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A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually
coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...
, oil or, rarely,
wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of ligni ...
) to heat water in the locomotive's boiler to the point where it becomes gaseous and its volume increases 1,700 times. Functionally, it is a
steam engine A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be ...
on wheels. In most locomotives, the steam is admitted alternately to each end of its
cylinders A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infini ...
, in which pistons are mechanically connected to the locomotive's main wheels. Fuel and water supplies are usually carried with the locomotive, either on the locomotive itself or in a
tender Tender may refer to: Entertainment Film * ''Illegal Tender'' (2007), a film directed by Franc. Reyes * ''Tender'' (2012), a short film by Liz Tomkins * ''Tender'' (2019), a short film by Darryl Jones and Anthony Lucido * ''Tender'' (2019), a sh ...
coupled to it. Variations in this general design include electrically-powered boilers, turbines in place of pistons, and using steam generated externally. Steam locomotives were first developed in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
during the early 19th century and used for railway transport until the middle of the 20th century. Richard Trevithick built the first steam locomotive known to have hauled a load over a distance at Pen-y-darren in 1804, although he produced an earlier locomotive for trial at Coalbrookdale in 1802. '' Salamanca'', built in 1812 by Matthew Murray for the Middleton Railway, was the first commercially successful steam locomotive. ''Locomotion'' No. 1, built by George Stephenson and his son Robert’s company Robert Stephenson and Company, was the first steam locomotive to haul passengers on a public railway, the Stockton and Darlington Railway, in 1825. Rapid development ensued; in 1830 George Stephenson opened the first public inter-city railway, the Liverpool and Manchester Railway, after the success of
Rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entire ...
at the 1829 Rainhill Trials had proved that steam locomotives could perform such duties. Robert Stephenson and Company was the pre-eminent builder of steam locomotives in the first decades of steam for railways in the United Kingdom, the United States, and much of Europe. Towards the end of the steam era, a longstanding British emphasis on speed culminated in a record, still unbroken, of by LNER Class A4 4468 ''Mallard''. In the United States, larger loading gauges allowed the development of very large, heavy locomotives such as the Union Pacific Big Boy, which weighed and had a tractive effort of .Comparable figures for the last-built British Railways freight locomotive, the Class 9F, were and . From the early 1900s, steam locomotives were gradually superseded by electric and diesel locomotives, with railways fully converting to electric and diesel power beginning in the late 1930s. The majority of steam locomotives were retired from regular service by the 1980s, although several continue to run on tourist and heritage lines.


History


Britain

The earliest railways employed horses to draw carts along rail tracks. In 1784, William Murdoch, a
Scottish Scottish usually refers to something of, from, or related to Scotland, including: *Scottish Gaelic, a Celtic Goidelic language of the Indo-European language family native to Scotland *Scottish English *Scottish national identity, the Scottish ide ...
inventor, built a small-scale prototype of a steam road locomotive in
Birmingham Birmingham ( ) is a city and metropolitan borough in the metropolitan county of West Midlands in England. It is the second-largest city in the United Kingdom with a population of 1.145 million in the city proper, 2.92 million in the We ...
. A full-scale rail steam locomotive was proposed by William Reynolds around 1787. An early working model of a steam rail locomotive was designed and constructed by steamboat pioneer John Fitch in the US during 1794. His steam locomotive used interior bladed wheels guided by rails or tracks. The model still exists at the Ohio Historical Society Museum in Columbus, US. The authenticity and date of this locomotive is disputed by some experts and a workable steam train would have to await the invention of the high-pressure steam engine by Richard Trevithick, who pioneered the use of steam locomotives. The first full-scale working railway steam locomotive was the gauge ''Coalbrookdale Locomotive'', built by Trevithick in 1802. It was constructed for the Coalbrookdale ironworks in
Shropshire Shropshire (; alternatively Salop; abbreviated in print only as Shrops; demonym Salopian ) is a landlocked historic county in the West Midlands region of England. It is bordered by Wales to the west and the English counties of Cheshire to ...
in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
though no record of it working there has survived. On 21 February 1804, the first recorded steam-hauled railway journey took place as another of Trevithick's locomotives hauled a train along the -wide tramway from the Pen-y-darren ironworks, near Merthyr Tydfil, to Abercynon in South Wales. Accompanied by Andrew Vivian, it ran with mixed success. The design incorporated a number of important innovations that included using high-pressure steam which reduced the weight of the engine and increased its efficiency. Trevithick visited the Newcastle area in 1804 and had a ready audience of colliery (coal mine) owners and engineers. The visit was so successful that the colliery railways in north-east England became the leading centre for experimentation and development of the steam locomotive. Trevithick continued his own steam propulsion experiments through another trio of locomotives, concluding with the '' Catch Me Who Can'' in 1808. In 1812, Matthew Murray's successful twin-cylinder rack locomotive '' Salamanca'' first ran on the edge-railed rack-and-pinion Middleton Railway. Another well-known early locomotive was '' Puffing Billy'', built 1813–14 by engineer William Hedley. It was intended to work on the Wylam Colliery near Newcastle upon Tyne. This locomotive is the oldest preserved, and is on static display at the Science Museum, London.


George Stephenson

George Stephenson, a former miner working as an engine-wright at Killingworth Colliery, developed up to sixteen Killingworth locomotives, including '' Blücher'' in 1814, another in 1815, and a (newly identified) ''Killingworth Billy'' in 1816. He also constructed ''The Duke'' in 1817 for the Kilmarnock and Troon Railway, which was the first steam locomotive to work in Scotland. In 1825, Stephenson built Locomotion No. 1 for the Stockton and Darlington Railway, north-east England, which was the first public steam railway in the world. In 1829, his son
Robert The name Robert is an ancient Germanic given name, from Proto-Germanic "fame" and "bright" (''Hrōþiberhtaz''). Compare Old Dutch ''Robrecht'' and Old High German ''Hrodebert'' (a compound of '' Hruod'' ( non, Hróðr) "fame, glory, h ...
built in Newcastle '' The Rocket'', which was entered in and won the Rainhill Trials. This success led to the company emerging as the pre-eminent builder of steam locomotives used on railways in the UK, US and much of Europe. The Liverpool and Manchester Railway opened a year later making exclusive use of steam power for passenger and goods trains.


United States

Before the arrival of British imports, some domestic steam locomotive prototypes were built and tested in the United States. An early miniature prototype was built by John Fitch, who demonstrated his miniature engine to George Washington during the 1780s. A prominent large example was Col. John Steven's "steam wagon" which was demonstrated on a loop of track in
Hoboken, New Jersey Hoboken ( ; Unami: ') is a city in Hudson County in the U.S. state of New Jersey. As of the 2020 U.S. census, the city's population was 60,417. The Census Bureau's Population Estimates Program calculated that the city's population was 58, ...
in 1825. Many of the earliest locomotives for commercial use on American railroads were imported from Great Britain, including first the '' Stourbridge Lion'' and later the '' John Bull''. However, a domestic locomotive-manufacturing industry was soon established. In 1830, the Baltimore and Ohio Railroad's '' Tom Thumb'', designed by Peter Cooper, was the first commercial US-built locomotive to run in America; it was intended as a demonstration of the potential of steam traction rather than as a revenue-earning locomotive. The '' DeWitt Clinton'', built in 1831 for the
Mohawk and Hudson Railroad Mohawk may refer to: Related to Native Americans *Mohawk people, an indigenous people of North America (Canada and New York) *Mohawk language, the language spoken by the Mohawk people *Mohawk hairstyle, from a hairstyle once thought to have been t ...
, was a notable early locomotive. , the original ''John Bull'' was on static display in the National Museum of American History in Washington, D.C. The replica is preserved at the Railroad Museum of Pennsylvania.


Continental Europe

The first railway service outside the United Kingdom and North America was opened in 1829 in
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan ar ...
between Saint-Etienne and
Lyon Lyon,, ; Occitan: ''Lion'', hist. ''Lionés'' also spelled in English as Lyons, is the third-largest city and second-largest metropolitan area of France. It is located at the confluence of the rivers Rhône and Saône, to the northwest of ...
; it was initially limited to animal traction and only converted to steam traction ca. 1837, the first French steam locomotive being ''La Gironde'' produced at Schneider-Creusot. The first steam locomotive in service in Europe was named ''The Elephant'', which on 5 May 1835 hauled a train on the first line in Belgium, linking Mechelen and Brussels. In Germany, the first working steam locomotive was a rack-and-pinion engine, similar to the ''Salamanca'', designed by the British locomotive pioneer John Blenkinsop. Built in June 1816 by
Johann Friedrich Krigar Johann, typically a male given name, is the German form of ''Iohannes'', which is the Latin form of the Greek name ''Iōánnēs'' (), itself derived from Hebrew name '' Yochanan'' () in turn from its extended form (), meaning " Yahweh is Grac ...
in the Royal Berlin Iron Foundry (''Königliche Eisengießerei'' zu Berlin), the locomotive ran on a circular track in the factory yard. It was the first locomotive to be built on the European mainland and the first steam-powered passenger service; curious onlookers could ride in the attached coaches for a fee. It is portrayed on a New Year's badge for the Royal Foundry dated 1816. Another locomotive was built using the same system in 1817. They were to be used on pit railways in Königshütte and in Luisenthal on the Saar (today part of Völklingen), but neither could be returned to working order after being dismantled, moved and reassembled. On 7 December 1835, the ''
Adler Adler may refer to: Places *Adler, Alabama, an unincorporated community in Perry County *Adler Planetarium, Chicago, Illinois, USA *Adler Township, Nelson County, North Dakota, USA *Adler University, formerly Adler School of Professional Psycholo ...
'' ran for the first time between Nuremberg and Fürth on the Bavarian Ludwig Railway. It was the 118th engine from the locomotive works of Robert Stephenson and stood under patent protection. In Russia, the first steam locomotive was built in 1834 by
Cherepanovs Yefim Alekseyevich Cherepanov (russian: Ефи́м Алексе́евич Черепа́нов; 1774 – 1842), and his son Miron Yefimovich Cherepanov (russian: Миро́н Ефи́мович Черепа́нов; 1803 – 1849) were Russian i ...
, however, it suffered from the lack of coal in the area and was replaced with horse traction after all the woods nearby had been cut down. The first Russian Tsarskoye Selo steam railway started in 1837 with locomotives purchased from Robert Stephenson and Company. In 1837, the first steam railway started in Austria on the Emperor Ferdinand Northern Railway between Vienna-Floridsdorf and Deutsch-Wagram. The oldest continually working steam engine in the world also runs in Austria: the GKB 671 built in 1860, has never been taken out of service, and is still used for special excursions. In 1838, the third steam locomotive to be built in Germany, the '' Saxonia'', was manufactured by the ''Maschinenbaufirma Übigau'' near
Dresden Dresden (, ; Upper Saxon: ''Dräsdn''; wen, label=Upper Sorbian, Drježdźany) is the capital city of the German state of Saxony and its second most populous city, after Leipzig. It is the 12th most populous city of Germany, the fourth ...
, built by Prof. Johann Andreas Schubert. The first independently designed locomotive in Germany was the '' Beuth'', built by August Borsig in 1841. The first locomotive produced by Henschel-Werke in Kassel, the ''Drache'', was delivered in 1848. The first steam locomotives operating in Italy were the ''Bayard'' and the ''Vesuvio'', running on the Napoli-Portici line, in the Kingdom of the Two Sicilies. The first railway line over Swiss territory was the StrasbourgBasle line opened in 1844. Three years later, in 1847, the first fully Swiss railway line, the ''Spanisch Brötli Bahn'', from Zürich to Baden was opened.


