1.
Rail yard
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A rail yard, railway yard or railroad yard is the US term for a complex series of railroad tracks for storing, sorting, or loading/unloading, railroad cars and/or locomotives. Railroad yards have many tracks in parallel for keeping rolling stock stored off the mainline, railroad cars are moved around by specially designed yard switchers, a type of locomotive. Cars in a railroad yard may be sorted by categories, including railroad company, loaded or unloaded, destination, car type. Railroad yards are built where there is a need to store cars while they are not being loaded or unloaded. Large yards may have a tower to control operations, many railway yards are located at strategic points on a main line. Main line yards are often composed of an Up yard and a Down yard, there are different types of yards, and different parts within a yard, depending on how they are built. They are decoupled and let to accelerate into the classification equipment lower down, a flat yard has no hump, and relies on locomotives for all car movements. A large sub-group of such yards are known as Staging yards, the long haul carrier makes the round trip with a minimal turn around time, and the local switch engine transfers empties to the loading yard when the industries output is ready to be shipped. In the staging yard, the locomotive is most likely operated by industry, since overall throughput speed matters, many have small pneumatic, hydraulic or spring driven braking retarders to adjust and slow speed both before and after yard switch points. Along with car tracking and load tracking to destination technologies such as RFID long trains can be broken down and reconfigured in transfer yards or operations in remarkable time. Transfer yard is a yard where consists are dropped off or picked up as a group by through service such as a Unit Train, but managed locally by local switching service locomotives. Unit tracks may be reserved for Unit trains, which carry a block of all of the same origin and destination. Such consists often stop in a yard for other purposes, inspection. Freight yards may have multiple industries adjacent to them where railroad cars are loaded or unloaded and then stored before they move on to their new destination. Major freight yards in the U. S. Major U. K. goods yards include those in Crewe, Reading and Bescot, near Walsall, coach yards are used for sorting, storing and repairing passenger cars. These yards are located in areas near large stations or terminals. An example of a major U. S. coach yard is Sunnyside Yard in New York City and those that are principally used for storage, such as the West Side Yard in New York, are called layup yards or stabling yards. Major U. K. coach stabling yards include those in Crewe and Longsight, Manchester, which are operated by various regional train companies
2.
Goods station
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This often takes the form of a container terminal and may also be known as a container station. Goods stations were more widespread in the days when the railways were common carriers and were converted from former passenger station whose traffic had moved elsewhere. The worlds first dedicated goods terminal was the 1830 Park Lane Goods Station at the South End Liverpool Docks, built in 1830 the terminal was reached by a 1. 24-mile tunnel from Edge Hill in the east of the city. The station was a part of the Liverpool and Manchester Railway, where individual goods wagons are dispatched to specific goods stations, they are usually delivered to special shunting stations or marshalling yards where they are sorted and then collected. Sometimes there are combined shunting and goods stations, a goods station is usually equipped with a large number of storage and loading sidings in order to fulfil its task. On the loading sidings there may be fixed facilities, such as cranes or conveyor belts, or temporary equipment, stations where the primary purpose of the station is the handling of containers are also known as container terminals. They are equipped with cranes and fork-lift vehicles for loading containers from lorries or ships onto the railway vehicles. If only a section of a station is used for the loading and unloading of goods, it may be referred to as the loading area or loading dock and has its own access. Often there are no facilities for loading and the firm has to organise its own loading equipment such as conveyor belts or lorry cranes. Such loading areas were mainly to be found on branch lines, narrow gauge railways, in many European countries they are also equipped with a hump yard. In combined goods and hub stations with a yard, the latter was closed if the station lost its role as a railway hub. As a result, most of the remaining goods stations today are just used as container or transshipment stations, in French, gare aux marchandises or gare de fret. Freight yard Goods shed Goods train Railway station, which information on passenger stations. Container terminal Blum, Otto, Personen- und Güterbahnhöfe, kurt Leibrand, Handbuch für Bauingenieurwesen, Berlin/Göttingen/Heidelberg, Springer-Verlag. Bände 1 und 2, East Berlin, Transpress VEB Verlag für Verkehrswesen, europe-wide goods station search Goods stations search - Germany Container services
3.
