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Diesel locomotive

Diesel locomotive

Overview


A diesel locomotive is a type of railroad locomotive
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...

 in which the prime mover
Prime mover (locomotive)
In engineering, a prime mover is an engine that converts fuel to useful work. In locomotives, the prime mover is thus the source of power for its propulsion. The term is generally used when discussing any locomotive powered by an internal combustion engine...

 is a diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel
Rudolf Diesel
Rudolf Christian Karl Diesel was a German inventor and mechanical engineer, famous for the invention of the diesel engine.-Early life:Diesel was born in Paris, France in 1858 the second of three children of Theodor and Elise Diesel. His parents were Bavarian immigrants living in Paris. Theodor...

. Several types of diesel locomotive have been developed, the principal distinction being in the means by which the prime mover's mechanical power is conveyed to the driving wheels (drivers).

Early internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

-powered locomotives used gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

 as their fuel.
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Encyclopedia


A diesel locomotive is a type of railroad locomotive
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...

 in which the prime mover
Prime mover (locomotive)
In engineering, a prime mover is an engine that converts fuel to useful work. In locomotives, the prime mover is thus the source of power for its propulsion. The term is generally used when discussing any locomotive powered by an internal combustion engine...

 is a diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel
Rudolf Diesel
Rudolf Christian Karl Diesel was a German inventor and mechanical engineer, famous for the invention of the diesel engine.-Early life:Diesel was born in Paris, France in 1858 the second of three children of Theodor and Elise Diesel. His parents were Bavarian immigrants living in Paris. Theodor...

. Several types of diesel locomotive have been developed, the principal distinction being in the means by which the prime mover's mechanical power is conveyed to the driving wheels (drivers).

Overview


Early internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

-powered locomotives used gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

 as their fuel. Soon after Dr. Rudolf Diesel
Rudolf Diesel
Rudolf Christian Karl Diesel was a German inventor and mechanical engineer, famous for the invention of the diesel engine.-Early life:Diesel was born in Paris, France in 1858 the second of three children of Theodor and Elise Diesel. His parents were Bavarian immigrants living in Paris. Theodor...

 patented his first compression ignition engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

 in 1892, its application for railway propulsion was considered. Progress was slow, however, because of the poor power-to-weight ratio
Power-to-weight ratio
Power-to-weight ratio is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power sources...

 of the early engines, as well as the difficulty inherent in mechanically applying power to multiple driving wheels on swiveling trucks (bogies).

Steady improvements in the diesel engine's design (many developed by Sulzer Ltd. of Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

, with whom Dr. Diesel was associated for a time) gradually reduced its physical size and improved its power-to-weight ratio to a point where one could be mounted in a locomotive. Once the concept of Diesel-electric drive was accepted the pace of development quickened, and by 1925 a small number of diesel locomotives of 600 horsepower were in service in the United States. In 1930, Armstrong Whitworth of the United Kingdom delivered two 1,200 hp locomotives, using engines of Sulzer design, to Buenos Aires Great Southern Railway
Buenos Aires Great Southern Railway
The Buenos Aires Great Southern Railway was one of the Big Four broad gauge, , British-owned companies that built and operated railway networks in Argentina...

 of Argentina.

By the mid 1950s, with economic recovery from the Second World War, series production of diesel locomotives had begun in many countries and the diesel locomotive was on its way to become the dominant type of locomotive in many countries and regions, offering greater flexibility and performance than the 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...

, as well as substantially lower operating and maintenance costs, other than where electric traction was in use due to policy decisions. Currently, almost all diesel locomotives are diesel-electric, although the diesel-hydraulic type was also widely used between the 1950s and 1970s.

Adaptation of the diesel engine for rail use


The world's first oil-engined railway locomotive was built for the Royal Arsenal
Royal Arsenal
The Royal Arsenal, Woolwich, originally known as the Woolwich Warren, carried out armaments manufacture, ammunition proofing and explosives research for the British armed forces. It was sited on the south bank of the River Thames in Woolwich in south-east London, England.-Early history:The Warren...

, Woolwich
Woolwich
Woolwich is a district in south London, England, located in the London Borough of Greenwich. The area is identified in the London Plan as one of 35 major centres in Greater London.Woolwich formed part of Kent until 1889 when the County of London was created...

, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, in 1896, using an engine designed by Herbert Akroyd Stuart
Herbert Akroyd Stuart
Herbert Akroyd-Stuart was an English inventor who is noted for his invention of the hot bulb engine, or heavy oil engine.-Life:...

. It was not, strictly, a diesel because it used a hot bulb engine
Hot bulb engine
The hot bulb engine, or hotbulb or heavy oil engine is a type of internal combustion engine. It is an engine in which fuel is ignited by being brought into contact with a red-hot metal surface inside a bulb....

 (also known as a semi-diesel) but it was the precursor of the diesel.

Following the expiration of Dr. Rudolph Diesel’s patent in 1912, his engine design was successfully applied to marine propulsion and stationary applications. However, the massiveness and poor power-to-weight ratio of these early engines made them unsuitable for propelling land-based vehicles. Therefore, the engine's potential as a railroad prime mover was not initially recognized. This changed as development reduced the size and weight of the engine.

The world’s first diesel-powered locomotive was operated in the summer of 1912 on the Winterthur-Romanshorn Railroad in Switzerland, but was not a commercial success. In 1906, Rudolf Diesel
Rudolf Diesel
Rudolf Christian Karl Diesel was a German inventor and mechanical engineer, famous for the invention of the diesel engine.-Early life:Diesel was born in Paris, France in 1858 the second of three children of Theodor and Elise Diesel. His parents were Bavarian immigrants living in Paris. Theodor...

, Adolf Klose
Adolf Klose
Adolf Klose was the chief engineer of the Royal Württemberg State Railways in southern Germany from June 1885 to 1896.Klose was born on 21 May 1844 in Bernstadt auf dem Eigen, in Saxony. Before his taking up his post in Stuttgart he had been the technical inspector of the United Swiss Railways...

 and the steam and Diesel engine manufacturer Gebrüder Sulzer founded Diesel-Sulzer-Klose GmbH for the manufacture of Diesel-powered locomotives. Sulzer had been manufacturing Diesel engines since 1898. Prussian State Railways ordered in 1909 a Diesel locomotive from the company, and after test runs between Winterthur and Romanshorn the Diesel-mechanical locomotive was delivered in Berlin in September 1912. During further test runs in 1913 several problems were found. After the first world war broke out in 1914, all further trials were stopped. The locomotive weight was 95 tonnes and the power was 883 kW with a maximum speed of 100 km/h. Small numbers of prototype diesel locomotives were produced in a number of countries through the mid 1920s.

Early American developments


Adolphus Busch
Adolphus Busch
Colonel Adolphus Busch was the German-born co-founder of Anheuser-Busch with his father-in-law, Eberhard Anheuser. His great-great-grandson, August Busch IV is now on the board of Anheuser-Busch InBev.-Biography:...

 purchased the American manufacturing rights for the Diesel engine in 1898 but never applied this new form of power to transportation. Only limited success was achieved in the early twentieth century with direct-driven gasoline and Diesel powered railcars.

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...

 (GE) entered the railcar
Railcar
A railcar, in British English and Australian English, is a self-propelled railway vehicle designed to transport passengers. The term "railcar" is usually used in reference to a train consisting of a single coach , with a driver's cab at one or both ends. Some railways, e.g., the Great Western...

 market in the early twentieth century, as Thomas Edison
Thomas Edison
Thomas Alva Edison was an American inventor and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. In addition, he created the world’s first industrial...

 possessed an outstanding patent on the electric locomotive, his design actually being a type of electrically propelled railcar. GE built its first electric locomotive prototype in 1895. However, high electrification costs caused GE to turn its attention to Diesel power to provide electricity for electric railcars. Problems related to co-coordinating the Diesel engine and electric motor
Traction motor
Traction motor refers to an electric motor providing the primary rotational torque of a machine, usually for conversion into linear motion ....

 were immediately encountered, primarily due to limitations of the Ward Leonard electric elevator drive system that had been chosen.