Australia

The arid nature of south Australia posed distinctive challenges to their early steam locomotion network. The high concentration of magnesium chloride in the well water ( bore water) used in locomotive boilers on the Trans-Australian Railway caused serious and expensive maintenance problems. At no point along its route does the line cross a permanent freshwater watercourse, so bore water had to be relied on. No inexpensive treatment for the highly mineralised water was available, and locomotive boilers were lasting less than a quarter of the time normally expected. In the days of steam locomotion, about half the total train load was water for the engine. The line's operator, Commonwealth Railways, was an early adopter of the diesel-electric locomotive.


Components


Boiler

The fire-tube boiler was standard practice for steam locomotive. Although other types of boiler were evaluated they were not widely used, except for some 1,000 locomotives in Hungary which used the water-tube Brotan boiler. A boiler consists of a firebox where the fuel is burned, a barrel where water is turned into steam and a smokebox which is kept at a slightly lower pressure than outside the firebox. Solid fuel, such as wood, coal or coke, is thrown into the firebox through a door by a fireman, onto a set of grates which hold the fuel in a bed as it burns. Ash falls through the grate into an ashpan. If oil is used as the fuel, a door is needed for adjusting the air flow, maintaining the firebox, and cleaning the oil jets. The fire-tube boiler has internal tubes connecting the firebox to the smokebox through which the combustion gases flow transferring heat to the water. All the tubes together provide a large contact area, called the tube heating surface, between the gas and water in the boiler. Boiler water surrounds the firebox to stop the metal from becoming too hot. This is another area where the gas transfers heat to the water and is called the firebox heating surface. Ash and char collect in the smokebox as the gas gets drawn up the chimney (''stack'' or ''smokestack'' in the US) by the exhaust steam from the cylinders. The pressure in the boiler has to be monitored using a gauge mounted in the cab. Steam pressure can be released manually by the driver or fireman. If the pressure reaches the boiler's design working limit, a safety valve opens automatically to reduce the pressure and avoid a catastrophic accident. The exhaust steam from the engine cylinders shoots out of a nozzle pointing up the chimney in the smokebox. The steam entrains or drags the smokebox gases with it which maintains a lower pressure in the smokebox than that under the firebox grate. This pressure difference causes air to flow up through the coal bed and keeps the fire burning. The search for thermal efficiency greater than that of a typical fire-tube boiler led engineers, such as Nigel Gresley, to consider the water-tube boiler. Although he tested the concept on the LNER Class W1, the difficulties during development exceeded the will to increase efficiency by that route. The steam generated in the boiler not only moves the locomotive, but is also used to operate other devices such as the whistle, the air compressor for the brakes, the pump for replenishing the water in the boiler and the passenger car heating system. The constant demand for steam requires a periodic replacement of water in the boiler. The water is kept in a tank in the locomotive tender or wrapped around the boiler in the case of a
tank locomotive A tank locomotive or tank engine is a steam locomotive that carries its water in one or more on-board water tanks, instead of a more traditional tender. Most tank engines also have bunkers (or fuel tanks) to hold fuel; in a tender-tank loco ...
. Periodic stops are required to refill the tanks; an alternative was a scoop installed under the tender that collected water as the train passed over a track pan located between the rails. While the locomotive is producing steam, the amount of water in the boiler is constantly monitored by looking at the water level in a transparent tube, or sight glass. Efficient and safe operation of the boiler requires keeping the level in between lines marked on the sight glass. If the water level is too high, steam production falls, efficiency is lost and water is carried out with the steam into the cylinders, possibly causing mechanical damage. More seriously, if the water level gets too low, the crown(top)sheet of the firebox becomes exposed. Without water on top of the sheet to transfer away the heat of combustion, it softens and fails, letting high-pressure steam into the firebox and the cab. The development of the fusible plug, a temperature-sensitive device, ensured a controlled venting of steam into the firebox to warn the fireman to add water. Scale builds up in the boiler and prevents adequate heat transfer, and corrosion eventually degrades the boiler materials to the point where it needs to be rebuilt or replaced. Start-up on a large engine may take hours of preliminary heating of the boiler water before sufficient steam is available. Although the boiler is typically placed horizontally, for locomotives designed to work in locations with steep slopes it may be more appropriate to consider a vertical boiler or one mounted such that the boiler remains horizontal but the wheels are inclined to suit the slope of the rails.


Steam circuit

The steam generated in the boiler fills the space above the water in the partially filled boiler. Its maximum working pressure is limited by spring-loaded safety valves. It is then collected either in a perforated tube fitted above the water level or by a dome that often houses the regulator valve, or throttle, the purpose of which is to control the amount of steam leaving the boiler. The steam then either travels directly along and down a steam pipe to the engine unit or may first pass into the wet header of a superheater, the role of the latter being to improve thermal efficiency and eliminate water droplets suspended in the "saturated steam", the state in which it leaves the boiler. On leaving the superheater, the steam exits the dry header of the superheater and passes down a steam pipe, entering the steam chests adjacent to the cylinders of a reciprocating engine. Inside each steam chest is a sliding valve that distributes the steam via ports that connect the steam chest to the ends of the cylinder space. The role of the valves is twofold: admission of each fresh dose of steam, and exhaust of the used steam once it has done its work. The cylinders are double-acting, with steam admitted to each side of the piston in turn. In a two-cylinder locomotive, one cylinder is located on each side of the vehicle. The cranks are set 90° out of phase. During a full rotation of the driving wheel, steam provides four power strokes; each cylinder receives two injections of steam per revolution. The first stroke is to the front of the piston and the second stroke to the rear of the piston; hence two working strokes. Consequently, two deliveries of steam onto each piston face in the two cylinders generates a full revolution of the driving wheel. Each piston is attached to the driving axle on each side by a connecting rod, and the driving wheels are connected together by coupling rods to transmit power from the main driver to the other wheels. Note that at the two "
dead centres In a reciprocating engine, the dead centre is the position of a piston in which it is either farthest from, or nearest to, the crankshaft. The former is known as Top Dead Centre (TDC) while the latter is known as Bottom Dead Centre (BDC). ...
", when the connecting rod is on the same axis as the crankpin on the driving wheel, the connecting rod applies no
torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of t ...
to the wheel. Therefore, if both cranksets could be at "dead centre" at the same time, and the wheels should happen to stop in this position, the locomotive could not start moving. Therefore, the crankpins are attached to the wheels at a 90° angle to each other, so only one side can be at dead centre at a time. Each piston transmits power through a crosshead, connecting rod (''Main rod'' in the US) and a crankpin on the driving wheel (''Main driver'' in the US) or to a
crank Crank may refer to: Mechanisms * Crank (mechanism), in mechanical engineering, a bent portion of an axle or shaft, or an arm keyed at right angles to the end of a shaft, by which motion is imparted to or received from it * Crankset, the compone ...
on a driving axle. The movement of the valves in the steam chest is controlled through a set of rods and linkages called the valve gear, actuated from the driving axle or from the crankpin; the valve gear includes devices that allow reversing the engine, adjusting valve travel and the timing of the admission and exhaust events. The cut-off point determines the moment when the valve blocks a steam port, "cutting off" admission steam and thus determining the proportion of the stroke during which steam is admitted into the cylinder; for example a 50% cut-off admits steam for half the stroke of the piston. The remainder of the stroke is driven by the expansive force of the steam. Careful use of cut-off provides economical use of steam and in turn, reduces fuel and water consumption. The reversing lever ('' Johnson bar'' in the US), or screw-reverser (if so equipped), that controls the cut-off, therefore, performs a similar function to a gearshift in an automobile – maximum cut-off, providing maximum tractive effort at the expense of efficiency, is used to pull away from a standing start, whilst a cut-off as low as 10% is used when cruising, providing reduced tractive effort, and therefore lower fuel/water consumption. Exhaust steam is directed upwards out of the locomotive through the chimney, by way of a nozzle called a blastpipe, creating the familiar "chuffing" sound of the steam locomotive. The blastpipe is placed at a strategic point inside the smokebox that is at the same time traversed by the combustion gases drawn through the boiler and grate by the action of the steam blast. The combining of the two streams, steam and exhaust gases, is crucial to the efficiency of any steam locomotive, and the internal profiles of the chimney (or, strictly speaking, the ''ejector'') require careful design and adjustment. This has been the object of intensive studies by a number of engineers (and often ignored by others, sometimes with catastrophic consequences). The fact that the draught depends on the exhaust pressure means that power delivery and power generation are automatically self-adjusting. Among other things, a balance has to be struck between obtaining sufficient draught for combustion whilst giving the exhaust gases and particles sufficient time to be consumed. In the past, a strong draught could lift the fire off the grate, or cause the ejection of unburnt particles of fuel, dirt and pollution for which steam locomotives had an unenviable reputation. Moreover, the pumping action of the exhaust has the counter-effect of exerting ''back pressure'' on the side of the piston receiving steam, thus slightly reducing cylinder power. Designing the exhaust ejector became a specific science, with engineers such as
Chapelon Chapelon () is a commune in the Loiret department Department may refer to: * Departmentalization, division of a larger organization into parts with specific responsibility Government and military *Department (administrative division), a ge ...
, Giesl and Porta making large improvements in thermal efficiency and a significant reduction in maintenance timeSee section of the LNER Class A1/A3 article on the sharp increase in availability brought about in this respect by the application of the Kylchap exhaust to Gresley Pacifics in the early 1960s and pollution. A similar system was used by some early gasoline/kerosene tractor manufacturers ( Advance-Rumely/ Hart-Parr) – the exhaust gas volume was vented through a cooling tower, allowing the steam exhaust to draw more air past the radiator.


Running gear

Running gear includes the brake gear, wheel sets, axleboxes, springing and the motion that includes connecting rods and valve gear. The transmission of the power from the pistons to the rails and the behaviour of the locomotive as a vehicle, being able to negotiate curves, points and irregularities in the track, is of paramount importance. Because reciprocating power has to be directly applied to the rail from 0 rpm upwards, this creates the problem of adhesion of the driving wheels to the smooth rail surface. Adhesive weight is the portion of the locomotive's weight bearing on the driving wheels. This is made more effective if a pair of driving wheels is able to make the most of its axle load, i.e. its individual share of the adhesive weight. Equalising beams connecting the ends of leaf springs have often been deemed a complication in Britain, however, locomotives fitted with the beams have usually been less prone to loss of traction due to wheel-slip. Suspension using equalizing levers between driving axles, and between driving axles and trucks, was standard practice on North American locomotives to maintain even wheel loads when operating on uneven track. Locomotives with total adhesion, where all of the wheels are coupled together, generally lack stability at speed. To counter this, locomotives often fit unpowered carrying wheels mounted on two-wheeled trucks or four-wheeled bogies centred by springs/inverted rockers/geared rollers that help to guide the locomotive through curves. These usually take on weight – of the cylinders at the front or the firebox at the rear – when the width exceeds that of the mainframes. Locomotives with multiple coupled-wheels on a rigid chassis would have unacceptable flange forces on tight curves giving excessive flange and rail wear, track spreading and wheel climb derailments. One solution was to remove or thin the flanges on an axle. More common was to give axles end-play and use lateral motion control with spring or inclined-plane gravity devices. Railroads generally preferred locomotives with fewer axles, to reduce maintenance costs. The number of axles required was dictated by the maximum axle loading of the railroad in question. A builder would typically add axles until the maximum weight on any one axle was acceptable to the railroad's maximum axle loading. A locomotive with a wheel arrangement of two lead axles, two drive axles, and one trailing axle was a high-speed machine. Two lead axles were necessary to have good tracking at high speeds. Two drive axles had a lower reciprocating mass than three, four, five or six coupled axles. They were thus able to turn at very high speeds due to the lower reciprocating mass. A trailing axle was able to support a huge firebox, hence most locomotives with the wheel arrangement of (American Type Atlantic) were called free steamers and were able to maintain steam pressure regardless of throttle setting.


