Trolley pole
Encyclopedia
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. Sprague
.
The term trolley is also used to describe the pole or the passenger car using the trolley pole is derived from the grooved
conductive
wheel
(trolley or troller) attached to the end of the pole that "trolls" the overhead wire.
An early development of an experimental tramway in Toronto
, Ontario
was built in 1883, having been developed by John Joseph Wright, brother of the mining entrepreneur Whitaker Wright
. While Wright may have assisted in the installation of electric railways at the Canadian National Exhibition (CNE), and may even have used a pole system, there's no hard evidence to prove it. Likewise, Wright never filed or was issued a patent. Official credit for the invention of the electric trolley pole has gone to an American, Frank J. Sprague
, who installed a working system in Richmond, Virginia, in 1888. Known as the Richmond Union Passenger Railway
, this 12 mile system was the first large-scale trolley line in the world, opening to great fanfare on February 12, 1888.
The grooved trolley wheel was used on many large city systems through the 1940s and 1950s; it was generally used on systems with "old" style round cross sectional overhead wire. The trolley wheel was problematic at best; the circumferential contact of the grooved wheel bearing on the underside of the overhead wire provided minimal electrical contact and tended to arc excessively, increasing overhead wire wear . The newer sliding carbon trolley shoe was generally used with a "newer" grooved overhead trolley wire of a figure "8" cross section. The sliding trolley shoe provided better electrical contact (with a reduction in arcing), and it dramatically reduced overhead wire wear. Many systems began converting to the sliding trolley shoe in the 1920s; Milwaukee, Wisconsin converted its large system in the late 1920s. Curiously, Philadelphia did not convert its trolley wheels on its remaining streetcars until 1978. Although a streetcar with a trolley wheel may evoke an antique look, the trolley shoe is modern and more practical as well as economical.
On systems with double-ended railway cars capable of running in both directions, the trolley pole must always be pulled behind the car and not pushed, or dewiring is very likely, which can cause damage to the overhead wires. At terminus points, the conductor must turn the trolley pole around to face the correct direction, pulling it off the wire either with a rope or a pole and walking it around to the other end. In some cases, two trolley poles are provided, one for each direction: in this case it is a matter of raising one and lowering the other. Since the operator could raise the pole at one end whilst the conductor lowered the other, this saved time and was much easier for the conductor. Care must be taken to raise the downed pole first, to eliminate the damage caused by arcing between the pole and wire. In the US, the dual-pole system was the most common arrangement on double-ended vehicles. However, pushing of the pole (called "back-poling" in the US or "spear-poling" in Australia), was quite common where the trams were moving at slow speeds, such as at wye terminals (also known as reversers) and whilst backing into the sheds.
Trolley poles are usually raised and lowered manually by a rope from the back of the vehicle. The rope feeds into a spring reel mechanism, called a trolley catcher or "trolley retriever". The trolley catcher contains a detent, like that in an automotive shoulder safety belt
, which "catches" the rope to prevent the trolley pole from flying upward if the pole is dewired. The similar looking retriever (see photo) adds a spring mechanism that yanks the pole downward if it should leave the wire, pulling it away from all overhead wire fittings. Catchers are commonly used on trams operating at lower speeds, as in a city, whilst retrievers are used on suburban and interurban linesto limit damage to the overhead at speed.
On some older systems, the poles were raised and lowered using a long pole with a metal hook. Where available, these may have been made of bamboo
due to its length, natural straightness and strength, combined with its relative light weight and the fact that it is an insulator. Trolleybuses usually carried one with the vehicle, for use in the event of dewirement, but tram systems usually had them placed along the route at locations where the trolley pole would need reversing.
The poles used on trolleybuses are typically longer than those used on trams, to allow the bus to take fuller advantage of its not being restricted to a fixed path in the street (the rails), by giving a degree of lateral steerability, enabling the trolleybus to board passengers at curbside.
, i.e., a railway vehicle, a single trolley pole usually collects current from the overhead wire, and the steel rails on the tracks act as the electrical return
. Trolleybus
es, on the other hand, must use two trolley poles and dual overhead wires, one pole and wire for the positive "live" current, the other for the negative or neutral return
. The tramway system in Havana
, Cuba
also utilised the dual wire system, as did the Cincinnati (Ohio)
streetcar system. To reduce electrolytic damage to underground pipes and metallic structures, most tram lines operated with the wire positive with respect to the rails.
and Lekov
.
