Table Bay Harbour 0-4-0T
The Table Bay Harbour 0-4-0T of 1874 was a South African steam locomotive from the pre-Union era in the Cape of Good Hope. In 1847, the government of the Cape of Good Hope established harbour boards at its three major ports, Table Bay, Port Elizabeth and East London. While railway lines were laid at all these harbours, trains were for the most part hauled by oxen or mules. Altogether seven 7 ft 1⁄4 in Brunel gauge locomotives are known to have been employed on the Table Bay Harbour project between 1862 and 1904; the first steam locomotive to see service at any of these harbours was a Brunel gauge engine, placed in service on breakwater construction at Table Bay Harbour in 1862. The third Table Bay harbour construction locomotive was this 0-4-0 side-tank engine which entered service in 1874; when the need for improved harbour facilities for the handling of ships and cargoes became apparent, the Cape Government established harbour boards at Table Bay, Port Elizabeth and East London in 1847. Each board consisted of five members increased to seven.
They were responsible for the management, improvement and maintenance of the facilities at these ports, empowered to levy wharfage dues. While Table Bay itself was a poor natural harbour, badly exposed to the Cape's notorious gale force Southeasters and Northwesters, it was preferred by early seafarers over the more suitable Saldanha Bay to the north and Simon's Town in False Bay because of the lack of fresh water at the latter two; as a result, the Mother City of Cape Town came to be. As Cape Town expanded, so did ship's traffic in Table Bay Harbour, but the inadequacy of its facilities resulted in considerable delays and also in loss of life and cargoes; the urgent necessity of harbour improvements began to be recognised upon the arrival of the first steam ship, the Enterprise, in Table Bay in October 1825. As at the Port Elizabeth and East London harbours, railway lines were an early feature at Table Bay Harbour. Work to improve the facilities at the harbour was started in 1860, using convict labour, consisted of the excavation of two basins and the construction of breakwater piers.
The first truckload of construction rocks to start the building of the breakwater was tipped on 17 September 1860 by Prince Alfred, the sixteen-year-old son of Queen Victoria. The Alfred Basin, named after the prince, was completed in 1870. A number of heavy iron railway tip-wagons were acquired to convey the rock to create the breakwater, they ran on 7 ft 1⁄4 in Brunel gauge track, to make it easier to drop rock from the wagons between the rails. The construction track was run out to sea on a timber framework, a method of construction, perfected by Sir John Coode; the wagons were hauled by either oxen or mules. Seven Brunel gauge locomotives are known to have been employed on the Table Bay Harbour project, but information on most of them are sketchy at best. Two locomotives were placed in service before 1874, one in 1862 and another at some stage before 19 July 1870, it is known that one of them was a 0-4-0 saddle-tank engine built by Hughes's Locomotive & Tramway Engine Works, while there is no knowledge about the builder or appearance of the other and no known photograph of either one has been found.
While early researchers believed that the first locomotive of 1862 was the one built by Hughes's, recent research seems to indicate that Hughes's first known locomotive was only delivered to the Carmarthen and Cardigan Railway in Wales in September 1863. It may therefore be; the first locomotive arrived on the ship Navarino on 2 October 1862. There is no known photograph of it, no information about either the builder or the tank configuration have been found. A painting by Otto Lansberg which depicts the breakwater under construction in 1869, shows a side- or well-tank locomotive at work and, since the second locomotive is known to have been a saddle-tank engine, this painting may well depict the first locomotive. Given the possibility of artistic licence, the painting cannot be accepted as factual confirmation of the locomotive's appearance or configuration. Reference to a second locomotive was made in a report in the Cape Argus on 19 July 1870, in which it was mentioned as "the first locomotive made in South Africa" while the activities were described as "wagons that were hauled along several lines of railway by two engines".
It was a 0-4-0 saddle-tank locomotive, now believed to have been built by Henry Hughes and Company, shipped to the Cape as a kit of parts to be assembled by the customer. Since Hughes's works started building locomotives around 1863, it would follow that the in-service date of the second locomotive was at some time between 1863 and 1870; the third locomotive to enter service at Table Bay Harbour, the 0-4-0 side-tank engine, the subject of this page, was obtained from Fletcher, Jennings & Co. in 1874. Apart from the photograph, not much is known about the locomotive, which had a cab roof with a spectacle plate front weatherboard to offer the crew some protection from the elements. In Harbour Board minutes at the time, one of the earlier two locomotives was now referred to as the "spare locomotive"; the fourth locomotive to enter service on the Table Bay harbour project was the 0-4-0WT of 1879 built by Fletcher, Jennings. Two Brunel gauge 0-4-0ST locomotives were placed in service on the Table Bay Harbour project in 1881, built by Black, Hawthorn & Co.
