Alocomotive is arail vehicle that provides the motive power for atrain. Traditionally, locomotives pulled trains from the front. However,push–pull operation has become common, and in the pursuit for longer and heavier freight trains, companies are increasingly usingdistributed power: single or multiple locomotives placed at the front and rear and at intermediate points throughout the train under the control of the leading locomotive.[1]
The wordlocomotive originates from theLatinloco 'from a place',ablative oflocus 'place', and theMedieval Latinmotivus 'causing motion', and is a shortened form of the termlocomotive engine,[2] which was first used in 1814[3] to distinguish between self-propelled andstationary steam engines.
Prior to locomotives, the motive force for railways had been generated by various lower-technology methods such as human power, horse power,gravity or stationary engines that drove cable systems. Few such systems are still in existence today. Locomotives may generate their power from fuel (wood, coal, petroleum or natural gas), or they may takepower from an outside source of electricity. It is common to classify locomotives by their source of energy. The common ones include:
A steam locomotive is a locomotive whose primary power source is asteam engine. The most common form of steam locomotive also contains aboiler to generate the steam used by the engine. The water in the boiler is heated by burning combustible material – usually coal, wood, or oil – to produce steam. The steam moves reciprocatingpistons which are connected to the locomotive's main wheels, known as the "driving wheels". Both fuel and water supplies are carried with the locomotive, either on the locomotive itself, inbunkers andtanks, (this arrangement is known as a "tank locomotive") or pulled behind the locomotive, intenders, (this arrangement is known as a "tender locomotive").
The first full-scale working railway steam locomotive was built byRichard Trevithick in 1802. It was constructed for theCoalbrookdale ironworks inShropshire in England though no record of it working there has survived.[4] On 21 February 1804, the first recorded steam-hauled railway journey took place as another of Trevithick's locomotives hauled a train from thePenydarren ironworks, inMerthyr Tydfil, toAbercynon in South Wales.[5][6] Accompanied byAndrew Vivian, it ran with mixed success.[7] The design incorporated a number of important innovations including the use of high-pressure steam which reduced the weight of the engine and increased its efficiency.
The steam locomotive remained by far the most common type of locomotive until afterWorld War II.[12] Steam locomotives are less efficient than modern diesel and electric locomotives, and a significantly larger workforce is required to operate and service them.[13]British Rail figures showed that the cost of crewing and fuelling a steam locomotive was about two and a half times larger than the cost of supporting an equivalent diesel locomotive, and the daily mileage they could run was lower.[citation needed] Between about 1950 and 1970, the majority of steam locomotives were retired from commercial service and replaced with electric and diesel–electric locomotives.[14][15] While North America transitioned from steam during the 1950s, and continental Europe by the 1970s, in other parts of the world, the transition happened later. Steam was a familiar technology that used widely-available fuels and in low-wage economies did not suffer as wide a cost disparity. It continued to be used in many countries until the end of the 20th century. By the end of the 20th century, almost the only steam power remaining in regular use around the world was onheritage railways.
Internal combustion locomotives use aninternal combustion engine, connected to thedriving wheels by a transmission. They typically keep the engine running at a near-constant speed whether the locomotive is stationary or moving. Internal combustion locomotives are categorised by their fuel type and sub-categorised by their transmission type.
The first internal combustion rail vehicle was akerosene-powereddraisine built byGottlieb Daimler in 1887,[16] but this was not technically a locomotive as it carried a payload.
The first commercially successfulpetrol locomotive in the United Kingdom was apetrol–mechanical locomotive built by theMaudslay Motor Company in 1902, for the Deptford Cattle Market inLondon. It was an 80 hp locomotive using a three-cylinder vertical petrol engine, with a two speed mechanical gearbox.
