Milwaukee Road class EP-2
Encyclopedia
The Milwaukee Road's class EP-2 comprised five electric locomotive
s built by General Electric
in 1919. They were often known as Bipolars, which referred to the bipolar electric motor
s they used. Among the most distinctive and powerful electric locomotives of their time, they epitomized the modernization of the Milwaukee Road. They came to symbolize the railroad during their nearly 40 years of use, and remain an enduring image of mainline electrification.
locomotives previously provided by GE for the initial electrification of the Mountain Division two years earlier. The Milwaukee Road was the only railroad to order this design of locomotive from GE.
The most remarkable mechanical improvement was arguably the traction motors used on the new locomotives. They were known as bipolar motor
s because each of the locomotive's 12 motors had only two field poles, mounted directly to the locomotive frame
beside the axle
. The motor armature
was mounted directly on the axle providing an entirely gearless
design. This design was almost entirely noiseless as it eliminated not only gear tooth growl but also the whine of higher-RPM electric motors typically used in standard nose-mounted applications. The EP-2s were not the first electric locomotives to use bipolar motors, which had first been designed by Asa F. Batchelder for the New York Central S-motors over a decade earlier, but at the time they were the largest.
The layout of the bipolars was unusual as well. The locomotive carbody consisted of three sections. A small center section contained a boiler
for heating passenger cars, while the larger end sections contained the locomotive's electrical equipment and operator cabs in distinctive round-topped hoods. The locomotive's frame was split into four sections, hinged at the joints, with the two middle sections attached to the end sections of the locomotive body. There were twelve sets of driving wheel
s, plus a single idler axle at each end, for a 1B+D+D+B1 wheel arrangement. All buffering forces were transmitted through the locomotive frame.
The bipolars were designed to be able to pull any Milwaukee Road passenger train singly, and were originally delivered without multiple unit
controls. GE claimed a top speed of 90 mph (145 km/h) for the locomotives but the Milwaukee Road rated them at 70 mph (115 km/h). They were rated at 3,180 continuous horsepower
(2.37 MW) with a continuous tractive effort
of 42000 lbf (186.8 kN) and a starting tractive effort of 116000 lbf (516 kN).
When the bipolars were introduced, their modernity and distinctive design made them the most famous of the Milwaukee Road's electric locomotives. They came to symbolize the Olympian, the railroad's premier train from Chicago to Seattle
. Their unique appearance and power made them ideal for publicity purposes, and there was a series of demonstrations in which a bipolar was able to out-pull contemporary steam locomotive
s. During a short period of testing on the Mountain Division, the EP-2s were shown to be less expensive to operate than the GE and Westinghouse
electric locomotives then in use.
The five EP-2s, numbered 10250-10254, were placed into regular service in 1919 on the Coast Division. The Milwaukee Road saw immediate cost savings over the steam locomotives previously in use, as the bipolars could run from Tacoma
to Othello
without stopping for servicing and could haul trains up grades that had required double-heading
steam engines.
The bipolars operated on the Coast Division from 1919 to 1957, for most of that period without any serious rebuilding. In 1939 they were renumbered E1-E5. In 1953 all five of the EP-2s, which were 35 years old and worn out from heavy wartime service, were heavily rebuilt by the Milwaukee Road at a cost of about $40,000 per locomotive. The rebuild included additional traction motor shunts
for increased speed, roller bearings
, multiple unit capability, flash boilers, and streamlining
. Unfortunately the Milwaukee Shop forces, unaccustomed to working on electric locomotives, did a "poor job" in the opinion of Electrification Department Head Laurence Wylie. Afterwards the bipolars were prone to electrical fires and failures.
Between 1954 and 1957 the bipolars saw decreased use, and in mid-1957 were transferred off the Coast Division to the Mountain Division. Their problems persisted, and between 1958 and 1960 all five were gradually retired. In 1962 all except for E2 were towed to Seattle and scrapped.
Locomotive E2 was donated to the Museum of Transportation
in St. Louis, Missouri
in 1962 and moved there that year. It has remained on static display ever since, and has been fully restored to its appearance immediately after its 1953 rebuilding.