A significant breakthrough occurred in 1914, when Hermann Lemp
Hermann Lemp
Hermann Lemp was a Swiss-American electrical engineer; he is credited as the inventor of the modern system of diesel electric traction co-ordination and control....

, a GE
Gê are the people who spoke Ge languages of the northern South American Caribbean coast and Brazil. In Brazil the Gê were found in Rio de Janeiro, Minas Gerais, Bahia, Piaui, Mato Grosso, Goias, Tocantins, Maranhão, and as far south as Paraguay....

 electrical engineer, developed and patented a reliable direct current
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...

 electrical control system (subsequent improvements were also patented by Lemp). Lemp's design used a single lever to control both engine and generator in a coordinated fashion, and was the prototype
Prototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...

 for all diesel-electric locomotive control systems.

In 1917–18, GE produced three experimental diesel-electric locomotives using Lemp's control design, the first known to be built in the United States. Following this development, the 1923 Kaufman Act
Kaufman Act
The Kaufman Electrification Act of 1923, enacted by the New York State Assembly, mandated electrification of all railroads in New York City by January 1, 1926. The bill was sponsored by recently elected Republican Assemblyman Victor R. Kaufman and signed by Governor Al Smith on June 2, 1923...

 banned steam locomotives from New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

 because of severe pollution problems. The response to this law was to electrify high-traffic rail lines. However, electrification was uneconomical to apply to lower-traffic areas.

The first regular use of diesel-electric locomotives was in switching (shunter) applications. General Electric produced several small switching locomotives in the 1930s (the famous "44-tonner" switcher was introduced in 1940) Westinghouse Electric and Baldwin collaborated to build switching locomotives starting in 1929. However, the Great Depression
Great Depression
The Great Depression was a severe worldwide economic depression in the decade preceding World War II. The timing of the Great Depression varied across nations, but in most countries it started in about 1929 and lasted until the late 1930s or early 1940s...

 curtailed demand for Westinghouse’s electrical equipment, and they stopped building locomotives internally, opting to supply electrical parts instead.

First American series production locomotives


General Electric continued to be interested in developing a practical diesel railway locomotive, and approached Ingersoll-Rand in 1924. The resulting 300 horsepower locomotive was fitted with an electrical generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...

 and traction motor
Traction motor
Traction motor refers to an electric motor providing the primary rotational torque of a machine, usually for conversion into linear motion ....

s supplied by GE
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...

, as well as a form of Lemp's control system, and was delivered in July 1925. This locomotive demonstrated that the diesel-electric power unit could provide many of the benefits of an electric locomotive
Electric locomotive
An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...

 without the railroad having to bear the sizeable expense of electrification. The unit successfully demonstrated—in switching, road freight and passenger service—on a baker’s dozen of railroads, and became the prototype for 33 600 horsepower AGEIR boxcab
ALCO boxcab
The ALCO boxcabs were diesel-electric switcher locomotives, otherwise known as AGEIR boxcabs as a contraction of the names of the builders. Produced by a partnership of three companies, ALCO built the chassis and running gear, General Electric the generator, motors and controls, and Ingersoll Rand...

 switching locomotives
Switcher
A switcher or shunter is a small railroad locomotive intended not for moving trains over long distances but rather for assembling trains ready for a road locomotive to take over, disassembling a train that has been...

 built by a consortium of GE, I-R and the American Locomotive Company
American Locomotive Company
The American Locomotive Company, often shortened to ALCO or Alco , was a builder of railroad locomotives in the United States.-Early history:...

 for several New York City railroads.

In June 1925, Baldwin Locomotive Works
Baldwin Locomotive Works
The Baldwin Locomotive Works was an American builder of railroad locomotives. It was located in Philadelphia, Pennsylvania, originally, and later in nearby Eddystone, Pennsylvania. Although the company was very successful as a producer of steam locomotives, its transition to the production of...

 outshopped a prototype diesel-electric locomotive for "special uses" (such as for runs where water for steam locomotives was scarce) using electrical equipment from Westinghouse Electric Company. Its twin-engine design was not successful, and the unit was scrapped after a short testing and demonstration period. Industry sources were beginning to suggest “the outstanding advantages of this new form of motive power.” In 1929, the Canadian National Railways became the first North American railway to use diesels in mainline service with two units, 9000 and 9001, from Westinghouse.

Diesel-electric railroad locomotion entered the American mainstream when the Burlington Railroad and Union Pacific used Diesel "streamliner
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...

s" to haul passengers. Following the successful 1939 tour of General Motors' EMD's FT
EMD FT
The EMD FT was a diesel-electric locomotive produced between November 1939, and November 1945, by General Motors' Electro-Motive Division . All told 555 cab-equipped A units were built, along with 541 cabless booster B units, for a grand total of 1,096 units. The locomotives were all sold to...

 demonstrator freight locomotive set, the transition from steam to Diesel power began, the pace substantially quickening in the years following the close of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. Fairbanks-Morse
Fairbanks-Morse
Fairbanks Morse and Company was a manufacturing company in the late 19th and early 20th century. Originally a weighing scale manufacturer, it later diversified into pumps, engines, windmills, locomotives and industrial supplies until it was merged in 1958...

 developed a unique opposed-piston engine that was used in their locomotives, as well as in submarines.

Early diesel-electric locomotives in the United States used direct current (DC) traction motors, but alternating current (AC) motors came into widespread use in the 1990s, starting with the Electromotive SD70MAC
EMD SD70 series
The EMD SD70 is a series of diesel-electric locomotives produced by the Electro-Motive Division of General Motors beginning in 1992. Over 4000 locomotives in this series have been produced, mostly of the SD70M and SD70MAC models. All locomotives of this series are hood units with C-C trucks...

 in 1993 and followed by the General Electric's AC4400CW
GE AC4400CW
The GE AC4400CW is a diesel-electric locomotive that was built by GE Transportation Systems between 1993 and 2004. It is similar to the Dash 9-44CW, but features AC traction motors instead of DC, with a separate inverter per motor. 2,598 examples of this locomotive were produced for North American...

 in 1994 and AC6000CW
GE AC6000CW
The AC6000CW is a diesel electric locomotive that is built by GE Transportation Systems. They are all used by major railroads in the United States, except for 8 units exported to BHP Billiton Iron Ore in Australia...

 in 1995.

Early diesel locomotives and railcars outside the United States


In 1935, Krauss-Maffei, MAN and Voith built the first diesel-hydraulic locomotive, the V140 in Germany. Because the German railways (DR) was very pleased with the performance of the locomotive, diesel-hydraulics became the mainstream in diesel locomotives in Germany. Series production of diesel locomotives in Germany began after the Second World War.

Diesel-powered or "oil-engined" railcars, generally diesel-mechanical, were developed by various European manufacturers in the 1930s, e.g. by William Beardmore and Company
William Beardmore and Company
William Beardmore and Company was a Scottish engineering and shipbuilding conglomerate based in Glasgow and the surrounding Clydeside area. It was active between about 1890 and 1930 and at its peak employed about 40,000 people...

 for the Canadian National Railways (the Beardmore Tornado
Beardmore Tornado
-Further reading:* Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9* Gunston, Bill. Development of Piston Aero Engines. Cambridge, England. Patrick Stephens Limited, 2006. ISBN 0-7509-4478-1* Lumsden, Alec. British Piston...

 engine was subsequently used in the R101
R101
R101 was one of a pair of British rigid airship completed in 1929 as part of a British government programme to develop civil airships capable of service on long-distance routes within the British Empire. It was designed and built by an Air Ministry-appointed team and was effectively in competition...

 airship), the Flying Hamburger two coach diesel railcar which entered service in Germany in 1933, and the Vulcan railcars
NZR RM class (Vulcan)
The NZR RM class Vulcan railcars were operated by the New Zealand Railways Department in the South Island of New Zealand. All New Zealand railcars were classified as RM, and these were known as Vulcan railcars, from the name of the manufacturer, Vulcan Foundry of Britain. - Background :On 9 May...

 of 1940 for New Zealand.