Chassis

The chassis, or locomotive frame, is the principal structure onto which the boiler is mounted and which incorporates the various elements of the running gear. The boiler is rigidly mounted on a "saddle" beneath the smokebox and in front of the boiler barrel, but the firebox at the rear is allowed to slide forward and backwards, to allow for expansion when hot. European locomotives usually use "plate frames", where two vertical flat plates form the main chassis, with a variety of spacers and a buffer beam at each end to form a rigid structure. When inside cylinders are mounted between the frames, the plate frames are a single large casting that forms a major support element. The axleboxes slide up and down to give some sprung suspension, against thickened webs attached to the frame, called "hornblocks". American practice for many years was to use built-up bar frames, with the smokebox saddle/cylinder structure and drag beam integrated therein. In the 1920s, with the introduction of "superpower", the cast-steel locomotive bed became the norm, incorporating frames, spring hangers, motion brackets, smokebox saddle and cylinder blocks into a single complex, sturdy but heavy casting. A SNCF design study using welded tubular frames gave a rigid frame with a 30% weight reduction.


Fuel and water

Generally, the largest locomotives are permanently coupled to a
tender Tender may refer to: Entertainment Film * ''Illegal Tender'' (2007), a film directed by Franc. Reyes * ''Tender'' (2012), a short film by Liz Tomkins * ''Tender'' (2019), a short film by Darryl Jones and Anthony Lucido * ''Tender'' (2019), a sh ...
that carries the water and fuel. Often, locomotives working shorter distances do not have a tender and carry the fuel in a bunker, with the water carried in tanks placed next to the boiler. The tanks can be in various configurations, including two tanks alongside ( side tanks or pannier tanks), one on top ( saddle tank) or one between the frames ( well tank). The fuel used depended on what was economically available to the railway. In the UK and other parts of Europe, plentiful supplies of coal made this the obvious choice from the earliest days of the steam engine. Until 1870, the majority of locomotives in the United States burned wood, but as the Eastern forests were cleared, coal gradually became more widely used until it became the dominant fuel worldwide in steam locomotives. Railways serving sugar cane farming operations burned bagasse, a byproduct of sugar refining. In the US, the ready availability and low price of oil made it a popular steam locomotive fuel after 1900 for the southwestern railroads, particularly the Southern Pacific. In the Australian state of Victoria, many steam locomotives were converted to heavy oil firing after World War II. German, Russian, Australian and British railways experimented with using coal dust to fire locomotives. During World War 2, a number of Swiss steam shunting locomotives were modified to use electrically heated boilers, consuming around 480 kW of power collected from an overhead line with a pantograph. These locomotives were significantly less efficient than electric ones; they were used because Switzerland was suffering a coal shortage because of the War, but had access to plentiful
hydroelectricity Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined a ...
. A number of tourist lines and heritage locomotives in Switzerland, Argentina and Australia have used light diesel-type oil. Water was supplied at stopping places and locomotive depots from a dedicated water tower connected to
water crane A water crane is a device used for delivering a large volume of water into the tank or tender of a steam locomotive A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of ...
s or gantries. In the UK, the US and France, water troughs (''track pans'' in the US) were provided on some main lines to allow locomotives to replenish their water supply without stopping, from rainwater or snowmelt that filled the trough due to inclement weather. This was achieved by using a deployable "water scoop" fitted under the tender or the rear water tank in the case of a large tank engine; the fireman remotely lowered the scoop into the trough, the speed of the engine forced the water up into the tank, and the scoop was raised again once it was full. Water is essential for the operation of a steam locomotive. As Swengel argued: Swengel went on to note that "at low temperature and relatively low boiler outputs", good water and regular boiler washout was an acceptable practice, even though such maintenance was high. As steam pressures increased, however, a problem of "foaming" or "priming" developed in the boiler, wherein dissolved solids in the water formed "tough-skinned bubbles" inside the boiler, which in turn were carried into the steam pipes and could blow off the cylinder heads. To overcome the problem, hot mineral-concentrated water was deliberately wasted (blown down) from the boiler periodically. Higher steam pressures required more blowing-down of water out of the boiler. Oxygen generated by boiling water attacks the boiler, and with increased steam pressure the rate of rust (iron oxide) generated inside the boiler increases. One way to help overcome the problem was water treatment. Swengel suggested that these problems contributed to the interest in electrification of railways. In the 1970s, L.D. Porta developed a sophisticated system of heavy-duty chemical water treatment ( Porta Treatment) that not only keeps the inside of the boiler clean and prevents corrosion, but modifies the foam in such a way as to form a compact "blanket" on the water surface that filters the steam as it is produced, keeping it pure and preventing carry-over into the cylinders of water and suspended abrasive matter. Some Steam Locomotives have been run on Alternative fuels such as
used cooking oil Yellow grease, also termed used cooking oil (UCO), used vegetable oil (UVO), recycled vegetable oil, or waste vegetable oil (WVO), is recovered from businesses and industry that use the oil for cooking. It is used to feed livestock, and to manufa ...
like Grand Canyon Railway 4960, Grand Canyon Railway 29, U.S. Sugar 148, and the Disneyland Railroad Locomotives.


Crew

A steam locomotive is normally controlled from the boiler's backhead, and the crew is usually protected from the elements by a cab. A crew of at least two people is normally required to operate a steam locomotive. One, the train driver or engineer (North America), is responsible for controlling the locomotive's starting, stopping, and speed, and the fireman is responsible for maintaining the fire, regulating steam pressure and monitoring boiler and tender water levels. Due to the historical loss of operational infrastructure and staffing, preserved steam locomotives operating on the mainline will often have a support crew travelling with the train.


Fittings and appliances

All locomotives are fitted with a variety of appliances. Some of these relate directly to the operation of the steam engine; others are for signalling, train control or other purposes. In the United States, the
Federal Railroad Administration The Federal Railroad Administration (FRA) is an agency in the United States Department of Transportation (DOT). The agency was created by the Department of Transportation Act of 1966. The purpose of the FRA is to promulgate and enforce rail s ...
mandated the use of certain appliances over the years in response to safety concerns. The most typical appliances are as follows:


Steam pumps and injectors

Water ( feedwater) must be delivered to the boiler to replace that which is exhausted as steam after delivering a working stroke to the pistons. As the boiler is under pressure during operation, feedwater must be forced into the boiler at a pressure that is greater than the steam pressure, necessitating the use of some sort of pump. Hand-operated pumps sufficed for the very earliest locomotives. Later engines used pumps driven by the motion of the pistons (axle pumps), which were simple to operate, reliable and could handle large quantities of water but only operated when the locomotive was moving and could overload the valve gear and piston rods at high speeds. Steam injectors later replaced the pump, while some engines transitioned to turbopumps. Standard practice evolved to use two independent systems for feeding water to the boiler; either two steam injectors or, on more conservative designs, axle pumps when running at service speed and a steam injector for filling the boiler when stationary or at low speeds. By the 20th century virtually all new-built locomotives used only steam injectors – often one injector was supplied with "live" steam straight from the boiler itself and the other used exhaust steam from the locomotive's cylinders, which was more efficient (since it made use of otherwise wasted steam) but could only be used when the locomotive was in motion and the regulator was open. Injectors became unreliable if the feedwater was at a high temperature, so locomotives with feedwater heaters,
tank locomotive A tank locomotive or tank engine is a steam locomotive that carries its water in one or more on-board water tanks, instead of a more traditional tender. Most tank engines also have bunkers (or fuel tanks) to hold fuel; in a tender-tank loco ...
s with the tanks in contact with the boiler and condensing locomotives sometimes used reciprocating steam pumps or turbopumps. Vertical glass tubes, known as water gauges or water glasses, show the level of water in the boiler and are carefully monitored at all times while the boiler is being fired. Before the 1870s it was more common to have a series of try-cocks fitted to the boiler within reach of the crew; each try cock (at least two and usually three were fitted) was mounted at a different level. By opening each try-cock and seeing if steam or water vented through it, the level of water in the boiler could be estimated with limited accuracy. As boiler pressures increased the use of try-cocks became increasingly dangerous and the valves were prone to blockage with scale or sediment, giving false readings. This led to their replacement with the sight glass. As with the injectors, two glasses with separate fittings were usually installed to provide independent readings.


Boiler insulation

The term for pipe and boiler insulation is "lagging" which derives from the cooper's term for a wooden
barrel stave ] A stave is a narrow length of wood with a slightly bevelled edge to form the sides of barrels, tanks, tubs, vats and pipelines, originally handmade by coopers. They have been used in the construction of large holding tanks and penstocks at h ...
. Two of the earliest steam locomotives used wooden lagging to insulate their boilers: the Salamanca, the first commercially successful steam locomotive, built in 1812, and the Locomotion No. 1, the first steam locomotive to carry passengers on a public rail line. Large amounts of heat are wasted if a boiler is not insulated. Early locomotives used lags, shaped wooden staves, fitted lengthways along the boiler barrel, and held in place by hoops, metal bands, the terms and methods are from Cooper (profession), cooperage. Improved insulating methods included applying a thick paste containing a porous mineral such as kieselgur, or attaching shaped blocks of insulating compound such as magnesia blocks. In the latter days of steam, "mattresses" of stitched asbestos cloth stuffed with asbestos fibre were fixed to the boiler, on separators so as not quite to touch the boiler. However, asbestos is currently banned in most countries for health reasons. The most common modern-day material is
glass wool Glass wool is an insulating material made from glass fiber arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation pro ...
, or wrappings of aluminium foil. The lagging is protected by a close-fitted sheet-metal casing known as boiler clothing or cleading. Effective lagging is particularly important for fireless locomotives; however, in recent times under the influence of L.D. Porta, "exaggerated" insulation has been practised for all types of locomotive on all surfaces liable to dissipate heat, such as cylinder ends and facings between the cylinders and the mainframes. This considerably reduces engine warmup time with a marked increase in overall efficiency.


