(redirected from Locomotives)
Also found in: Dictionary, Thesaurus, Medical, Legal.


vehicle used to pull a train of unpowered railroadrailroad
or railway,
form of transportation most commonly consisting of steel rails, called tracks, on which trains of freight cars, passenger cars, and other rolling stock are drawn by one locomotive or more.
..... Click the link for more information.

Types of Locomotives

The steam-powered locomotive played a key role during the development and golden age of railroading, but, despite its long and picturesque history, it has been superseded in developed nations by electric and diesel-electric locomotives for economic and environmental reasons. The few steam locomotives that remain in operation in developed nations are mostly nostalgic relics used chiefly to pull tourist trains.

Steam Locomotives

The reciprocating steam locomotive is a self-contained power unit consisting essentially of a steam engine and a boilerboiler,
device for generating steam. It consists of two principal parts: the furnace, which provides heat, usually by burning a fuel, and the boiler proper, a device in which the heat changes water into steam.
..... Click the link for more information.
 with fuel and water supplies. Superheated steam, controlled by a throttle, is admitted to the cylinders by a suitable valve arrangement, the pressure on the pistons being transmitted through the main rod to the driving wheels. The driving wheels, which vary in number, are connected by side rods. Steam locomotives are usually classified under the Whyte system, that is, by the number and arrangement of the wheels; for example, an engine classified as 2–6–0 has one pair of wheels under the front truck, three pairs of coupled or driving wheels, and no wheels under the trailing truck. In some cases the truck wheels of the tender (fuel carrier) are added.

Electric Locomotives

Electric locomotives range from the small type used in factories and coal mines for local hauling to the large engines used on railroads. Electric locomotives generally have two or more motors. Power is collected from an electric trolley, or pantograph, running on an overhead wire or from a third rail at one side of the track. Battery locomotives, used only for local haulage, carry electric storage batteries that act as their primary source of power. Electric railroad locomotives are used chiefly on steep grades and on runs of high traffic density; although highly efficient they are not more widely used because of the cost of electric substations and overhead wires or third rails.

Diesel Locomotives

Diesel-electric locomotives were introduced in the United States in 1924, and have become the most widely used type of locomotive. The modern diesel-electric locomotive is a self-contained, electrically propelled unit. Like the electric locomotive, it has electric drive, in the form of traction motors driving the axles and controlled with electronic controls. It also has many of the same auxiliary systems for cooling, lighting, heating, and braking. It differs principally in that it has its own generating station instead of being connected to a remote generating station through overhead wires or a third rail. The generating station consists of a large diesel enginediesel engine,
type of internal-combustion engine invented by the German engineer Rudolf Diesel and patented by him in 1892. Although his engine was designed to use coal dust as fuel, the diesel engine now burns fuel oil.
..... Click the link for more information.
 coupled to an alternator or generator that provides the power for the traction motors. These motors drive the driving wheels by means of spur gears. The ratio of the gearing regulates the hauling power and maximum speed of the locomotive. A modern diesel-electric locomotive produces about 35% of the power of a electric locomotive of similar weight. Diesel-mechanical locomotives have a direct mechanical link consisting of a clutch and a series of gears and shafts between the engine and the wheels, similar to the transmission in an automobile. Because mechanical drives deliver less power to the wheels than electric and diesel-electric systems, they are only used with the smallest locomotives. In diesel-hydraulic locomotives the engine drives a torque converter, which uses fluids under pressure to transmit and regulate power to the wheels. Hydraulic drives are little used in the United States but are widely used in some countries, such as Germany.

Gas turbine–electric locomotives are similar to the diesel-electric but use a gas turbineturbine,
rotary engine that uses a continuous stream of fluid (gas or liquid) to turn a shaft that can drive machinery.

A water, or hydraulic, turbine is used to drive electric generators in hydroelectric power stations.
..... Click the link for more information.
 to drive the generator. The technology is used primarily on turbotrains, high-speed passenger trains that do not have locomotives but instead are powered by units built into one or more of their cars.