In 1945 a batch of 30 Baldwin diesel-electric locomotives, Baldwin 0-6-6-0 1000
Baldwin 0-6-6-0 1000
The Baldwin 0-6-6-0 1000/1 DE is a cab unit diesel-electric locomotive built by Baldwin Locomotive Works in 1945. The 0-6-6-0 1000/1 DEs were powered by an eight-cylinder diesel engine rated at , and rode on a pair of three-axle trucks in a C-C wheel arrangement...

, was delivered from the United States to the railways of the Soviet Union, although a first Russian diesel-electric locomotive (designed by a team led by Yuri Lomonosov) is reported to have entered service in 1924.

Fiat
Fiat
FIAT, an acronym for Fabbrica Italiana Automobili Torino , is an Italian automobile manufacturer, engine manufacturer, financial, and industrial group based in Turin in the Italian region of Piedmont. Fiat was founded in 1899 by a group of investors including Giovanni Agnelli...

 claims a first Italian diesel-electric locomotive built in 1922, but little detail is available. A Fiat-TIBB diesel-locomotive "A", of 440CV, is reported to have entered service on the Ferrovie Calabro Lucane in southern Italy in 1926, following trials in 1924-5. http://www.ferrovie.it/forum/viewtopic.php?f=22&t=13653 Series production of diesel locomotives in Italy began in the mid 1950s.

In 1948, the London Midland & Scottish Railway introduced the first of a pair of 1,600 hp Co-Co diesel-electric locomotives (later British Rail Class D16/1
British Rail Class D16/1
British Railways Class D16/1 or 10000 and 10001 were the first mainline diesel locomotives in Great Britain. They were built by the London, Midland and Scottish Railway at its Derby Works, using the EE16SVT 1600 hp diesel engine with electric transmission, in association with English Electric and...

) for regular use in the United Kingdom, although British manufacturers such as Armstrong Whitworth had been exporting diesel locomotives since 1930. Fleet deliveries to British Railways, of other designs such as Class 20 and Class 31, began in 1957.

Series production of China's first diesel locomotive class, the DFH 1, began in 1964 following construction of a prototype in 1959.

Diesel’s advantages over steam


Diesel engines slowly eclipsed those powered by steam as the manufacturing and operational efficiencies of the former made them cheaper to own and operate. While initial costs of diesel engines were high, 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 were custom-made for specific railway routes and lines and, as such, economies of scale were difficult to achieve. Though more complex to produce with exacting manufacturing tolerances (1/10000 in for diesel, compared with 1/100 in for steam), diesel locomotive parts were more conducive to mass production. While the steam engine manufacturer Baldwin
Baldwin Locomotive Works
The Baldwin Locomotive Works was an American builder of railroad locomotives. It was located in Philadelphia, Pennsylvania, originally, and later in nearby Eddystone, Pennsylvania. Although the company was very successful as a producer of steam locomotives, its transition to the production of...

 offered almost five hundred steam models in its heyday, EMD offered fewer than ten diesel varieties.

Diesel locomotives offer significant operating advantages over steam locomotives. They can safely be operated by one person, making them ideal for switching/shunting duties in yards (although for safety reasons many main-line diesel locomotives continue to have 2-man crews) and the operating environment is much more attractive, being much quieter, fully weatherproof and without the dirt and heat that is an inevitable part of operating a steam locomotive.

Diesel engines can be started and stopped almost instantly, meaning that a diesel locomotive has the potential to incur no costs when not being used. However, it is still the practice of large North American railroads to use straight water as a coolant in diesel engines instead of coolants that incorporate anti-freezing properties; this results in diesel locomotives being left idling when parked in cold climates instead of being completely shut down. Still, a diesel engine can be left idling unattended for hours or even days, especially since practically every diesel engine used in locomotives has systems that automatically shut the engine down if a problem such as a loss of oil pressure or coolant loss occur.

Steam locomotives, by comparison, require intensive maintenance, lubrication and cleaning before, during and after use. Preparing and firing a steam locomotive for use from cold can take many hours, although it may be kept in readiness between uses with a small fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....

 to maintain a slight heat in the 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:...

, but this requires regular stoking and frequent attention to maintain the level of water in the boiler. This may be necessary to prevent the water in the boiler freezing in cold climates, so long as the water supply itself is not frozen.

Moreover, maintenance and operational costs of steam locomotives were much higher than diesel counterparts even though it would take diesel locomotives almost 50 years to reach the same power output that steam locomotives could achieve at their technological height. Annual maintenance costs for steam locomotives accounted for 25% of the initial purchase price. Spare parts were cast from wooden masters for specific locomotives. The sheer number of unique steam locomotives meant that there was no feasible way for spare-part inventories to be maintained.

Steam engines also required large quantities of coal and water, which were expensive variable operating costs. Further, the thermal efficiency
Thermal efficiency
In thermodynamics, the thermal efficiency is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, a boiler, a furnace, or a refrigerator for example.-Overview:...

 of steam was considerably less than that of diesel engines. Diesel’s theoretical studies demonstrated potential thermal efficiencies for a compression ignition engine of 36% (compared with 6-10% for steam), and a 1897 one-cylinder prototype operated at a remarkable 26% efficiency.

The Trans-Australian Railway
Trans-Australian Railway
The Trans-Australian Railway crosses the Nullarbor Plain of Australia from Port Augusta in South Australia to Kalgoorlie in Western Australia...

 built 1912 to 1917 by Commonwealth Railways (CR) passes through 2000 km of waterless (or salt watered) desert terrain unsuitable for steam locomotives. The original engineer Henry Deane
Henry Deane (engineer)
Henry Deane was an Australian engineer, responsible for electrifying the Sydney tramway system and for building the Wolgan Valley Railway and Trans-Australian Railway.- Biography :...

 envisaged diesel operation
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

 to overcome such problems. Some have suggested that the CR worked with the South Australian Railways to trial diesel traction. However, the technology was not developed enough to be reliable.

By the mid 1960s, diesel locomotives had effectively replaced steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

s where electric traction was not in use.

Transmission types


Unlike steam engines, internal combustion engines require a transmission to power the wheels. The engine must be allowed to continue to run when the locomotive is stopped.

Diesel-mechanical



A diesel-mechanical locomotive uses a mechanical transmission in a fashion similar to that employed in most road vehicles. This type of transmission is generally limited to low-powered, low speed shunting (switching)
Switcher
A switcher or shunter is a small railroad locomotive intended not for moving trains over long distances but rather for assembling trains ready for a road locomotive to take over, disassembling a train that has been...

 locomotives, lightweight 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...

s and self-propelled railcar
Railcar
A railcar, in British English and Australian English, is a self-propelled railway vehicle designed to transport passengers. The term "railcar" is usually used in reference to a train consisting of a single coach , with a driver's cab at one or both ends. Some railways, e.g., the Great Western...

s.
The mechanical transmissions used for railroad propulsion are generally more complex and much more robust than road versions. There is usually a fluid coupling
Fluid coupling
A fluid coupling is a hydrodynamic device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch...

 interposed between the engine and gearbox, and the gearbox is often of the epicyclic (planetary)
Epicyclic gearing
Epicyclic gearing or planetary gearing is a gear system consisting of one or more outer gears, or planet gears, revolving about a central, or sun gear. Typically, the planet gears are mounted on a movable arm or carrier which itself may rotate relative to the sun gear...

 type to permit shifting while under load. Various systems have been devised to minimise the break in transmission during gear changing, e.g. the S.S.S. (synchro-self-shifting) gearbox used by Hudswell Clarke
Hudswell Clarke
Hudswell, Clarke and Company Limited was an engineering and locomotive building company in Jack Lane, Hunslet, Leeds, West Yorkshire, England.-History:...

.

Diesel-mechanical propulsion is limited by the difficulty of building a reasonably sized transmission capable of coping with the power and torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

 required to move a heavy train. A number of attempts to use Diesel-mechanical propulsion in high power applications have been made (e.g. the 1,500 kW (2000 horsepower) British Rail 10100
British Rail 10100
British Railways 10100 was an unusual experimental diesel locomotive known informally as The Fell Diesel Locomotive . It was the joint production of Davey Paxman & Co, Shell Refining & Marketing Co and Lt-Col L.F.R. Fell, built for them by the London, Midland and Scottish Railway at Derby. Sir...

 locomotive), although none have proved successful in the end.

