Richard Trevithick was a British inventor and mining engineer from Cornwall, England. The son of a mining captain, born in the mining heartland of Cornwall, Trevithick was immersed in mining and engineering from an early age, he performed poorly in school, but went on to be an early pioneer of steam-powered road and rail transport. His most significant contribution was the development of the first high-pressure steam engine, he built the first full-scale working railway steam locomotive. The world's first locomotive-hauled railway journey took place on 21 February 1804, when Trevithick's unnamed steam locomotive hauled a train along the tramway of the Penydarren Ironworks, in Merthyr Tydfil, Wales. Turning his interests abroad, Trevithick worked as a mining consultant in Peru and explored parts of Costa Rica. Throughout his professional career, he went through many ups and downs, at one point faced financial ruin suffering from the strong rivalry of many mining and steam engineers of the day.
During the prime of his career, he was a well-respected and known figure in mining and engineering, but near the end of his life he fell out of the public eye. Richard Trevithick was born at Tregajorran, between Camborne and Redruth, in the heart of one of the rich mineral-mining areas of Cornwall, he was the only boy in a family of six children. He was tall for the era at 6 ft 2in, as well as athletic and concentrated more on sport than schoolwork. Sent to the village school at Camborne, he did not take much advantage of the education provided. An exception was arithmetic, for which he had an aptitude, though arriving at the correct answers by unconventional means. Trevithick was the son of mine "captain" Richard Trevithick and of miner's daughter Ann Teague; as a child he would watch steam engines pump water from the deep copper mines in Cornwall. For a time he was a neighbour of William Murdoch, the steam carriage pioneer, would have been influenced by his experiments with steam-powered road locomotion.
Trevithick first went to work at the age of 19 at the East Stray Park Mine. He was enthusiastic and gained the status of a consultant, unusual for such a young person, he was popular with the miners. In 1797, Trevithick married Jane Harvey of Hayle, they raised six children: Richard Trevithick Anne Ellis Elizabeth Banfield John Harvey Trevithick Francis Trevithick Frederick Henry Trevithick Jane's father, John Harvey a blacksmith from Carnhell Green, formed the local foundry, Harveys of Hayle. His company became famous worldwide for building huge stationary "beam" engines for pumping water from mines. Up to this time such steam engines were of the condensing or atmospheric type invented by Thomas Newcomen in 1712, which became known as low-pressure engines. James Watt, on behalf of his partnership with Matthew Boulton, held a number of patents for improving the efficiency of Newcomen's engine—including the "separate condenser patent", which proved the most contentious. Trevithick became engineer at the Ding Dong Mine in 1797, there he pioneered the use of high-pressure steam.
He worked on building and modifying steam engines to avoid the royalties due to Watt on the separate condenser patent. Boulton & Watt served an injunction on him at Ding Dong, posted it "on the minestuffs" and "most on the door" of the Count House which, although now a ruin, is the only surviving building from Trevithick's time there, he experimented with the plunger-pole pump, a type of pump—with a beam engine—used in Cornwall's tin mines, in which he reversed the plunger to change it into a water-power engine. As his experience grew, he realised that improvements in boiler technology now permitted the safe production of high-pressure steam, which could move a piston in a steam engine on its own account, instead of using pressure near to atmospheric, in a condensing engine, he was not the first to think of steam of about 30 psi. William Murdoch had developed and demonstrated a model steam carriage in 1784, demonstrated it to Trevithick at his request in 1794. In fact, Trevithick lived next door to Murdoch in Redruth in 1797 and 1798.