Another one was delivered in 1893, with works number 1079. These three locomotives bore engine numbers 4, 5 and 8. Work on the project continued into the 20th century, since further harbour expansion soon became necessary, brought about by developments in the interior
Germiston
Germiston is a small city in the East Rand region of Gauteng, South Africa, administratively forming part of the City of Ekurhuleni Metropolitan Municipality since the latter's establishment in 2000. It functions as the municipal seat of Ekurhuleni, hosting the municipal administration, it was established in the early days of the gold rush when two prospectors, John Jack from the farm of Germiston near Glasgow and August Simmer from Vacha in Germany, struck paydirt on the farm of Elandsfontein. In August 1887, the pair were on their way to the Eastern Transvaal when they outspanned on the farm Elandsfontein and decided to stay and buy the land. Both men made fortunes and the town sprang up 2 km from the Simmer and Jack mine named after Jack's fathers farm. In 1921 the world's largest gold refinery, the Rand Refinery, was established at Germiston. Seventy percent of the western world's gold passes through this refinery. Although gold mining wound down in Germiston, to the point that by the end of the 20th century it was no longer a mining centre, the Rand Refinery remains as busy as ever.
The city has a number of historic buildings. Among these are the St Andrew's Presbyterian Church, built in 1905, St Boniface Church designed by Sir Herbert Baker, built in 1910; the church houses the historic 1910 English Romantic Norman and Beard Organ. The Alexander Hotel was partly designed by Baker, using his traditional stone appearance; this building has been renovated and now houses a well-known law firm. The builder of the hotel, Alexander Stuart, some of whose descendants still live in Germiston, died when the RMS Lusitania was torpedoed in the First World War on 7 May 1915; the hotel thus remains a memorial to his pioneer work in the city over a hundred years ago. According to the 2001 census, the population of Germiston consisted of 139,719 people living in 49,062 households, its land area was 129 square kilometres. Of this population, 49.8% described themselves as "White", 46.8% as "Black African", 1.9% as "Coloured", 1.5% as "Indian or Asian". No language was predominant, with the breakdown of first languages being as follows: South African Airways moved its head office from Durban to Rand Airport in Germiston on 1 July 1935.
It moved the offices first to Johannesburg to Kempton Park. The city is an industrial centre with steel manufacture and distribution being the largest industries, it has large railway workshops, a large glassworks, engineering companies, gas distribution firms, many other heavy and light industries. Victoria Lake is better known today as Germiston Lake, the famous Sailing and Rowing Club retains the name of the Victoria Lake Club; the club is home to some of the best canoeists and rowing crews in the country, including the twenty-time South African School Champions, St Benedict's College. The lake is popular at weekends for water-skiing and regattas; the lake grounds have been re-landscaped and the braai areas and shelters rebuilt. The WesBank Raceway motorsports facility was located in the city, but it was sold to industrial estate developers in November 2007; the Raceway was the Gosforth Park Race Club, one of the major horse racing facilities in Gauteng. Germiston Stadium, home stadium of Moroka Swallows FC is located in the city.
This is the home ground for the Germiston Simmer Rugby Club and has a tartan track for athletics. Municipal By 1931, the Germiston municipality had assumed a pseudo-heraldic coat of arms, depicting buck in the veld, a scene showing mineshafts, a railway train in a landscape, a half-tented ox-wagon in a landscape, the quarters separated by a red cross; the motto was Salus populi suprema lex. Municipal A proper coat of arms was granted by the College of Arms in August 1935, it was registered with the Transvaal Provincial Administration in August 1963 and at the Bureau of Heraldry in February 1968. The arms were three bezants; the crest was a rising falcon. Germiston is well connected to five mayor freeways or motorways that service the Greater Johannesburg region; these include to the west of Germiston, the M2 motorway that connects the southern Johannesburg CBD, the N3 Eastern Bypass, the N12 South. On the southern side, the N17 and N3 and in the north, the N12 East and the R24 service the city.