Diesel-electric

For locomotives powered by both external electricity and diesel fuel, see electro-diesel below. For locomotives powered by a combination of diesel or fuel cells and batteries or ultracapacitors, see hybrid locomotive
Hybrid locomotive
A hybrid train is a locomotive, railcar or train that uses an onboard rechargeable energy storage system , placed between the power source and the traction transmission system connected to the wheels....

.


In a Diesel-electric locomotive, the Diesel engine drives an electrical generator whose output provides power to the traction motor
Traction motor
Traction motor refers to an electric motor providing the primary rotational torque of a machine, usually for conversion into linear motion ....

s. There is no mechanical connection between the engine and the wheels.
The important components of Diesel-electric propulsion are the Diesel engine (also known as the prime mover
Prime mover (locomotive)
In engineering, a prime mover is an engine that converts fuel to useful work. In locomotives, the prime mover is thus the source of power for its propulsion. The term is generally used when discussing any locomotive powered by an internal combustion engine...

), the main generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...

, traction motor
Traction motor
Traction motor refers to an electric motor providing the primary rotational torque of a machine, usually for conversion into linear motion ....

s and a control system consisting of the engine governor
Governor (device)
A governor, or speed limiter, is a device used to measure and regulate the speed of a machine, such as an engine. A classic example is the centrifugal governor, also known as the Watt or fly-ball governor, which uses a rotating assembly of weights mounted on arms to determine how fast the engine...

 as well as electrical and/or electronic components used to control or modify the electrical supply to the traction motors, including switchgear
Switchgear
The term switchgear, used in association with the electric power system, or grid, refers to the combination of electrical disconnects, fuses and/or circuit breakers used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults...

, rectifiers and other components. In the most elementary case, the generator may be directly connected to the motors with only very simple switchgear.

Originally, the traction motors and generator were DC
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...

 machines. Following the development of high-capacity silicon rectifiers in the 1960s, the DC generator was replaced by an alternator
Alternator
An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current.Most alternators use a rotating magnetic field but linear alternators are occasionally used...

 using a diode bridge
Diode bridge
A diode bridge is an arrangement of four diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. When used in its most common application, for conversion of an alternating current input into direct current a output, it is known as a...

 to convert its output to DC. This advance greatly improved locomotive reliability and decreased generator maintenance costs by elimination of the commutator
Commutator (electric)
A commutator is a rotary electrical switch in certain types of electric motors or electrical generators that periodically reverses the current direction between the rotor and the external circuit. In a motor, it applies power to the best location on the rotor, and in a generator, picks off power...

 and brushes
Brush (electric)
A brush is a device which conducts current between stationary wires and moving parts, most commonly in a rotating shaft. Typical applications include electric motors, alternators and electric generators.-Etymology:...

 in the generator. Elimination of the brushes and commutator, in turn, disposed of the possibility of a particularly destructive type of event referred to as a flashover
Flashover
A flashover is the near simultaneous ignition of most of the directly exposed combustible material in an enclosed area. When certain organic materials are heated they undergo thermal decomposition and release flammable gases...

, which could result in immediate generator failure and, in some cases, start an engine room fire.

More recently, the development of high-power variable-frequency/variable-voltage (VVVF) drives, or "traction inverters," has allowed the use of polyphase AC traction motors, thus also eliminating the motor commutator and brushes. The result is a more efficient and reliable drive that requires relatively little maintenance and is better able to cope with overload conditions that often destroyed the older types of motors.


Diesel-electric control



A Diesel-electric locomotive's power output is independent of road speed, as long as the unit’s generator current and voltage limits are not exceeded. Therefore, the unit's ability to develop 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...

 (also referred to as drawbar pull
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...

 or tractive force, which is what actually propels the train) will tend to inversely vary with speed within these limits. (See power curve below). Maintaining acceptable operating parameters was one of the principal design considerations that had to be solved in early Diesel-electric locomotive development and, ultimately, led to the complex control systems in place on modern units.

Throttle operation


The prime mover's power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...

 output is primarily determined by its rotational speed (RPM) and fuel rate, which are regulated by a governor
Governor (device)
A governor, or speed limiter, is a device used to measure and regulate the speed of a machine, such as an engine. A classic example is the centrifugal governor, also known as the Watt or fly-ball governor, which uses a rotating assembly of weights mounted on arms to determine how fast the engine...

 or similar mechanism. The governor is designed to react to both the throttle setting, as determined by the engine driver and the speed at which the prime mover is running.

Locomotive power output, and thus speed, is typically controlled by the engine driver using a stepped or "notched" throttle
Throttle
A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases , but usually decreased. The term throttle has come to refer, informally and incorrectly, to any mechanism by which...

 that produces binary-like electrical signals corresponding to throttle position. This basic design lends itself well to 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...

 (MU) operation by producing discrete conditions that assure that all units in a consist
Consist
A consist , in North American railway terminology, is used as a noun to describe the group of rail vehicles that make up a train. A near-equivalent UK term is rake but this excludes the locomotive....

 respond in the same way to throttle position. Binary encoding also helps to minimize the number of trainlines (electrical connections) that are required to pass signals from unit to unit. For example, only four trainlines are required to encode all throttle positions.

North American locomotives, such as those built by EMD or 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...

, have nine throttle positions, one idle and eight power (as well as an emergency stop position that shuts down the prime mover). Many UK-built locomotives have a ten-position throttle. The power positions are often referred to by locomotive crews as "run 3" or "notch 7", depending upon the throttle setting.

In older locomotives, the throttle mechanism was ratcheted
Ratchet (device)
A ratchet is a device that allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction. Because most socket wrenches today use ratcheting handles, the term "ratchet" alone is often used to refer to a ratcheting wrench, and the terms "ratchet"...

 so that it was not possible to advance more than one power position at a time. The engine driver could not, for example, pull the throttle from notch 2 to notch 4 without stopping at notch 3. This feature was intended to prevent rough train handling due to abrupt power increases caused by rapid throttle motion ("throttle stripping," an operating rules violation on many railroads). Modern locomotives no longer have this restriction, as their control systems are able to smoothly modulate power and avoid sudden changes in train
Train
A train is a connected series of vehicles for rail transport that move along a track to transport cargo or passengers from one place to another place. The track usually consists of two rails, but might also be a monorail or maglev guideway.Propulsion for the train is provided by a separate...

 loading regardless of how the engine driver operates the controls.

When the throttle is in the idle position, the prime mover will be receiving minimal fuel, causing it to idle at low RPM. In addition, the traction motors will not be connected to the main generator and the generator's field windings will not be excited (energized) — the generator will not produce electricity with no excitation. Therefore, the locomotive will be in "neutral". Conceptually, this is the same as placing an automobile's transmission into neutral while the engine is running.

To set the locomotive in motion, the reverser control handle
Reverser handle
A reverser handle is an operating control for a railroad locomotive that is used to determine the direction of travel. The reverser usually has three positions: forward, reverse, and neutral....

 is placed into the correct position (forward or reverse), the brake
Air brake (rail)
An air brake is a conveyance braking system actuated by compressed air. Modern trains rely upon a fail-safe air brake system that is based upon a design patented by George Westinghouse on March 5, 1872. The Westinghouse Air Brake Company was subsequently organized to manufacture and sell...

 is released and the throttle is moved to the run 1 position (the first power notch). An experienced engine driver can accomplish these steps in a coordinated fashion that will result in a nearly imperceptible start. The positioning of the reverser and movement of the throttle together is conceptually like shifting an automobile's automatic transmission into gear while the engine is idling

Placing the throttle into the first power position will cause the traction motors to be connected to the main generator and the latter's field coils to be excited. With excitation applied, the main generator will deliver electricity to the traction motors, resulting in motion. If the locomotive is running "light" (that is, not coupled to a train) and is not on an ascending grade, it will easily accelerate. On the other hand, if a long train is being started, the locomotive may stall as soon as some of the slack has been taken up, as the drag imposed by the train will exceed the tractive force being developed. An experienced engine driver will be able to recognize an incipient stall and will gradually advance the throttle as required to maintain the pace of acceleration.

