Conduit current collection - AbsoluteAstronomy.com

Conduit current collection is a system of electric current

Electric current

Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...

collection used by electric tram

Tram

A tram is a passenger rail vehicle which runs on tracks along public urban streets and also sometimes on separate rights of way. It may also run between cities and/or towns , and/or partially grade separated even in the cities...

s, where the power supply is carried in a channel under the roadway, rather than located overhead.

Description

The power rails for conduit cars are contained in a vault between and underneath the running rails, much in the same fashion as the cable

Cable

A cable is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. In mechanics cables, otherwise known as wire ropes, are used for lifting, hauling and towing or conveying force through tension. In electrical engineering cables are used to carry...

for cable car

Cable car (railway)

A cable car or cable railway is a mass transit system using rail cars that are hauled by a continuously moving cable running at a constant speed. Individual cars stop and start by releasing and gripping this cable as required...

s. The vault contains two "T" section steel power rails of opposite polarity facing each other, about 12 inches (30.5 cm) apart and about 18 inches (45.7 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 that pushed sideways against the power rails and connected to the car's controller and motor(s)

Electric motor

An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

. The running rails are not part of the electrical circuit. In the United States, the cars were sometimes popularly but incorrectly called trolleys

Tram

but did not typically draw power through a trolley pole

Trolley pole

A trolley pole is a tapered cylindrical pole of wood or metal, used to transfer electricity from a "live" overhead wire to the control and propulsion equipment of a tram or trolley bus. The use of overhead wire in a system of current collection is reputed to be the 1880 invention of Frank J....

from an overhead wire

Overhead lines

Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...

as (strictly defined) trolley cars

Trolleybus

A trolleybus is an electric bus that draws its electricity from overhead wires using spring-loaded trolley poles. Two wires and poles are required to complete the electrical circuit...

do.

Usage

Conduit current collection was one of the first ways of supplying power to electric tramcars 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 which did not permit overhead wires. These included London, Paris, Berlin, Marseilles, Budapest and Prague in Europe and parts of New York City and Washington DC in the United States.

In Denver, Colorado, the world's second electrically operated street railway, starting in 1885, pioneered the use of conduit current collection. Difficulties with the conduit and the electric streetcars led to the replacement of all conduit cars and lines with cable cars by 1888.

New York City

New York City

New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

had the largest installation of conduit cars, due to the prohibition of stringing 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

Brooklyn

Brooklyn is the most populous of New York City's five boroughs, with nearly 2.6 million residents, and the second-largest in area. Since 1896, Brooklyn has had the same boundaries as Kings County, which is now the most populous county in New York State and the second-most densely populated...

and Queens

Queens

Queens is the easternmost of the five boroughs of New York City. The largest borough in area and the second-largest in population, it is coextensive with Queens County, an administrative division of New York state, in the United States....

also entered Manhattan under wire, but did not use city streets. The primary reason for the initial adoption of the conduit "plow" in Manhattan was the fact that return currents from conventional overhead wires using track return grounds were eroding gas mains.

The expense of creating conduit lines in New York was reduced to where it was possible to convert the cable vaults from discontinued cable car lines to conduit use. The huge expense of building new conduit, however, gave New York the distinction of having one of the last horsecar

Horsecar

A horsecar or horse-drawn tram is an animal-powered streetcar or tram.These early forms of public transport developed out of industrial haulage routes that had long been in existence, and from the omnibus routes that first ran on public streets in the 1820s, using the newly improved iron or steel...

lines (the Bleecker Street Line

Bleecker Street Line

The Bleecker Street Line was a public transit line in Manhattan, New York City, United States, running mostly along Bleecker Street, Crosby Street, and Lafayette Street from the West 14th Street Ferry in Chelsea to the Fulton Ferry in the Financial District...

) in the U.S., not closing until 1917. (Pittsburgh

Pittsburgh, Pennsylvania

Pittsburgh is the second-largest city in the US Commonwealth of Pennsylvania and the county seat of Allegheny County. Regionally, it anchors the largest urban area of Appalachia and the Ohio River Valley, and nationally, it is the 22nd-largest urban area in the United States...

actually ran the very last U.S. horsecar, with service ending finally in 1923.)