Being a mining and industrial city, Germiston is serviced by passenger rail and the CBD has several stations, the main one being Germiston Station. The industrial areas are service by rail spurs and stations and the Transnet has a large depot north of the CBD in Keswick Road. Germiston is the location of Rand Airport, at one time one of the busiest in Africa and the southern hemisphere. Today it caters for light aircraft and flying schools, but is home to the South African Airways Museum; as a result of this, two of the earlier Boeing 747 Jumbo aircraft used by SAA now reside there on permanent display. Germiston is served by a public state hospital. Other private hospitals include Life Roseacres Hospital in Primrose. There are a number of schools in the city; the oldest high school in
Distinguished Service Order
The Distinguished Service Order is a military decoration of the United Kingdom, of other parts of the Commonwealth, awarded for meritorious or distinguished service by officers of the armed forces during wartime in actual combat. Since 1993 all ranks have been eligible. Instituted on 6 September 1886 by Queen Victoria in a Royal Warrant published in The London Gazette on 9 November, the first DSOs awarded were dated 25 November 1886; the order was established to reward individual instances of meritorious or distinguished service in war. It was a military order, until for officers only, awarded to officers ranked major or higher, with awards to ranks below this for a high degree of gallantry, just short of deserving the Victoria Cross. While given for service under fire or under conditions equivalent to service in actual combat with the enemy, a number of awards made between 1914 and 1916 were under circumstances not under fire to staff officers, causing resentment among front-line officers.
After 1 January 1917, commanders in the field were instructed to recommend this award only for those serving under fire. From 1916, ribbon bars could be authorised for subsequent awards of the DSO, worn on the ribbon of the original award. In 1942, the award was extended to officers of the Merchant Navy who had performed acts of gallantry while under enemy attack. A requirement that the order could be given only to someone mentioned in despatches was removed in 1943. Since 1993, reflecting the review of the British honours system which recommended removing distinctions of rank in respect of operational awards, the DSO has been open to all ranks, with the award criteria redefined as'highly successful command and leadership during active operations'. At the same time, the Conspicuous Gallantry Cross was introduced as the second highest award for gallantry. Despite some fierce campaigns in Iraq and Afghanistan, the DSO has yet to be awarded to a non-commissioned rank; the DSO had been awarded by Commonwealth countries but by the 1990s most, including Canada and New Zealand, were establishing their own honours systems and no longer recommended British honours.
Recipients of the order are known as Companions of the Distinguished Service Order, are entitled to use the post-nominal letters "DSO". All awards are announced in the London Gazette; the medal signifying the award of the DSO is a silver-gilt cross with curved ends, 1.6 in wide, enamelled white and edged in gilt. It is manufactured by the Crown Jewellers. In the centre of the obverse, within a green enamelled laurel wreath, is the imperial crown in gold upon a red enamelled background; the reverse has the royal cypher of the reigning monarch in gold within a similar wreath and background. A ring at the top of the medal attaches to a ring at the bottom of a gilt suspension bar, ornamented with laurel. Since 1938 the year of award engraved on the back of the suspension bar. At the top of the ribbon is a second gilt bar ornamented with laurel; the medals are issued unnamed but some recipients have had their names engraved on the reverse of the suspension bar. The red ribbon is 1.125 in wide with narrow blue edges.
The bar for an additional award is plain gold with an Imperial Crown in the centre. Since about 1938, the year of the award has been engraved on the back of the bar. A rosette is worn on the ribbon in undress uniform to signify the award of each bar. From 1918 to 2017 the insignia of the Distinguished Service Order has been awarded 16,935 times, in addition to 1,910 bars; the figures to 1979 are laid out in the table below, the dates reflecting the relevant entries in the London Gazette: In addition, between 1980 and 2017 90 DSOs have been earned, including awards for the Falklands and the wars in the Gulf and Afghanistan, in addition to three second-award bars. The above figures include awards to the Commonwealth:In all, 1,220 DSOs have gone to Canadians, plus 119 first bars and 20 second bars. From 1901 to 1972, when the last Australian to receive the DSO was announced, 1,018 awards were made to Australians, plus 70 first bars and one second bar; the DSO was awarded to over 300 New Zealanders during the two World Wars.