Safety valves

Early locomotives were fitted with a valve controlled by a weight suspended from the end of a lever, with the steam outlet being stopped by a cone-shaped valve. As there was nothing to prevent the weighted lever from bouncing when the locomotive ran over irregularities in the track, thus wasting steam, the weight was later replaced by a more stable spring-loaded column, often supplied by Salter, a well-known spring scale manufacturer. The danger of these devices was that the driving crew could be tempted to add weight to the arm to increase pressure. Most early boilers were fitted with a tamper-proof "lockup" direct-loaded ball valve protected by a cowl. In the late 1850s, John Ramsbottom introduced a safety valve that became popular in Britain during the latter part of the 19th century. Not only was this valve tamper-proof, but tampering by the driver could only have the effect of easing pressure. George Richardson's safety valve was an American invention introduced in 1875, and was designed to release the steam only at the moment when the pressure attained the maximum permitted. This type of valve is in almost universal use at present. Britain's
Great Western Railway The Great Western Railway (GWR) was a British railway company that linked London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 mill ...
was a notable exception to this rule, retaining the direct-loaded type until the end of its separate existence, because it was considered that such a valve lost less pressure between opening and closing.


Pressure gauge

The earliest locomotives did not show the pressure of steam in the boiler, but it was possible to estimate this by the position of the safety valve arm which often extended onto the firebox back plate; gradations marked on the spring column gave a rough indication of the actual pressure. The promoters of the Rainhill trials urged that each contender have a proper mechanism for reading the boiler pressure, and Stephenson devised a nine-foot vertical tube of mercury with a sight-glass at the top, mounted alongside the chimney, for his ''Rocket''. The Bourdon tube gauge, in which the pressure straightens an oval-section coiled tube of brass or bronze connected to a pointer, was introduced in 1849 and quickly gained acceptance, and is still used today. Some locomotives have an additional pressure gauge in the steam chest. This helps the driver avoid wheel-slip at startup, by warning if the regulator opening is too great.


Spark arrestors and smokeboxes

;Spark arrestor and self-cleaning smokebox Wood-burners emit large quantities of flying sparks which necessitate an efficient spark-arresting device generally housed in the smokestack. Many different types were fitted, the most common early type being the Bonnet stack that incorporated a cone-shaped deflector placed before the mouth of the chimney pipe, and a wire screen covering the wide stack exit. A more-efficient design was the Radley and Hunter centrifugal stack patented in 1850 (commonly known as the diamond stack), incorporating baffles so oriented as to induce a swirl effect in the chamber that encouraged the embers to burn out and fall to the bottom as ash. In the self-cleaning smokebox the opposite effect was achieved: by allowing the flue gasses to strike a series of deflector plates, angled in such a way that the blast was not impaired, the larger particles were broken into small pieces that would be ejected with the blast, rather than settle in the bottom of the smokebox to be removed by hand at the end of the run. As with the arrestor, a screen was incorporated to retain any large embers. Locomotives of the British Railways standard classes fitted with self-cleaning smokeboxes were identified by a small cast oval plate marked "S.C.", fitted at the bottom of the smokebox door. These engines required different disposal procedures and the plate highlighted this need to depot staff.


Stokers

A factor that limits locomotive performance is the rate at which fuel is fed into the fire. In the early 20th century some locomotives became so large that the fireman could not shovel coal fast enough. In the United States, various steam-powered mechanical stokers became standard equipment and were adopted and used elsewhere including Australia and South Africa.


Feedwater heating

Introducing cold water into a boiler reduces power, and from the 1920s a variety of heaters were incorporated. The most common type for locomotives was the exhaust steam feedwater heater that piped some of the exhaust through small tanks mounted on top of the boiler or smokebox or into the tender tank; the warm water then had to be delivered to the boiler by a small auxiliary steam pump. The rare economiser type differed in that it extracted residual heat from the exhaust gases. An example of this is the pre-heater drum(s) found on the Franco-Crosti boiler. The use of live steam and exhaust steam injectors also assists in the pre-heating of boiler feedwater to a small degree, though there is no efficiency advantage to live steam injectors. Such pre-heating also reduces the thermal shock that a boiler might experience when cold water is introduced directly. This is further helped by the top feed, where water is introduced to the highest part of the boiler and made to trickle over a series of trays. George Jackson Churchward fitted this arrangement to the high end of his domeless coned boilers. Other British lines such as the London, Brighton & South Coast Railway fitted some locomotives with the top feed inside a separate dome forward of the main one.


Condensers and water re-supply

Steam locomotives consume vast quantities of water because they operate on an open cycle, expelling their steam immediately after a single use rather than recycling it in a closed loop as stationary and marine steam engines do. Water was a constant logistical problem, and condensing engines were devised for use in desert areas. These engines had huge radiators in their tenders and instead of exhausting steam out of the funnel it was captured, passed back to the tender and condensed. The cylinder lubricating oil was removed from the exhausted steam to avoid a phenomenon known as priming, a condition caused by foaming in the boiler which would allow water to be carried into the cylinders causing damage because of its incompressibility. The most notable engines employing condensers (Class 25, the "puffers which never puff") worked across the Karoo desert of South Africa from the 1950s until the 1980s. Some British and American locomotives were equipped with scoops which collected water from "water troughs" ( ''track pans'' in the US) while in motion, thus avoiding stops for water. In the US, small communities often did not have refilling facilities. During the early days of railroading, the crew simply stopped next to a stream and filled the tender using leather buckets. This was known as "jerking water" and led to the term "jerkwater towns" (meaning a small town, a term which today is considered derisive). In Australia and South Africa, locomotives in drier regions operated with large oversized tenders and some even had an additional water wagon, sometimes called a "canteen" or in Australia (particularly in New South Wales) a "water gin". Steam locomotives working on underground railways (such as London's Metropolitan Railway) were fitted with condensing apparatus to prevent steam from escaping into the railway tunnels. These were still being used between King's Cross and
Moorgate Moorgate was one of the City of London's northern gates in its defensive wall, the last to be built. The gate took its name from the Moorfields, an area of marshy land that lay immediately north of the wall. The gate was demolished in 1762, b ...
into the early 1960s.


Braking

Locomotives have their own braking system, independent from the rest of the train. Locomotive brakes employ large shoes which press against the driving wheel treads. With the advent of compressed air brakes, a separate system allowed the driver to control the brakes on all cars. A single-stage, steam-driven, air compressor was mounted on the side of the boiler. Long freight trains needed more air and a two-stage compressor with LP and HP cylinders, driven by cross-compound HP and LP steam cylinders, was introduced. It had three and a half times the capacity of the single stage. Most were made by Westinghouse. Two were fitted in front of the smokebox on big articulated locomotives. Westinghouse systems were used in the United States, Canada, Australia and New Zealand. An alternative to the air brake is the vacuum brake, in which a steam-operated ejector is mounted on the engine instead of the air pump, to create a vacuum and release the brakes. A secondary ejector or crosshead vacuum pump is used to maintain the vacuum in the system against the small leaks in the pipe connections between carriages and wagons. Vacuum systems existed on British, Indian, West Australian and South African railway networks. Steam locomotives are fitted with sandboxes from which sand can be deposited on top of the rail to improve traction and braking in wet or icy weather. On American locomotives, the sandboxes, or sand domes, are usually mounted on top of the boiler. In Britain, the limited loading gauge precludes this, so the sandboxes are mounted just above, or just below, the running plate.


Lubrication

The pistons and valves on the earliest locomotives were lubricated by the enginemen dropping a lump of tallow down the blast pipe. More sophisticated methods of delivering the substance were soon developed. Tallow adheres well to cylinder walls and is more effective than mineral oil in resisting the action of water. It remains a constituent of modern steam cylinder oil formulation. As speeds and distances increased, mechanisms were developed that injected thick mineral oil into the steam supply. The first, a displacement lubricator, mounted in the cab, uses a controlled stream of steam condensing into a sealed container of oil. Water from the condensed steam displaces the oil into pipes. The apparatus is usually fitted with sight-glasses to confirm the rate of supply. A later method uses a mechanical pump worked from one of the crossheads. In both cases, the supply of oil is proportional to the speed of the locomotive. Lubricating the frame components (axle bearings, horn blocks and bogie pivots) depends on capillary action: trimmings of worsted yarn are trailed from oil reservoirs into pipes leading to the respective component. The rate of oil supplied is controlled by the size of the bundle of yarn and not the speed of the locomotive, so it is necessary to remove the trimmings (which are mounted on wire) when stationary. However, at regular stops (such as a terminating station platform), oil finding its way onto the track can still be a problem. Crankpin and crosshead bearings carry small cup-shaped reservoirs for oil. These have feed pipes to the bearing surface that start above the normal fill level, or are kept closed by a loose-fitting pin, so that only when the locomotive is in motion does oil enter. In United Kingdom practice, the cups are closed with simple corks, but these have a piece of porous cane pushed through them to admit air. It is customary for a small capsule of pungent oil (aniseed or garlic) to be incorporated in the bearing metal to warn if the lubrication fails and excess heating or wear occurs.


Blower

When the locomotive is running under power, a draught on the fire is created by the exhaust steam directed up the chimney by the blastpipe. Without draught, the fire will quickly die down and steam pressure will fall. When the locomotive is stopped, or coasting with the regulator closed, there is no exhaust steam to create a draught, so the draught is maintained by means of a blower. This is a ring placed either around the base of the chimney, or around the blast pipe orifice, containing several small steam nozzles directed up the chimney. These nozzles are fed with steam directly from the boiler, controlled by the blower valve. When the regulator is open, the blower valve is closed; when the driver intends to close the regulator, he will first open the blower valve. It is important that the blower be opened before the regulator is closed, since without draught on the fire, there may be
backdraught A backdraft (North American English) or backdraught (British English) is the abrupt combustion, burning of superheated gasses in a fire, caused when oxygen rapidly enters a hot, oxygen-depleted environment; for example, when a window or door to an ...
– where atmospheric air blows down the chimney, causing the flow of hot gases through the boiler tubes to be reversed, with the fire itself being blown through the firehole onto the footplate, with serious consequences for the crew. The risk of backdraught is higher when the locomotive enters a tunnel because of the pressure shock. The blower is also used to create draught when steam is being raised at the start of the locomotive's duty, at any time when the driver needs to increase the draught on the fire, and to clear smoke from the driver's line of vision. Blowbacks were fairly common. In a 1955 report on an accident near Dunstable, the Inspector wrote, "In 1953 twenty-three cases, which were not caused by an engine defect, were reported and they resulted in 26 enginemen receiving injuries. In 1954, the number of occurrences and of injuries were the same and there was also one fatal casualty." They remain a problem, as evidenced by the 2012 incident with BR Standard Class 7 70013 ''Oliver Cromwell''.


Buffers

In British and European (except former Soviet Union countries) practice, locomotives usually have buffers at each end to absorb compressive loads ("buffets"''
Oxford English Dictionary The ''Oxford English Dictionary'' (''OED'') is the first and foundational historical dictionary of the English language, published by Oxford University Press (OUP). It traces the historical development of the English language, providing a com ...
'': Buff 1
). The tensional load of drawing the train (draft force) is carried by the coupling system. Together these control slack between the locomotive and train, absorb minor impacts and provide a bearing point for pushing movements. In Canadian and American practice, all of the forces between the locomotive and cars are handled through the coupler – particularly the Janney coupler, long standard on American railroad rolling stock – and its associated draft gear, which allows some limited slack movement. Small dimples called "poling pockets" at the front and rear corners of the locomotive allowed cars to be pushed onto an adjacent track using a pole braced between the locomotive and the cars. In Britain and Europe, North American style "buckeye" and other couplers that handle forces between items of rolling stock have become increasingly popular.