As the throttle is moved to higher power notches, the fuel rate to the prime mover will increase, resulting in a corresponding increase in RPM and horsepower output. At the same time, main generator field excitation will be proportionally increased to absorb the higher power. This will translate into increased electrical output to the traction motors, with a corresponding increase in tractive force. Eventually, depending on the requirements of the train's schedule, the engine driver will have moved the throttle to the position of maximum power and will maintain it there until the train has accelerated to the desired speed.

As will be seen in the following discussion, the propulsion system is designed to produce maximum traction motor torque at start-up, which explains why modern locomotives are capable of starting trains weighing in excess of 15,000 tons, even on ascending grades. Current technology allows a locomotive to develop as much as 30 percent of its loaded driver weight in tractive force, amounting to some 120,000 pounds of drawbar pull for a large, six-axle freight (goods) unit. In fact, a consist
Consist
A consist , in North American railway terminology, is used as a noun to describe the group of rail vehicles that make up a train. A near-equivalent UK term is rake but this excludes the locomotive....

 of such units can produce more than enough drawbar pull at start-up to damage or derail cars (if on a curve) or break couplers (the latter being referred to in North American railroad slang as "jerking a lung"). Therefore, it is incumbent upon the engine driver to carefully monitor the amount of power being applied at start-up to avoid damage. In particular, "jerking a lung" could be a calamitous matter if it were to occur on an ascending grade.

Propulsion system operation


As previously explained, the locomotive's control system is designed so that the main generator electrical power output is matched to any given engine speed. Given the innate characteristics of traction motors, as well as the way in which the motors are connected to the main generator, the generator will produce high current and low voltage at low locomotive speeds, gradually changing to low current and high voltage as the locomotive accelerates. Therefore, the net power produced by the locomotive will remain constant for any given throttle setting (see power curve graph for notch 8).

In older designs, the prime mover's governor and a companion device, the load regulator, play a central role in the control system. The governor has two external inputs: requested engine speed, determined by the engine driver's throttle setting, and actual engine speed (feedback
Feedback
Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...

). The governor has two external control outputs: fuel injector setting, which determines the engine fuel rate, and load regulator position, which affects main generator excitation. The governor also incorporates a separate overspeed protective mechanism that will immediately cut off the fuel supply to the injectors and sound an alarm in the cab
Cab (locomotive)
The cab, crew compartment or driver's compartment of a locomotive is the part of the locomotive housing the train driver or engineer, the fireman or driver's assistant , and the controls necessary for the locomotive's operation....

 in the event the prime mover exceeds a defined RPM. Not all of these inputs and outputs are necessarily electrical.

The load regulator is essentially a large potentiometer
Potentiometer
A potentiometer , informally, a pot, is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. If only two terminals are used , it acts as a variable resistor or rheostat. Potentiometers are commonly used to control electrical devices such as volume controls on...

 that controls the main generator power output by varying its field excitation and hence the degree of loading applied to the engine. The load regulator's job is relatively complex, because although the prime mover's power output is proportional to RPM and fuel rate, the main generator's output is not (which characteristic was not correctly handled by the Ward Leonard
Ward Leonard control
Ward Leonard Control, also known as the Ward Leonard Drive System, was a widely used DC motor speed control system introduced by Harry Ward Leonard in 1891. In early 1900s, the control system of Ward Leonard was adopted by the U.S. Navy and also used in passenger lift of large mines...

 elevator drive system that was initially tried in early locomotives).

As the load on the engine changes, its rotational speed will also change. This is detected by the governor through a change in the engine speed feedback signal. The net effect is to adjust both the fuel rate and the load regulator position so that engine RPM and torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

 (and thus power output) will remain constant for any given throttle setting, regardless of actual road speed.

In newer designs controlled by a “traction computer,” each engine speed step is allotted an appropriate power output, or “kW reference”, in software. The computer compares this value with actual main generator power output, or “kW feedback”, calculated from traction motor current and main generator voltage feedback values. The computer adjusts the feedback value to match the reference value by controlling the excitation of the main generator, as described above. The governor still has control of engine speed, but the load regulator no longer plays a central role in this type of control system. However, the load regulator is retained as a “back-up” in case of engine overload. Modern locomotives fitted with electronic fuel injection (EFI) may have no mechanical governor, however a “virtual” load regulator and governor are retained with computer modules.

Traction motor performance is controlled either by varying the DC voltage output of the main generator, for DC motors, or by varying the frequency and voltage output of the VVVF for AC motors. With DC motors, various connection combinations are utilized to adapt the drive to varying operating conditions.

At standstill, main generator output is initially low voltage/high current, often in excess of 1000 ampere
Ampere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...

s per motor at full power. When the locomotive is at or near standstill, current flow will be limited only by the DC resistance of the motor windings and interconnecting circuitry, as well as the capacity of the main generator itself. Torque in a series-wound motor
Traction motor
Traction motor refers to an electric motor providing the primary rotational torque of a machine, usually for conversion into linear motion ....

 is approximately proportional to the square of the current. Hence, the traction motors will produce their highest torque, causing the locomotive to develop maximum 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...

, enabling it to overcome the inertia of the train. This effect is analogous to what happens in an automobile automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

 at start-up, where it is in first gear and thus producing maximum torque multiplication.

As the locomotive accelerates, the now-rotating motor armatures will start to generate a counter-electromotive force
Counter-electromotive force
The counter-electromotive force also known as back electromotive force is the voltage, or electromotive force, that pushes against the current which induces it. CEMF is caused by a changing electromagnetic field. It is the effect of Lenz's Law of electromagnetism...

 (back EMF, meaning the motors are also trying to act as generators), which will oppose the output of the main generator and cause traction motor current to decrease. Main generator voltage will correspondingly increase in an attempt to maintain motor power, but will eventually reach a plateau. At this point, the locomotive will essentially cease to accelerate, unless on a downgrade. Since this plateau will usually be reached at a speed substantially less than the maximum that may be desired, something must be done to change the drive characteristics to allow continued acceleration. This change is referred to as "transition," a process that is analogous to shifting gears in an automobile.

Transition methods include:
  • Series / Parallel or "motor transition".
    • Initially, pairs of motors are connected in series across the main generator. At higher speed, motors are reconnected in parallel across the main generator.
  • "Field shunting", "field diverting", or "weak fielding".
    • Resistance is connected in parallel with the motor field. This has the effect of increasing the 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....

       current, producing a corresponding increase in motor torque and speed.


Both methods may also be combined, to increase the operating speed range.
  • Generator transition
    • Reconnecting the two separate internal main generator stator windings
      Alternator
      An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current.Most alternators use a rotating magnetic field but linear alternators are occasionally used...

       from parallel to series to increase the output voltage.


In older locomotives, it was necessary for the engine driver to manually execute transition by use of a separate control. As an aid to performing transition at the right time, the load meter
Ammeter
An ammeter is a measuring instrument used to measure the electric current in a circuit. Electric currents are measured in amperes , hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters...

 (an indicator that informs the engine driver on how much current is being drawn by the traction motors) was calibrated to indicate at which points forward or backward transition should take place. Automatic transition was subsequently developed to produce better operating efficiency, and to protect the main generator and traction motors from overloading from improper transition.

Dynamic braking



A common option on Diesel-electric locomotives is dynamic (rheostatic) braking
Dynamic braking
Dynamic braking is the use of the electric traction motors of a railroad vehicle as generators when slowing the Locomotive. It is termed rheostatic if the generated electrical power is dissipated as heat in brake grid resistors, and regenerative if the power is returned to the supply line...

.