Honorary awards to members of allied foreign forces include at least 1,329 for World War I, with further awards for World War II. The following received the DSO and three bars: Archibald Walter Buckle, rose from naval rating in the Royal Naval Volunteer Reserve to command the Anson Battalion of the Royal Naval Division during the First World War William Denman Croft, First World War army officer William Robert Aufrere Dawson, Queen's Own Royal West Kent Regiment during the First World War, wounded nine times and mentioned in despatches four times Basil Embry, Second World War Royal Air Force officer Bernard Freyberg awarded the Victoria Cross Edward Albert Gibbs, Second World War destroyer captain Arnold Jackson, First World War British Army officer and 1500 metres Olympic gold medal winner in 1912 Douglas Kendrew, served as a brigade commander in Italy and the Middle East between 1944 and 1946. Subsequently appointed Governor of Western Australia. Robert Sinclair Knox, First World War British Army officer Frederick William Lumsden, British First World War Army officer awarded the Victoria Cross Paddy Mayne, Special Air Service commander in the Second World War and Irish rugby player Sir Richard George Onslow, Second World War destroyer captain and admiral Alastair Pearson, a British Army officer who received his four awards within the space of two years during the Second World War James Brian Tait, RAF pilot awarded the DFC and bar, completed
Track gauge
In rail transport, track gauge or track gage is the spacing of the rails on a railway track and is measured between the inner faces of the load-bearing rails. All vehicles on a rail network must have running gear, compatible with the track gauge, in the earliest days of railways the selection of a proposed railway's gauge was a key issue; as the dominant parameter determining interoperability, it is still used as a descriptor of a route or network. In some places there is a distinction between the nominal gauge and the actual gauge, due to divergence of track components from the nominal. Railway engineers use a device, like a caliper, to measure the actual gauge, this device is referred to as a track gauge; the terms structure gauge and loading gauge, both used, have little connection with track gauge. Both refer to two-dimensional cross-section profiles, surrounding the track and vehicles running on it; the structure gauge specifies the outline into which altered structures must not encroach.
The loading gauge is the corresponding envelope within which rail vehicles and their loads must be contained. If an exceptional load or a new type of vehicle is being assessed to run, it is required to conform to the route's loading gauge. Conformance ensures. In the earliest days of railways, single wagons were manhandled on timber rails always in connection with mineral extraction, within a mine or quarry leading from it. Guidance was not at first provided except by human muscle power, but a number of methods of guiding the wagons were employed; the spacing between the rails had to be compatible with that of the wagon wheels. The timber rails wore rapidly. In some localities, the plates were made L-shaped, with the vertical part of the L guiding the wheels; as the guidance of the wagons was improved, short strings of wagons could be connected and pulled by horses, the track could be extended from the immediate vicinity of the mine or quarry to a navigable waterway. The wagons were built to a consistent pattern and the track would be made to suit the wagons: the gauge was more critical.
The Penydarren Tramroad of 1802 in South Wales, a plateway, spaced these at 4 ft 4 in over the outside of the upstands. The Penydarren Tramroad carried the first journey by a locomotive, in 1804, it was successful for the locomotive, but unsuccessful for the track: the plates were not strong enough to carry its weight. A considerable progressive step was made. Edge rails required a close match between rail spacing and the configuration of the wheelsets, the importance of the gauge was reinforced. Railways were still seen as local concerns: there was no appreciation of a future connection to other lines, selection of the track gauge was still a pragmatic decision based on local requirements and prejudices, determined by existing local designs of vehicles. Thus, the Monkland and Kirkintilloch Railway in the West of Scotland used 4 ft 6 in; the Arbroath and Forfar Railway opened in 1838 with a gauge of 5 ft 6 in, the Ulster Railway of 1839 used 6 ft 2 in Locomotives were being developed in the first decades of the 19th century.