Electric locomotive
An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...
s built by General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
in 1919. They were often known as Bipolars, which referred to the bipolar electric motor
Bipolar electric motor
A bipolar electric motor is an electric motor with only two poles to its stationary field. They are an example of the simple brushed DC motor, with a commutator. This field may be generated by either a permanent magnet or a field coil....
s they used. Among the most distinctive and powerful electric locomotives of their time, they epitomized the modernization of the Milwaukee Road. They came to symbolize the railroad during their nearly 40 years of use, and remain an enduring image of mainline electrification.
Design
In 1917, following the tremendous success of the 1915 electrification of the Mountain Division, the Milwaukee Road decided to proceed with electrifying the Coast Division. As part of this project it ordered five new electric locomotives from General Electric for $200,000 apiece. Their design was radically different from the boxcabBoxcab
A boxcab, in railroad terminology, is a locomotive in which the machinery and crew areas are enclosed in a box-like superstructure . It is a term mostly used in North America while in Victoria , such locomotives have been nicknamed "butterboxes"...
locomotives previously provided by GE for the initial electrification of the Mountain Division two years earlier. The Milwaukee Road was the only railroad to order this design of locomotive from GE.
The most remarkable mechanical improvement was arguably the traction motors used on the new locomotives. They were known as bipolar motor
Bipolar electric motor
A bipolar electric motor is an electric motor with only two poles to its stationary field. They are an example of the simple brushed DC motor, with a commutator. This field may be generated by either a permanent magnet or a field coil....
s because each of the locomotive's 12 motors had only two field poles, mounted directly to the locomotive frame
Chassis
A chassis consists of an internal framework that supports a man-made object. It is analogous to an animal's skeleton. An example of a chassis is the underpart of a motor vehicle, consisting of the frame with the wheels and machinery.- Vehicles :In the case of vehicles, the term chassis means the...
beside the axle
Axle
An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...
. The motor armature
Armature (electrical engineering)
In electrical engineering, an armature generally refers to one of the two principal electrical components of an electromechanical machine–generally in a motor or generator, but it may also mean the pole piece of a permanent magnet or electromagnet, or the moving iron part of a solenoid or relay....
was mounted directly on the axle providing an entirely gearless
Direct drive mechanism
A Direct drive mechanism is one that takes the power coming from a motor without any reductions .-Advantages:* Increased efficiency: The power is not wasted in friction...
design. This design was almost entirely noiseless as it eliminated not only gear tooth growl but also the whine of higher-RPM electric motors typically used in standard nose-mounted applications. The EP-2s were not the first electric locomotives to use bipolar motors, which had first been designed by Asa F. Batchelder for the New York Central S-motors over a decade earlier, but at the time they were the largest.
The layout of the bipolars was unusual as well. The locomotive carbody consisted of three sections. A small center section contained a boiler
Boiler
A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...
for heating passenger cars, while the larger end sections contained the locomotive's electrical equipment and operator cabs in distinctive round-topped hoods. The locomotive's frame was split into four sections, hinged at the joints, with the two middle sections attached to the end sections of the locomotive body. There were twelve sets of driving wheel
Driving wheel
On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons...
s, plus a single idler axle at each end, for a 1B+D+D+B1 wheel arrangement. All buffering forces were transmitted through the locomotive frame.
The bipolars were designed to be able to pull any Milwaukee Road passenger train singly, and were originally delivered without multiple unit
Multiple unit
The term multiple unit or MU is used to describe a self-propelled carriages capable of coupling with other units of the same or similar type and still being controlled from one driving cab. The term is commonly used to denote passenger trainsets consisting of more than one carriage...
controls. GE claimed a top speed of 90 mph (145 km/h) for the locomotives but the Milwaukee Road rated them at 70 mph (115 km/h). They were rated at 3,180 continuous horsepower
Horsepower
Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...
(2.37 MW) with a continuous tractive effort
Tractive effort
As used in mechanical engineering, the term tractive force is the pulling or pushing force exerted by a vehicle on another vehicle or object. The term tractive effort is synonymous with tractive force, and is often used in railway engineering to describe the pulling or pushing capability of a...
of 42000 lbf (186.8 kN) and a starting tractive effort of 116000 lbf (516 kN).