Oliver Evans in the U. S. had concerned himself with the concept, but there is no indication that his ideas had come to Trevithick's attention. Independently of this, Arthur Woolf was experimenting with higher pressures whilst working as the Chief Engineer of the Griffin Brewery; this was an Engine designed by Hornblower and Maberly, the proprietors were keen to have the best steam engine in London. Around 1796, Woolf believed. According to his son Francis, Trevithick was the first to make high-pressure steam work in England in 1799, although other sources say he had invented his first high-pressure engine by 1797. Not only would a high-pressure steam engine eliminate the condenser, but it would allow the use of a smaller cylinder, saving space and weight, he reasoned that his engine could now be more compact and small enough to carry its own weight with a carriage attached. Trevithick began building his first models of high-pressure steam engines - first a stationary one and subsequently one attached to a road car
The Butterley Company was an English manufacturing firm founded as Benjamin Outram and Company in 1790. Portions of it existed until 2009; this area of Derbyshire had been known for its outcrops of iron ore, exploited at least since the Middle Ages. After the Norman Conquest, nearby Duffield Frith was the property of the de Ferrers family who were iron masters in Normandy. In 1793, William Jessop, with the assistance of Benjamin Outram, constructed the Cromford Canal to connect Pinxton and Cromford with the Erewash Canal. In digging Butterley Tunnel for the Cromford Canal and iron were discovered. Fortuitously, Butterley Hall fell vacant and in 1790 Outram, with the financial assistance of Francis Beresford, bought it and its estate; the following year they were joined by Jessop and John, the grandson of Ichabod Wright, a wealthy Nottingham banker, betrothed to Beresford's daughter and who owned the Butterley Park estate. In 1793 the French Revolutionary Wars broke out and by 1796 the blast furnace was producing nearly a thousand tons of pig iron a year.
By the second decade of the next century the company had expanded with another works at Codnor Park in Codnor, both works having two blast furnaces, output had risen to around 4,500 tons per year. Outram died in 1805 and the name changed to the Butterley Company, with one of Jessop's sons William, taking over. In 1814 the company produced the iron work for Vauxhall Bridge over the River Thames; the company owned Hilt's Quarry at Crich, which supplied limestone for the ironworks and for the limekilns at Bullbridge, providing lime for farmers and for the increasing amount of building work. The steep wagonway to the Cromford Canal at Bullbridge was called the Butterley Gangroad and incorporated the world's oldest surviving railway tunnel, at Fritchley. In 1812, William Brunton, an engineer for the company, produced his remarkable Steam Horse locomotive In 1817, in the depression following the Napoleonic Wars, the works at Butterley was the scene of the Pentrich Revolution; the intention of the rebels was to ransack the works for weapons.
When they arrived they were confronted by George Goodwin the factory agent, with a few constables, faced them down. There is little to be seen of the event, but the hexagonal office where Goodwin stood his ground is a listed building in the yard of the works. Following this the country entered a long period of the company with it. In 1830 it was considered to be the largest coal owner and the second-largest iron producer in the East Midlands. By this time the company owned a considerable number of quarries for limestone and mines for coal and iron, installed a third blast furnace at Codnor Park. One of the two drainage engines at Pode Hole and the engine in the Pinchbeck Engine land drainage museum were built by Butterley, as were the Scoop wheel pumps, they produced a vast array of goods, from rails for wagonways to heaters for tea urns. Thomas Telford's Caledonian Canal used lock gates and machinery with castings produced at Butterley, two steam dredgers designed by Jessop; the company produced steam locomotives for its own use, but it provided two for the Midland Counties Railway.
It produced all the necessary castings for the new railways and two complete lines, the Croydon and Godstone Iron Railway and the Cromford and High Peak Railway. A winding engine for the latter exists in working order at Middleton Top near Wirksworth; the company was quick to invest in the new Bessemer process for steel manufacture in 1856, being one of four businesses that took out a licence from Sir Henry Bessemer within a month of his announcing his method. The licences were spread around the country in order to protect the trading interests of the licensees. Notable patents were taken out by Sir John Alleyne. In December 1859 Alleyne patented a method of producing a load-bearing iron beam known as the Butterley Bulb, used in many early iron steam ships including HMS Warrior In 1861 Alleyne patented a method that allowed hot ingots to be moved around a roller after they had passed by just one person. During the production of steel sections the bar has to be put through rollers. Allowing this to happen using just one person was a substantial increase in productivity.
By 1863 the company was rolling the largest masses of iron of any foundry in the country. Among its most famous buildings are the Barlow train shed at St Pancras station in London, which included 240-foot spans. Alleyne's next invention was the two high reversing steel mill patented in 1870, which used two steam engines to allow metal ingots to be rolled to get the correct size and section. With this technique the steel did not have to be moved to re-enter the rolling process but had to be moved back into the rolling machine once it had passed through. There was an extensive brickworks for railways, thousands of factories and domestic dwellings. By 1874 company workers were starting to fight for better conditions; the company sacked 11 miners "without a charge" on 5 May 1874. At its peak in the 1950s the company employed around 10,000 people. In 1957, a partnership with Air Products of the USA helped establish that company in the United Kingdom. In the early 1960s the company acquired locomotive manufacturer F. C.