Pilots

A pilot was usually fixed to the front end of locomotives, although in European and a few other railway systems including
New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...
, they were considered unnecessary. Plough-shaped, sometimes called "cow catchers", they were quite large and were designed to remove obstacles from the track such as cattle, bison, other animals or tree limbs. Though unable to "catch" stray cattle, these distinctive items remained on locomotives until the end of steam. Switching engines usually replaced the pilot with small steps, known as ''footboards''. Many systems used the pilot and other design features to produce a distinctive appearance.


Headlights

When night operations began, railway companies in some countries equipped their locomotives with lights to allow the driver to see what lay ahead of the train, or to enable others to see the locomotive. Headlights were originally oil or acetylene lamps, but when electric arc lamps became available in the late 1880s, they quickly replaced the older types. Britain did not adopt bright headlights as they would affect night vision and so could mask the low-intensity oil lamps used in the semaphore signals and at each end of trains, increasing the danger of missing signals, especially on busy tracks. Locomotive stopping distances were also normally much greater than the range of headlights, and the railways were well-signalled and fully fenced to prevent livestock and people from straying onto them, largely negating the need for bright lamps. Thus low-intensity oil lamps continued to be used, positioned on the front of locomotives to indicate the class of each train. Four "lamp irons" (brackets on which to place the lamps) were provided: one below the chimney and three evenly spaced across the top of the buffer beam. The exception to this was the Southern Railway and its constituents, who added an extra lamp iron each side of the smokebox, and the arrangement of lamps (or in daylight, white circular plates) told railway staff the origin and destination of the train. On all vehicles, equivalent lamp irons were also provided on the rear of the locomotive or tender for when the locomotive was running tender- or bunker-first. In some countries, heritage steam operation continues on the national network. Some railway authorities have mandated powerful headlights on at all times, including during daylight. This was to further inform the public or track workers of any active trains.


Bells and whistles

Locomotives used bells and steam whistles from earliest days of steam locomotion. In the United States, India and Canada, bells warned of a train in motion. In Britain, where all lines are by law fenced throughout, bells were only a requirement on railways running on a road (i.e. not fenced off), for example a tramway along the side of the road or in a dockyard. Consequently, only a minority of locomotives in the UK carried bells. Whistles are used to signal personnel and give warnings. Depending on the terrain the locomotive was being used in, the whistle could be designed for long-distance warning of impending arrival, or for more localised use. Early bells and whistles were sounded through pull-string cords and levers. Automatic bell ringers came into widespread use in the US after 1910.


Automatic control

From the early 20th century operating companies in such countries as Germany and Britain began to fit locomotives with Automatic Warning System (AWS) in-cab signalling, which automatically applied the brakes when a signal was passed at "caution". In Britain, these became mandatory in 1956. In the United States, the Pennsylvania Railroad also fitted their locomotives with such devices.


Booster engines

The booster engine was an auxiliary steam engine which provided extra tractive effort for starting. It was a low-speed device, usually mounted on the trailing truck. It was dis-engaged via an idler gear at a low speed, e.g. 30 km/hr. Boosters were widely used in the US and tried experimentally in Britain and France. On the narrow-gauged New Zealand railway system, six Kb 4-8-4 locomotives were fitted with boosters, the only gauge engines in the world to have such equipment. Booster engines were also fitted to tender trucks in the US and known as auxiliary locomotives. Two and even three truck axles were connected together using side rods which limited them to slow-speed service.


Firedoor

The firedoor is used to cover the firehole when coal is not being added. It serves two purposes, first, it prevents air being drawn over the top of the fire, rather forcing it to be drawn through it. The second purpose is to safeguard the train crew against blowbacks. It does, however, have a means to allow some air to pass over the top of the fire (referred to as "secondary air") to complete the combustion of gases produced by the fire. Firedoors come in multiple designs, the most basic of which is a single piece which is hinged on one side and can swing open onto the footplate. This design has two issues. First, it takes up much room on the footplate, and second, the draught will tend to pull it completely shut, thus cutting off any secondary air. To compensate for this some locomotives are fitted with a latch that prevents the firedoor from closing completely whereas others have a small vent on the door that may be opened to allow secondary air to flow through. Though it was considered to design a firedoor that opens inwards into the firebox thus preventing the inconvenience caused on the footplate, such a door would be exposed to the full heat of the fire and would likely deform, thus becoming useless. A more popular type of firedoor consists of a two-piece sliding door operated by a single lever. There are tracks above and below the firedoor which the door runs along. These tracks are prone to becoming jammed by debris and the doors required more effort to open than the aforementioned swinging door. In order to address this some firedoors use powered operation which utilized a steam or air cylinder to open the door. Among these are the butterfly doors which pivot at the upper corner, the pivoting action offers low resistance to the cylinder that opens the door.


Variations

Numerous variations on the basic locomotive occurred as railways attempted to improve efficiency and performance.


Cylinders

Early steam locomotives had two cylinders, one either side, and this practice persisted as the simplest arrangement. The cylinders could be mounted between the mainframes (known as "inside" cylinders), or mounted outside the frames and driving wheels ("outside" cylinders). Inside cylinders drive cranks built into the driving axle; outside cylinders drive cranks on extensions to the driving axles. Later designs employed three or four cylinders, mounted both inside and outside the frames, for a more even power cycle and greater power output. This was at the expense of more complicated valve gear and increased maintenance requirements. In some cases the third cylinder was added inside simply to allow for smaller diameter outside cylinders, and hence reduce the width of the locomotive for use on lines with a restricted loading gauge, for example the SR K1 and U1 classes. Most British express-passenger locomotives built between 1930 and 1950 were or types with three or four cylinders (e.g. GWR 6000 Class, LMS Coronation Class, SR Merchant Navy Class, LNER Gresley Class A3). From 1951, all but one of the 999 new British Rail standard class steam locomotives across all types used 2-cylinder configurations for easier maintenance.


Valve gear

Early locomotives used a simple valve gear that gave full power in either forward or reverse. Soon the Stephenson valve gear allowed the driver to control cut-off; this was largely superseded by Walschaerts valve gear and similar patterns. Early locomotive designs using slide valves and outside admission were relatively easy to construct, but inefficient and prone to wear. Eventually, slide valves were superseded by inside admission piston valves, though there were attempts to apply
poppet valve A poppet valve (also called mushroom valve) is a valve typically used to control the timing and quantity of gas or vapor flow into an engine. It consists of a hole or open-ended chamber, usually round or oval in cross-section, and a plug, usual ...
s (commonly used in stationary engines) in the 20th century. Stephenson valve gear was generally placed within the frame and was difficult to access for maintenance; later patterns applied outside the frame were more readily visible and maintained.


Compounding

Compound locomotives were used from 1876, expanding the steam twice or more through separate cylinders – reducing thermal losses caused by cylinder cooling. Compound locomotives were especially useful in trains where long periods of continuous efforts were needed. Compounding contributed to the dramatic increase in power achieved by André Chapelon's rebuilds from 1929. A common application was in articulated locomotives, the most common being that designed by Anatole Mallet, in which the high-pressure stage was attached directly to the boiler frame; in front of this was pivoted a low-pressure engine on its own frame, which takes the exhaust from the rear engine.


Articulated locomotives

Very powerful locomotives tend to be longer than those with lower power output, but long rigid-framed designs are impracticable for the tight curves frequently found on narrow-gauge railways. Various designs for articulated locomotives were developed to overcome this problem. The Mallet and the Garratt were the two most popular. They had a single boiler and two engine units (sets of cylinders and driving wheels): both of the Garratt's engine units were on swivelling frames, whereas one of the Mallet's was on a swivelling frame and the other was fixed under the boiler unit. A few
triplex Triplex may refer to: * Triplex (building), a dwelling composed of three units * Triplex (espionage), code name of a British World War II espionage operation * ''Triplex'' (film), a 1991 French film * Triplex (genetics), triple-stranded DNA * Tr ...
locomotives were also designed, with a third engine unit under the tender. Other less common variations included the Fairlie locomotive, which had two boilers back-to-back on a common frame, with two separate engine units.


Duplex types

Duplex locomotives, containing two engines in one rigid frame, were also tried, but were not notably successful. For example, the Pennsylvania Railroad class T1, designed for very fast running, suffered recurring and ultimately unfixable slippage problems throughout their careers.


Geared locomotives

For locomotives where a high starting torque and low speed were required, the conventional direct drive approach was inadequate. "Geared" steam locomotives, such as the Shay, the Climax and the Heisler, were developed to meet this need on industrial, logging, mine and quarry railways. The common feature of these three types was the provision of reduction gearing and a drive shaft between the crankshaft and the driving axles. This arrangement allowed the engine to run at a much higher speed than the driving wheels compared to the conventional design, where the ratio is 1:1.


Cab forward

In the United States on the
Southern Pacific Railroad The Southern Pacific (or Espee from the railroad initials- SP) was an American Railroad classes#Class I, Class I Rail transport, railroad network that existed from 1865 to 1996 and operated largely in the Western United States. The system was ...
, a series of cab forward locomotives were produced with the cab and the firebox at the front of the locomotive and the tender behind the smokebox, so that the engine appeared to run backwards. This was only possible by using oil-firing. Southern Pacific selected this design to provide air free of smoke for the engine driver to breathe as the locomotive passed through mountain tunnels and snow sheds. Another variation was the Camelback locomotive, with the cab situated halfway along the boiler. In England, Oliver Bulleid developed the
SR Leader class The Leader was a class of experimental articulated steam locomotive, produced in the United Kingdom to the design of the innovative engineer Oliver Bulleid. The Leader was an attempt to extend the life of steam traction by eliminating many of ...
locomotive during the nationalisation process in the late 1940s. The locomotive was heavily tested but several design faults (such as coal firing and sleeve valves) meant that this locomotive and the other part-built locomotives were scrapped. The cab-forward design was taken by Bulleid to Ireland, where he moved after nationalisation, where he developed the "turfburner". This locomotive was more successful, but was scrapped due to the dieselisation of the Irish railways. The only preserved cab forward locomotive is Southern Pacific 4294 in Sacramento, California. In France, the three Heilmann locomotives were built with a cab forward design.


Steam turbines

Steam turbines were created as an attempt to improve the operation and efficiency of steam locomotives. Experiments with steam turbines using direct-drive and electrical transmissions in various countries proved mostly unsuccessful. The London, Midland & Scottish Railway built the Turbomotive, a largely successful attempt to prove the efficiency of steam turbines. Had it not been for the outbreak of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, more may have been built. The Turbomotive ran from 1935 to 1949, when it was rebuilt into a conventional locomotive because many parts required replacement, an uneconomical proposition for a "one-off" locomotive. In the United States, Union Pacific, Chesapeake & Ohio and Norfolk & Western (N&W) railways all built turbine-electric locomotives. The Pennsylvania Railroad (PRR) also built turbine locomotives, but with a direct-drive gearbox. However, all designs failed due to dust, vibration, design flaws or inefficiency at lower speeds. The final one remaining in service was the N&W's, retired in January 1958. The only truly successful design was the TGOJ MT3, used for hauling iron ore from Grängesberg in Sweden to the ports of Oxelösund. Despite functioning correctly, only three were built. Two of them are preserved in working order in museums in Sweden.