Diesel locomotives are powered bydiesel engines. In the early days of diesel propulsion development, various transmission systems were employed with varying degrees of success, with electric transmission proving to be the most popular. In 1914,Hermann Lemp, aGeneral Electric electrical engineer, developed and patented a reliabledirect current electrical control system (subsequent improvements were also patented by Lemp).[18] Lemp's design used a single lever to control both engine and generator in a coordinated fashion, and was theprototype for alldiesel–electric locomotive control. In 1917–18, GE produced three experimental diesel–electric locomotives using Lemp's control design.[19] In 1924, a diesel–electric locomotive (Eel2 original number Юэ 001/Yu-e 001) started operations. It had been designed by a team led byYury Lomonosov and built 1923–1924 byMaschinenfabrik Esslingen in Germany. It had five driving axles (1'E1'). After several test rides, it hauled trains for almost three decades from 1925 to 1954.[20]
An electric locomotive is a locomotive powered only by electricity. Electricity is supplied to moving trains with a (nearly) continuousconductor running along the track that usually takes one of three forms: anoverhead line, suspended from poles or towers along the track or from structure or tunnel ceilings; athird rail mounted at track level; or an onboardbattery. Both overhead wire and third-rail systems usually use the running rails as the return conductor but some systems use a separate fourth rail for this purpose. The type of electrical power used is eitherdirect current (DC) oralternating current (AC).
Various collection methods exist: atrolley pole, which is a long flexible pole that engages the line with a wheel or shoe; abow collector, which is a frame that holds a long collecting rod against the wire; apantograph, which is a hinged frame that holds the collecting shoes against the wire in a fixed geometry; or acontact shoe, which is a shoe in contact with the third rail. Of the three, the pantograph method is best suited for high-speed operation.
Electric locomotives almost universally use axle-hung traction motors, with one motor for each powered axle. In this arrangement, one side of the motor housing is supported by plain bearings riding on a ground and polished journal that is integral to the axle. The other side of the housing has a tongue-shaped protuberance that engages a matching slot in the truck (bogie) bolster, its purpose being to act as a torque reaction device, as well as a support. Power transfer from motor to axle is effected byspur gearing, in which apinion on the motor shaft engages abull gear on the axle. Both gears are enclosed in a liquid-tight housing containing lubricating oil. The type of service in which the locomotive is used dictates the gear ratio employed. Numerically high ratios are commonly found on freight units, whereas numerically low ratios are typical of passenger engines.
Electricity is typically generated in large and relatively efficientgenerating stations, transmitted to the railway network and distributed to the trains. Some electric railways have their own dedicated generating stations andtransmission lines but most purchase power from anelectric utility. The railway usually provides its own distribution lines, switches andtransformers.
Electric locomotives usually cost 20% less than diesel locomotives, their maintenance costs are 25–35% lower, and cost up to 50% less to run.[21]
Werner von Siemens experimental DC electric train, 1879Baltimore & Ohio electric engine, 1895
The earliest systems wereDC systems. The first electric passenger train was presented byWerner von Siemens atBerlin in 1879. The locomotive was driven by a 2.2 kW, series-wound motor, and the train, consisting of the locomotive and three cars, reached a speed of 13 km/h. During four months, the train carried 90,000 passengers on a 300-meter-long (980-foot) circular track. The electricity (150 V DC) was supplied through a third insulated rail between the tracks. A contact roller was used to collect the electricity. The world's first electric tram line opened in Lichterfelde near Berlin, Germany, in 1881. It was built by Werner von Siemens (seeGross-Lichterfelde Tramway andBerlin Straßenbahn). TheVolk's Electric Railway opened in 1883 in Brighton, and is the oldest surviving electric railway. Also in 1883,Mödling and Hinterbrühl Tram opened near Vienna in Austria. It was the first in the world in regular service powered from an overhead line. Five years later, in the U.S. electrictrolleys were pioneered in 1888 on theRichmond Union Passenger Railway, using equipment designed byFrank J. Sprague.[22]
The first electrically workedunderground line was theCity & South London Railway, prompted by a clause in its enabling act prohibiting use of steam power.[23] It opened in 1890, using electric locomotives built byMather & Platt. Electricity quickly became the power supply of choice for subways, abetted by the Sprague's invention ofmultiple-unit train control in 1897.
