SR V Schools class
The SR V class, more known as the Schools class, is a class of steam locomotive designed by Richard Maunsell for the Southern Railway. The class was a cut down version of his Lord Nelson class but incorporated components from Urie and Maunsell's LSWR/SR King Arthur class, it was the last locomotive in Britain to be designed with a 4-4-0 wheel arrangement, was the most powerful class of 4-4-0 produced in Europe. All 40 of the class were named after English public schools, were designed to provide a powerful class of intermediate express passenger locomotive on semi-fast services for lines which could cope with high axle loads but some of which had short turntables; because of the use of a ‘’King Arthur’’ firebox, rather than the square-topped Belpaire firebox used on the Lord Nelsons, the class could be used on lines with a restricted loading gauge and some of the best performance by the class was on the restricted Tonbridge to Hastings line. The locomotives performed well from the beginning but were subject to various minor modifications to improve their performance over the years.
The class operated until 1961 when mass withdrawals took place and all had gone by December 1962. Three examples are now preserved on heritage railways in Britain. By 1928 the Southern Railway was well served by large 4-6-0 express passenger locomotives, but there was an urgent need for a class to fulfill intermediate roles throughout the system. Maunsell’s previous attempt at developing his predecessor’s L class for this task had proven a disappointment, the Drummond D15 and L12 classes were approaching the end of their useful lives on these services. An new secondary express passenger locomotive was required to operate over the main lines throughout the system including those that had short turntables. Maunsell’s original plan was to use large-wheeled 2-6-4 tank engines for this purpose, but the Sevenoaks railway accident made him have second thoughts, he therefore chose a short wheelbase 4-4-0 design although by this period 4-6-0 was more usual for this type of work. Authorities disagree as to whether Maunsell had in mind the restricted loading gauge of the Tonbridge to Hastings line when he designed the class, or whether this was an "unexpected bonus" when he was forced to substitute a "King Arthur" round-topped firebox to his planned Belpaire design to reduce the axle load on the driving wheels to acceptable limits.
In either event the class was undoubtedly Maunsell’s most successful design, the locomotives did some of their best work on the Hastings route. The basic layout of the class was influenced by the existing ‘’Lord Nelson’’ class 4-6-0 design, but the use of the round topped firebox enabled Maunsell to design the cab's curved profile to fit the gauge restrictions of the Hastings line while allowing adequate forward visibility; the short frame length of the 4-4-0 locomotive meant little overhang on the line's tight curves. To maintain the high power rating required for express passenger engines, Maunsell opted for a three-cylinder design. In terms of tractive effort, the class was the most powerful 4-4-0 built in Britain, were the only 4-4-0 type to be given the power classification of 5P by British Railways, they were well liked by crews. They had a higher tractive effort than the nominally more powerful King Arthur class 4-6-0s, but at the cost of high axle-loading: 21 long tons; the permanent way on the Hastings line therefore had to be upgraded during 1929 and 1930 to accept the new locomotive.
Permission was granted for the first batch of fifteen locomotives in March 1928, but this was reduced to ten when it became apparent that they would not be able to operate on the Hastings route. Production delays at Eastleigh railway works meant that they were not delivered until between March and July 1930. Once the original batch had proved their worth and had been well received by the crews a further twenty locomotives were ordered in March 1931 for delivery between December 1932 and March 1934. A third batch of twenty were ordered from Eastleigh in March 1932 for delivery after the completion of the previous order, but this was subsequently reduced to ten locomotives because of the continuing trade depression; the final locomotive in the class was delivered in July 1935. For location details and current status of the preserved locomotives including surviving artifacts of scrapped class members, see: List of SR V "Schools" class locomotives The Southern Railway continued its 1923 naming policy for express passenger locomotives with this class.