Fireless locomotive

In a fireless locomotive the boiler is replaced by a steam accumulator, which is charged with steam (actually water at a temperature well above boiling point, () from a stationary boiler. Fireless locomotives were used where there was a high fire risk (e.g. oil refineries), where cleanliness was important (e.g. food-production plants) or where steam is readily available (e.g. paper mills and power stations where steam is either a by-product or is cheaply available). The water vessel ("boiler") is heavily insulated, the same as with a fired locomotive. Until all the water has boiled away, the steam pressure does not drop except as the temperature drops. Another class of fireless locomotive is a compressed-air locomotive.


Mixed power


Steam diesel hybrid locomotive

Mixed power locomotives, utilising both steam and diesel propulsion, have been produced in Russia, Britain and Italy.


Electric-steam locomotive

Under unusual conditions (lack of coal, abundant hydroelectricity) some locomotives in Switzerland were modified to use electricity to heat the boiler, making them electric-steam locomotives.


Steam-electric locomotive

A steam-electric locomotive uses electric transmission, like diesel-electric locomotives, except that a steam engine instead of a diesel engine is used to drive a generator. Three such locomotives were built by the French engineer in the 1890s.


Categorisation

Steam locomotives are categorised by their wheel arrangement. The two dominant systems for this are the Whyte notation and UIC classification. The Whyte notation, used in most English-speaking and Commonwealth countries, represents each set of wheels with a number. These numbers typically represented the number of unpowered leading wheels, followed by the number of driving wheels (sometimes in several groups), followed by the number of un-powered trailing wheels. For example, a yard engine with only 4 driven wheels would be categorised as a wheel arrangement. A locomotive with a 4-wheel leading truck, followed by 6 drive wheels, and a 2-wheel trailing truck, would be classed as a . Different arrangements were given names which usually reflect the first usage of the arrangement; for instance, the "Santa Fe" type () is so called because the first examples were built for the Atchison, Topeka and Santa Fe Railway. These names were informally given and varied according to region and even politics. The UIC classification is used mostly in European countries apart from the United Kingdom. It designates consecutive pairs of wheels (informally "axles") with a number for non-driving wheels and a capital letter for driving wheels (A=1, B=2, etc.) So a Whyte designation would be an equivalent to a 2-C-1 UIC designation. On many railroads, locomotives were organised into classes. These broadly represented locomotives which could be substituted for each other in service, but most commonly a class represented a single design. As a rule classes were assigned some sort of code, generally based on the wheel arrangement. Classes also commonly acquired nicknames, such as '' Pug'' (a small shunting locomotive), representing notable (and sometimes uncomplimentary) features of the locomotives.


Performance


Measurement

In the steam locomotive era, two measures of locomotive performance were generally applied. At first, locomotives were rated by tractive effort, defined as the average force developed during one revolution of the driving wheels at the railhead. This can be roughly calculated by multiplying the total piston area by 85% of the boiler pressure (a rule of thumb reflecting the slightly lower pressure in the steam chest above the cylinder) and dividing by the ratio of the driver diameter over the piston stroke. However, the precise formula is : t = \frac, where is the bore of the cylinder (diameter) in inches, is the cylinder stroke, in inches, is boiler pressure in pounds per square inch, is the diameter of the driving wheel in inches, and is a factor that depends on the effective cut-off. In the US, is usually set at 0.85, but lower on engines that have maximum cutoff limited to 50–75%. The tractive effort is only the "average" force, as not all effort is constant during the one revolution of the drivers. At some points of the cycle, only one piston is exerting turning moment and at other points, both pistons are working. Not all boilers deliver full power at starting, and the tractive effort also decreases as the rotating speed increases. Tractive effort is a measure of the heaviest load a locomotive can start or haul at very low speed over the ruling grade in a given territory. However, as the pressure grew to run faster goods and heavier passenger trains, tractive effort was seen to be an inadequate measure of performance because it did not take into account speed. Therefore, in the 20th century, locomotives began to be rated by power output. A variety of calculations and formulas were applied, but in general railways used dynamometer cars to measure tractive force at speed in actual road testing. British railway companies have been reluctant to disclose figures for drawbar horsepower and have usually relied on continuous tractive effort instead.


Relation to wheel arrangement

Classification is indirectly connected to locomotive performance. Given adequate proportions of the rest of the locomotive, power output is determined by the size of the fire, and for a bituminous coal-fuelled locomotive, this is determined by the grate area. Modern non-compound locomotives are typically able to produce about 40 drawbar horsepower per square foot of grate. Tractive force, as noted earlier, is largely determined by the boiler pressure, the cylinder proportions and the size of the driving wheels. However, it is also limited by the weight on the driving wheels (termed "adhesive weight"), which needs to be at least four times the tractive effort. The weight of the locomotive is roughly proportional to the power output; the number of axles required is determined by this weight divided by the axleload limit for the trackage where the locomotive is to be used. The number of driving wheels is derived from the adhesive weight in the same manner, leaving the remaining axles to be accounted for by the leading and trailing bogies. Passenger locomotives conventionally had two-axle leading bogies for better guidance at speed; on the other hand, the vast increase in the size of the grate and firebox in the 20th century meant that a trailing bogie was called upon to provide support. In Europe, some use was made of several variants of the ''
Bissel bogie A Bissell or Bissel truck (also Bissel bogie or Pony truck) is a single-axle bogie which pivots towards the centre of a steam locomotive to enable it to negotiate curves more easily. Invented in 1857 by and usually then known as a ''pony truck'' ...
'' in which the swivelling movement of a single axle truck controls the lateral displacement of the front driving axle (and in one case the second axle too). This was mostly applied to 8-coupled express and mixed traffic locomotives, and considerably improved their ability to negotiate curves whilst restricting overall locomotive wheelbase and maximising adhesion weight. As a rule, shunting engines (US: ''switching engines'') omitted leading and trailing bogies, both to maximise tractive effort available and to reduce wheelbase. Speed was unimportant; making the smallest engine (and therefore smallest fuel consumption) for the tractive effort was paramount. Driving wheels were small and usually supported the firebox as well as the main section of the boiler. Banking engines (US: ''helper engines'') tended to follow the principles of shunting engines, except that the wheelbase limitation did not apply, so banking engines tended to have more driving wheels. In the US, this process eventually resulted in the Mallet type engine with its many driven wheels, and these tended to acquire leading and then trailing bogies as guidance of the engine became more of an issue. As locomotive types began to diverge in the late 19th century, freight engine designs at first emphasised tractive effort, whereas those for passenger engines emphasised speed. Over time, freight locomotive size increased, and the overall number of axles increased accordingly; the leading bogie was usually a single axle, but a trailing truck was added to larger locomotives to support a larger firebox that could no longer fit between or above the driving wheels. Passenger locomotives had leading bogies with two axles, fewer driving axles, and very large driving wheels in order to limit the speed at which the reciprocating parts had to move. In the 1920s, the focus in the United States turned to horsepower, epitomised by the "super power" concept promoted by the Lima Locomotive Works, although tractive effort was still the prime consideration after World War I to the end of steam. Goods trains were designed to run faster, while passenger locomotives needed to pull heavier loads at speed. This was achieved by increasing the size of grate and firebox without changes to the rest of the locomotive, requiring the addition of a second axle to the trailing truck. Freight s became s while s became s. Similarly, passenger s became s. In the United States this led to a convergence on the dual-purpose and the articulated configuration, which was used for both freight and passenger service. Mallet locomotives went through a similar transformation, evolving from bank engines into huge mainline locomotives with much larger fireboxes; their driving wheels were also increased in size in order to allow faster running.


Manufacture


Most-manufactured classes

The most-manufactured single class of steam locomotive in the world is the Russian locomotive class E steam locomotive with around 11,000 produced both in Russia and other countries such as Czechoslovakia, Germany, Sweden, Hungary and Poland. The
Russian locomotive class O The Russian steam locomotive class O (from russian: Основной) was an early type of Russian steam locomotives. 9,129 locomotives were built between 1890 and 1928; hence it was the second most numerous class of locomotive in Russia, after ...
numbered 9,129 locomotives, built between 1890 and 1928. Around 7,000 units were produced of the German DRB Class 52
Kriegslok ''Kriegslokomotiven'' (german: for "war locomotives", singular: ''Kriegslokomotive'') or ''Kriegsloks'' were locomotives produced in large numbers during the Second World War under Nazi Germany. Their construction was tailored to the economic cir ...
. In Britain, 863 of the GWR 5700 Class were built, and 943 of the DX class of the London and North Western Railway including 86 engines built for the Lancashire and Yorkshire Railway.


United Kingdom

Before the 1923 Grouping Act, production in the UK was mixed. The larger railway companies built locomotives in their own workshops, with the smaller ones and industrial concerns ordering them from outside builders. A large market for outside builders existed due to the home-build policy exercised by the main railway companies. An example of a pre-grouping works was the one at Melton Constable, which maintained and built some of the locomotives for the Midland and Great Northern Joint Railway. Other works included one at Boston (an early GNR building) and Horwich Works. Between 1923 and 1947, the Big Four railway companies (the Great Western Railway, the London, Midland & Scottish Railway, the London & North Eastern Railway and the Southern Railway) all built most of their own locomotives, only buying locomotives from outside builders when their own works were fully occupied (or as a result of government-mandated standardisation during wartime). From 1948, British Railways (BR) allowed the former Big Four companies (now designated as "Regions") to continue to produce their own designs, but also created a range of standard locomotives which supposedly combined the best features from each region. Although a policy of dieselisation was adopted in 1955, BR continued to build new steam locomotives until 1960, with the final engine being named '' Evening Star''.British Railways' Last Steam Locomotive '' Railway Gazette'' 23 March 1960 p. 355 Some independent manufacturers produced steam locomotives for a few more years, with the last British-built industrial steam locomotive being constructed by Hunslet in 1971. Since then, a few specialised manufacturers have continued to produce small locomotives for narrow gauge and miniature railways, but as the prime market for these is the tourist and heritage railway sector, the demand for such locomotives is limited. In November 2008, a new build main line steam locomotive, 60163 ''Tornado'', was tested on UK mainlines for eventual charter and tour use.


Sweden

In the 19th and early 20th centuries, most Swedish steam locomotives were manufactured in Britain. Later, however, most steam locomotives were built by local factories including NOHAB in
Trollhättan Trollhättan () is the 23rd-largest city in Sweden, the seat of Trollhättan Municipality, Västra Götaland County. It is situated by Göta älv, near the lake Vänern, and has a population of approximately 50,000 in the city proper. It is l ...
and ASJ in Falun. One of the most successful types was the class "B" (), inspired by the Prussian class P8. Many of the Swedish steam locomotives were preserved during the Cold War in case of war. During the 1990s, these steam locomotives were sold to non-profit associations or abroad, which is why the Swedish class B, class S () and class E2 () locomotives can now be seen in Britain, the Netherlands, Germany and Canada.


