 | This article needs additional citations for verification .(March 2013) |
Conduit current collection is an obsolete system that was used by some electric tramways to pass current to streetcars via a "conduit", a small tunnel under the roadway. Modern systems fall under the term ground-level power supply.
The power rails are contained in a conduit midway between and below the two surface rails on which the cars operate, in much the same fashion as the cable for cable cars. The conduit contains two "T" section steel power rails of opposite polarity facing each other, about 12 inches (30 cm) apart and about 18 inches (46 cm) below the street surface. Power reached the car by means of an attachment, called a plough (US – plow), that rode in the conduit beneath the car. The plough had two metal shoes attached to springs that pushed sideways against the power rails. The plough was normally connected to a platform that could slide laterally to conform with variations in the placement of the conduit. For example, some trackage had a conduit for cable cars next to the one for electric cars.
The current was carried by a flexible cable from the plough through the platform to the car's controller and motors. The running rails are not part of the electrical circuit. In the United States, the cars were sometimes popularly called trolleys but did not typically draw power through a trolley pole from an overhead wire.
Conduit current collection was one of the first ways of supplying power to trams, but it proved to be much more expensive, complicated, and trouble-prone than overhead wires. When electric street railways became ubiquitous, it was only used in those cities that did not permit overhead wires, including London, Paris, Berlin, Marseilles, Vienna, Budapest, and Prague in Europe, and the New York City borough of Manhattan and Washington, D.C., in the United States. [3]
Conduit current collection was pioneered in 1885 in Denver, Colorado, the world's second electric street railway. The balky system was replaced three years later.[ citation needed ][ clarification needed ]
Also in 1885, a conduit system was used on Britain's first electric tramway in the seaside resort of Blackpool. The conduit was replaced with overhead electrification, as sand and saltwater entered the it and caused breakdowns, and there was a problem with voltage drop. However the line survives to this day as part of the Blackpool tramway, and some sections of track still had the conduit slot visible until refurbishment in 2012. Car 4 of the original conduit line also still survives, and is preserved at the National Tramway Museum in Crich, Derbyshire. [4]
New York City had the largest installation of conduit cars, due to the prohibition of overhead wires on Manhattan Island, although a few Bronx-based trolley lines entered the northern reaches of Manhattan using overhead wire. Trolley lines from Brooklyn and Queens also entered Manhattan under wire, but did not use city streets. The primary reason for the initial adoption of conduit systems was for aesthetic reasons as an alternative to overhead wiring that was often objected to as being unsightly.
The expense of creating conduit lines in New York was reduced where it was possible to convert the cable vaults from discontinued cable car lines. The huge cost of building new conduits gave New York the distinction of having one of the country's last horsecar lines: the Bleecker Street Line, which operated until 1917.
In some old photographs, two "slots" may be seen between the rails. In New York City, sometimes one slot was used for a cable line and the other for electric cars. Occasionally, two competing lines shared a common track and had independent slots for the ploughs of the respective cars. In London, two slots were sometimes used on a single-track stretch in a narrow road so that cars in each direction used separate conduits. Known as twin-conduit track, examples were found in York Road, Wandsworth and London Street, Greenwich. [5]
In New York City, the Queensboro Bridge between Manhattan and Queens had tracks installed on the outer lanes with conduits for Manhattan cars in addition to overhead wires. The conduit allowed them to run to Queens Plaza terminus without need for removing the plough and raising the poles. In later years the conduit was removed and only trolley wire remained.
In London, the London County Council Tramways experimented with side conduit, where the conduit was in one of the side rails. This was tried along Kingsland Road between Bentley Road and Basing Place, Hoxton, but the stresses and strains of the weight of the cars weakened the conduit, so it was not tried elsewhere. [5]
In the centre of Brussels some tram lines were fitted with conduits, the last ones being converted to overhead operation during World War II.