As several public schools were located on the Southern Railway network, the locomotives were named after them. This was another marketing success for both railway and schools concerned, continuing in the tradition of the N15 King Arthur and Lord Nelson classes. Where possible, the Southern sent the newly constructed locomotive to a station near the school after which it was named for its official naming ceremony, when pupils were allowed to view the cab of "their" engine. Extension of the class meant that names from "foreign" schools outside the Southern Railway catchment area were used, including Rugby and Malvern; the class performed well from the outset, but there were a number of minor modifications over the years. The first ten were built without smoke deflectors, but these were added from August 1931, the remaining thirty were fitted with them from new. Following the successful introduction of the Lemaître multiple jet blastpipes on to the Lord Nelson class, Maunsell's successor Oliver Bulleid began to fit them to the Schools class.
However no discernible improvement to draughting was experienced, only twenty examples were so modified, the most obvious change in their appearance being the large diameter chimney. The origin
SR Lord Nelson class
The SR class LN or Lord Nelson class is a type of 4-cylinder 4-6-0 steam locomotive designed for the Southern Railway by Richard Maunsell in 1926. They were intended for Continental boat trains between London and Dover harbour, but were later used for express passenger work to the South-West of England. Sixteen of them were constructed, they were all named after famous admirals. The class continued to operate with British Railways until withdrawn during 1961 and 1962. Only one example of the class – the first engine, Lord Nelson itself – has been saved from scrapping; this has been preserved railways throughout Britain. Although the improved ”King Arthur” class 4-6-0 locomotives were capable of the heaviest express passenger work between London and South-West England, there was a growth in demand for Continental traffic travelling via Dover and Folkestone. By the mid-1920s the Southern Railway Traffic Department wished to begin operating 500-long-ton express trains on these routes during peak periods.
These would require a more powerful locomotive, able to pull heavier loads at sustained speeds of 55 mph, so as not to impede the congested electrified lines around London. However, any enlargement of the existing 2-cylinder design was not possible due to weight restrictions imposed by the railway’s Civil Engineer. After examining the practice of other British railways, Richard Maunsell, the Chief Mechanical Engineer, secured agreement for a 4-cylinder design, with an improved boiler and Belpaire firebox; the drive would be divided between the front coupled axle for the inside cylinders and the middle coupled axle for the outside cylinders giving better weight distribution and reduced hammer blow. The new design was an inevitable compromise between the need for additional power and to keep the weight down to an acceptable limit. There were two unusual features of the design: the first of, the setting of the crank axles at 135°, rather than the standard 90° of other locomotive types; this design necessitated four sets of valve gear, gave rise to eight beats per revolution, rather than the usual four, designed to give a more draw on the fire and less chance of wheelslip when starting.
The second difference was that fire grate was in two sections, the rear portion was horizontal and the front sloped away sharply. The prototype E850 named Lord Nelson was ordered from Eastleigh railway works in June 1925 but production proceeded at Maunsell’s insistence, to ensure that the weight was kept to a minimum at every stage, so the locomotive did not appear until August 1926, it was tested on a variety of duties over the next year, with sufficiently encouraging results for an initial order for ten more locomotives for delivery between May 1928 and April 1929 to be placed. These were scheduled to be allocated to Battersea depot and fitted with 4,000 gallon 6-wheeled tenders suitable for the Continental ports. However, during construction, it was decided to equip half of the class with 5,000 gallon 8-wheeled tenders necessary for the longer West of England routes and to allocate them to Nine Elms depot. A further batch of ten locomotives was ordered in 1928, before the previous batch had been delivered, but when it became apparent that the Stock Market Crash of 1929 would be to reduce the demand for Continental travel, this second order was reduced to five.
The locomotives were all named after famous Royal Navy admirals, with the doyen of the class being named Lord Nelson. As a result, the rest of the locomotives belonged to the Lord Nelson class; the performance of the new locomotives was mixed, depending upon the experience of the crew and the circumstances under which they were operating. At times it was no better than their smaller predecessors. Maunsell therefore undertook a number of experiments to try to improve the performance of the new locomotives. No. E859 was fitted with smaller 6 ft 3 in driving wheels to see if this would improve performance over the graded London-Dover line, but the difference was marginal. No. E860 was fitted with a heavier boiler but once again with little improvement; the whole class however benefitted from the fitting of smoke deflectors during the late 1920s. Maunsell was aware of the reputation for poor steaming enjoyed by the class and attempted to address it by the fitting of twin Kylchap blastpipes to No. 860 in 1934.