United States

Locomotives for American railroads were nearly always built in the United States with very few imports, except in the earliest days of steam engines. This was due to the basic differences of markets in the United States which initially had many small markets located large distances apart, in contrast to Europe's higher density of markets. Locomotives that were cheap and rugged and could go large distances over cheaply built and maintained tracks were required. Once the manufacture of engines was established on a wide scale there was very little advantage to buying an engine from overseas that would have to be customised to fit the local requirements and track conditions. Improvements in engine design of both European and US origin were incorporated by manufacturers when they could be justified in a generally very conservative and slow-changing market. With the notable exception of the USRA standard locomotives built during World War I, in the United States, steam locomotive manufacture was always semi-customised. Railroads ordered locomotives tailored to their specific requirements, though some basic design features were always present. Railroads developed some specific characteristics; for example, the Pennsylvania Railroad and the Great Northern Railway had a preference for the Belpaire firebox. In the United States, large-scale manufacturers constructed locomotives for nearly all rail companies, although nearly all major railroads had shops capable of heavy repairs and some railroads (for example, the Norfolk and Western Railway and the Pennsylvania Railroad, which had two erecting shops) constructed locomotives entirely in their own shops. Companies manufacturing locomotives in the US included Baldwin Locomotive Works, American Locomotive Company (ALCO), and Lima Locomotive Works. Altogether, between 1830 and 1950, over 160,000 steam locomotives were built in the United States, with Baldwin accounting for the largest share, nearly 70,000.. Steam locomotives required regular and, compared to a diesel-electric engine, frequent service and overhaul (often at government-regulated intervals in Europe and the US). Alterations and upgrades regularly occurred during overhauls. New appliances were added, unsatisfactory features removed, cylinders improved or replaced. Almost any part of the locomotive, including boilers, was replaced or upgraded. When service or upgrades got too expensive the locomotive was traded off or retired. On the Baltimore and Ohio Railroad two locomotives were dismantled; the boilers were placed onto two new Class T locomotives and the residual wheel machinery made into a pair of Class U switchers with new boilers. Union Pacific's fleet of 3-cylinder engines were converted into two-cylinder engines in 1942, because of high maintenance problems.


Australia

In Sydney, Clyde Engineering and the Eveleigh Railway Workshops both built steam locomotives for the
New South Wales Government Railways The New South Wales Government Railways (NSWGR) was the agency of the Government of New South Wales that administered rail transport in New South Wales, Australia, between 1855 and 1932. Management The agency was managed by a range of diffe ...
. These include the C38 class ; the first five were built at Clyde with streamlining, the other 25 locomotives were built at Eveleigh (13) and Cardiff Workshops (12) near Newcastle. In Queensland, steam locomotives were locally constructed by Walkers. Similarly, the South Australian Railways also manufactured steam locomotives locally at Islington Railway Workshops in
Adelaide Adelaide ( ) is the list of Australian capital cities, capital city of South Australia, the state's largest city and the list of cities in Australia by population, fifth-most populous city in Australia. "Adelaide" may refer to either Greater A ...
. Victorian Railways constructed most of their locomotives at its Newport Workshops and in Bendigo, while in the early days locomotives were built at the Phoenix Foundry in Ballarat. Locomotives constructed at the Newport shops ranged from the nA class built for the narrow gauge, up to the H class – the largest conventional locomotive ever to operate in Australia, weighing 260 tons. However, the title of largest locomotive ever used in Australia goes to the 263-ton New South Wales AD60 class locomotive Garratt, built by
Beyer, Peacock & Company Beyer, Peacock and Company was an English railway locomotive manufacturer with a factory in Openshaw, Manchester. Founded by Charles Beyer, Richard Peacock and Henry Robertson, it traded from 1854 until 1966. The company exported locomotives ...
in England. Most steam locomotives used in Western Australia were built in the United Kingdom, though some examples were designed and built locally at the Western Australian Government Railways' Midland Railway Workshops. The 10 WAGR S class locomotives (introduced in 1943) were the only class of steam locomotive to be wholly conceived, designed and built in Western Australia, while the Midland workshops notably participated in the Australia-wide construction program of Australian Standard Garratts – these wartime locomotives were built at Midland in Western Australia, Clyde Engineering in New South Wales, Newport in Victoria and Islington in South Australia and saw varying degrees of service in all Australian states.


The end of steam in general use

The introduction of electric locomotives around the turn of the 20th century and later diesel-electric locomotives spelled the beginning of a decline in the use of steam locomotives, although it was some time before they were phased out of general use. As diesel power (especially with electric transmission) became more reliable in the 1930s, it gained a foothold in North America. The full transition away from steam power in North America took place during the 1950s. In continental Europe, large-scale electrification had replaced steam power by the 1970s. Steam was a familiar technology, adapted well to local facilities, and also consumed a wide variety of fuels; this led to its continued use in many countries until the end of the 20th century. Steam engines have considerably less thermal efficiency than modern diesels, requiring constant maintenance and labour to keep them operational. Water is required at many points throughout a rail network, making it a major problem in desert areas, as are found in some regions of the United States, Australia and South Africa. In places where water is available, it may be hard, which can cause "
scale Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number ...
" to form, composed mainly of calcium carbonate, magnesium hydroxide and calcium sulfate. Calcium and magnesium carbonates tend to be deposited as off-white solids on the inside the surfaces of pipes and heat exchangers. This precipitation is principally caused by thermal decomposition of bicarbonate ions but also happens in cases where the
carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonat ...
ion is at saturation concentration. The resulting build-up of scale restricts the flow of water in pipes. In boilers, the deposits impair the flow of heat into the water, reducing the heating efficiency and allowing the metal boiler components to overheat. The reciprocating mechanism on the driving wheels of a two-cylinder single expansion steam locomotive tended to pound the rails (see hammer blow), thus requiring more maintenance. Raising steam from coal took a matter of hours, and created serious pollution problems. Coal-burning locomotives required fire cleaning and ash removal between turns of duty. Diesel or electric locomotives, by comparison, drew benefit from new custom-built servicing facilities. The smoke from steam locomotives was also deemed objectionable; the first electric and diesel locomotives were developed in response to smoke abatement requirements, although this did not take into account the high level of less-visible pollution in diesel exhaust smoke, especially when idling. In some countries, however, power for electric locomotives is derived from steam generated in power stations, which are often run by coal.


Revival

Dramatic increases in the cost of diesel fuel prompted several initiatives to revive steam power. However none of these has progressed to the point of production and, as of the early 21st century, steam locomotives operate only in a few isolated regions of the world and in tourist operations. As early as 1975, railway enthusiasts in the United Kingdom began building new steam locomotives. That year, Trevor Barber completed his gauge locomotive ''Trixie'' which ran on the Meirion Mill Railway. From the 1990s onwards, the number of new builds being completed rose dramatically with new locos completed by the narrow-gauge Ffestiniog and Corris railways in Wales. The Hunslet Engine Company was revived in 2005, and began building steam locomotives on a commercial basis. A standard-gauge LNER Peppercorn Pacific "Tornado" was completed at Hopetown Works,
Darlington Darlington is a market town in the Borough of Darlington, County Durham, England. The River Skerne flows through the town; it is a tributary of the River Tees. The Tees itself flows south of the town. In the 19th century, Darlington under ...
, and made its first run on 1 August 2008. It entered main line service later in 2008. over half-a-dozen projects to build working replicas of extinct steam engines are going ahead, in many cases using existing parts from other types to build them. Examples include BR 72010 ''Hengist'', BR Class 3MT No. 82045, BR Class 2MT No. 84030, Brighton Atlantic ''Beachy Head'', the LMS 5551 ''The Unknown Warrior'' project, GWR " 47xx 4709, 2999 ''Lady of Legend'', 1014 ''County of Glamorgan'' and 6880 ''Betton Grange'' projects. These United Kingdom based new build projects are further complemented by the new build Pennsylvania Railroad 5550 project in the United States. One of the group's goals is to surpass the steam locomotive speed record held by the 4468 ''Mallard'' when the 5550 is completed and for the 5550 to fill in a huge gap in steam locomotive preservation. In 1980, American financier Ross Rowland established American Coal Enterprises to develop a modernised coal-fired steam locomotive. His ACE 3000 concept attracted considerable attention, but was never built. In 1998, in his book ''The Red Devil and Other Tales from the Age of Steam'', David Wardale put forward the concept of a high-speed high-efficiency "Super Class 5 4-6-0" locomotive for future steam haulage of tour trains on British main lines. The idea was formalised in 2001 by the formation of 5AT Project dedicated to developing and building the
5AT Advanced Technology Steam Locomotive The 5AT Advanced Technology steam locomotive was a conceptual design conceived by the British engineer David Wardale, and first described in his definitive work on modern steam, ''The Red Devil and Other Tales from the Age of Steam.'' Wardale's ...
, but it never received any major railway backing. Locations where new builds are taking place include: * GWR 1014 ''County of Glamorgan'' & GWR 2999 ''Lady of Legend'', both being built at Didcot Railway Centre * GWR 6880 ''Betton Grange'', GWR 4709 & LMS 5551 ''The Unknown Warrior'', all being built at Llangollen Railway * LNER 2007 ''Prince of Wales'',
Darlington Locomotive Works The A1 Steam Locomotive Trust is a Darlington, England based charitable trust formed in 1990 for the primary purpose of completing the next stage of the locomotive heritage movement, the building of a new steam locomotive from scratch (i.e. not ...
* LNER 2001 Cock O' The North, Doncaster * Pennsylvania Railroad 5550, Pottstown, Pennsylvania * BR 72010 ''Hengist'', Great Central Railway * BR 77021, TBA * BR 82045, Severn Valley Railway * BR 84030 & LBSCR 32424 Beachy Head, both being built at Bluebell Railway * MS&LR/GCR 567, Ruddington Great Central Railway, Northern Section * VR V499, Victoria, Australia In 2012, the Coalition for Sustainable Rail project was started in the US with the goal of creating a modern higher-speed steam locomotive, incorporating the improvements proposed by Livio Dante Porta and others, and using torrefied biomass as solid fuel. The fuel has been recently developed by the
University of Minnesota The University of Minnesota, formally the University of Minnesota, Twin Cities, (UMN Twin Cities, the U of M, or Minnesota) is a public university, public Land-grant university, land-grant research university in the Minneapolis–Saint Paul, Tw ...
in a collaboration between the university's
Institute on the Environment An institute is an organisational body created for a certain purpose. They are often research organisations (research institutes) created to do research on specific topics, or can also be a professional body. In some countries, institutes can ...
(IonE) and Sustainable Rail International (SRI), an organisation set up to explore the use of steam traction in a modern railway setup. The group have received the last surviving (but non-running)
ATSF 3460 class The Atchison, Topeka and Santa Fe Railway's 3460 class comprised six 4-6-4 "Super Hudson" type steam locomotives built in 1937 by the Baldwin Locomotive Works for service between La Junta, Colorado and Chicago, Illinois, a fairly flat division of ...
steam locomotive (No. 3463) via donation from its previous owner in Kansas, the Great Overland Station Museum. They hope to use it as a platform for developing "the world's cleanest, most powerful passenger locomotive", capable of speeds up to . Named "Project 130", it aims to break the world steam-train speed record set by LNER Class A4 4468 Mallard in the UK at . However, any demonstration of the project's claims is yet to be seen. In Germany, a small number of fireless steam locomotives are still working in industrial service, e.g. at power stations, where an on-site supply of steam is readily available. The small town of Wolsztyn,
Poland Poland, officially the Republic of Poland, , is a country in Central Europe. Poland is divided into Voivodeships of Poland, sixteen voivodeships and is the fifth most populous member state of the European Union (EU), with over 38 mill ...
, approximately from the historic city of Poznan, is the last place in the world where one can ride a regularly scheduled passenger train pulled by steam power. The locomotive shed at Wolsztyn is the last of its kind in the world. There are several working locomotives that haul daily commuter service between Wolsztyn, Poznan, Leszo and other neighboring cities. One can partake in footplate courses via The Wolsztyn Experience. There is no place left in the world that still operates daily, non-tourist steam powered commuter/passenger service other than here at Wolsztyn. There are several Polish-built OL49-class 2-6-2 general purpose locomotives and one PT47 class 2-8-2 in regular service. Each May, Wolsztyn is the site of a steam locomotive festival which brings visiting locomotives - often well over a dozen each year all operating. These operations are not done for tourism or museum/historical purposes; this is the last non-diesel rail line on the PKP (Polish State Network) that has been converted to diesel power. The Swiss company Dampflokomotiv- und Maschinenfabrik DLM AG delivered eight steam locomotives to rack railways in Switzerland and Austria between 1992 and 1996. Four of them are now the main traction on the Brienz Rothorn Bahn; the four others were built for the Schafbergbahn in Austria, where they run 90% of the trains. The same company also rebuilt a German DR Class 52.80 2-10-0 locomotive to new standards with modifications such as roller bearings, light oil firing and boiler insulation.