Development of the Locomotive

Richard TrevithickTrevithick, Richard
, 1771–1833, British engineer and inventor, b. Cornwall. He is known as the father of locomotive power because of his invention (1800) of the high-pressure steam engine.
..... Click the link for more information.
, a British engineer and inventor, built and operated (1803–4) the first successful steam enginesteam engine,
machine for converting heat energy into mechanical energy using steam as a medium, or working fluid. When water is converted into steam it expands, its volume increasing about 1,600 times. The force produced by the conversion is the basis of all steam engines.
..... Click the link for more information.
 locomotive for hauling cars on a track. The British engineer George StephensonStephenson, George,
1781–1848, British engineer, noted as a locomotive builder. He learned to read and write in night school at the age of 18, while working in a colliery.
..... Click the link for more information.
 built his first locomotive, the Blucher, in 1814, and in 1829 he demonstrated the practicability of the steam engine for commercial transportation; his locomotive, the Rocket, attained 29 mi per hr (47 km per hr). The first American-built locomotive was designed and tested on a private track by the American engineer John Stevens in 1826. The English-built Stourbridge Lion, imported c.1829, was not a commercial success, being too heavy for American tracks.

The Tom Thumb (1830), built by Peter CooperCooper, Peter,
1791–1883, American inventor, industrialist, and philanthropist, b. New York City. After achieving success in the glue business, Cooper, with two partners, erected (1829) the Canton Iron Works in Baltimore.
..... Click the link for more information.
, an American manufacturer, for the Baltimore & Ohio RRBaltimore & Ohio Railroad
(B&O), first U.S. public railroad, chartered in 1827 by a group of Baltimore businessmen to regain trans-Allegheny traffic lost to the newly opened Erie Canal.
..... Click the link for more information.
, was the first practical American-built locomotive. The American manufacturer Matthias BaldwinBaldwin, Matthias William,
1795–1866, American industrialist and philanthropist, b. Elizabethtown (now Elizabeth), N.J. After earlier business successes, Baldwin became interested in steam-engine production and completed in 1832 the locomotive Old Ironsides
..... Click the link for more information.
's first locomotive, Old Ironsides, built in 1832, long remained in operation. In 1832 the American engineer John B. Jervis built the first locomotive with a swivel truck, a wheel assembly on which part of the body was mounted. Placed at the forward end of a locomotive, a swivel truck permitted a locomotive to negotiate curves more safely. In 1865, Robert F. Fairlie produced an articulated (jointed) locomotive that could traverse the sharp curves of passes through the western mountains. Electric locomotives were introduced on the Baltimore & Ohio RR in 1895, and diesel locomotives—introduced in yard service in 1924—were in general use by 1935.


See C. Garrat, The Last of Steam (1980); D. Weitzman, Superpower: The Making of a Steam Locomotive (1987); R. Loewy, Locomotive (1988); E. A. Haine, The Steam Locomotive (1990); B. Solomon, The American Steam Locomotive (1998); B. Solomon, The American Diesel Locomotive (2000); see also bibliography under steam enginesteam engine,
machine for converting heat energy into mechanical energy using steam as a medium, or working fluid. When water is converted into steam it expands, its volume increasing about 1,600 times. The force produced by the conversion is the basis of all steam engines.
..... Click the link for more information.



a means of tractive transportation associated with rolling stock and used to move either trains or single cars along rail tracks. Originally the word “locomotive” was used solely for steam engines. Later the concept was extended to all means of railroad traction.