Washington, D.C., had a large network of conduit lines to avoid wires, as required by an 1889 law. Some lines used overhead wires when they approached rural or suburban areas. The last such line ran to Cabin John, Maryland. The current collector "plow" was mounted underneath the car on a fitting just forward of the rear truck on PCC streetcars. It had two cables with female connectors on cables to attach to matching cables of the car's electrical system. A "plowman" was assigned at each changeover point from overhead trolley wire to conduit to remove the cable attachments to the car and stow the plow, which did not remain with the car and was reattached in an incoming car running on overhead wire. The lower section of the plow "board" was drawn by the moving car within the cavity of the conduit. Because of this usage, many of Washington's streetcars carried trolley poles, which were lowered while operating in the central part of the city; when the cars reached a point where they switched to overhead operation, they stopped over a plow pit where the conduit plows were detached and the trolley poles raised, the reverse operation taking place on inbound runs. The 'pit' here has the meaning analogous to racing circuit pits rather than a depression in the road.
In the UK, London had a hybrid network of double-deck trams: overhead collection was used in the outer sections and conduit in the centre. At the changeover from conduit to overhead wire, at a change pit, the process was largely automatic. The conductor put the trolley pole onto the wire, and as the tram moved forward the conduit channel veered sideways to outside the running track, automatically ejecting the plough - the tram was said to be 'shooting the plough'. At the changeover from overhead wire to conduit the process was a little more complicated. The tram pulled up alongside a ploughman, who engaged a two-pronged plough fork over the plough in a short length of unelectrified conduit and into the plough channel underneath the centre of the tram. As the tram drew forward, the conduit channel moved under the tram, carrying the plough into position. [6] The conductor pulled down the trolley pole and stowed it. The ploughman's job was a fairly skilled one because, if he failed to locate the plough fork correctly, it or the plough could jam in the plough channel and cause lengthy delays. Some tram designs required an extra carrier to be located with the plough and these frequently caused problems for ploughmen not used to the design (particularly if the tram had been diverted from its normal route).
New conduit track was laid in 1951 for the Festival of Britain, which commemorated the Great Exhibition of 1851. The last tram was withdrawn in June 1952 and virtually all the tracks had been removed by the 1970s, although a short section can still be seen at the entrance to the former Kingsway Tramway Subway.
Conduit current collection systems were used in several major cities, including Monaco, Dresden, Prague, Tours, Washington, and London, [7] : 44 Other European hybrid tramway networks included Paris, Nice, Lyon, Lille and Bordeaux in France; Berlin, Vienna and Budapest. In Paris, the conduit sections were frequently very short, requiring cars to change from overhead to conduit and back several times in one journey. The last conduit line in Paris closed in 1936.[ citation needed ] The last Bordeaux conduit car ran in 1958. [8] The conduit systems in Berlin, Vienna and Budapest were very short lived, being replaced by overhead wires before World War I.[ citation needed ]
A tram is a type of urban rail transit consisting of either individual railcars or self-propelled multiple unit trains that run on tramway tracks on urban public streets; some include segments on segregated right-of-way. The tramlines or tram networks operated as public transport are called tramways or simply trams/streetcars. Due to their close similarities, trams are commonly included in the wider term light rail, which also includes systems separated from other traffic.
An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, electric multiple units, trolleybuses or trams. The generic term used by the International Union of Railways for the technology is overhead line. It is known variously as overhead catenary, overhead contact line (OCL), overhead contact system (OCS), overhead equipment (OHE), overhead line equipment, overhead lines (OHL), overhead wiring (OHW), traction wire, and trolley wire.
A third rail, also known as a live rail, electric rail or conductor rail, is a method of providing electric power to a railway locomotive or train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost fully segregated from the outside environment. Third-rail systems are usually supplied from direct current electricity.
The interurban is a type of electric railway, with tram-like electric self-propelled railcars which run within and between cities or towns. The term "interurban" is usually used in North America, with other terms used outside it. They were very prevalent in many parts of the world before the Second World War and were used primarily for passenger travel between cities and their surrounding suburban and rural communities. Interurban as a term encompassed the companies, their infrastructure, their cars that ran on the rails, and their service. In the United States, the early 1900s interurban was a valuable economic institution, when most roads between towns, many town streets were unpaved, and transportation and haulage was by horse-drawn carriages and carts.
A trolley pole is a tapered cylindrical pole of wood or metal, used to transfer electricity from a "live" (electrified) overhead wire to the control and the electric traction motors of a tram or trolley bus. It is a type of current collector. The use of overhead wire in a system of current collection is reputed to be the 1880 invention of Frank J. Sprague, but the first working trolley pole was developed and demonstrated by Charles Van Depoele, in autumn 1885.