However, on most railway vehicles using overhead wire, the trolley pole has given way to the bow collector
or, later, the pantograph
, a folding metal device that presses a wide contact pan against the overhead wire. While more complex than the trolley pole, the pantograph has the advantage of being almost free from dewiring, being more stable at high speed, and being easier to raise and lower automatically. Also, on double-ended trams, they eliminate the need to manually turn the trolley pole when changing direction. The use of pantographs (or bow collectors) exclusively also eliminates the need for wire frogs (switches in the overhead wiring) to make sure the pole goes in the correct direction at junctions.
Apart from heritage streetcar
lines, very few tram/streetcar systems worldwide continue to use trolley poles on vehicles used in normal service. Among the largest exceptions are the streetcar systems of Toronto, Ontario
; Philadelphia (the "Subway-Surface" lines and route 15); Riga, Latvia
, Kolkata (formerly Calcutta), India
and Alexandria, Egypt. Smaller systems still using trolley poles for regular service include Hong Kong Tramways
, the Daugavpils, Latvia system
, and Rio de Janeiro
's Santa Teresa Tramway.
These systems and a few others worldwide retain use of trolley poles, even on new streetcars, in order to avoid the difficulty and expense of modifying long stretches of existing overhead wires to accept pantographs. Trams or light rail
cars equipped with pantographs normally cannot operate on lines with overhead wiring designed for trolley-pole collection. It is possible to construct overhead wiring that is capable of accommodating both trolley poles and pantographs, but such designs are more expensive to maintain and are generally seen only in cities where modern streetcars or light rail cars share tracks with preserved historic cars.
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
or metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
, used to transfer electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
from a "live" 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...
to the control and propulsion equipment of a 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...
or trolley bus. The use of overhead wire in a system of current collection is reputed to be the 1880 invention of Frank J. Sprague
Frank J. Sprague
Frank Julian Sprague was an American naval officer and inventor who contributed to the development of the electric motor, electric railways, and electric elevators...
.
Origin of the term
The term 'trolley' predates the invention of the trolley pole. The earliest electric cars did not use a pole, but rather a system in which each car dragged behind it an overhead cable connected to a small cart that rode on a 'track' of overhead wires. From the side, the dragging lines made the car seem to be 'trolling' as in fishing. Later, when a pole was added, it came to be known as a trolley pole.The term trolley is also used to describe the pole or the passenger car using the trolley pole is derived from the grooved
Groove (machining)
In manufacturing or mechanical engineering a groove is a long and narrow indentation built into a material, generally for the purpose of allowing another material or part to move within the groove and be guided by it. Examples include:...
conductive
Electrical conductor
In physics and electrical engineering, a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons...
wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...
(trolley or troller) attached to the end of the pole that "trolls" the overhead wire.
An early development of an experimental tramway in Toronto
Toronto
Toronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...
, Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
was built in 1883, having been developed by John Joseph Wright, brother of the mining entrepreneur Whitaker Wright
Whitaker Wright
James Whitaker Wright was an exceptionally wealthy English mining company owner. He became infamous when he committed suicide at the Royal Courts of Justice in London immediately following his conviction for fraud....
. While Wright may have assisted in the installation of electric railways at the Canadian National Exhibition (CNE), and may even have used a pole system, there's no hard evidence to prove it. Likewise, Wright never filed or was issued a patent. Official credit for the invention of the electric trolley pole has gone to an American, Frank J. Sprague
Frank J. Sprague
Frank Julian Sprague was an American naval officer and inventor who contributed to the development of the electric motor, electric railways, and electric elevators...
, who installed a working system in Richmond, Virginia, in 1888. Known as the Richmond Union Passenger Railway
Richmond Union Passenger Railway
The Richmond Union Passenger Railway, in Richmond, Virginia, was the first practical electric trolley system, and set the pattern for most subsequent electric trolley systems around the world. It is an IEEE milestone in engineering....
, this 12 mile system was the first large-scale trolley line in the world, opening to great fanfare on February 12, 1888.
The grooved trolley wheel was used on many large city systems through the 1940s and 1950s; it was generally used on systems with "old" style round cross sectional overhead wire. The trolley wheel was problematic at best; the circumferential contact of the grooved wheel bearing on the underside of the overhead wire provided minimal electrical contact and tended to arc excessively, increasing overhead wire wear . The newer sliding carbon trolley shoe was generally used with a "newer" grooved overhead trolley wire of a figure "8" cross section. The sliding trolley shoe provided better electrical contact (with a reduction in arcing), and it dramatically reduced overhead wire wear. Many systems began converting to the sliding trolley shoe in the 1920s; Milwaukee, Wisconsin converted its large system in the late 1920s. Curiously, Philadelphia did not convert its trolley wheels on its remaining streetcars until 1978. Although a streetcar with a trolley wheel may evoke an antique look, the trolley shoe is modern and more practical as well as economical.