Hibberd & Co Ltd. The Codnor Park works closed in 1965; the company was acquired by Lord Hanson in 1968 for £4.7 million. The company was subsequently split up into Butterley Engineering, Butterley Brick and Butterley Aggregates. Butterley Hall, Outram's home and the companies offices, was sold off to become the headquarters of Derbyshire Constabulary. In the mid 1980s the foundry closed down; when surplus buildings were demolished the original blast fur
A rack railway is a steep grade railway with a toothed rack rail between the running rails. The trains pinions that mesh with this rack rail; this allows the trains to operate on steep grades above around 7 to 10%, the maximum for friction-based rail. Most rack railways are mountain railways, although a few are transit railways or tramways built to overcome a steep gradient in an urban environment; the first cog railway was the Middleton Railway between Middleton and Leeds in West Yorkshire, United Kingdom, where the first commercially successful steam locomotive, ran in 1812. This used a pinion system designed and patented in 1811 by John Blenkinsop; the first mountain cog railway was the Mount Washington Cog Railway in the U. S. state of New Hampshire, which carried its first fare-paying passengers in 1868. The track was completed to reach the summit of Mount Washington in 1869; the first mountain rack railway in continental Europe was the Vitznau-Rigi-Bahn on Mount Rigi in Switzerland, which opened in 1871.
Both lines are still running. A number of different rack systems have been developed. With the exception of some early Morgan and Blenkinsop rack installations, rack systems place the rack rail halfway between the running rails. Today, most rack railways use the Abt system. John Blenkinsop thought that the friction would be too low from metal wheels on metal rails, so he built his locomotives for the Middleton Railway in 1812 with a 20-tooth, 3 feet diameter cog wheel on the left side that engaged in rack teeth on the outer side of the rail, the metal "fishbelly" edge rail with its side rack being cast all in one piece, in three feet lengths. Blenkinsop's system remained in use for 25 years on the Middleton Railway, but it became a curiosity because simple friction was found to be sufficient for railroads operating on level ground; the first successful rack railway in the United States was the Mount Washington Cog Railway, developed by Sylvester Marsh. Marsh was issued a U. S. patent for the general idea of a rack railway in September 1861, in January 1867 for a practical rack where the gear teeth take the form of rollers arranged like the rungs of a ladder between two L-shaped wrought-iron rails.
The first public trial of the Marsh rack on Mount Washington was made on August 29, 1866, when only one quarter of a mile of track had been completed. The Mount Washington railway opened to the public on August 14, 1868; the pinion wheels on the locomotives have deep teeth that ensure that at least two teeth are engaged with the rack at all times. The Fell mountain railway system, developed in the 1860s, is not speaking a rack railway, since there are no cogs with teeth. Rather, this system uses a smooth raised centre rail between the two running rails on steep sections of lines, gripped on both sides to improve friction. Trains are propelled by wheels or braked by shoes pressed horizontally onto the centre rail, as well as by means of the normal running wheels; the Riggenbach rack system was invented by Niklaus Riggenbach working at about the same time as, but independently from Marsh. Riggenbach was granted a French patent in 1863 based on a working model which he used to interest potential Swiss backers.
During this time, the Swiss Consul to the United States visited Marsh's Mount Washington Cog Railway and reported back with enthusiasm to the Swiss government. Eager to boost tourism in Switzerland, the government commissioned Riggenbach to build a rack railway up Mount Rigi. Following the construction of a prototype locomotive and test track in a quarry near Bern, the Vitznau-Rigi-Bahn opened on 22 May 1871; the Riggenbach system is similar in design to the Marsh system. It uses a ladder rack, formed of steel plates or channels connected by round or square rods at regular intervals; the Riggenbach system suffers from the problem that its fixed ladder rack is more complex and expensive to build than the other systems. Following the success of the Vitznau-Rigi-Bahn, Riggenbach established the Maschinenfabrik der Internationalen Gesellschaft für Bergbahnen – a company that produced rack locomotives to his design; the Abt system was devised by a Swiss locomotive engineer. Abt worked for Riggenbach at his works in Olten and at his IGB rack locomotive company.