However, the problem was solved by Oliver Bulleid, Maunsell's replacement as Chief Mechanical Engineer of the Southern in 1938. He fitted larger diameter chimneys and Lemaître multiple jet blastpipes, which transformed their performance. Thereafter the class was respected. For location details and current status of the preserved locomotive, see: List of Lord Nelson class locomotivesFor a period after its introduction to the Southern Railway network, the Lord Nelson class held the title of "most powerful locomotive in Britain" – a claim based on its tractive effort; the advanced design of the locomotive led to the GWR introducing the GWR 6000 Class in order to regain the title lost by their GWR Castle class locomotives when the Lord Nelsons were constructed. The planned 500-ton trains never materialised, but the class was used on 460 ton trains such as the Golden Arrow. After the Second World War they were frequently used on laden Boat Trains between London Waterloo station and Southampton docks.
The Lord Nelsons were notoriously difficult for inexperienced crews to fire properly, due to their long firebox, specific crews who had proven experience in firing the locomotives were therefore allocated to them. This was due to the few locomotives
Cast iron is a group of iron-carbon alloys with a carbon content greater than 2%. Its usefulness derives from its low melting temperature; the alloy constituents affect its colour when fractured: white cast iron has carbide impurities which allow cracks to pass straight through, grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks, ductile cast iron has spherical graphite "nodules" which stop the crack from further progressing. Carbon ranging from 1.8 to 4 wt%, silicon 1–3 wt% are the main alloying elements of cast iron. Iron alloys with lower carbon content are known as steel. While this technically makes the Fe–C–Si system ternary, the principle of cast iron solidification can be understood from the simpler binary iron–carbon phase diagram. Since the compositions of most cast irons are around the eutectic point of the iron–carbon system, the melting temperatures range from 1,150 to 1,200 °C, about 300 °C lower than the melting point of pure iron of 1,535 °C.
Cast iron tends to be brittle, except for malleable cast irons. With its low melting point, good fluidity, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications and are used in pipes and automotive industry parts, such as cylinder heads, cylinder blocks and gearbox cases, it is resistant to weakening by oxidation. The earliest cast-iron artifacts date to the 5th century BC, were discovered by archaeologists in what is now Jiangsu in China. Cast iron was used in ancient China for warfare and architecture. During the 15th century, cast iron became utilized for cannon in Burgundy, in England during the Reformation; the amounts of cast iron used for cannon required large scale production. The first cast-iron bridge was built during the 1770s by Abraham Darby III, is known as The Iron Bridge. Cast iron was used in the construction of buildings. Cast iron is made from pig iron, the product of smelting iron ore in a blast furnace.
Cast iron can be made directly from the molten pig iron or by re-melting pig iron along with substantial quantities of iron, limestone and taking various steps to remove undesirable contaminants. Phosphorus and sulfur may be burnt out of the molten iron, but this burns out the carbon, which must be replaced. Depending on the application and silicon content are adjusted to the desired levels, which may be anywhere from 2–3.5% and 1–3%, respectively. If desired, other elements are added to the melt before the final form is produced by casting. Cast iron is sometimes melted in a special type of blast furnace known as a cupola, but in modern applications, it is more melted in electric induction furnaces or electric arc furnaces. After melting is complete, the molten cast iron is poured into ladle. Cast iron's properties alloyants. Next to carbon, silicon is the most important alloyant. A low percentage of silicon allows carbon to remain in solution forming iron carbide and the production of white cast iron.
