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Origins The first successful locomotives were built by Cornish inventor Richard Trevithick. In 1804 his unnamed locomotive hauled a train along the tramway of the Penydarren ironworks, near Merthyr Tydfil in Wales. Although the locomotive hauled a train of 10 tons of iron and 70 passengers in five wagons over nine miles it was too heavy for the cast iron rails used at the time. The locomotive only ran three journeys before it was abandoned. In 1813, George Stephenson persuaded the manager of the Killingworth colliery where he worked to allow him to build a steam-powered machine. He built the Blucher, the first successful flanged-wheel adhesion locomotive. The flanges enabled the trains to run on top of the rails instead of in sunken tracks. This greatly simplified construction of switches (called "points" in UK) and rails, and opened the way to the modern railroad. Locomotives vs. self-propelled vehicles There are many reasons why the motive power for trains has been traditionally isolated in a locomotive, rather than in self-propelled vehicles. These include: Classification by motive power Locomotives may generate mechanical work from fuel, or they may take power from an outside source. It is common to classify locomotives by their means of providing motive work - the common ones include: Steam
Diesel locomotives main article: diesel locomotive Steam locomotives were eventually displaced by locomotives using diesel engines. Diesel locomotives vary in the form of transmission used to convey the power from a diesel engine (or engines) to the wheels, the primary types being mechanical, electric, and hydraulics. Diesel locomotives require less maintenance than steam, and their exhaust, while still polluting, is less noxious than coal smoke. They require fewer personnel to operate and obviate the standpipes and towers required to replenish steam locomotives at intervals. The dynamic brakes of diesel electric locomotives have proven to be a major boon in mountainous areas. On the other hand, diesels, unlike other locomotive types, are limited to a single fuel: petroleum. Demand for diesel fuel is high and subject to political and economic shocks. In addition, the exhaust emissions make them unsuitable for underground application, where electric locomotives remain the motive power of choice. Gas turbine-electric 68, one of Union Pacific's 4,500 hp 'veranda' turbines. From the http://donsdepot.donrossgroup.net Don Ross Collection A gas turbine-electric locomotive, or GTEL, is a locomotive that uses a gas turbine to drive an electric generator or alternator. The electric current thus produced is used to power traction motors. This type of locomotive was first experimented with in 1920 but reached its peak in the 1950s to 1960s. The turbine (similar to a turboshaft engine) drives an output shaft, which drives the alternator via a system of gears. Aside from the unusual prime mover, a GTEL is very similar to a diesel-electric. In fact, the turbines built by GE used many of the same parts as their diesels. A turbine offers some advantages over a piston engine. The number of moving parts is much smaller, and the power to weight ratio is much higher. A turbine of a given power output is also physically smaller than an equally powerful piston engine, allowing a locomotive to be very powerful without being inordinately large. However, a turbine's power output and efficiency both drop dramatically with rotational speed, unlike a piston engine, which has a comparatively flat power curve. Gas turbine locomotives are very powerful, but also tend to be very loud. Union Pacific operated the largest fleet of such locomotives of any railroad in the world, and was the only railroad to use them for hauling freight. Most other GTELs have been built for small passenger trains, and only a few have seen any real success in that role. After the oil crisis in the 1970s and the subsequent rise in fuel costs, gas turbine locomotives became uneconomic to operate, and many were taken out of service. This type of locomotive is now rare. Electric The electric locomotive is supplied externally with electric power, either through an overhead pickup or through a third rail. While the capital cost of electrifying track is high, electric trains and locomotives are capable of higher performance and in some cases lower operational costs than steam or diesel power. The world speed record for a wheeled train was set in 1990 by a French TGV which reached a speed of 515.3 km/h (320 mph). Some electric locomotives can also operate off battery power to enable short journeys or shunting on non-electrified lines or yards. Battery-powered locomotives are used in mines and other underground locations where diesel fumes or smoke would endanger crews, and where external electricity supplies cannot be used due to the danger of sparks igniting flammable gas. Battery locomotives are also used on many underground railways for maintenance operations, as they are required when operating in areas where the electricity supply has been temporarily disconnected. However the cost and weight of the batteries are prohibitive for using battery-powered locomotives on extended runs. See also: Railway electrification system Magnetic levitation
Hybrid A hybrid locomotive is a Locomotive that uses an on-board rechargeable energy storage system (RESS) and a fuelled power source for propulsion. Hybrid trains typically are powered either by Fuel Cell technology or the slightly more conventional diesel-electric hybrid which reduces fuel consumption through regenerative braking and switching off the hydrocarbon engine when idling or stationary (as used in autmobiles such as the Toyota Prius). Experimental There are other forms of motive power in experimental use. The Parry PeopleMover is an experimental light rail railcar that is powered by energy stored in a flywheel. The flywheel is powered from an onboard battery-driven motor or internal combustion engine and is also recharged through regenerative braking. A proposed alternative is to recharge the flywheel from external electric motors installed at station stops; although this would increase installation costs it would substantially reduce the weight of the vehicles. It would also still cost less than providing a continuous electrical supply. Parry People Movers have been tested on several railways, including the Ffestiniog Railway, the Welsh Highland Railway and the Welshpool and Llanfair Light Railway. The first mainstream timetable service for the flywheel railcar was launched in February 2006 providing the Sunday service on the short link between Stourbridge junction and Stourbridge Town in the United Kingdom. Classification by use The three main categories of locomotives are often subdivided in their usage in rail transport operations. There are passenger locomotives, freight locomotives and switcher (or shunting) locomotives. These categories mainly depend on manoeuvrability, traction power and speed. Freight locomotives are normally designed to provide a high torque and deliver high power levels to the rails, while passenger locomotives are designed to operate at high speeds, typically with lower loads. Mixed traffic locomotives (us: General purpose locomotives) are built to provide elements of both requirements, and trade efficiency for a given job with flexibility. Most steam engines are direct drive (that is, they have no gearbox), and the effective transmission ratios were determined by the wheel sizes. Thus steam locomotives for freight purposes generally have many smaller wheels, while steam passenger locomotives have larger wheels. With diesel and electric locomotives, the gearing is more flexible, and it is easier to create good general-purpose locomotives. Special-purpose locomotives Some locomotives are designed specifically to work mountain railways, and feature extensive additional braking mechanisms and sometimes rack and pinion. Steam locomotives built for steep rack and pinion railways frequently have the boiler tilted relative to the wheels, so that the boiler remains roughly level on steep climbs. "Fantasy Job" Programs Several railroad museums in the United States and in the UK offer chances for visitors to fulfill a childhood fantasy and actually run a real locomotive. One of the earliest and most well known such programs is the Run A Locomotive at the Western Pacific Railroad Museum in Portola, California. The program is so popular that it is often reserved months in advance. See also Citations Books on steam locomotives | |||||||||||||
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