The first use of electrification on a main line was on a four-mile stretch of theBaltimore Belt Line of theBaltimore & Ohio (B&O) in 1895 connecting the main portion of the B&O to the new line to New York through a series of tunnels around the edges of Baltimore's downtown. ThreeBo+Bo units were initially used, at the south end of the electrified section; they coupled onto the locomotive and train and pulled it through the tunnels.[24]
DC was used on earlier systems. These systems were gradually replaced by AC. Today, almost all main-line railways use AC systems. DC systems are confined mostly to urban transit such as metro systems, light rail and trams, where power requirement is less.
A prototype of a Ganz AC electric locomotive in Valtellina, Italy, 1901
The first practicalAC electric locomotive was designed byCharles Brown, then working forOerlikon, Zürich. In 1891, Brown had demonstrated long-distance power transmission, usingthree-phase AC, between ahydro-electric plant atLauffen am Neckar andFrankfurt am Main West, a distance of 280 km. Using experience he had gained while working forJean Heilmann on steam–electric locomotive designs, Brown observed thatthree-phase motors had a higher power-to-weight ratio thanDC motors and, because of the absence of acommutator, were simpler to manufacture and maintain.[a] However, they were much larger than the DC motors of the time and could not be mounted in underfloorbogies: they could only be carried within locomotive bodies.[26]
In 1894, Hungarian engineerKálmán Kandó developed a new type 3-phase asynchronous electric drive motors and generators for electric locomotives. The new 3-phase asynchronous electric drive motors were more effective than the synchronous electric motors of earlier locomotive designs. Kandó's early 1894 designs were first applied in a short three-phase AC tramway in Evian-les-Bains (France), which was constructed between 1896 and 1898.[27][28][29][30][31] In 1918,[32] Kandó invented and developed therotary phase converter, enabling electric locomotives to use three-phase motors whilst supplied via a single overhead wire, carrying the simple industrial frequency (50 Hz) single phase AC of the high voltage national networks.[33]
In 1896, Oerlikon installed the first commercial example of the system on theLugano Tramway. Each 30-tonne locomotive had two 110 kW (150 hp) motors run by three-phase 750 V 40 Hz fed from double overhead lines. Three-phase motors run at constant speed and provideregenerative braking, and are well suited to steeply graded routes, and the first main-line three-phase locomotives were supplied by Brown (by then in partnership withWalter Boveri) in 1899 on the 40 kmBurgdorf—Thun line, Switzerland. The first implementation of industrial frequency single-phase AC supply for locomotives came from Oerlikon in 1901, using the designs ofHans Behn-Eschenburg andEmil Huber-Stockar; installation on the Seebach-Wettingen line of the Swiss Federal Railways was completed in 1904. The 15 kV, 50 Hz 345 kW (460 hp), 48 tonne locomotives used transformers and rotary converters to power DC traction motors.[34]
Italian railways were the first in the world to introduce electric traction for the entire length of a main line rather than just a short stretch. The 106 km Valtellina line was opened on 4 September 1902, designed by Kandó and a team from the Ganz works.[35][33] The electrical system was three-phase at 3 kV 15 Hz. The voltage was significantly higher than used earlier and it required new designs for electric motors and switching devices.[36][37] The three-phase two-wire system was used on several railways in Northern Italy and became known as "the Italian system". Kandó was invited in 1905 to undertake the management of Società Italiana Westinghouse and led the development of several Italian electric locomotives.[36]
ALondon Underground battery–electric locomotive used for hauling engineers' trains, atWest Ham stationA narrow-gauge battery–electric locomotive used for mining
A battery–electric locomotive (or battery locomotive) is an electric locomotive powered by onboardbatteries; a kind ofbattery electric vehicle.