His designs were so successful that they became the standard, when the Stockton and Darlington Railway was opened in 1825, it used his locomotives, with the same gauge as the Killingworth line, 4 ft 8 in. The Stockton and Darlington line was immensely successful, when the Liverpool and Manchester Railway, the first intercity line, was built, it used the same gauge, it was hugely successful, the gauge, became the automatic choice: "standard gauge". The Liverpool and Manchester was followed by other trunk railways, with the Grand Junction Railway and the London and Birmingham Railway forming a huge critical mass of standard gauge; when Bristol promoters planned a line from London, they employed the innovative engineer Isambard Kingdom Brunel. He decided on a wider gauge, to give greater stability, the Great Western Railway adopted a gauge of 7 ft eased to 7 ft 1⁄4 in; this became known as broad gauge. The Great Western Railway was successful and was expanded and through friendly associated companies, widening the scope of broad gauge.
At the same time, other parts of Britain built railways to standard gauge, British technology was exported to European countries and parts of North America using standard gauge. Britain polarised into two areas: those that used standard gauge. In this context, standard gauge was referred to as "narrow gauge" to indicate the contrast; some smaller concerns selected other non-standard gauges: the Eastern Counties Railway adopted 5 ft. Most of them converted to standard gauge at an early date, but the GWR's broad gauge continued to grow; the larger railway companies wished to expand geographically, large areas were considered to be under their control. When a new
Whyte notation
The Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte, came into use in the early twentieth century following a December 1900 editorial in American Engineer and Railroad Journal. The notation counts the number of leading wheels the number of driving wheels, the number of trailing wheels, numbers being separated by dashes. Other classification schemes, like UIC classification and the French and Swiss systems for steam locomotives, count axles rather than wheels. In the notation a locomotive with two leading axles in front three driving axles and one trailing axle is classified as 4-6-2, is known as a Pacific. Articulated locomotives such as Garratts, which are two locomotives joined by a common boiler, have a + between the arrangements of each engine, thus a "double Pacific" type Garratt is a 4-6-2+2-6-4. For Garratt locomotives the + sign is used when there are no intermediate unpowered wheels, e.g. the LMS Garratt 2-6-0+0-6-2. This is because the two engine units are more than just power bogies.
They are complete engines, carrying fuel and water tanks. The + sign represents the bridge that links the two engines. Simpler articulated types such as Mallets have a jointed frame under a common boiler where there are no unpowered wheels between the sets of powered wheels; the forward frame is free to swing, whereas the rear frame is rigid with the boiler. Thus a Union Pacific Big Boy is a 4-8-8-4; this numbering system is shared by duplex locomotives, which have powered wheel sets sharing a rigid frame. No suffix means a tender locomotive. T indicates a tank locomotive: in European practice, this is sometimes extended to indicate the type of tank locomotive: T means side tank, PT pannier tank, ST saddle tank, WT well tank. T+T means a tank locomotive that has a tender. In Europe, the suffix R can signify rack or reversible, the latter being Bi-cabine locomotives used in France; the suffix F indicates a fireless locomotive. This locomotive has no tender. Other suffixes have been used, including ng for narrow-gauge and CA or ca for compressed air.
In Britain, small diesel and petrol locomotives are classified in the same way as steam locomotives, e.g. 0-4-0, 0-6-0, 0-8-0. This may be followed by D for diesel or P for petrol, another letter describing the transmission: E for electric, H hydraulic, M mechanical. Thus, 0-6-0DE denotes a six-wheel diesel locomotive with electric transmission. Where the axles are coupled by chains or shafts or are individually driven, the terms 4w, 6w or 8w are used. Thus, 4wPE indicates a four-wheel petrol locomotive with electric transmission. For large diesel locomotives the UIC classification is used; the main limitation of Whyte Notation is that it does not cover non-standard types such as Shay locomotives, which use geared trucks rather than driving wheels. The most used system in Europe outside the United Kingdom is UIC classification, based on German practice, which can define the exact layout of a locomotive. In American practice, most wheel arrangements in common use were given names, sometimes from the name of the first such locomotive built.