Car
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A car is a wheeled, self-powered motor vehicle used for transportation and a product of the automotive industry. The year 1886 is regarded as the year of the modern car. In that year, German inventor Karl Benz built the Benz Patent-Motorwagen, cars did not become widely available until the early 20th century. One of the first cars that was accessible to the masses was the 1908 Model T, an American car manufactured by the Ford Motor Company. Cars were rapidly adopted in the United States of America, where they replaced animal-drawn carriages and carts, cars are equipped with controls used for driving, parking, passenger comfort and safety, and controlling a variety of lights. Over the decades, additional features and controls have been added to vehicles, examples include rear reversing cameras, air conditioning, navigation systems, and in car entertainment. Most cars in use in the 2010s are propelled by a combustion engine. Both fuels cause air pollution and are blamed for contributing to climate change. Vehicles using alternative fuels such as ethanol flexible-fuel vehicles and natural gas vehicles are also gaining popularity in some countries, electric cars, which were invented early in the history of the car, began to become commercially available in 2008. There are costs and benefits to car use, the costs of car usage include the cost of, acquiring the vehicle, interest payments, repairs and auto maintenance, fuel, depreciation, driving time, parking fees, taxes, and insurance. The costs to society of car use include, maintaining roads, land use, road congestion, air pollution, public health, health care, road traffic accidents are the largest cause of injury-related deaths worldwide. The benefits may include transportation, mobility, independence. The ability for humans to move flexibly from place to place has far-reaching implications for the nature of societies and it was estimated in 2010 that the number of cars had risen to over 1 billion vehicles, up from the 500 million of 1986. The numbers are increasing rapidly, especially in China, India, the word car is believed to originate from the Latin word carrus or carrum, or the Middle English word carre. In turn, these originated from the Gaulish word karros, the Gaulish language was a branch of the Brythoic language which also used the word Karr, the Brythonig language evolved into Welsh where Car llusg and car rhyfel still survive. It originally referred to any wheeled vehicle, such as a cart, carriage. Motor car is attested from 1895, and is the formal name for cars in British English. Autocar is a variant that is attested from 1895
4.
Factory
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Factories arose with the introduction of machinery during the Industrial Revolution when the capital and space requirements became too great for cottage industry or workshops. Early factories that contained small amounts of machinery, such as one or two spinning mules, and fewer than a dozen workers have been called glorified workshops, most modern factories have large warehouses or warehouse-like facilities that contain heavy equipment used for assembly line production. Large factories tend to be located with access to multiple modes of transportation, with some having rail, highway, factories may either make discrete products or some type of material continuously produced such as chemicals, pulp and paper, or refined oil products. Oil refineries have most of their equipment outdoors, discrete products may be final consumer goods, or parts and sub-assemblies which are made into final products elsewhere. Factories may be supplied parts from elsewhere or make them from raw materials, continuous production industries typically use heat or electricity to transform streams of raw materials into finished products. The term mill originally referred to the milling of grain, which usually used natural resources such as water or wind power until those were displaced by steam power in the 19th century. Because many processes like spinning and weaving, iron rolling, and paper manufacturing were originally powered by water, according to translations of Demosthenes and Herodotus, Naucratis was a, or the only, factory in the entirety of ancient Egypt. A source of 1983, states the largest factory production in ancient times was of 120 slaves within 4th century BC Athens, although The Cambridge Online Dictionary definition of factory states, a building or set of buildings where large amounts of goods are made using machines elsewhere. The wheel was invented circa 3000 BC, the spoked wheel c.2000 BC, the Iron Age began approximately 1200-1000 BC. However, other sources define machinery as a means of production, according to one text the water-mill was first made in 555 A. D. by Belisarius, although according to another they were known to Pliny the Elder and Vitruvius in the first century B. C. By the time of the 4th century A. D. mills with a capacity to grind 3 tonnes of cereal an hour, the Venice Arsenal provides one of the first examples of a factory in the modern sense of the word. Founded in 1104 in Venice, Republic of Venice, several hundred years before the Industrial Revolution, the Venice Arsenal apparently produced nearly one ship every day and, at its height, employed 16,000 people. One of the earliest factories was John Lombes water-powered silk mill at Derby, by 1746, an integrated brass mill was working at Warmley near Bristol. Raw material went in at one end, was smelted into brass and was turned into pans, pins, wire, housing was provided for workers on site. Josiah Wedgwood in Staffordshire and Matthew Boulton at his Soho Manufactory were other prominent early industrialists, the factory system began widespread use somewhat later when cotton spinning was mechanized. Richard Arkwright is the credited with inventing the prototype of the modern factory. After he patented his water frame in 1769, he established Cromford Mill, in Derbyshire, England, the factory system was a new way of organizing labour made necessary by the development of machines which were too large to house in a workers cottage. Working hours were as long as they had been for the farmer, overall, this practice essentially reduced skilled and unskilled workers to replaceable commodities
5.