In 1885, he founded his own civil engineering company. During the early 1880s, Abt worked to devise an improved rack system that overcame the limitations of the Riggenbach system. In particular, the Riggenbach rack was expensive to manufacture and maintain and the switches were complex. In 1882, Abt designed a new rack using solid bars with vertical teeth machined into them. Two or three of these bars are mounted centrally with the teeth offset; the use of multiple bars with offset teeth ensures that the pinions on the locomotive driving wheels are engaged with the rack. The Abt system is cheaper to build than the Riggenbach because it requires a lower weight of rack over a given length; however the Riggenbach system exhibits greater wear resistance than the Abt. Abt developed a system for smoothing the transition from friction to rack traction, using a spring-mounted rack section to bring the pinion teeth into engagement; the first use of the Abt system was on the Harzbahn in Germany, which opened in 1885.
The pinion wheels can be driven separately. The steam locomotives on the Mount Lyell Mining and Railway Company had separate cylinders driving the pinion wheel, as d
Sans Pareil is a steam locomotive built by Timothy Hackworth which took part in the 1829 Rainhill Trials on the Liverpool and Manchester Railway, held to select a builder of locomotives. The name is French and means'peerless' or'without equal'. While a capable locomotive for the day, its technology was somewhat antiquated compared to George and Robert Stephenson's Rocket, the winner of the Rainhill Trials and the £500 prize money. Instead of the fire tube boiler of Rocket, Sans Pareil had a double return flue. To increase the heating surface area, the two flues were joined by a U shaped tube at the forward end of the boiler. Sans Pareil had two cylinders, mounted vertically at the opposite end to the chimney, driving one pair of driving wheels directly - the other pair were driven via connecting rods, in the typical steam locomotive fashion. At the Rainhill Trials, Sans Pareil was excluded from the prize because it was over the maximum permitted weight, it performed well but had a strange rolling gait due to its vertical cylinders.
The'blast' from the blastpipe was, in Hackworth's trademark style strong, so most of the coke was expelled out of the chimney unburnt. It was pulled out of the competition because of a cracked cylinder: the design thickness for the cylinder walls was some 1 3⁄4 inches, but at the point of failure, it was found to be a mere 5⁄8 inch. Hackworth's supporters cried'foul!', but as he had had over twenty cylinders cast, choosing the best two for the locomotive, skulduggery on the part of the Stephensons whose firm cast the cylinders, who were direct competitors at Rainhill, is unlikely. After the trials, the Liverpool and Manchester Railway bought Sans Pareil as well as Rocket, it was subsequently leased to the Bolton and Leigh Railway where it ran until 1844. It was used by John Hargreaves as a stationary boiler at the Coppull Colliery, Chorley until 1863. Thereafter, Sans Pareil was presented to the Patent Office Museum in 1864 by John Hick; the engine now resides at the Shildon Locomotion Museum on static display.
A replica locomotive, built in 1980, is now preserved by the National Railway Museum at its new Shildon Locomotion Museum annex, home to what remains of the original locomotive. London, Midland & Scottish Railway Royal Scot Class 4-6-0 locomotive 6126 was named Sans Pareil; this loco was built by the North British Locomotive Company at Glasgow in September 1927 and withdrawn in October 1963 as 46126 Royal Army Service Corps. An AL6 electric locomotive built at Doncaster Works in 1965, number E3106 carried the name'Sans Pareil' between 1981 and 2005. 86214 was scrapped in 2006. Sans Pareil Pictured at Locomotion
Leeds is a city in West Yorkshire, England. Leeds has one of the most diverse economies of all the UK's main employment centres and has seen the fastest rate of private-sector jobs growth of any UK city, it has the highest ratio of private to public sector jobs of all the UK's Core Cities, with 77% of its workforce working in the private sector. Leeds has the third-largest jobs total by local authority area, with 480,000 in employment and self-employment at the beginning of 2015. Leeds is ranked as a gamma world city by World Cities Research Network. Leeds is the cultural and commercial heart of the West Yorkshire Urban Area. Leeds is served by four universities, has the fourth largest student population in the country and the country's fourth largest urban economy. Leeds was a small manorial borough in the 13th century, in the 17th and 18th centuries it became a major centre for the production and trading of wool, in the Industrial Revolution a major mill town. From being a market town in the valley of the River Aire in the 16th century, Leeds expanded and absorbed the surrounding villages to become a populous urban centre by the mid-20th century.