For example, the 2-2-0 type arrangement is named Planet, after the 1830 locomotive on which it was first used. The most common wheel arrangements are listed below. In the diagrams, the front of the locomotive is to the left. AAR wheel arrangement Swiss locomotive and railcar classification UIC classification Wheel arrangement Boylan, Richard. "American Steam Locomotive Wheel Arrangements". SteamLocomotive.com. Retrieved 2008-02-08. Media related to Whyte notation at Wikimedia Commons
Springs, Gauteng
Springs is a main place, independent town, in the east of Ekurhuleni in the Gauteng province of South Africa. It lies 72 km southeast from Pretoria; the name of Springs derives from the large number of springs in the area. Springs was divided during the Apartheid era into the middle- and upper-income white suburbs around the city centre, the Indian area of Bakerton east of the CBD, while black people were relocated to KwaThema, southwest of the CBD; the city of Springs, east of Johannesburg, is on the East Rand, or what is now known as the Metropolitan area of Ekurhuleni, in the Gauteng Province. It was founded as a coal and gold mining town in 1904, but its history can be traced back to the second half of the 19th century. From about 1840 farmers moved into the area and declared farms for themselves after the Zuid-Afrikaansche Republiek became an independent republic with the signing of the Sand River Convention in 1852; these initial farms were large, but the measurements of the borders were inaccurate and when the correct borders of the farms had to be documented, there were several extra or odd pieces of land that did not belong to any farm.
These odd pieces of land became state property. Such an odd piece existed between three neighbouring farms on the Witwatersrand, namely Geduld, De Rietfontein and Brakpan; the 685 ha odd piece was given the name'The Springs' by the land surveyor James Brooks because of all the fountains on the land. Another story is that he wanted to name it after himself, but because his name resembled the Afrikaans word'broek' so he feared that the Afrikaans farmers in the area would mock it. On 16 September 1884 the official map of The Springs was registered in Pretoria, the Republic's capital; the land's value was equal to R200. But the discovery of coal and gold and its subsequent mining increased the value considerably; the coal discovered in The Springs was of a good quality and in 1888 the first contract was signed to mine coal there. Mining was on a small scale, but rose when the Great Eastern mine was established. There were a number of corrugated iron houses around the mine and, although there was a few small hotels and general dealers, it was not a town yet.
The settlement grew and in 1902 a health committee was appointed to look after the building and location of structures and the hygiene in the growing township. In 1904 the Grootvlei Proprietary Mines were registered and shafts were sunk; this followed the discovery in 1899 of gold on the farm Geduld and the further discovery of the main reef in 1902. In April 1904 The Springs was proclaimed a town, called Springs, the health committee replaced by a town council, it flourished as a mining town. In 1962, Springs produced 9 % of its uranium. However, by the end of the 1960s the last mine in town, the Daggafonteinmyn, was emptied; the town instead developed into an industrial centre. The original 7 km² farm on which the city of Springs was to be built, The Springs, was surveyed in 1883. Coal was discovered in the area in 1887 and three years in 1890-1891, the Transvaal Republic's first railway, the Randtram Line, was built by the Netherlands-South African Railway Company to carry coal from the East Rand coalfields to the gold mines of the Witwatersrand.
After coal was discovered further east in South Africa in Witbank, the Springs collieries were closed. In the meanwhile, gold had been discovered in the area. A village was laid out in 1904 and in 1908 the first gold mining began. Springs was granted municipal status in 1912. By the late 1930s, there were eight gold mines near Springs, making it the largest single gold-producing area in the world. Springs is one of the industrial centers of the Witwatersrand and the Eastern Gateway of Gauteng towards Mpumalanga and Northern Kwazulu Natal. Mining has been replaced by engineering industries of economic importance. Although Springs is a industrial city, its suburbs are treelike with many parks and giving some suburban character; the following are the main suburbs of Springs: Today, Springs is well known for its architecture: it has the second largest collection of small scale Art Deco buildings in the world, after Miami in Florida, in the United States. These Art Deco buildings were constructed during the period between the two World Wars.