Port
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A port is a location on a coast or shore containing one or more harbors where ships can dock and transfer people or cargo to or from land. Port locations are selected to optimize access to land and navigable water, for commercial demand, Ports with deeper water are rarer, but can handle larger ships. Since ports throughout history handled every kind of traffic, support and storage facilities vary widely, may extend for miles, some ports have an important military role. One of the worlds oldest known artificial harbors is at Wadi al-Jarf on the Red Sea, along with the finding of harbor structures, ancient anchors have also been found. Guangzhou was an important port during the ancient times as far back as the Qin Dynasty, canopus was the principal port in Egypt for Greek trade before the foundation of Alexandria. Athens port of Piraeus was the base for the Athenian fleet, lothal is one of the most prominent cities of the ancient Indus valley civilisation, located in the Bhāl region of the modern state of Gujarāt and dating from 3700 BCE. Ostia Antica was the port of ancient Rome with Portus established by Claudius, Ports often have cargo-handling equipment, such as cranes and forklifts for use in loading ships, which may be provided by private interests or public bodies. Often, canneries or other processing facilities will be located nearby, some ports feature canals, which allow ships further movement inland. Access to intermodal transportation, such as railroads and highways, is critical to a port, so that passengers, Ports with international traffic have customs facilities. Harbor pilots and tugboats may maneuver large ships in tight quarters when near docks, the terms port and seaport are used for different types of port facilities that handle ocean-going vessels, and river port is used for river traffic, such as barges and other shallow-draft vessels. An inland port is a port on a lake, river, or canal with access to a sea or ocean. An example of this is the St. Lawrence Seaway which allows ships to travel from the Atlantic Ocean several thousand kilometers inland to Great Lakes ports like Duluth-Superior, a fishing port is a port or harbor for landing and distributing fish. It may be a facility, but it is usually commercial. A fishing port is the port that depends on an ocean product. In recent decades, regulations to save fishing stock may limit the use of a fishing port, a dry port is an inland intermodal terminal directly connected by road or rail to a seaport and operating as a centre for the transshipment of sea cargo to inland destinations. A warm-water port is one where the water does not freeze in wintertime, because they are available year-round, warm-water ports can be of great geopolitical or economic interest. A seaport is further categorized as a port or a cargo port. Additionally, cruise ports are known as a home port or a port of call
6.
Coal
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Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon, along with quantities of other elements, chiefly hydrogen, sulfur, oxygen. A fossil fuel, coal forms when plant matter is converted into peat, which in turn is converted into lignite, then sub-bituminous coal, after that bituminous coal. This involves biological and geological processes that take place over time, throughout history, coal has been used as an energy resource, primarily burned for the production of electricity and heat, and is also used for industrial purposes, such as refining metals. Coal is the largest source of energy for the generation of electricity worldwide, the extraction of coal, its use in energy production and its byproducts are all associated with environmental and health effects including climate change. Coal is extracted from the ground by coal mining, since 1983, the worlds top coal producer has been China. In 2015 China produced 3,747 million tonnes of coal –47. 7% of 7,861 million tonnes world coal production, in 2015 other large producers were United States, India, European Union and Australia. The word originally took the col in Old English, from Proto-Germanic *kula. In Old Turkic languages, kül is ash, cinders, öčür is quench, the compound charcoal in Turkic is öčür kül, literally quenched ashes, cinders, coals with elided anlaut ö- and inflection affixes -ülmüş. At various times in the geologic past, the Earth had dense forests in low-lying wetland areas, due to natural processes such as flooding, these forests were buried underneath soil. As more and more soil deposited over them, they were compressed, the temperature also rose as they sank deeper and deeper. As the process continued the plant matter was protected from biodegradation and oxidation and this trapped the carbon in immense peat bogs that were eventually covered and deeply buried by sediments. Under high pressure and high temperature, dead vegetation was slowly converted to coal, as coal contains mainly carbon, the conversion of dead vegetation into coal is called carbonization. The wide, shallow seas of the Carboniferous Period provided ideal conditions for coal formation, the exception is the coal gap in the Permian–Triassic extinction event, where coal is rare. Coal is known from Precambrian strata, which predate land plants — this coal is presumed to have originated from residues of algae, in its dehydrated form, peat is a highly effective absorbent for fuel and oil spills on land and water. It is also used as a conditioner for soil to make it able to retain. Lignite, or brown coal, is the lowest rank of coal, jet, a compact form of lignite, is sometimes polished and has been used as an ornamental stone since the Upper Palaeolithic
7.