Dynamic braking takes advantage of the fact that the traction motor
Traction motor
Traction motor refers to an electric motor providing the primary rotational torque of a machine, usually for conversion into linear motion ....

 armatures are always rotating when the locomotive is in motion and that a motor can be made to act as a generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...

 by separately exciting the field winding. When dynamic braking is utilized, the traction control circuits are configured as follows:
  • The field winding of each traction motor is connected across the main generator.
  • The armature of each traction motor is connected across a forced-air cooled resistance grid
    Resistor
    A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...

     (the dynamic braking grid) in the roof of the locomotive's hood.
  • The prime mover RPM is increased and the main generator field is excited, causing a corresponding excitation of the traction motor fields.


The aggregate effect of the above is to cause each traction motor to generate electric power and dissipate it as heat in the dynamic braking grid. A fan connected across the grid provides forced-air cooling. Consequently, the fan is powered by the output of the traction motors and will tend to run faster and produce more airflow as more energy is applied to the grid.

Ultimately, the source of the energy dissipated in the dynamic braking grid is the motion of the locomotive as imparted to the traction motor armatures. Therefore, the traction motors impose drag and the locomotive acts as a brake. As speed decreases, the braking effect decays and usually becomes ineffective below approximately 16 km/h (10 mph), depending on the gear ratio between the traction motors and 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...

s.

Dynamic braking is particularly beneficial when operating in mountainous regions, where there is always the danger of a runaway due to overheated friction brakes during descent (see also comments in the air brake article regarding loss of braking due to improper train handling). In such cases, dynamic brakes are usually applied in conjunction with the air brakes
Air brake (rail)
An air brake is a conveyance braking system actuated by compressed air. Modern trains rely upon a fail-safe air brake system that is based upon a design patented by George Westinghouse on March 5, 1872. The Westinghouse Air Brake Company was subsequently organized to manufacture and sell...

, the combined effect being referred to as blended braking. The use of blended braking can also assist in keeping the slack in a long train stretched as it crests a grade, helping to prevent a "run-in", an abrupt bunching of train slack that can cause a derailment. Blended braking is also commonly used with commuter trains to reduce wear and tear on the mechanical brakes that is a natural result of the numerous stops such trains typically make during a run.

Electro-diesel


These special locomotives can operate as an electric locomotive
Electric locomotive
An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...

 or as a Diesel locomotive. The Long Island Rail Road
Long Island Rail Road
The Long Island Rail Road or LIRR is a commuter rail system serving the length of Long Island, New York. It is the busiest commuter railroad in North America, serving about 81.5 million passengers each year. Established in 1834 and having operated continuously since then, it is the oldest US...

 and Metro-North Railroad
Metro-North Railroad
The Metro-North Commuter Railroad , trading as MTA Metro-North Railroad, or, more commonly, Metro-North, is a suburban commuter rail service that is run and managed by the Metropolitan Transportation Authority , an authority of New York State. It is the busiest commuter railroad in the United...

 operate dual-mode diesel-electric/third-rail locomotives between non-electrified territory and New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

 because of a local law banning diesel-powered locomotives in Manhattan
Manhattan
Manhattan is the oldest and the most densely populated of the five boroughs of New York City. Located primarily on the island of Manhattan at the mouth of the Hudson River, the boundaries of the borough are identical to those of New York County, an original county of the state of New York...

 tunnels. For the same reason, Amtrak
Amtrak
The National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...

 operates a fleet of dual-mode locomotives in the New York area. British Rail
British Rail
British Railways , which from 1965 traded as British Rail, was the operator of most of the rail transport in Great Britain between 1948 and 1997. It was formed from the nationalisation of the "Big Four" British railway companies and lasted until the gradual privatisation of British Rail, in stages...

 operated dual diesel-electric/electric locomotives designed to run primarily as electric locomotives with reduced power available when running on diesel power. This allowed railway yards to remain un-electrified, as the third rail power system is extremely hazardous in a yard area.

Diesel-hydraulic


Diesel-hydraulic locomotives use a torque converter
Torque converter
In modern usage, a torque converter is generally a type of hydrodynamic fluid coupling that is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load...

 or hydraulic drive system
Hydraulic drive system
A hydraulic drive system is a drive or transmission system that uses pressurized hydraulic fluid to drive hydraulic machinery. The term hydrostatic refers to the transfer of energy from flow and pressure, not from the kinetic energy of the flow....

 to convey the power from the diesel engine to the wheels.

Hydrokinetic transmission




Hydrokinetic transmission (also called hydrodynamic transmission) uses a torque converter
Torque converter
In modern usage, a torque converter is generally a type of hydrodynamic fluid coupling that is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load...

. A torque converter consists of three main parts, two of which rotate, and one that has a lock preventing backwards rotation and adding output torque by redirecting the oil flow at low output RPM. All three main parts are sealed in an oil-filled housing. To match engine speed to load speed over the entire speed range of a locomotive some additional method is required to give sufficient range. One method is to follow the torque converter with a mechanical gearbox which switches ratios automatically, similar to an automatic transmission on a car. Another method is to provide several torque converters each with a range of variability covering part of the total required; all the torque converters are mechanically connected all the time, and the appropriate one for the speed range required is selected by filling it with oil and draining the others. The filling and draining is carried out with the transmission under load, and results in very smooth range changes with no break in the transmitted power.
Multiple units

Diesel-hydraulic multiple units, a less arduous duty, often use a simplification of this system, with a torque converter for the lower speed ranges and a fluid coupling
Fluid coupling
A fluid coupling is a hydrodynamic device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch...

 for the high speed range. A fluid coupling is similar to a torque converter but it lacks the stator. The output torque is equal to the input torque regardless of the ratio of input to output speed; loading the output shaft results not in torque multiplication and constant power throughput but in reduction of the input speed with consequent lower power throughput. (In car terms, the fluid coupling provides top gear and the torque converter provides all the lower gears.) The result is that the power available at the rail is reduced when operating in the lower speed part of the fluid coupling range, but the less arduous duty of a passenger multiple unit compared to a locomotive makes this an acceptable trade-off for reduced mechanical complexity.
Locomotives

Diesel-hydraulic locomotives are less efficient than diesel-electrics. The first-generation BR diesel hydraulics were significantly less efficient (c. 65%) than diesel electrics (c. 80%)—but initial versions were found in many countries to be mechanically more complicated and more likely to break down. Hydraulic transmission for locomotives was developed in Germany. The bad reputation of diesel-hydraulic principle was caused by the poor durability and reliability of the Maybach Mekydro hydraulic transmission. The Mekydro consisted of a hydraulic torque converter followed by a four speed automatic mechanical gearbox. Voith
Voith
The Voith GmbH, which is headquartered in Germany, is a family-run corporation in the mechanical engineering sector with worldwide operations....

 developed a different solution using several torque converters, and it has proven to be extremely durable and very well-suited for the purpose.
Reliability

In Germany and Finland, diesel-hydraulic systems have achieved extremely high reliability in operation. Persistent argument continues over the relative reliability of hydraulic systems, with continuing questions over whether data were manipulated politically to favour local suppliers over German ones. In the US and Canada, they are now greatly outnumbered by diesel-electric locomotives, while they remain dominant in some European countries.
Examples


The most famous diesel-hydraulic locomotive is the German V 200
DB class V 200
DB Class V 200.0 was one of the first diesel-hydraulic express locomotives of the German Deutsche Bundesbahn and - as Am 4/4 - of the SBB-CFF-FFS in Switzerland.-DB Service:...

, which were built from 1953 in a total number of 136. The only diesel-electric locomotives of the Deutsche Bundesbahn
Deutsche Bundesbahn
The Deutsche Bundesbahn or DB was formed as the state railway of the newly established Federal Republic of Germany on September 7, 1949 as a successor of the Deutsche Reichsbahn-Gesellschaft '...

were BR 288 (V 188), of which the Deutsche Reichsbahn
Deutsche Reichsbahn
Deutsche Reichsbahn was the name of the following two companies:* Deutsche Reichsbahn, the German Imperial Railways during the Weimar Republic, the Third Reich and the immediate aftermath...

 built 12 in 1939.