Ground-level power supply, also known as surface current collection or, in French, alimentation par le sol, is a concept and group of technologies whereby electric vehicles collect electric power at ground level from individually-powered segments instead of the more common overhead lines. Ground-level power supply was developed for aesthetic reasons, to avoid the presence of overhead lines in city centres.
There have been two separate generations of trams in London, from 1860 to 1952 and from 2000 to the present. There were no trams at all in London between 1952 and 2000.
A pantograph is an apparatus mounted on the roof of an electric train, tram or electric bus to collect power through contact with an overhead line. The term stems from the resemblance of some styles to the mechanical pantographs used for copying handwriting and drawings.
A horsecar, horse-drawn tram, horse-drawn streetcar (U.S.), or horse-drawn railway (historical), is an animal-powered tram or streetcar.
A bow collector is one of the three main devices used on tramcars to transfer electric current from the wires above to the tram below. While once very common in continental Europe, it was replaced by the pantograph or the trolley pole, itself often later replaced by the pantograph.
The Great Orme Tramway is a cable-hauled 3 ft 6 in gauge tramway in Llandudno in north Wales. Open seasonally from late March to late October, it takes over 200,000 passengers each year from Llandudno Victoria Station to just below the summit of the Great Orme headland. From 1932 onwards it was known as the Great Orme Railway, reverting to its original name in 1977.
The Denver Tramway, operating in Denver, Colorado, was a streetcar system incorporated in 1886. The tramway was unusual for a number of reasons: the term "tramway" is generally not used in the United States, and it is not known why the company was named as such. The track was 3 ft 6 in narrow gauge, an unusual gauge in the United States, but in general use by railways in Japan, southern Africa, New Zealand, and Queensland, Australia.
Tramway track is used on tramways or light rail operations. As with standard rail tracks, tram tracks have two parallel steel rails, the distance between the heads of the rails being the track gauge. When there is no need for pedestrians or road vehicles to traverse the track, conventional flat-bottom rail is used. However, when such traffic exists, such as in urban streets, grooved rails are used.
The history of trams, streetcars, or trolleys began in the early nineteenth century. It can be divided up into several discrete periods defined by the principal means of motive power used.
The stud contact system is an obsolete ground-level power supply system for electric trams. Power supply studs were set in the road at intervals and connected to a buried electric cable by switches operated by magnets on the tramcars. Current was collected from the studs by a "skate" or "ski collector" under the tramcar. The system was popular for a while in the early 1900s but soon fell out of favour because of the unreliability of the magnetic switches, largely due to friction and rapid corrosion affecting its cast iron moving components.
A current collector is a device used in trolleybuses, trams, electric locomotives and EMUs to carry electric power (current) from overhead lines, electric third rails, or ground-level power supplies to the electrical equipment of the vehicles. Those for overhead wires are roof-mounted devices, those for rails are mounted on the bogies.
Road powered electric vehicles (RPEV) collect any form of potential energy from the road surface to supply electricity to locomotive motors and ancillary equipment within the vehicle.
Torquay Tramways operated electric street trams in Torquay, Devon, England, from 1907. They were initially powered by the unusual Dolter stud-contact electrification, but in 1911 was converted to more conventional overhead-line supply. The line was extended into neighbouring Paignton in 1911 but the whole network was closed in 1934.
Stalybridge, Hyde, Mossley & Dukinfield Tramways & Electricity Board (SHMD) was a public transport and electricity supply organisation formed by Act of the British Parliament in August 1901. It was a joint venture between the borough councils of Stalybridge, Hyde, Mossley and Dukinfield. The system was officially opened on 21 May 1904.
Alstom APS, also known as Alimentation par Sol or Alimentation Par le Sol, is a form of ground-level power supply for street trams and, potentially, other vehicles. APS was developed by Innorail, a subsidiary of Spie Enertrans, but was sold to Alstom when Spie was acquired by Amec. It was originally created for the Bordeaux tramway, which began construction in 2000 and opened in 2003. From 2011, the technology has been used in a number of other cities around the world.