117</span> 91 A units,<br/>26 B units
|[[AAR wheel arrangement#A1A-A1A|A1A-A1A]]
||[[EMD 567]]
|2,000&nbsp;hp<br />(1,490&nbsp;kW)
|[[File:Rock Island locomotive 630.jpg|100px]]
|- align="center"
|[[EMD E7|E7]]
||1945–1949
||<span style="display:none">510</span> 428 A units,<br>82 B units
|[[AAR wheel arrangement#A1A-A1A|A1A-A1A]]
||[[EMD 567|EMD 567A]]
|2,000&nbsp;hp<br>(1,490&nbsp;kW)
||[[File:RR76.37 No. 5901 Front Side.jpg|100px]]
|- align="center"
|[[EMD E8|E8]]
||1949–1954
||<span style="display:none">496</span> 450 A units,<br>46 B units
|[[AAR wheel arrangement#A1A-A1A|A1A-A1A]]
||[[EMD 567|EMD 567B]]
|2,250&nbsp;hp<br>(1,678&nbsp;kW)
||[[File:Rock Island locomotive 652.jpg|100px]]
|- align="center"
|[[EMD E9|E9]]
||1954–1964
||<span style="display:none">144</span> 100 A units,<br>44 B units
|[[AAR wheel arrangement#A1A-A1A|A1A-A1A]]
||[[EMD 567|EMD 567C]]
|2,400&nbsp;hp<br>(1,790&nbsp;kW)
||[[File:19950813 10 UP Clinton, Iowa (5368209041).jpg|100px]]
|}

== Surviving E-units ==
A number of E-units survive, many are in good running order.  Several railroads retain sets that haul passenger specials, management inspection specials, etc. Others survive in museums or on short lines. 

The [[Illinois Railway Museum]] in Union, Illinois has one of the largest collections of operable and preserved E's including CB&Q E5 9911A and WSOR 102, one of the few remaining operable B units.

The [[Southeastern Railway Museum]] in [[Duluth, Georgia]] has [[Southern Railway (U.S.)|Southern Railway]] #6901, an E8 that once powered the ''[[Crescent (train)|Southern Crescent]]''.

== References ==

===Notes===
{{Notelist-lr}}
{{Reflist|group="nb"}}

=== Citations===
{{Reflist}}

===Bibliography===
{{refbegin}}
* {{Lamb-Evolution}}
* {{Marre-diesel-50}}
* {{Pinkepank diesel spotters guide 2}}
* {{Schafer-Vintage Diesel}}
* {{Solomon-American Diesel|pages=53–56, 63, 65, 67, 68, 70}}
* {{Solomon-EMD Locomotives}}
* {{Solomon-Vintage Diesel}}
* {{Solomon-Electro-Motive}}
* {{Solomon-North American Locomotives}}
* {{Wilson-E Units}}
{{refend}}


{{EMD cab and cowl}}

[[Category:Electro-Motive Division locomotives|E]]
[[Category:A1A-A1A locomotives]]
[[Category:North American streamliner trains]]
[[Category:Passenger locomotives]]
[[Category:Diesel locomotives of the United States]]
[[Category:Locomotives with cabless variants]]
[[Category:Standard-gauge locomotives of the United States]]