Other landmarks include several monuments to important figures in the city's development, like Paul Kruger, the war cemetery where many Coloured soldiers are buried who died during the Second World War fighting in the Allied Forces. There is the War Monument at the northern entrance of the Springs CBD, The Old Springs Fire Station, the Dutch Windmill in the Pioneer Park, Springs. There is a small scale replica of the Voortrekker Monument in the Springs CBD near the library. Springs has an art gallery next to the Springs Library. At the entrance of the Springs Railway station there is an old orange tree planted by the Dutch people when Queen Wilhelmina of the Netherlands visited the old South African Republic accompanied by the South African president Paul Kruger. Many theatrical productions are performed at the Springs Civic Theater; the Springs Civic Centre and City Hall is a unique building complex as it rested on hey logs with water underneath. The Springs Fire
Valve gear
The valve gear of a steam engine is the mechanism that operates the inlet and exhaust valves to admit steam into the cylinder and allow exhaust steam to escape at the correct points in the cycle. It can serve as a reversing gear, it is sometimes referred to as the "motion". In the simple case, this can be a simple task as in the internal combustion engine in which the valves always open and close at the same points; this is not the ideal arrangement for a steam engine, because greatest power is achieved by keeping the inlet valve open throughout the power stroke while peak efficiency is achieved by only having the inlet valve open for a short time and letting the steam expand in the cylinder. The point at which steam stops being admitted to the cylinder is known as the cutoff, the optimal position for this varies depending on the work being done and the tradeoff desired between power and efficiency. Steam engines are fitted with regulators to vary the restriction on steam flow, but controlling the power via the cutoff setting is preferable since it makes for more efficient use of boiler steam.
A further benefit may be obtained by admitting the steam to the cylinder before front or back dead centre. This advanced admission assists in cushioning the inertia of the motion at high speed. In the internal combustion engine, this task is performed by cams on a camshaft driving poppet valves, but this arrangement is not used with steam engines because achieving variable engine timing using cams is complicated. Instead, a system of eccentrics and levers is used to control a D slide valve or piston valve from the motion. Two simple harmonic motions with different fixed phase angles are added in varying proportions to provide an output motion, variable in phase and amplitude. A variety of such mechanisms have been devised with varying success. Both slide and piston valves have the limitation that intake and exhaust events are fixed in relation to each other and cannot be independently optimised. Lap is provided on steam edges of the valve, so that although the valve stroke reduces as cutoff is advanced, the valve is always opened to exhaust.
However, as cutoff is shortened, the exhaust events advance. The exhaust release point occurs earlier in the power stroke and compression earlier in the exhaust stroke. Early release wastes some energy in the steam, early closure wastes energy in compressing an otherwise unnecessarily large quantity of steam. Another effect of early cutoff is that the valve is moving quite at the cutoff point, this causes'wire drawing' of the steam, another wasteful thermodynamic effect visible on an indicator diagram; these inefficiencies drove the widespread experimentation in poppet valve gears for locomotives. Intake and exhaust poppet valves could be moved and controlled independently of each other, allowing for better control of the cycle. In the end, not a great number of locomotives were fitted with poppet valves, but they were common in steam cars and lorries, for example all Sentinel lorries and railcars used poppet valves. A late British design, the SR Leader class, used sleeve valves adapted from internal combustion engines, but this class was not a success.
In stationary steam engines, traction engines and marine engine practice, the shortcomings of valves and valve gears were among the factors that lead to compound expansion. In stationary engines trip valves were extensively used. Valve gear was a fertile field of invention, with several hundred variations devised over the years. However, only a small number of these saw any widespread use, they can be divided into those that drove the standard reciprocating valves, those used with poppet valves, stationary engine trip gears used with semi-rotary Corliss valves or drop valves. Slip-eccentric - This gear is now confined to model steam engines, low power hobby applications such as steam launch engines, ranging to a few horsepower; the eccentric is loose on the crankshaft but there are stops to limit its rotation relative to the crankshaft. Setting the eccentric to the forward running and reverse running positions can be accomplished manually by rotating the eccentric on a stopped engine, or for many engines by turning the engine in the desired rotation direction, where the eccentric positions itself automatically.
The engine is pushed forwards to put the eccentric in the forward gear position and backwards to put it in the backward gear position. There is no variable control of cutoff. On the London and North Western Railway, some of the three-cylinder compounds designed by Francis William Webb from 1889 used a slip eccentric to operate the valve of the single low-pressure cylinder; these included Greater Britain and John Hick classes. Gab or hook gear - used on earliest locomotives. Allowed reversing but no control of cutoff. One component of the motion comes from a eccentric; the other component comes from a separate source the crosshead. Walschaerts or Heusinger valve gear - most common valve gear on locomotives externally mounted. Deeley valve gear - fitted to several express locomotives on the Midland Railway; the combination levers were driven, as normal, from the crossheads. Each expansion link was driven from the crosshead on the opposite side of the engine. Young valve gear - used the piston rod motion on one side of the locomotive to drive the valve gear on the other side.
Similar to the Deeley gear, but with deta
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