Service history
Seattle, Washington
Seattle is the county seat of King County, Washington. With 608,660 residents as of the 2010 Census, Seattle is the largest city in the Northwestern United States. The Seattle metropolitan area of about 3.4 million inhabitants is the 15th largest metropolitan area in the country...
. Their unique appearance and power made them ideal for publicity purposes, and there was a series of demonstrations in which a bipolar was able to out-pull contemporary steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
s. During a short period of testing on the Mountain Division, the EP-2s were shown to be less expensive to operate than the GE and Westinghouse
Milwaukee Road class EP-3
The Milwaukee Road's class EP-3 comprised ten electric locomotives built in 1919 by Baldwin and Westinghouse. They were nicknamed Quills because of their use of a quill drive...
electric locomotives then in use.
The five EP-2s, numbered 10250-10254, were placed into regular service in 1919 on the Coast Division. The Milwaukee Road saw immediate cost savings over the steam locomotives previously in use, as the bipolars could run from Tacoma
Tacoma, Washington
Tacoma is a mid-sized urban port city and the county seat of Pierce County, Washington, United States. The city is on Washington's Puget Sound, southwest of Seattle, northeast of the state capital, Olympia, and northwest of Mount Rainier National Park. The population was 198,397, according to...
to Othello
Othello, Washington
Othello is a city in Adams County, Washington, United States. The population was 5,847 at the 2000 census and grew 25.9% over the next decade to 7,364 at the 2010 census. Othello refers to the city as being in the "Heart" of the Columbia Basin Project...
without stopping for servicing and could haul trains up grades that had required double-heading
Double-heading
In railroad terminology, double-heading or double heading indicates the use of two locomotives at the front of a train, each operated individually by its own crew. The practice of triple-heading involves the use of three locomotives....
steam engines.
The bipolars operated on the Coast Division from 1919 to 1957, for most of that period without any serious rebuilding. In 1939 they were renumbered E1-E5. In 1953 all five of the EP-2s, which were 35 years old and worn out from heavy wartime service, were heavily rebuilt by the Milwaukee Road at a cost of about $40,000 per locomotive. The rebuild included additional traction motor shunts
Shunt (electrical)
In electronics, a shunt is a device which allows electric current to pass around another point in the circuit. The term is also widely used in photovoltaics to describe an unwanted short circuit between the front and back surface contacts of a solar cell, usually caused by wafer damage.-Defective...
for increased speed, roller bearings
Rolling-element bearing
A rolling-element bearing, also known as a rolling bearing, is a bearing which carries a load by placing round elements between the two pieces...
, multiple unit capability, flash boilers, and streamlining
Streamliner
A streamliner is a vehicle incorporating streamlining in a shape providing reduced air resistance. The term is applied to high-speed railway trainsets of the 1930s to 1950s, and to their successor "bullet trains". Less commonly, the term is applied to fully faired recumbent bicycles...
. Unfortunately the Milwaukee Shop forces, unaccustomed to working on electric locomotives, did a "poor job" in the opinion of Electrification Department Head Laurence Wylie. Afterwards the bipolars were prone to electrical fires and failures.
Between 1954 and 1957 the bipolars saw decreased use, and in mid-1957 were transferred off the Coast Division to the Mountain Division. Their problems persisted, and between 1958 and 1960 all five were gradually retired. In 1962 all except for E2 were towed to Seattle and scrapped.
Locomotive E2 was donated to the Museum of Transportation
Museum of Transportation
The Museum of Transportation of the St. Louis County, Missouri, United States Parks Department is a museum located in the Greater St. Louis area. It was first founded in 1944 by a group of individuals dedicated to preserving the past and has a wide variety of vehicles from American history...
in St. Louis, Missouri
St. Louis, Missouri
St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...
in 1962 and moved there that year. It has remained on static display ever since, and has been fully restored to its appearance immediately after its 1953 rebuilding.