In the UK, the Western Region of British Rail bought a number of Diesel-hydraulic locomotives, ranging from small light-duty freight locomotives to high-powered mainline passenger locomotives, but these were withdrawn early because they were non-standard, and also in some cases suffering from reliability problems (see above), being replaced by diesel-electrics. A number were rescued for preservation though, and some are capable of running on the mainline.

In Finland, over 200 Finnish-built VR class Dv12
VR Class Dv12
The Dv12 is the standard Finnish medium-weight diesel-hydraulic road locomotive operated by VR. As all the main lines of Finnish railway network have been electrificied, the locomotive is designated mostly to unelectrified, less frequently used side lines. Occasionally it may still pull cargo...

 and Dr14 diesel-hydraulics with Voith
Voith
The Voith GmbH, which is headquartered in Germany, is a family-run corporation in the mechanical engineering sector with worldwide operations....

 transmissions have been continuously used since the early 1960s. All units of Dr14 class and most units of Dv12 class are still in service. VR has abandoned some weak-conditioned units of 2700 series Dv12s.

In the 1950s, General Motors Diesel
General Motors Diesel
General Motors Diesel was a Canadian railway diesel locomotive manufacturer.-History:General Motors Diesel, Limited, was created in 1949 as the Canadian subsidiary of the Electro Motive Division of General Motors located in the United States...

 of Canada built 4 GMD GMDH-1
GMD GMDH-1
The GMD GMDH-1 was an experimental diesel-hydraulic switching locomotive built by General Motors Diesel of Canada. Four examples were built. It was a double-ended, center-cab design...

 experimental locomotives.

In 1959 the South African Railways (SAR) placed seven Henschel
Henschel & Son
Henschel & Son was a German company, situated in Kassel, best known during the 20th century as a maker of transportation equipment, including locomotives, trucks, buses and trolleybuses, and armoured fighting vehicles and weapons....

 built diesel-hydraulic locomotives in service. Designated as South African Class 61-000
South African Class 61-000
Between May and July 1959, in order to also gain experience with other forms of diesel motive power, the South African Railways placed seven Class 1-DH diesel-hydraulic locomotives in service. These were later reclassified to Class 61-000...

, all but one were later sold to Rhodesia Railways, where they became RR Class DH1.

In the 1960s, the Southern Pacific (SP) bought 18 diesel-hydraulic locomotives KM ML-4000
KM ML-4000
The Krauss-Maffei ML 4000 C'C is a diesel-hydraulic locomotive, built between 1960 and 1969 by German manufacturer Krauss-Maffei in Munich, Germany. It generated 4000 horsepower from two Maybach V16 engines...

 from the Kraus-Maffei company. The Denver & Rio Grande Western also bought three, all of which it later sold to SP.
Only the outer shell of one of these (converted into a camera car by SP in the 1970s) exists today, the other 20 having been scrapped when SP terminated the experiment in 1970.

Hydrostatic transmission


Hydrostatic transmission
Hydraulic drive system
A hydraulic drive system is a drive or transmission system that uses pressurized hydraulic fluid to drive hydraulic machinery. The term hydrostatic refers to the transfer of energy from flow and pressure, not from the kinetic energy of the flow....

 is limited to small shunting locomotives and rail maintenance equipment. The diesel engine drives a hydraulic pump
Hydraulic pump
Hydraulic pumps are used in hydraulic drive systems and can be hydrostatic or hydrodynamic.Hydrostatic pumps are positive displacement pumps while hydrodynamic pumps can be fixed displacement pumps, in which the displacement cannot be adjusted, or variable displacement pumps, which have a more...

 which supplies oil under pressure to hydraulic motor
Hydraulic motor
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement . The hydraulic motor is the rotary counterpart of the hydraulic cylinder....

s which drive the axles.

Diesel-steam



Steam-diesel hybrid locomotives can use steam generated from a boiler or diesel to power a piston engine. The Cristiani Compressed Steam System used a diesel engine to power a compressor to drive and recirculate steam produced by a boiler; effectively using steam as the power transmission medium, with the diesel engine being the prime mover
Prime mover (locomotive)
In engineering, a prime mover is an engine that converts fuel to useful work. In locomotives, the prime mover is thus the source of power for its propulsion. The term is generally used when discussing any locomotive powered by an internal combustion engine...


Diesel-pneumatic


The diesel-pneumatic locomotive was of interest in the 1930s because it offered the possibility of converting existing steam locomotives to diesel operation. The frame and cylinders of the steam locomotive would be retained and the boiler would be replaced by a diesel engine driving an air compressor
Air compressor
An air compressor is a device that converts power into kinetic energy by compressing and pressurizing air, which, on command, can be released in quick bursts...

. The problem was low thermal efficiency
Thermal efficiency
In thermodynamics, the thermal efficiency is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, a boiler, a furnace, or a refrigerator for example.-Overview:...

 because of the large amount of energy wasted as heat in the air compressor. Attempts were made to compensate for this by using the diesel exhaust to re-heat the compressed air but these had limited success. A German proposal of 1929 did result in a prototype but a similar British proposal of 1932, to use an LNER Class R1 locomotive, never got beyond the design stage.

Multiple-unit operation



Most Diesel locomotives are capable of multiple unit operation (MU)
Multiple-unit train control
Multiple-unit train control, sometimes abbreviated to multiple-unit or MU, is a method of simultaneously controlling all the traction equipment in a train from a single location, whether it is a Multiple unit comprising a number of self-powered passenger cars or a set of locomotives.A set of...

 as a means of increasing 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...

 and 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...

 when hauling heavy trains. All North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

n locomotives, including export models, use a standardised AAR
Association of American Railroads
The Association of American Railroads is an industry trade group representing primarily the major freight railroads of North America . Amtrak and some regional commuter railroads are also members...

 electrical control system interconnected by a 27-pin jumper cable
Cable
A cable is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. In mechanics cables, otherwise known as wire ropes, are used for lifting, hauling and towing or conveying force through tension. In electrical engineering cables are used to carry...

 between the units. For UK-built locomotives, a number of incompatible control systems are used, but the most common is the Blue Star system, which is electro-pneumatic and fitted to most early diesel classes. A small number of types, typically higher-powered locomotives intended for passenger only work, do not have multiple control systems. In all cases, the electrical control connections made common to all units in a consist
Consist
A consist , in North American railway terminology, is used as a noun to describe the group of rail vehicles that make up a train. A near-equivalent UK term is rake but this excludes the locomotive....

 are referred to as trainlines. The result is that all locomotives in a consist
Consist
A consist , in North American railway terminology, is used as a noun to describe the group of rail vehicles that make up a train. A near-equivalent UK term is rake but this excludes the locomotive....

 behave as one in response to the engine driver's control movements.

The ability to MU Diesel-electric locomotives was first introduced in the EMD FT
EMD FT
The EMD FT was a diesel-electric locomotive produced between November 1939, and November 1945, by General Motors' Electro-Motive Division . All told 555 cab-equipped A units were built, along with 541 cabless booster B units, for a grand total of 1,096 units. The locomotives were all sold to...

 four-unit demonstrator that toured the USA in 1939. At the time, American railroad work rules required that each operating locomotive in a train had to have on board a full crew. EMD circumvented that requirement by joining the individual units of the demonstrator with drawbar
Drawbar (haulage)
A drawbar is a solid coupling between a hauling vehicle and its hauled load. Drawbars are in common use with rail transport, road trailers, both large and small, industrial and recreational, and with agricultural equipment.-Agriculture:...

s instead of conventional knuckle coupler
Coupling (railway)
A coupling is a mechanism for connecting rolling stock in a train. The design of the coupler is standard, and is almost as important as the railway gauge, since flexibility and convenience are maximised if all rolling stock can be coupled together.The equipment that connects the couplings to the...

s and declaring the combination to be a single locomotive. Electrical interconnections were made so one engine driver could operate the entire consist from the head-end unit. Later on, work rules were amended and the semi-permanent joining of units with drawbars was eliminated in favour of couplers, as servicing had proved to be somewhat cumbersome owing to the total length of the consist (about 200 feet or nearly 61 meters).