A high percentage of silicon forces carbon out of solution forming graphite and the production of grey cast iron. Other alloying agents, chromium, molybdenum and vanadium counteracts silicon, promotes the retention of carbon, the formation of those carbides. Nickel and copper increase strength, machinability, but do not change the amount of graphite formed; the carbon in the form of graphite results in a softer iron, reduces shrinkage, lowers strength, decreases density. Sulfur a contaminant when present, forms iron sulfide, which prevents the formation of graphite and increases hardness; the problem with sulfur is. To counter the effects of sulfur, manganese is added because the two form into manganese sulfide instead of iron sulfide; the manganese sulfide is lighter than the melt, so it tends to float out of the melt and into the slag. The amount of manganese required to neutralize sulfur is 1.7 × sulfur content + 0.3%. If more than this amount of manganese is added manganese carbide forms, which increases hardness and chilling, except in grey iron, where up to 1% of manganese increases strength and density.
Nickel is one of the most common alloying elements because it refines the pearlite and graphite structure, improves toughness, evens out hardness differences between section thicknesses. Chromium is added in small amounts to reduce free graphite, produce chill, because it is a powerful carbide stabilizer. A small amount of tin can be added as a substitute for 0.5% chromium. Copper is added in the ladle or in the furnace, on the order of 0.5–2.5%, to decrease chill, refine graphite, increase fluidity. Molybdenum is added on the order of 0.3–1% to increase chill and refine the graphite and pearlite structure. Titanium is added as a degasser and deoxidizer, but it increases fluidity. 0.15–0.5% vanadium is added to cast iron to stabilize cementite, increase hardness, increase resistance to wear and heat. 0.1–0.3% zirconium helps to form graphite and increase fluidity. In malleable iron melts, bismuth is added, on the scale of 0.002–0.01%, to increase how much silicon can be added. In white iron, boron is added to aid in the production of malleable iron.
LNER Class A4
The Class A4 is a class of streamlined 4-6-2 steam locomotive designed by Nigel Gresley for the London and North Eastern Railway in 1935. Their streamlined design gave them high-speed capability as well as making them recognisable, one of the class, 4468 Mallard, holds the world record as the fastest steam locomotive. Thirty-five of the class were built to haul express passenger trains on the East Coast Main Line route from London Kings Cross via York to Newcastle, via Newcastle to Edinburgh, Scotland, they remained in service on the East Coast Main Line until the early 1960s when they were replaced by Deltic diesel locomotives. Several A4s saw out their remaining days until 1966 in Scotland on the Aberdeen - Glasgow express trains, for which they were used to improve the timing from 3.5 to 3 hours. Gresley introduced the Class A4 locomotives in 1935 to haul a new streamlined train called the Silver Jubilee to run between London King's Cross and Newcastle; the new service was named in celebration of the 25th year of King George V's reign.
During a visit to Germany in 1933, Gresley had been inspired by the high-speed streamlined Flying Hamburger diesel trains, indeed the London and North Eastern Railway had considered purchasing similar trains for use from London to Newcastle. However, the diesel units of the time did not have the desired passenger carrying capacity and the capital investment in the new technology was prohibitive. Gresley was sure that steam could do the job well and with a decent fare-paying load behind the locomotive and so, following trials in 1935 with one of Gresley's A3 Pacifics No.2750 Papyrus, which recorded a new maximum of 108 mph and completed the journey in under four hours, the LNER's Chief General Manager Ralph Wedgwood took the initiative, authorising Gresley to produce a streamlined development of the A3. Four locomotives were built, all with the word'silver' as part of their names; the first was 2509 Silver Link, followed by 2510 Quicksilver, 2511 Silver King and 2512 Silver Fox. During a press run to publicise the service, Silver Link twice achieved a speed of 112.5 mph, breaking the British speed record and sustained an average of 100 mph, over a distance of 43 mi.