Locomotives currently in use can be classified, according to their primary energy source, as either thermal or electric. The former includes steam engines, steam-turbine locomotives, dieseis and other locomotives driven by internal combustion engines, and gas-turbine locomotives; they have their own power plants on board as energy sources. Electric locomotives are either of the contact type or of the storage battery type. Electric locomotives of the contact type have no power source of their own; energy for their operation is supplied through a trolley or third-rail system. Battery-powered electric locomotives have their batteries charged periodically, using some continuously available current source. In addition to the basic types of locomotives, various combined types—such as diesel and electric, steam and diesel, trolley and battery, and other types—have also existed, although none ever came into wide use. A motor car may also function as a locomotive; such cars are powered by diesels, turbines, or electricity. Motor cars are also used singly as rail service cars. In contrast to locomotives, motor cars and rail service cars include space for passengers and baggage.

According to the kind of service, locomotives can be classified as main-line locomotives and industrial locomotives. Main-line locomotives utilized by general-purpose railroads can in turn be categorized as freight or passenger locomotives, which supply the tractive effort for trains, and switch locomotives, which work within a switchyard. Industrial locomotives are used within a factory area or in mines, pits, and the like. Locomotives are manufactured for standard-gauge and narrow-gauge tracks.

All the types of locomotives are described in terms of their power rating, tractive force, speed, and efficiency. In addition, electric locomotives are characterized by the kind of current and the voltage used, and diesel and gas turbine locomotives, by the means of transmitting power to the wheels.

The first steam locomotives were built in the early 19th century in Great Britain (1803, 1814); in Russia the first locomotives were built in 1834. Throughout almost the entire 19th century the steam locomotive was the only means of traction for railroads. Increases in train weight and in running speed required more power and a greater tractive force. This requirement in turn necessitated improvements in locomotive design and efficieny. The latest type of main-line steam freight locomotive has a power rating of about 1,800 kilowatts (kW; 2,400 hp) and a rated speed of 80 km/hr; the latest passenger steam locomotives develop 1,900 kW and have a top speed of 125 km/hr. The most efficient locomotives have efficiencies of up to 9 percent, with average operational efficiencies being about 4 percent. In the early 20th century steam engines began to be replaced by internal-combustion locomotives and electric locomotives, which are more economical and efficient and have greater power per unit. The concept of powering a locomotive with an internal combustion engine originated in Russia as early as the end of the 19th century. However, the world’s first main-line diesel locomotive, which had a power rating of 750 kW (1,000 hp) and an electric transmission, was built only in 1924 (USSR). Later, hydraulic transmissions were used in diesel locomotives for regulating the tractive force and speed. Two-section freight diesel locomotives built in the USSR have a power rating of 2,200 kW (3,000 hp) per section; their rated speed is 100 km/hr. Passenger diesel locomotives develop a speed up to 160 km/hr. The maximum efficiencies of currently used diesel locomotives range from 29 to 32 percent; average operating efficiencies run around 20–21 percent.

Experiments on the use of electric traction for railroads were conducted in Russia in 1876. In 1895 in the USA the first electric DC locomotive was built, with current supplied through a contact system. In the USSR electric traction was first utilized in 1926 for a suburban line. Electric locomotives built in the USSR started service in 1933. They had six traction motors with a power rating of 340 kW each and developed speeds of up to 90 km/hr. Electric locomotives have a high power rating, require no fueling, and provide running speeds up to 110 km/hr. Electric engines designed for passenger service use either AC or DC power and can run at speeds up to 180 km/hr. The efficiency of the locomotive proper can be as high as 88–90 percent; the total efficiency of electric traction (including the efficiencies of the traction system, the power transmission system, and the power station generating system) ranges from 22 to 24 percent. Gas turbine locomotives attain a still higher power rating, up to 6,300 kW (8,500 hp). However, because of complexity in manufacturing and because of low efficiency (12–18 percent) this locomotive type is being built in the USSR only as single prototypes and in foreign countries only in small lots.

The main stock of locomotives in all industrially developed countries is represented by diesel and electric locomotives. All other locomotive types have the drawbacks of low power, low efficiency, or complexity of design and therefore are not widely used. They are utilized mainly where necessary to ensure work safety, to conduct work in congested or tight areas (as in quarries), and in similar cases.