Mining
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Mining is extraction of valuable minerals or other geological materials from the earth usually from an orebody, lode, vein, seam, reef or placer deposits. These deposits form a mineralized package that is of economic interest to the miner, ores recovered by mining include metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay. Mining is required to obtain any material that cannot be grown through agricultural processes, Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water. Mining of stones and metal has been a human activity since pre-historic times, Mining operations usually create a negative environmental impact, both during the mining activity and after the mine has closed. Hence, most of the nations have passed regulations to decrease the impact. Work safety has long been a concern as well, and modern practices have significantly improved safety in mines, levels of metals recycling are generally low. Unless future end-of-life recycling rates are stepped up, some rare metals may become unavailable for use in a variety of consumer products, due to the low recycling rates, some landfills now contain higher concentrations of metal than mines themselves. Since the beginning of civilization, people have used stone, ceramics and, later and these were used to make early tools and weapons, for example, high quality flint found in northern France, southern England and Poland was used to create flint tools. Flint mines have been found in areas where seams of the stone were followed underground by shafts. The mines at Grimes Graves and Krzemionki are especially famous, other hard rocks mined or collected for axes included the greenstone of the Langdale axe industry based in the English Lake District. The oldest-known mine on archaeological record is the Lion Cave in Swaziland, at this site Paleolithic humans mined hematite to make the red pigment ochre. Mines of an age in Hungary are believed to be sites where Neanderthals may have mined flint for weapons. Ancient Egyptians mined malachite at Maadi, at first, Egyptians used the bright green malachite stones for ornamentations and pottery. Later, between 2613 and 2494 BC, large building projects required expeditions abroad to the area of Wadi Maghareh in order to secure minerals and other resources not available in Egypt itself. Quarries for turquoise and copper were found at Wadi Hammamat, Tura, Aswan and various other Nubian sites on the Sinai Peninsula. Mining in Egypt occurred in the earliest dynasties, the gold mines of Nubia were among the largest and most extensive of any in Ancient Egypt. These mines are described by the Greek author Diodorus Siculus, who mentions fire-setting as one used to break down the hard rock holding the gold. One of the complexes is shown in one of the earliest known maps, the miners crushed the ore and ground it to a fine powder before washing the powder for the gold dust
8.
Power station
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A power station, also referred to as a power plant or powerhouse and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Most power stations contain one or more generators, a machine that converts mechanical power into electrical power. The relative motion between a field and a conductor creates an electrical current. The energy source harnessed to turn the generator varies widely, most power stations in the world burn fossil fuels such as coal, oil, and natural gas to generate electricity. Others use nuclear power, but there is an use of cleaner renewable sources such as solar, wind, wave. There is some debate within utility and engineering circles over whether a solar array, or wind farm, should be referred to as a power station, in 1868 a hydro electric power station was designed and built by Lord Armstrong at Cragside, England. It used water from lakes on his estate to power Siemens dynamos, the electricity supplied power to lights, heating, produced hot water, ran an elevator as well as labor-saving devices and farm buildings. In the early 1870s Belgian inventor Zénobe Gramme invented a powerful enough to produce power on a commercial scale for industry. In the autumn of 1882, a central station providing public power was built in Godalming and it was proposed after the town failed to reach an agreement on the rate charged by the gas company, so the town council decided to use electricity. It used hydroelectric power that was used to street and household lighting, the system was not a commercial success and the town reverted to gas. In 1882 a the worlds first coal-fired public power station, the Edison Electric Light Station, was built in London, a Babcock & Wilcox boiler powered a 125-horsepower steam engine that drove a 27-ton generator. This supplied electricity to premises in the area that could be reached through the culverts of the viaduct without digging up the road, the customers included the City Temple and the Old Bailey. Another important customer was the Telegraph Office of the General Post Office, Johnson arranged for the supply cable to be run overhead, via Holborn Tavern and Newgate. In September 1882 in New York, the Pearl Street Station was established by Edison to provide lighting in the lower Manhattan Island area. The station ran until destroyed by fire in 1890, the station used reciprocating steam engines to turn direct-current generators. Because of the DC distribution, the area was small. The War of Currents eventually resolved in favor of AC distribution and utilization, DC systems with a service radius of a mile or so were necessarily smaller, less efficient of fuel consumption, and more labor-intensive to operate than much larger central AC generating stations. AC systems used a range of frequencies depending on the type of load, lighting load using higher frequencies
9.