Following the commercial success of the Silver Jubilee train, other streamlined services were introduced: The Coronation and the West Riding Limited for which more A4s were specially built. The A4 Pacifics were designed for high-speed passenger services; the application of internal streamlining to the steam circuit, higher boiler pressure and the extension of the firebox to form a combustion chamber all contributed to a more efficient locomotive than the A3. A further improvement to the design was the fitting of a Kylchap double-chimney first introduced on 4468 Mallard, built in March 1938; this device improved the capability of the locomotives further, the final three locomotives of the class were fitted with the Kylchap exhaust from new. The rest of the class acquired it in the late 1950s; this class was noted for its streamlined design, which not only improved its aerodynamics, thus increasing its speed capabilities, but created an updraught to lift smoke away from the driver's vision, a problem inherent in many steam locomotives those operated with short cut off valve events, smoke deflectors being an alternative answer to the same problem.
The distinctive design made it a attractive subject for artists and film-makers. The A4 Class locomotives were known affectionately by train spotters as "streaks"; the streamlining side skirts that were designed by Oliver Bulleid to aerofoil shape, fitted to all the A4 locomotives, were removed during the Second World War to improve access to the valve gear for maintenance and were not replaced. This apart, the A4 was one of few streamlined steam locomotive designs in the world to retain its casing throughout its existence. Many similar designs, including the contemporary Coronation class, had their streamlining removed or cancelled to cut costs, simplify maintenance and increase driver visibility. On 3 July 1938 4468 Mallard. However, Gresley never accepted this as the record-breaking maximum, he claimed this speed could only have been attained over a few yards, though he was comfortable that the German speed record of 124.5 mph had been surpassed. Close analysis of the dynamometer roll of the record run confirms that Mallard's speed did in fact exceed that of the German BR 05 002.
The Mallard record reached its maximum speed on a downhill run and failed technically in due course, whereas 05 002's journey was on level grade and the engine did not yet seem to be at its limit. On the other hand, the German train was only four coaches long, but Mallard's train was seven coaches. One fact, ignored when considering rival claims is that Gresley and the LNER had just one serious attempt at the record, far from a perfect run with a 15 mph permanent way check just North of Grantham. Despite this a record was set. Gresley planned to have another attempt in September 1939, but this was prevented by the outbreak of World War II. Prior to the record run on 3 July 1938, it was calculated that 130 mph was possible, in fact Driver Duddington and LNER Inspector Sid Jenkins both said they might well hav
GWR 4900 Class
The Great Western Railway 4900 Class or Hall Class is a class of 4-6-0 mixed traffic steam locomotives designed by Charles Collett. A total of 259 were built, numbered 4900–4999, 5900–5999 and 6900–6958; the LMS Stanier Class 5 4-6-0 and LNER Thompson Class B1 both drew on design features of the Hall Class. After nationalisation in 1948, British Railways gave them the power classification 5MT. By the end of 1923 the GWR was well served with express passenger locomotives of the Saint and Star classes and had introduced the Castle Class; however the mixed traffic 2-6-0 locomotives of the 4300 Class were beginning to struggle with the increasing loads. George Jackson Churchward had recognised this with the introduction of the 4700 class 2-8-0 with 5 ft 8 in driving wheels, intended for express goods and relief passenger trains. However, Collett preferred the idea of a Saint Class with smaller wheels to undertake these duties as this would provide a leading bogie, he therefore rebuilt number 2925 Saint Martin with 6 ft driving wheels.
The prototype of the new class was rebuilt in 1924 and the cylinders were realigned in relation to the driving axle and a more modern'Castle'-type cab was fitted. Saint Martin embarked on three years of trials. During this period Collett introduced other modifications such a changing the pitch of the taper boiler and adding outside steam pipes. After extensive trials during 1925-1927, Collett was satisfied with the performance of his prototype, subject to minor amendments and placed an order for eighty more with Swindon works in 1928; the prototype was renumbered 4900 in December 1928 and the new locomotives were numbered 4901-80 and appeared at regular intervals until February 1930. They were named after English and Welsh country houses with'Hall' in their titles and so became known as the'Hall Class', they differed little from the prototype. The overall weight of the locomotive had increased by 2 long tons 10 cwt to 75 long tons 0 cwt but a tractive effort of 27,275 lbf compared favourably with the 24,935 lbf of the'Saint'.