The future development of the locomotive-building industry depends on increases in unit power ratings and in running speeds. Since the late 1960’s design work has been done in the USSR and abroad on AC electric locomotives with power ratings of 8,000 kW (10,700 hp), and on diesel locomotives with power ratings of up to 4,500 kW (6,000 hp) per unit. Turbine trains with aviation gas turbines have been built; they are capable of speeds in excess of 200 km/hr. Locomotives with jet engines and with turbo-propeller engines are being tested. Still higher speeds are expected from the development of locomotives running on magnetic or air cushions and equipped with asynchronous linear induction motors; such a design makes possible speeds of up to 500 km/hr. Proposals have been made to design locomotives with fuel-cell power plants and with nuclear reactors.


Rakov, V. A. Lokomotivy i motorvagonnyi podvizhnoi sostav zheleznykh dorog Sovetskogo Soiuza, 1956–1965. Moscow, 1966.


(mechanical engineering)
A self-propelling machine with flanged wheels, for moving loads on railroad tracks; utilizes fuel (for steam or internal combustion engines), compressed air, or electric energy.


a. a self-propelled engine driven by steam, electricity, or diesel power and used for drawing trains along railway tracks
b. (as modifier): a locomotive shed
References in classic literature ?
It is not true that, as they changed engines at Fort Madison, Cheyne passed over to the Amalgamated Brotherhood of Locomotive Engineers an endowment sufficient to enable them to fight him and his fellows on equal terms for evermore.
I raced on the heels of the Master Mechanic, carrying one of his babies for him, for the locomotives that was just pulling out.
Whether I look at home, or abroad; whether I behold the peaceful industrious communities of our island home: her rivers covered with steamboats, her roads with locomotives, her streets with cabs, her skies with balloons of a power and magnitude hitherto unknown in the history of aeronautics in this or any other nation--I say, whether I look merely at home, or, stretching my eyes farther, contemplate the boundless prospect of conquest and possession--achieved by British perseverance and British valour--which is outspread before me, I clasp my hands, and turning my eyes to the broad expanse above my head, exclaim, "Thank Heaven, I am a Briton
They said that old Windpeter stood up on the seat of his wagon, raving and swearing at the onrushing locomotive, and that he fairly screamed with delight when the team, maddened by his inces- sant slashing at them, rushed straight ahead to cer- tain death.
One of the stanchest patrons was little Ned Higgins, the devourer of Jim Crow and the elephant, who to-day signalized his omnivorous prowess by swallowing two dromedaries and a locomotive.
A door opened, and I found myself in the compartment where Captain Nemo--certainly an engineer of a very high order--had arranged his locomotive machinery.
Just then the locomotive gave a sharp screech, and the train passed out into the darkness of the night.
We have our clothes, some more splendid than others, -- this is our credit; but when a man dies he has only his skin; in the same way, on retiring from business, you have nothing but your real principal of about five or six millions, at the most; for third-rate fortunes are never more than a fourth of what they appear to be, like the locomotive on a railway, the size of which is magnified by the smoke and steam surrounding it.
As Grandfather's chair had no locomotive properties, and did not even run on castors, it cannot be supposed to have marched in person to the old French War.
Surely all other leisure is hurry compared with a sunny walk through the fields from "afternoon church"--as such walks used to be in those old leisurely times, when the boat, gliding sleepily along the canal, was the newest locomotive wonder; when Sunday books had most of them old brown-leather covers, and opened with remarkable precision always in one place.
He claimed that he was impelled, rather than drawn by his own volition, to journey as he did, and that he traversed the world like the locomotive, which does not direct itself, but is guided and directed by the track it runs on.
Whenever I see the movement of a locomotive I hear the whistle and see the valves opening and wheels turning; but I have no right to conclude that the whistling and the turning of wheels are the cause of the movement of the engine.