Shunting (rail)
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Shunting, in railway operations, is the process of sorting items of rolling stock into complete trains, or the reverse. In the United States this activity is known as switching, motive power is normally provided by a locomotive known as a shunter or switcher. Most shunter/switchers are now diesel-powered but steam and even electric locomotives have been used, where locomotives could not be used shunting operations have in the past been effected by horses or capstans. The terms shunter and switcher are applied not only to locomotives and this was particularly so in the past. The Midland Railway company, for example, kept an ambulance wagon permanently stationed at Toton Yard to give treatment to injured shunters, marshalling or classification yard Shunter or switcher Switching and terminal railroad Bostel, Nathalie, and Pierre Dejax. Models and algorithms for container allocation problems on trains in a rapid transshipment shunting yard, shunting yard operations, Theoretical aspects and applications. European Journal of Operational Research 220.1, 1-14
10.
Chicago and North Western Transportation Company
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The Chicago and North Western Transportation Company was a Class I railroad in the Midwestern United States. It was also known as the North Western, the railroad operated more than 5,000 miles of track as of the turn of the 20th century, and over 12,000 miles of track in seven states before retrenchment in the late 1970s. Until 1972, when the company was sold to its employees, it was named the Chicago and North Western Railway. The C&NW became one of the longest railroads in the United States as a result of mergers with other railroads, such as the Chicago Great Western Railway, Minneapolis and St. Louis Railway and others. By 1995, track sales and abandonment had reduced the total back to about 5,000. The majority of the abandoned and sold lines were lightly trafficked branches in Iowa, Illinois, Minnesota, South Dakota and Wisconsin. Large line sales, such as those that resulted in the Dakota, Minnesota and Eastern Railroad further helped reduce the railroad to a core with several regional feeders. The company was purchased by Union Pacific Railroad in April 1995, the Chicago and North Western Railway was chartered on June 7,1859. It had purchased the assets of the bankrupt Chicago, St. Paul, on February 15,1865, it officially merged with the Galena and Chicago Union Railroad, which had been chartered on January 16,1836. The Winona and St. Peter Railroad was added to the network in 1867, the North Western had owned a majority of the stock of the Chicago, St. Paul, Minneapolis and Omaha Railway since 1882. On January 1,1957 it leased the company, and merged it into the North Western in 1972. The Omaha Roads main line ran from an interchange with the North Western at Elroy, Wisconsin, to the Twin Cities, down to Sioux City, Iowa, the North Western picked up several important short railroads during its later years. It finalized acquisition of the Litchfield and Madison Railway on January 1,1958, the Litchfield and Madison railroad was a 44-mile bridge road from East St. Louis to Litchfield, Illinois. On July 30,1968, the North Western acquired two former interurbans — the 36-mile Des Moines and Central Iowa Railway, and the 110-mile Fort Dodge, Des Moines and Southern Railway. The DM&CI gave access to the Firestone plant in Des Moines, Iowa, on November 1,1960, the North Western acquired the rail properties of the 1, 500-mile Minneapolis and St. Louis Railway. In spite of its name, it ran only from Minneapolis, Minnesota, to Peoria and this acquisition provided traffic and modern rolling stock, and eliminated competition. On July 1,1968 the 1,500 mi Chicago Great Western Railway was merged into the North Western and this railroad went from Chicago to Oelwein, Iowa. From there lines went to the Twin Cities, Omaha, Nebraska, a connection from Hayfield, Minnesota, to Clarion, Iowa, provided a Twin Cities to Omaha main line
11.