The original locomotives were built with Churchward 3,500 imp gal tenders but after 4958 Collett's larger 4,000 imp gal types became standard although a few locomotives were fitted with smaller tenders if these were available as they entered service. The first fourteen examples were despatched to the arduous proving grounds of the Cornish main line, they were so successful here and elsewhere on the GWR system that by the time the first production batch had been completed a further twenty were on order. Further orders followed throughout early 1940s. By 1935, 150 were in service and the 259th and last Hall, No. 6958 Oxburgh Hall, was delivered in 1943. Thereafter further deliveries were of the'6959 Modified Hall' class; as indicated by their continuing production, the Hall class proved to be successful in a variety of different roles, although barred from several cross-country and branch lines because of their red weight classification. According to Peter Herring,'they were the first true mixed traffic locomotives, as such precursors of the Stanier'Black Five', Thompson B1 and BR Standard 5MT 4-6-0.'
Although the GWR had been at the forefront of British locomotive development between 1900 and 1930, the 1930s saw a degree of complacency at Swindon reflected in the fact that the design had originated in the 1900s and had not fundamentally changed since the mid 1920s. Collett was replaced by F. W. Hawksworth in 1941 who created a modified version of the design, known as the Modified Hall Class; these remained in production under British Railways until 1950, by which time there were a further seventy-one locomotives. On 30 April 1941, Locomotive No. 4911 Bowden Hall took a direct hit during a bombing raid on the Keyham area of Plymouth and was broken up. The locomotive had stopped at a signal box because of an air raid, the crew survived by sheltering under the steps of the signal box. No. 4911 was one of two GWR locomotives damaged beyond repair in Britain during World War II. The other was GWR 1854 Class No. 1729. At the same time, the locomotive's relative, 4936 Kinlet Hall, accidentally ran into a bomb crater in that area and was damaged, but it was repaired into service and acquired by the Woodham Brothers in the early 1960s.
On 13 February 1961, Locomotive No. 6949 Haberfield Hall was in collision with a freight train, being shunted at Baschurch, Shropshire due to a signalman's error. Three people were killed and two were injured. On 25 August 1962, a passenger train stopped at Torquay, Devon due to the failure of the locomotive hauling it. Locomotive No. 4932 Hatherton Hall was hauling a passenger train that overran signals and was in a rear-end collision with it. Twenty-three people were injured. All but one of the original Collett Halls entered British Railways service in 1948, the exception being No. 4911 Bowden Hall. Official withdrawals began in 1959 with the prototype Saint Martin, its accumulated mileage, both in its original form and rebuilt form, was a remarkable 2,092,500 miles. Further withdrawals of the production series took place during the 1960s and the class was extinc
LMS Coronation Class
The London Midland and Scottish Railway Coronation Class is a class of express passenger steam locomotives designed by William Stanier. They were an improved version of his previous design, the LMS Princess Royal Class; the locomotives were designed for power as it was intended to use them on express services between London Euston and Glasgow Central. The first ten locomotives of the Coronation class were built in a streamlined form in 1937 by the addition of a steel streamlined casing. Five of these ten were set aside to pull the Coronation Scot. Although a batch of five unstreamlined locomotives was produced in 1938, most of the ensuing Coronation class were outshopped as streamliners. From 1944 to 1949, all new engines would be built in unstreamlined form and all the streamliners would have their casings removed; the last of the 38 locomotives was completed in 1948. The Coronation class was painted in more styles of livery than any other engine class, seven in the LMS era up to 1947 and five more during the British Railways era from 1948 onwards.
