Locomotive (redirected from Light engine)

locomotive, vehicle used to pull a train of unpowered railroad cars.

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role during the development and golden age of railroading, but, despite its long and picturesque history, it has been superseded in developed nations by electric and diesel-electric locomotives for economic and environmental reasons.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 boiler 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 engine 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 turbine 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 Trevithick, a British engineer and inventor, built and operated (1803–4) the first successful steam engine locomotive for hauling cars on a track. The British engineer George Stephenson 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 Cooper, an American manufacturer, for the Baltimore & Ohio RR, was the first practical American-built locomotive. The American manufacturer Matthias Baldwin'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.

Bibliography

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 engine.

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locomotive

Self-propelled vehicle used for hauling railroad cars on tracks. Early experimental steam locomotives were built in Wales and England by Richard Trevithick from 1803. The first practical steam locomotive, the Rocket, was developed in 1829 by George Stephenson, in whose “steam blast” system the steam from a multitube boiler drove pistons connected to a pair of flanged driving wheels. The first U.S. steam locomotive was built by John Stevens in 1825, and the first commercially usable locomotive, the Tom Thumb, by Peter Cooper in Baltimore in 1830. Later improvements enabled a locomotive to move up to 200 freight cars at 75 mph (120 kph). Steam from wood or coal fuel was the main source of power until the mid-20th century, though electric power had been used from the early 20th century, especially in Europe. After World War II diesel power replaced steam because of its higher efficiency and lower cost, though diesel-electric and gas turbine-electric combinations were also used.

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locomotive

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

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locomotive [‚lō·kə′mōd·iv]

(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.

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Locomotive 

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.

REFERENCE

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