It now lies within the West Yorkshire Urban Area, the United Kingdom's fourth-most populous urban area, with a population of 2.6 million. Today, Leeds has become the largest legal and financial centre, outside London with the financial and insurance services industry worth £13 billion to the city's economy; the finance and business service sector account for 38% of total output with more than 30 national and international banks located in the city, including an office of the Bank of England. Leeds is the UK's third-largest manufacturing centre with around 1,800 firms and 39,000 employees, Leeds manufacturing firms account for 8.8% of total employment in the city and is worth over £7 billion to the local economy. The largest sub-sectors are engineering and publishing, food and drink and medical technology. Other key sectors include retail and the visitor economy and the creative and digital industries; the city saw several firsts, including the oldest-surviving film in existence, Roundhay Garden Scene, the 1767 invention of soda water.
Public transport and road communications networks in the region are focused on Leeds, the second phase of High Speed 2 will connect it to London via East Midlands Hub and Sheffield Meadowhall. Leeds has the third busiest railway station and the tenth busiest airport outside London; the name derives from the old Brythonic word Ladenses meaning "people of the fast-flowing river", in reference to the River Aire that flows through the city. This name referred to the forested area covering most of the Brythonic kingdom of Elmet, which existed during the 5th century into the early 7th century. Bede states in the fourteenth chapter of his Ecclesiastical History, in a discussion of an altar surviving from a church erected by Edwin of Northumbria, that it is located in...regione quae vocatur Loidis. An inhabitant of Leeds is locally known as a word of uncertain origin; the term Leodensian is used, from the city's Latin name. The name has been explained as a derivative of Welsh lloed, meaning "a place".
Leeds developed as a market town in the Middle Ages as part of the local agricultural economy. Before the Industrial Revolution, it became a co-ordination centre for the manufacture of woollen cloth, white broadcloth was traded at its White Cloth Hall. Leeds handled one sixth of England's export trade in 1770. Growth in textiles, was accelerated by the building of the Aire and Calder Navigation in 1699 and the Leeds and Liverpool Canal in 1816. In the late Georgian era, William Lupton, Lord of the Manor of Leeds, was one of a number of central Leeds landowners with the mesne lord title, some of whom, like him, were textile manufacturers. At the time of his death in 1828, Lupton's land in Briggate in central Leeds included a mill, manor house and outbuildings; the railway network constructed around Leeds, starting with the Leeds and Selby Railway in 1834, provided improved communications with national markets and for its development, an east-west connection with Manchester and the ports of Liverpool and Hull giving improved access to international markets.
Alongside technological advances and industrial expansion, Leeds retained an interest in trading in agricultural commodities, with the Corn Exchange opening in 1864. Marshall's Mill was one of the first of many factories constructed in Leeds from around 1790 when the most significant were woollen finishing and flax mills. Manufacturing diversified by 1914 to printing, engineering and clothing manufacture. Decline in manufacturing during the 1930s was temporarily reversed by a switch to producing military uniforms and munitions during World War II. However, by the 1970s, the clothing industry was in irreversible decline, facing cheap foreign competition; the contemporary economy has been shaped by Leeds City Council's vision of building a'24-hour European city' and'capital of the north'. The city has developed from the decay of the post-industrial era to become a telephone banking centre, connected to the electronic infrastructure of the modern global economy. There has been growth in the corporate and legal sectors, increased local affluence has led to an expanding retail sector, including the luxury goods market.
Leeds City Region Enterprise Zone was launched in April 2012 to promote development in four sites along the A63 East Leeds Link Road. Leeds was a manor and townshi
Wagonways consisted of the horses and tracks used for hauling wagons, which preceded steam-powered railways. The terms plateway and dramway were used; the advantage of wagonways was. The earliest evidence is of the 6 to 8.5 km long Diolkos paved trackway, which transported boats across the Isthmus of Corinth in Greece from around 600 BC. Wheeled vehicles pulled by men and animals ran in grooves in limestone, which provided the track element, preventing the wagons from leaving the intended route; the Diolkos was in use for over 650 years, until at least the 1st century AD. Paved trackways were built in Roman Egypt; such an operation was illustrated in Germany in 1556 by Georgius Agricola in his work De re metallica. This line used "Hund" carts with unflanged wheels running on wooden planks and a vertical pin on the truck fitting into the gap between the planks to keep it going the right way; the miners called the wagons Hunde from the noise. Around 1568, German miners working in the Mines Royal near Keswick used such a system.