In mountainous regions, it is common to interpose helper locomotives in the middle of the train, both to provide the extra power needed to ascend a grade and to limit the amount of stress applied to the draft gear
Coupling (railway)
A coupling is a mechanism for connecting rolling stock in a train. The design of the coupler is standard, and is almost as important as the railway gauge, since flexibility and convenience are maximised if all rolling stock can be coupled together.The equipment that connects the couplings to the...

 of the car coupled to the head-end power. The helper units in such distributed power
Distributed power
In rail transport distributed power refers to the placing of additional locomotives at intermediate points in the middle of the train, remotely controlled from the leading locomotive, to allow longer trains where operational considerations or economics require it. Distributed power thus describes...

 configurations are controlled from the lead unit's cab through coded radio signals. Although this is technically not MUing, the behaviour is the same as with physically interconnected units.

Cab arrangements


Cab arrangements vary by builder and operator. Practice in the U.S. has traditionally been for a cab at one end of the locomotive with limited visibility if the locomotive is not operated cab forward. This is not usually a problem as U.S. locomotives are usually operated in pairs, or threes, and arranged so that a cab is at each end of each set. European practice is usually for a cab at each end of the locomotive as trains are usually light enough to operate with one locomotive. Early U.S. practice was to add power units without cabs (booster or B-units) and the arrangement was often A-B, A-B-A, or A-B-B-A where A was a unit with a cab. Center cabs were sometimes used for switch locomotives.

Cow-calf



In North American railroading, a cow-calf
Cow-calf
In North American railroading, a cow-calf locomotive is a set of switcher-type diesel locomotives. The set usually is a pair; some 3-unit sets were built, but this was rare. A cow is equipped with a driving cab; a calf is not...

 set is a pair of switcher-type locomotives: one (the cow) equipped with a driving cab, the other (the calf) without a cab, and controlled from the cow through cables. Cow-calf sets are used in heavy switching and hump yard service. Some are radio controlled without an operating engineer present in the cab. This arrangement is also known as master-slave.

Flameproof diesel locomotive


A standard diesel locomotive presents a very low fire risk but “flameproofing” can reduce the risk even further. This involves fitting a water-filled box to the exhaust pipe to quench any red-hot carbon particles that may be emitted. Other precautions may include a fully insulated electrical system (neither side earthed to the frame) and all electric wiring enclosed in conduit.

The flameproof diesel locomotive has replaced the fireless steam locomotive in areas of high fire risk such as oil refineries and ammunition dump
Ammunition dump
An ammunition dump, ammunition compound, ammunition depot, bomb dump, ammunition supply point or ammo dump, is a military storage facility for live ammunition and explosives....

s. Preserved examples of flameproof diesel locomotives include:
  • Francis Baily of Thatcham (ex-RAF Welford
    RAF Welford
    RAF Welford is an active Royal Air Force station in Berkshire, England. The airfield is located approximately northwest of Newbury; about west-southwest of London...

    ) at Southall Railway Centre
    Southall Railway Centre
    Southall Railway Centre is a railway heritage centre at Southall in west London, near to Southall railway station and the Grand Union Canal. It is run by the GWR Preservation Group Limited .-History:...

  • Naworth (ex-National Coal Board
    National Coal Board
    The National Coal Board was the statutory corporation created to run the nationalised coal mining industry in the United Kingdom. Set up under the Coal Industry Nationalisation Act 1946, it took over the mines on "vesting day", 1 January 1947...

    ) at the South Tynedale Railway
    South Tynedale Railway
    The South Tynedale Railway is a heritage railway in England and is England's highest narrow gauge railway. The route runs from Alston in Cumbria to Kirkhaugh in Northumberland via the South Tyne Viaduct, the Gilderdale Viaduct and the Whitley Viaduct...


Latest development of the "Flameproof Diesel Vehicle Applied New Exhaust Gas Dry Type Treatment System " does not need the water supply.

Lights



The lights fitted to diesel locomotives vary from country to country. North American locomotives have a powerful headlight and a pair of ditch lights. The latter are fitted low down at the front and are designed to make the locomotive easily visible as it approaches a grade crossing. Older locomotives may be fitted with a Gyralite or Mars Light
Mars Light
Mars Lights are signal-safety lights used in the United States and built by Mars Signal Light Company for railroad locomotives and fire apparatus...

 instead of the ditch lights.

Environmental impact



Although diesel locomotives pollute
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 considerably less than 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, they still emit diesel exhaust that contributes to health effects (especially cardiovascular
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

) and global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

. In 2008, the United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

 (EPA) mandated regulations requiring all new or refurbished diesel locomotives to meet pollution standards that slash the amount of allowable soot by 90% and require an 80% reduction in nitrogen oxide
Nitrogen oxide
Nitrogen oxide can refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:* Nitric oxide, also known as nitrogen monoxide, , nitrogen oxide* Nitrogen dioxide , nitrogen oxide...

 emissions. For years, it was thought by government scientists who measure air pollution
Air pollution
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....

 that diesel locomotive engines were relatively clean and emitted far less health-threatening emissions than that of diesel trucks or other vehicles; however, the scientists discovered that because they used faulty estimates of the amount of fuel consumed by diesel locomotives, they grossly understated the amount of pollution generated annually. After revising their calculations, they concluded that the annual emissions of nitrogen oxide, a major ingredient in smog
Smog
Smog is a type of air pollution; the word "smog" is a portmanteau of smoke and fog. Modern smog is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine...

, and soot would be by 2030 nearly twice what they originally assumed.

This would mean that diesel locomotives would be releasing more than 800,000 tons of nitrogen oxide and 25,000 tons of soot every year within a quarter of a century, in contrast to the EPA's previous projections of 480,000 tons of nitrogen dioxide
Nitrogen dioxide
Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...

 and 12,000 tons of soot. Since this was discovered, to reduce the effects of the diesel locomotive on human
Human
Humans are the only living species in the Homo genus...

s (who are breathing the noxious emissions) and on plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s and animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, it is considered practical to install traps in the diesel engines to reduce pollution levels and other forms (e.g., use of biodiesel
Biodiesel
Biodiesel refers to a vegetable oil- or animal fat-based diesel fuel consisting of long-chain alkyl esters. Biodiesel is typically made by chemically reacting lipids with an alcohol....

).

Diesel locomotive pollution has been of particular concern in the city of Chicago
Chicago (band)
Chicago is an American rock band formed in 1967 in Chicago, Illinois. The self-described "rock and roll band with horns" began as a politically charged, sometimes experimental, rock band and later moved to a predominantly softer sound, becoming famous for producing a number of hit ballads. They had...

. The Chicago Tribune reported levels of diesel soot inside locomotives leaving Chicago at levels hundreds of times above what is normally found on streets outside. Residents of several neighborhoods are most likely exposed to diesel emissions at levels several times higher than the national average for urban areas.

See also

  • Diesel multiple unit
    Diesel multiple unit
    A diesel multiple unit or DMU is a multiple unit train consisting of multiple carriages powered by one or more on-board diesel engines. They may also be referred to as a railcar or railmotor, depending on country.-Design:...

  • Diesel-electric transmission
  • Diesel engine
    Diesel engine
    A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

  • Electric locomotive
    Electric locomotive
    An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...

  • Electro-diesel locomotive
    Electro-diesel locomotive
    An Electro-diesel locomotive is powered either from an electricity supply or by using the onboard diesel engine...

  • Electrification
    Railway electrification system
    A railway electrification system supplies electrical energy to railway locomotives and multiple units as well as trams so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world...

  • Hybrid locomotive
    Hybrid locomotive
    A hybrid train is a locomotive, railcar or train that uses an onboard rechargeable energy storage system , placed between the power source and the traction transmission system connected to the wheels....

  • Hybrid electric vehicle
    Hybrid electric vehicle
    A hybrid electric vehicle is a type of hybrid vehicle and electric vehicle which combines a conventional internal combustion engine propulsion system with an electric propulsion system. The presence of the electric powertrain is intended to achieve either better fuel economy than a conventional...


External links