Such locomotives are used where a conventional diesel or electric locomotive would be unsuitable. An example is maintenance trains on electrified lines when the electricity supply is turned off. Another use is in industrial facilities where a combustion-powered locomotive (i.e.,steam- ordiesel-powered) could cause a safety issue due to the risks of fire, explosion or fumes in a confined space. Battery locomotives are preferred for mines where gas could be ignited bytrolley-powered unitsarcing at the collection shoes, or whereelectrical resistance could develop in the supply or return circuits, especially at rail joints, and allow dangerous current leakage into the ground.[38] Battery locomotives in over-the-road service can recharge while absorbing dynamic-braking energy.[39]
The first known electric locomotive was built in 1837 by chemistRobert Davidson ofAberdeen, and it was powered bygalvanic cells (batteries). Davidson later built a larger locomotive namedGalvani, exhibited at theRoyal Scottish Society of Arts Exhibition in 1841. The seven-ton vehicle had twodirect-drivereluctance motors, with fixed electromagnets acting on iron bars attached to a wooden cylinder on each axle, and simplecommutators. It hauled a load of six tons at four miles per hour (6 kilometers per hour) for a distance of one and a half miles (2.4 kilometres). It was tested on theEdinburgh and Glasgow Railway in September of the following year, but the limited power from batteries prevented its general use.[40][41][42]
Another example was at theKennecott Copper Mine,Latouche, Alaska, where in 1917 the underground haulage ways were widened to enable working by two battery locomotives of4+1⁄2 tons.[43] In 1928, Kennecott Copper ordered four 700-series electric locomotives with on-board batteries. These locomotives weighed 85 tons and operated on 750-volt overhead trolley wire with considerable further range whilst running on batteries.[44] The locomotives provided several decades of service usingNickel–iron battery (Edison) technology. The batteries were replaced withlead-acid batteries, and the locomotives were retired shortly afterward. All four locomotives were donated to museums, but one was scrapped. The others can be seen at theBoone and Scenic Valley Railroad, Iowa, and at theWestern Railway Museum in Rio Vista, California. TheToronto Transit Commission previously operated a battery electric locomotive built byNippon Sharyo in 1968 and retired in 2009.[45]
In the early 1950s, Lyle Borst of theUniversity of Utah was given funding by various US railroad line and manufacturers to study the feasibility of an electric-drive locomotive, in which an onboard atomic reactor produced the steam to generate the electricity. At that time, atomic power was not fully understood; Borst believed the major stumbling block was the price of uranium. With the Borst atomic locomotive, the center section would have a 200-ton reactor chamber and steel walls 5 feet thick to prevent releases of radioactivity in case of accidents. He estimated a cost to manufacture atomic locomotives with 7000 h.p. engines at approximately $1,200,000 each.[46] Consequently, trains with onboard nuclear generators were generally deemed unfeasible due to prohibitive costs.
In 2002, the first 3.6 tonne, 17 kWhydrogen-(fuel-cell)–powered mining locomotive was demonstrated inVal-d'Or,Quebec. In 2007 the educational mini-hydrail inKaohsiung,Taiwan went into service. TheRailpower GG20B finally is another example of a fuel cell–electric locomotive.
There are many different types of hybrid or dual-mode locomotives using two or more types of motive power. The most common hybrids areelectro-diesel locomotives powered either from an electricity supply or else by an onboarddiesel engine. These are used to provide continuous journeys along routes that are only partly electrified. Examples include theEMD FL9 andBombardier ALP-45DP
Freight locomotives are normally designed to deliver high startingtractive effort and high sustained power. This allows them to start and move long, heavy trains, but usually comes at the cost of relatively low maximum speeds. Passenger locomotives usually develop lower starting tractive effort but are able to operate at the high speeds required to maintain passenger schedules. Mixed-traffic locomotives (US English: general purpose or road switcher locomotives) meant for both passenger and freight trains do not develop as much starting tractive effort as a freight locomotive but are able to haul heavier trains than a passenger locomotive.[dubious –discuss]
Most steam locomotives have reciprocating engines, with pistons coupled to the driving wheels by means of connecting rods, with no intervening gearbox. This means the combination of starting tractive effort and maximum speed is greatly influenced by the diameter of the driving wheels. Steam locomotives intended for freight service generally have smaller diameter driving wheels than passenger locomotives.