Archaeological work at the Mines Royal site at Caldbeck in the English Lake District confirmed the use of "hunds". In 1604, Huntingdon Beaumont completed the Wollaton Wagonway, built to transport coal from the mines at Strelley to Wollaton Lane End, just west of Nottingham, England. Wagonways have been discovered between Broseley and Jackfield in Shropshire from 1605, used by James Clifford to transport coal from his mines in Broseley to the Severn River, it has been suggested. The Middleton Railway in Leeds, built in 1758 as a wagonway became the world's first operational railway, albeit in an upgraded form. In 1764, the first railway in the America was built in New York as a wagonway. Wagonways improved coal transport by allowing one horse to deliver between 10 to 13 long tons of coal per run— an approximate fourfold increase. Wagonways were designed to carry the loaded wagons downhill to a canal or boat dock and return the empty wagons back to the mine; until the beginning of the Industrial Revolution, rails were made of wood, were a few inches wide and were fastened end to end, on logs of wood or "sleepers", placed crosswise at intervals of two or three feet.
In time, it became common to cover them with a thin flat sheathing or "plating" of iron, in order to add to their life and reduce friction. This caused more wear on the wooden rollers of the wagons and towards the middle of the 18th century, led to the introduction of iron wheels. However, the iron sheathing was not strong enough to resist buckling under the passage of the loaded wagons, so rails made wholly of iron were invented. In 1760 the Coalbrookdale Iron Works began to reinforce their wooden railed tramway with iron bars, which were found to facilitate passage and diminish expenses; as a result, in 1767, they began to make cast iron rails. These were 6 ft long, with four projecting ears or lugs 3 in by 3 3⁄4 in to enable them to be fixed to the sleepers; the rails were 3 3⁄4 in 1 1⁄4 in thick. Descriptions refer to rails 3 ft long and only 2 in wide. A system involved "L" shaped iron rails or plates, each 3 ft long and 4 in wide, having on the inner side an upright ledge or flange, 3 in high at the centre and tapering to 2 in at the ends, for the purpose of keeping the flat wheels on the track.
Subsequently, to increase strength, a similar flange might be added below the rail. Wooden sleepers continued to be used—the rails were secured by spikes passing through the extremities—but, circa 1793, stone blocks began to be used, an innovation associated with Benjamin Outram, although he was not the originator; this type of rail was known as the plate-rail, tramway-plate or way-plate, names that are preserved in the modern term "platelayer" applied to the workers who lay and maintain the permanent way. The wheels of flangeway wagons were plain, but they could not operate on ordinary roads as the narrow rims would dig into the surface. Another form of rail, the edge rail, was first used by William Jessop on a line, opened as part of the Charnwood Forest Canal between Loughborough and Nanpantan in Leicestershire in 1789; this line was designed as a plateway on the Outram system, but objections were laying raised to rails with upstanding ledges or flanges on the turnpike. This difficulty was overcome by paving or "causewaying" the road up to the level of the top of the flanges.
In 1790, Jessop and his partner Outram began to manufacture edge-rails. Another example of the edge rail application was the Lake Lock Rail Road used for coal transport; this was a public railway and opened for traffic in 1798, making it the world's oldest public railway. The route started at Lake Lock, Stanley, on the Aire & Calder Navigation, running from Wakefield to Outwood, a distance of 3 miles. Edge-rails were used on the nearby Middleton-Leeds rack railway; the wheels of an edgeway have flanges, like modern tramways. Causewaying is done on modern level crossings and tramways; these two systems of constructing iron railways continued to exist until the early 19th century. In most parts of England the plate-rail was preferred. Plate-rails were used from Wandsworth to West Croydon; the SIR was sanctioned by Parliament in 1801 and finished in 1803. Like the Lake Lock Rail Road, the SIR was available to
An adhesion railway relies on adhesion traction to move the train. Adhesion traction is the friction between the steel rail; the term "adhesion railway" is only used when there is need to distinguish adhesion railways from railways moved by other means, e.g. by a stationary engine pulling on a cable attached to the cars, by railways which are moved by a pinion meshing with a rack, etc. This article focuses on the technical detail of what happens as a result of friction between the wheels and rails in what is known as the wheel-rail interface or contact patch. There are the good forces, e.g. the traction force, the braking forces, the centering forces, all of which contribute to stable running. There are the bad forces which increase costs by requiring more fuel consumption and increasing maintenance, needed to address fatigue damage, wear on rail heads and on the wheel rims, rail movement from traction and braking forces; the interface between the wheel and the rail is a specialist subject with continual research being done.