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 electrical purposes. Occasionally, two competitive lines would share a common track and would have independent slots for the ploughs of the respective cars.

In New York City, the Queensboro Bridge between Manhattan and Queens had tracks installed on the outer lanes with conduit, for Manhattan cars in addition to overhead wire. 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 the centre of Brussels

Brussels

Brussels , officially the Brussels Region or Brussels-Capital Region , is the capital of Belgium and the de facto capital of the European Union...

, a number of tram lines were fitted with conduit, the last ones being converted to overhead operation during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

.

The system was tried in the beachside resort of Blackpool

Blackpool

Blackpool is a borough, seaside town, and unitary authority area of Lancashire, in North West England. It is situated along England's west coast by the Irish Sea, between the Ribble and Wyre estuaries, northwest of Preston, north of Liverpool, and northwest of Manchester...

, UK (see Blackpool tramway

Blackpool tramway

The Blackpool tramway runs from Blackpool to Fleetwood on the Fylde Coast in Lancashire, England, and is the only surviving first-generation tramway in the United Kingdom. The tramway dates back to 1885 and is one of the oldest electric tramways in the world. It is run by Blackpool Transport as...

) but was soon abandoned as sand and saltwater was found to enter the conduit and cause breakdowns and there was a problem with voltage drop. Some sections of tramway track still have the slot rails visible.

Hybrid installations

Washington, D.C.

Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....

had a large network of conduit lines

Washington streetcars

For just under 100 years, between 1862 and 1962, streetcars in Washington, D.C. transported people across the city and region.The first streetcars in Washington D.C...

, to save the capital city from unsightly wires. Some lines used overhead wires

Overhead lines

Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...

when they approached rural

Rural

Rural areas or the country or countryside are areas that are not urbanized, though when large areas are described, country towns and smaller cities will be included. They have a low population density, and typically much of the land is devoted to agriculture...

or suburban areas. The last such line ran to Cabin John, Maryland

Cabin John, Maryland

Cabin John is a census-designated place and an unincorporated area in Montgomery County, Maryland, United States. The placename is a corruption of its original name of "Captain John's Mills."-Geography:...

. The current collector "plow" as it was called, was mounted underneath the car on fitting just forward of the rear truck on D.C. Transit's PCC cars. 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 point to remove the cable attachments to the car and stow the plow, which would not remain with the car, but which would be reattached in an incoming car running on overhead wire. The lower section of the plow "board" was drawn by the moving car above within the cavity of the conduit. Because of this usage, many of Washington's streetcars carried trolley pole

Trolley pole

s, 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

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

also had a hybrid network of double-deck trams: overhead collection was used in the outer sections and conduit in the centre. At the change over from conduit to overhead wire (at what was known as the 'change pit') the change process was largely automatic. The conductor released the trolley pole onto the wire then, as the tram moved forward, the conduit channel veered sideways to outside the running track automatically ejecting the collector plough. The tram was said to be 'shooting the plough'. At the change-over between overhead wire and conduit, the process was a little more complicated. The tram pulled up alongside a ploughman who engaged a two-pronged guide (known as a '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. The conductor could then pull down the trolley pole and stow it. The process is illustrated here. The ploughman's job was a fairly skilled one because, if he failed to locate the plough fork correctly, it or the plough itself 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 track was laid as late as 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 in the Holborn area at the entrance to the former Kingsway Tramway Subway

Kingsway tramway subway

The Kingsway Tramway Subway is a cut-and-cover Grade II Listed tunnel in central London, built by the London County Council, the only one of its kind in Britain...

.

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, while the last Bordeaux conduit car ran in 1953. The conduit systems in Berlin, Vienna and Budapest were very short-lived. All three were replaced by overhead working before World War I.

External links

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Description

Usage

Hybrid installations

See also

External links