In diesel-electric and electric locomotives the control system between thetraction motors andaxles adapts the power output to the rails for freight or passenger service. Passenger locomotives may include other features, such ashead-end power (also referred to as hotel power or electric train supply) or asteam generator.
Some locomotives are designed specifically to worksteep grade railways, and feature extensive additional braking mechanisms and sometimes rack and pinion. Steam locomotives built for steeprack and pinion railways frequently have the boiler tilted relative to thelocomotive frame, so that the boiler remains roughly level on steep grades.
Locomotives are also used on some high-speed trains. Some of them are operated inpush-pull formation with trailercontrol cars at another end of a train, which often have a cabin with the same design as a cabin of locomotive; examples of such trains with conventional locomotives areRailjet andIntercity 225.
Also many high-speed trains, including allTGV, manyTalgo (250 / 350 / Avril / XXI), someKorea Train Express,ICE 1/ICE 2 andIntercity 125, use dedicatedpower cars, which do not have places for passengers and technically are special single-ended locomotives. The difference from conventional locomotives is that these power cars are integral part of a train and are not adapted for operation with any other types of passenger coaches. On the other hand, many high-speed trains such as theShinkansen network never use locomotives. Instead of locomotive-like power-cars, they useelectric multiple units (EMUs) or diesel multiple units (DMUs) – passenger cars that also have traction motors and power equipment. Using dedicated locomotive-like power cars allows for a high ride quality and less electrical equipment;[47]but EMUs have less axle weight, which reduces maintenance costs, and EMUs also have higher acceleration and higher seating capacity.[47]Also some trains, includingTGV PSE,TGV TMST andTGV V150, use both non-passenger power cars and additional passenger motor cars.
Locomotives occasionally work in a specific role, such as:
Train engine is the technical name for a locomotive attached to the front of a railwaytrain to haul that train. Alternatively, where facilities exist forpush-pull operation, the train engine might be attached to the rear of the train;
Banking engine – a locomotive temporarily assisting a train from the rear, due to a difficult start or a sharp incline gradient;
Light engine – a locomotive operating without a train behind it, for relocation or operational reasons. Occasionally, a light engine is referred to as a train in and of itself.
In the second half of the twentieth centuryremote control locomotives started to enter service in switching operations, being remotely controlled by an operator outside of the locomotive cab.The main benefit is one operator can control the loading of grain, coal, gravel, etc. into the cars. In addition, the same operator can move the train as needed. Thus, the locomotive is loaded or unloaded in about a third of the time.[citation needed]
^Heilmann evaluated both AC and DC electric transmission for his locomotives, but eventually settled on a design based onThomas Edison's DC system.[25]
^"Most Important and highly Valuable Sea-Sale Colliery, Near Newcastle-on-Tyne, to be sold by auction, by Mr. Burrell".Leeds Mercury. 12 February 1814. p. 2.
^Francis Trevithick (1872).Life of Richard Trevithick: With an Account of His Inventions, Volume 1. E.&F.N.Spon.
^"Steam train anniversary begins".BBC News. 21 February 2004.Archived from the original on 3 June 2020. Retrieved13 June 2009.A south Wales town has begun months of celebrations to mark the 200th anniversary of the invention of the steam locomotive. Merthyr Tydfil was the location where, on 21 February 1804, Richard Trevithick took the world into the railway age when he set one of his high-pressure steam engines on a local iron master's tram rails
^Lemp, Hermann. US Patent No. 1,154,785, filed 8 April 1914, and issued 28 September 1915.Accessed via Google Patent Search at:US Patent #1,154,785Archived 22 December 2012 at theWayback Machine on 8 February 2007.
Churella, Albert J. (1998).From Steam To Diesel: Managerial Customs and Organizational Capabilities in the Twentieth-Century American Locomotive Industry. Princeton:Princeton University Press.ISBN978-0-691-02776-0.
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