Traction or friction is reduced when the top of the rail is wet or frosty or contaminated with grease, oil or decomposing leaves which compact into a hard slippery lignin coating. Leaf contamination can be removed by applying "Sandite" from maintenance trains, using scrubbers and water jets, can be reduced with long-term management of railside vegetation. Locomotives and streetcars/trams use sand to improve traction. Adhesion is caused by friction, with maximum tangential force produced by a driving wheel before slipping given by: Fmax= coefficient of friction × Weight on wheelUsually the force needed to start sliding is greater than that needed to continue sliding; the former is concerned with static friction or "limiting friction", whilst the latter is dynamic friction called "sliding friction". For steel on steel, the coefficient of friction can be as high as 0.78, under laboratory conditions, but on railways it is between 0.35 and 0.5, whilst under extreme conditions it can fall to as low as 0.05.
Thus a 100-tonne locomotive could have a tractive effort of 350 kilonewtons, under the ideal conditions, falling to a 50 kilonewtons under the worst conditions. Steam locomotives suffer badly from adhesion issues because the traction force at the wheel rim fluctuates and, on large locomotives, not all wheels are driven; the "factor of adhesion", being the weight on the driven wheels divided by the theoretical starting tractive effort, was designed to be a value of 4 or higher, reflecting a typical wheel-rail friction coefficient of 0.25. A locomotive with a factor of adhesion much lower than 4 would be prone to wheelslip, although some 3-cylinder locomotives, such as the SR V Schools class, operated with a factor of adhesion below 4 because the traction force at the wheel rim do not fluctuate as much. Other factors affecting the likelihood of wheelslip include wheel size and the sensitivity of the regulator/skill of the driver; the term all-weather adhesion is used in North America, refers to the adhesion available during traction mode with 99% reliability in all weather conditions.
The maximum speed a train can proceed around a turn is limited by the radius of turn, the position of the centre of mass of the units, the wheel gauge and whether the track is superelevated or canted. Toppling will occur when the overturning moment due to the side force is sufficient to cause the inner wheel to begin to lift off the rail; this may result in loss of adhesion - preventing toppling. Alternatively, the inertia may be sufficient to cause the train to continue to move at speed causing the vehicle to topple completely. For a wheel gauge of 1.5 m, no canting, a centre of gravity height of 3 m and speed of 30 m/s, the radius of turn is 360 m. For a modern high speed train at 80 m/s, the toppling limit would be about 2.5 km. In practice, the minimum radius of turn is much greater than this, as contact between the wheel flanges and rail at high speed could cause significant damage to both. For high speed, the minimum adhesion limit again appears appropriate, implying a radius of turn of about 13 km.
In practice, curved lines used for high speed travel are superelevated or canted so that the turn limit is closer to 7 km. During the 19th century, it was believed that coupling the drive wheels would compromise performance and was avoided on engines intended for express passenger service. With a single drive wheelset, the Herzian contact stress between the wheel and rail necessitated the largest diameter wheels that could be accommodated; the weight of locomotive was restricted by the stress on the rail and sandboxes were required under reasonable adhesion conditions. It may be thought. However, close examination of a typical railway wheel reveals that the tread is burnished but the flange is not—the flanges make contact with the rail and, when they do, most of the contact is sliding; the rubbing of a flange on the track dissipates large amounts of energy as heat but including noise and, if sustained, would lead to excessive wheel wear. Centering is accomplished through shaping of the wheel.
The tread of the wheel is tapered. When the train is in the centre of the track, the region of the wheels in contact with the rail traces out a circle which has the same diameter for both wheels; the velocities of the two wheels are equal, so the train moves in a straight line. If, the wheelset is displaced to one side, the