Chicago
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Chicago, officially the City of Chicago, is the third-most populous city in the United States. With over 2.7 million residents, it is the most populous city in the state of Illinois, and it is the county seat of Cook County. In 2012, Chicago was listed as a global city by the Globalization and World Cities Research Network. Chicago has the third-largest gross metropolitan product in the United States—about $640 billion according to 2015 estimates, the city has one of the worlds largest and most diversified economies with no single industry employing more than 14% of the workforce. In 2016, Chicago hosted over 54 million domestic and international visitors, landmarks in the city include Millennium Park, Navy Pier, the Magnificent Mile, Art Institute of Chicago, Museum Campus, the Willis Tower, Museum of Science and Industry, and Lincoln Park Zoo. Chicagos culture includes the arts, novels, film, theater, especially improvisational comedy. Chicago also has sports teams in each of the major professional leagues. The city has many nicknames, the best-known being the Windy City, the name Chicago is derived from a French rendering of the Native American word shikaakwa, known to botanists as Allium tricoccum, from the Miami-Illinois language. The first known reference to the site of the current city of Chicago as Checagou was by Robert de LaSalle around 1679 in a memoir, henri Joutel, in his journal of 1688, noted that the wild garlic, called chicagoua, grew abundantly in the area. In the mid-18th century, the area was inhabited by a Native American tribe known as the Potawatomi, the first known non-indigenous permanent settler in Chicago was Jean Baptiste Point du Sable. Du Sable was of African and French descent and arrived in the 1780s and he is commonly known as the Founder of Chicago. In 1803, the United States Army built Fort Dearborn, which was destroyed in 1812 in the Battle of Fort Dearborn, the Ottawa, Ojibwe, and Potawatomi tribes had ceded additional land to the United States in the 1816 Treaty of St. Louis. The Potawatomi were forcibly removed from their land after the Treaty of Chicago in 1833, on August 12,1833, the Town of Chicago was organized with a population of about 200. Within seven years it grew to more than 4,000 people, on June 15,1835, the first public land sales began with Edmund Dick Taylor as U. S. The City of Chicago was incorporated on Saturday, March 4,1837, as the site of the Chicago Portage, the city became an important transportation hub between the eastern and western United States. Chicagos first railway, Galena and Chicago Union Railroad, and the Illinois, the canal allowed steamboats and sailing ships on the Great Lakes to connect to the Mississippi River. A flourishing economy brought residents from rural communities and immigrants from abroad, manufacturing and retail and finance sectors became dominant, influencing the American economy. The Chicago Board of Trade listed the first ever standardized exchange traded forward contracts and these issues also helped propel another Illinoisan, Abraham Lincoln, to the national stage
12.
Wheel chock
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Wheel chocks are wedges of sturdy material placed closely against a vehicles wheels to prevent accidental movement. Chocks are placed for safety in addition to setting the brakes, the bottom surface is sometimes coated in rubber to enhance grip with the ground. For ease of removal, a rope may be tied to the chock or a set of two chocks, one edge of the wedge has a concave profile to contour to the wheel and increase the force necessary to overrun the chock. Most commonly, chocks are seen on aircraft and train cars, automobiles usually have parking brakes on the rear wheels. If the rear axle is jacked off the ground with only the parking brake set, chocking the front wheels prevents this mishap. Motorcycle and bicycle chocks are bifurcated and fit around the wheel, supporting the bike, the mining industry uses wheel chocks to protect lubrication trucks and heavy maintenance vehicles from slipping on off-road terrain when placed in Park. The huge haul trucks, which can weigh up to 450 tonnes and these circumstances will benefit from urethane wheel chocks that are lightweight enough to be maneuvered, yet can withstand the responsibility of holding a truck if a brake should fail. To use, wheel chocks must be selected to match the size of the tires on the vehicle and used in pairs, as the size of the tire is designed to be proportional to the vehicles weight and size. For a maximum slope of approximately 15.6 degrees, use a chock 1/4 height of the wheel as per SAE J348. The maximum slope angle for any given chock is c h o c k h e i g h t r a d i u s o f t h e w h e e l ÷0.032. For example, for a chock 1/6 the height of the wheel, some manufacturers recommend wheel chocks that are slightly bigger than 1/4 the height of the wheel. Three main factors affect the performance of wheel chocks, The angle of the road surface, parking on an angle greater than 10 degrees increases the risk of the car rolling off or over the chock. The size of the wheel compared to the wheel height. Extra large wheel chocks are suitable for e. g. parked air craft where wind forces may come into effect, the surface slip or friction of the road surface, as the wheel chock may slide downhill due to wet grass or ice. Increasing the size of the wheel chock will not necessary allow the parking on inclines greater than 30% gradient, Wheel chocks must be used on a level surface, some rubber wheel chocks have steel grates and ice cleat accessories. The vehicle is placed in park and the parking or emergency brake is applied, the wheel chocks are then snugly positioned against the center of the tires in the direction of the grade, on both the left and right side of the vehicle. On even surfaces, chocks are applied to the rear-facing as well as the side of each tire. A parking space commonly contains a parking chock, a barrier which is used to prevent cars from pulling too far into the space and obstructing an adjacent parking space, curb, in a parking garage, the barrier will often be a concrete wall