That does not mean. The only style that all 38 bore was the British Railways lined Brunswick Green and the entire class was turned out thus between 1955 and 1958, it was customary on all British mainline journeys to change engines at convenient locations to avoid the lengthy process of re-coaling. The Coronation locomotives were therefore strategically stationed at key points between London and Glasgow and they would be assigned to the shed at that location; the chosen locations were at London, Crewe and Glasgow. It was only in the latter days of steam. Whilst the Coronation class was represented at the 1948 British Railways locomotive exchange trials, designed to compare the performances of similar locomotives from all four of the pre-nationalised companies, the representative engine performed disastrously. Gone was any hint of the power. If the trials were forgettable, other achievements of the class are memorable. Firstly, No. 6220 Coronation held the British steam speed record between 1937 and 1939.
Secondly, No. 6234 Duchess of Abercorn holds the record to this day for the greatest British power output to be recorded on an attached dynamometer car, achieved in 1939. The most memorable event in the history of the class was the Harrow and Wealdstone rail crash precipitated by 46242 City of Glasgow; this was the second worst rail crash in British history, the death toll being 112. After a successful decade of operations in the 1950s, the 1960s' modernisation plan was the ultimate undoing of the Coronations. Not only did the increasing use of diesel locomotives make many of the class redundant, but the electrification of the main line between London Euston and Crewe resulted in their banishment from this important section of the main line as there was insufficient clearance between the locomotives and the live wires. With no useful role to play, the survivors were scrapped en masse in late 1964. Three locomotives were saved for preservation; as at October 2016, two are static in museums whilst the third is certificated for main line service Although the prior introduction of the Princess Royal class had provided the London Midland and Scottish Railway with more powerful locomotives to be used on the main line between London Euston and Glasgow Central, the board of directors were persuaded in 1936 that more such locomotives would be needed as they were being asked to approve the introduction of a new non-stop service between those cities, designated the Coronation Scot.
The Chief Mechanical Engineer, William Stanier, planned to build five more Princess Royals, but the Chief Technical Assistant and Chief Draughtsman at the LMS Derby Works, Tom Coleman, argued that it would be preferable to design a new class of locomotive, more powerful, more reliable and easier to maintain. Stanier was convinced and the drawing office commenced designing the new class; when Stanier was called on to perform an assignment in India, Coleman became responsible for most of the detailed design in his absence. Compared to the Princess Royal Class, there were important differences which would lead to an improved performance. Increased power was obtained by adopting a bigger boiler with greater steam-raising capacity. In order to allow higher speeds, the diameter of the driving wheels was increased to 6 ft 9 in and the cylinder diameters were increased by 1⁄4 in; the outside cylinders were moved forward with rocking shafts operating the inside cylinders. Just as the new design was approaching finalisation, the LMS marketing department created a problem, close to being insurmountable.
The London & North Eastern Railway had introduced its streamlined Class A4 locomotive which had captured the imagination of the public, the marketing department persuaded the board that the LMS's new locomotives should be streamlined too. This was problematic in that t
The slide valve is a rectilinear valve used to control the admission of steam into, emission of exhaust from, the cylinder of a steam engine. In the 19th century, most steam locomotives used slide valves to control the flow of steam into and out of the cylinders. In the 20th century, slide valves were superseded by piston valves in engines using superheated steam. There were two reasons for this: With piston valves, the steam passages can be made shorter; this improves efficiency. It is difficult to lubricate slide valves adequately in the presence of superheated steam; the D slide valve, or more Long D slide valve, is a form of slide valve, invented by William Murdoch and patented in 1799. It is named after the hollow central D-sectioned piston; this valve worked by "connecting the upper and lower valves so as to be worked by one rod or spindle, in making the stem or tube which connects them hollow, so as to serve for an induction pipe to the upper end of the cylinder." This allowed two valves to do the work of four.
The above description relates to an engine with a vertical cylinder, such as a beam engine. Where the cylinders are horizontal, as in a steam locomotive, the valves would be side-by-side; the balanced slide valve was invented by the Scottish engineer Alexander Allan. It was not much used in the UK but, at one time, had great popularity in the United States, it gave some of the advantages of a piston valve to a slide valve by relieving the pressure on the back of the valve, thus reducing friction and wear. The Slide Valve