Climate change

The future use of steam locomotives in the United Kingdom is in doubt because of government policy on
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
. The Heritage Railway Association is working with the All-Party Parliamentary Group on Heritage Rail in an effort to continue running steam locomotives on coal. Many tourist railroads use oil-fired steam locomotives (or have converted their locomotives to run on oil) to reduce their environmental footprint, and because fuel oil can be easier to obtain than coal of the proper type and sizing for locomotives. For example, the Grand Canyon Railway runs its steam locomotives on used vegetable oil. An organization called the Coalition for Sustainable Rail (CSR) is developing an environmentally friendly coal substitute made from
torrefied Torrefaction of biomass, e.g., wood or grain, is a mild form of pyrolysis at temperatures typically between 200 and 320 °C. Torrefaction changes biomass properties to provide a better fuel quality for combustion and gasification applications. ...
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms biom ...
. In early 2019, they performed a series of tests using Everett Railroad to evaluate the performance of the biofuel, with positive results. The biofuel was found to burn slightly faster and hotter than coal. The goal of the project is primarily to find a sustainable fuel for historic steam locomotives on tourist railroads, but CSR has also suggested that, in the future, steam locomotives powered by torrefied biomass could be an environmentally and economically superior alternative to diesel locomotives. Also, a large vat containing (salt) may be used without needing to replenishing the medium. See Masdar asdar.ae Large heating elements would be one method of recharging the system however, it is possible to pump molten salt as well, removing the cooled salt and replenishing from facilities which contain a much larger vat.


Steam locomotives in popular culture

Steam locomotives have been present in popular culture since the 19th century. Folk songs from that period including "
I've Been Working on the Railroad "I've Been Working on the Railroad" is an American folk song. The first published version appeared as "Levee Song" in ''Carmina Princetonia'', a book of Princeton University songs published in 1894. The earliest known recording is by the Shannon ...
" and the " Ballad of John Henry" are a mainstay of American music and culture. Many steam locomotive toys have been made, and railway modelling is a popular hobby. Steam locomotives are often portrayed in fictional works, notably ''
The Railway Series ''The Railway Series'' is a series of British books about a railway known as the North Western Railway, located on the fictional Island of Sodor. There are 42 books in the series, the first published in May 1945 by the Rev. Wilbert Awdry. T ...
'' by the Rev W. V. Awdry, '' The Little Engine That Could'' by Watty Piper, '' The Polar Express'' by Chris Van Allsburg, and the
Hogwarts Express Hogwarts School of Witchcraft and Wizardry () is a fictional Scottish boarding school of magic for students aged eleven to eighteen, and is the primary setting for the first six books in J. K. Rowling's ''Harry Potter'' series and serves as a maj ...
from J.K. Rowling's Harry Potter series. They have also been featured in many children's television shows, such as ''
Thomas & Friends ''Thomas & Friends'' (originally known as ''Thomas the Tank Engine & Friends'' and later ''Thomas & Friends: Big World! Big Adventures!'') is a British children's television series that aired across 24 series from 1984 to 2021. Based on ''The ...
'', based on characters from the books by Awdry, and '' Ivor the Engine'' created by Oliver Postgate. The Hogwarts Express also appears in the Harry Potter series of films, portrayed by GWR 4900 Class 5972 Olton Hall in a special Hogwarts livery. The Polar Express appears in the animated movie of the same name. An elaborate, themed funicular Hogwarts Express ride is featured in the Universal Orlando Resort in Florida, connecting the Harry Potter section of Universal Studios with the Islands of Adventure theme park. The Polar Express is recreated on many heritage railroads in the United States, including the North Pole Express pulled by the Pere Marquette 1225 locomotive, which is operated by the Steam Railroading Institute in Owosso, Michigan. According to author Van Allsburg, this locomotive was the inspiration for the story and it was used in the production of the movie. A number of computer and video games feature steam locomotives. '' Railroad Tycoon'', produced in 1990, was named "one of the best computer games of the year". There are two notable examples of steam locomotives used as
charges Charge or charged may refer to: Arts, entertainment, and media Films * '' Charge, Zero Emissions/Maximum Speed'', a 2011 documentary Music * ''Charge'' (David Ford album) * ''Charge'' (Machel Montano album) * ''Charge!!'', an album by The Aqu ...
on heraldic coats of arms. One is that of
Darlington Darlington is a market town in the Borough of Darlington, County Durham, England. The River Skerne flows through the town; it is a tributary of the River Tees. The Tees itself flows south of the town. In the 19th century, Darlington under ...
, which displays '' Locomotion No. 1''. The other is the original coat of arms of Swindon, not currently in use, which displays a basic steam locomotive. Steam locomotives are a popular topic for coin collectors. The 1950 Silver 5 Peso coin of Mexico has a steam locomotive on its reverse as the prominent feature. The 20 euro Biedermeier Period coin, minted 11 June 2003, shows on the obverse an early model steam locomotive (the '' Ajax'') on Austria's first railway line, the Kaiser Ferdinands-Nordbahn. The ''Ajax'' can still be seen today in the Technisches Museum Wien. As part of the 50 State Quarters program, the quarter representing the US state of Utah depicts the ceremony where the two halves of the First transcontinental railroad met at Promontory Summit in 1869. The coin recreates a popular image from the ceremony with steam locomotives from each company facing each other while the golden spike is being driven. The novel " Night on the Galactic Railroad" by Kenji Miyazawa is centered on the idea of a steam train traveling among the stars. Miyazawa's novel later inspired Leiji Matsumoto's successful " Galaxy Express 999" series. Another Japanese televisual franchise, Super Sentai, features monsters based on steam locomotives. Charge Man, a Robot Master from the fifth installment of the Mega Man series is based on a steam locomotive.


See also


General

* History of rail transport * List of steam technology patents * Live steam * Reciprocating motion * Timeline of railway history


Types of steam locomotives

* Articulated locomotive ** Beyer-Garratt locomotive ** Fairlie locomotive ** Mallet locomotive * Cab forward locomotive * Compound locomotive * Duplex locomotive * Electric-steam locomotive * Geared steam locomotive * Heilmann locomotive * High-pressure steam locomotive *
Steam dummies A steam dummy or dummy engine, in the United States and Canada, was a steam locomotive enclosed in a wooden box structure made to resemble a railroad passenger coach. Steam dummies had some popularity in the first decades of railroading in the U. ...
and
Steam tram Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. ...
s *
Steam turbine locomotive A steam turbine locomotive is a steam locomotive which transmits steam power to the wheels via a steam turbine. Numerous attempts at this type of locomotive were made, mostly without success. In the 1930s this type of locomotive was seen as a way ...
* Streamliner *
Tank locomotive A tank locomotive or tank engine is a steam locomotive that carries its water in one or more on-board water tanks, instead of a more traditional tender. Most tank engines also have bunkers (or fuel tanks) to hold fuel; in a tender-tank loco ...
* Triplex locomotive * Whyte Notation


Notes


References


Bibliography

*


Further reading

* C. E. Wolff, ''Modern Locomotive Practice: A Treatise on the Design, Construction, and Working of Steam Locomotives'' (Manchester, England, 1903) * Henry Greenly, ''Model Locomotive'' (New York, 1905) * G. R. Henderson, ''Cost of Locomotive Operation'' (New York, 1906) * W. E. Dalby, ''Economical Working of Locomotives'' (London, 1906) * A. I. Taylor, ''Modern British Locomotives'' (New York, 1907) * E. L. Ahrons, ''The Development of British Locomotive Design'' (London, 1914) * E. L. Ahrons
''Steam Engine Construction and Maintenance''
(London, 1921) * J. F. Gairns, ''Locomotive Compounding and Superheating'' (Philadelphia, 1907) * Angus Sinclair, ''Development of the Locomotive Engine'' (New York, 1907) * Vaughn Pendred, ''The Railway Locomotive, What it is and Why it is What it is'' (London, 1908) * Brosius and Koch, ''Die Schule des Lokomotivführers'' (thirteenth edition, three volumes, Wiesbaden, 1909–1914) * G. L. Fowler, ''Locomotive Breakdowns, Emergencies, and their Remedies'' (seventh edition, New York, 1911) * Fisher and Williams, ''Pocket Edition of Locomotive Engineering'' (Chicago, 1911) * T. A. Annis, ''Modern Locomotives'' (Adrian Michigan, 1912) * C. E. Allen, ''Modern Locomotive'' (Cambridge, England, 1912) * W. G. Knight, ''Practical Questions on Locomotive Operating'' (Boston, 1913) * G. R. Henderson, ''Recent Development of the Locomotive'' (Philadelphia, 1913) * Wright and Swift (editors) ''Locomotive Dictionary'' (third edition, Philadelphia, 1913) * Roberts and Smith, ''Practical Locomotive Operating'' (Philadelphia, 1913) * E. Prothero, ''Railways of the World'' (New York, 1914) * M. M. Kirkman, ''The Locomotive'' (Chicago, 1914) * C. L. Dickerson, ''The Locomotive and Things You Should Know About it'' (Clinton, Illinois, 1914) * P. W. B. Semmens, A. J. Goldfinch, ''How Steam Locomotives Really Work'' (Oxford University Press, US, 2004) * Gerald A Dee, ''A Lifetime of Railway Photography'' in ''Photographer Profile'', Train Hobby Publications, Studfield, 1998. (Australian steam) * Swengel, F. M. ''The American Steam Locomotive; Vol. 1. The Evolution of the American Steam Locomotive'', Midwest Rail Publication, Iowa, 1967. * Раков В.А. ''Локомотивы отечественных железных дорог 1845–1955'' Транспорт, Москва, 1995
(Rakov V.A. ''Locomotives of fatherland's railways 1845–1955'' Transport, Moscow, 1995 ''(in Russian)'') * J.J.G. Koopmans: ''The fire burns much better ...'' NL-Venray 2006,


External links


TV and Radio programmes from the BBC archives celebrating steam trains

Database of surviving steam locomotives in North America

UK heritage railways and preserved locomotives database

Advanced Steam Traction Trust

UK Steam Train Photos
{{DEFAULTSORT:Steam Locomotive * British inventions Articles containing video clips Locomotive