Description of the device
A trolley pole is not "attached" to the overhead wire. The pole sits atop a sprung base on the roof of the vehicle, with springs providing the pressure to keep the trolley wheel or shoe in contact with the wire. If the pole is made of wood, a cable brings the electrical current down to the vehicle. A metal pole may use such a cable, or may itself be electrically "live", requiring the base to be insulated from the vehicle body.On systems with double-ended railway cars capable of running in both directions, the trolley pole must always be pulled behind the car and not pushed, or dewiring is very likely, which can cause damage to the overhead wires. At terminus points, the conductor must turn the trolley pole around to face the correct direction, pulling it off the wire either with a rope or a pole and walking it around to the other end. In some cases, two trolley poles are provided, one for each direction: in this case it is a matter of raising one and lowering the other. Since the operator could raise the pole at one end whilst the conductor lowered the other, this saved time and was much easier for the conductor. Care must be taken to raise the downed pole first, to eliminate the damage caused by arcing between the pole and wire. In the US, the dual-pole system was the most common arrangement on double-ended vehicles. However, pushing of the pole (called "back-poling" in the US or "spear-poling" in Australia), was quite common where the trams were moving at slow speeds, such as at wye terminals (also known as reversers) and whilst backing into the sheds.
Trolley poles are usually raised and lowered manually by a rope from the back of the vehicle. The rope feeds into a spring reel mechanism, called a trolley catcher or "trolley retriever". The trolley catcher contains a detent, like that in an automotive shoulder safety belt
Seat belt
A seat belt or seatbelt, sometimes called a safety belt, is a safety harness designed to secure the occupant of a vehicle against harmful movement that may result from a collision or a sudden stop...
, which "catches" the rope to prevent the trolley pole from flying upward if the pole is dewired. The similar looking retriever (see photo) adds a spring mechanism that yanks the pole downward if it should leave the wire, pulling it away from all overhead wire fittings. Catchers are commonly used on trams operating at lower speeds, as in a city, whilst retrievers are used on suburban and interurban linesto limit damage to the overhead at speed.
On some older systems, the poles were raised and lowered using a long pole with a metal hook. Where available, these may have been made of bamboo
Bamboo
Bamboo is a group of perennial evergreens in the true grass family Poaceae, subfamily Bambusoideae, tribe Bambuseae. Giant bamboos are the largest members of the grass family....
due to its length, natural straightness and strength, combined with its relative light weight and the fact that it is an insulator. Trolleybuses usually carried one with the vehicle, for use in the event of dewirement, but tram systems usually had them placed along the route at locations where the trolley pole would need reversing.
The poles used on trolleybuses are typically longer than those used on trams, to allow the bus to take fuller advantage of its not being restricted to a fixed path in the street (the rails), by giving a degree of lateral steerability, enabling the trolleybus to board passengers at curbside.
Single- and double-pole usage
When used on a trolley car or tramTram
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...
, i.e., a railway vehicle, a single trolley pole usually collects current from the overhead wire, and the steel rails on the tracks act as the electrical return
Ground (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
. Trolleybus
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...
es, on the other hand, must use two trolley poles and dual overhead wires, one pole and wire for the positive "live" current, the other for the negative or neutral return
Ground (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
. The tramway system in Havana
Havana
Havana is the capital city, province, major port, and leading commercial centre of Cuba. The city proper has a population of 2.1 million inhabitants, and it spans a total of — making it the largest city in the Caribbean region, and the most populous...
, Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
also utilised the dual wire system, as did the Cincinnati (Ohio)
Cincinnati streetcars
Cincinnati streetcars were the main form of public transportation in Cincinnati, Ohio at the turn of the twentieth century. The original streetcar system was dismantled in 1951....
streetcar system. To reduce electrolytic damage to underground pipes and metallic structures, most tram lines operated with the wire positive with respect to the rails.
Decline in usage on railways
All trolleybuses use trolley poles, and thus trolley poles remain in use worldwide, wherever trolleybuses are in operation (currently, some 315 cities), and several manufacturers continue to make them, including Vossloh-Kiepe, ŠkodaŠkoda Works
Škoda Works was the largest industrial enterprise in Austro-Hungary and later in Czechoslovakia, one of its successor states. It was also one of the largest industrial conglomerates in Europe in the 20th century...
and Lekov
Lekov (Czech Republic)
Lekov is a Czech company, builder of electrical parts.-Customers:Production of LEKOV is used by the following companies:*Alstom*ELIN EBG Traction*Bombardier Transportation*GE Transportation Systems*Jihlavská lokomotivní společnost s.r.o....
.
However, on most railway vehicles using overhead wire, the trolley pole has given way to the bow collector
Bow collector
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 has now been largely replaced by the pantograph.-Origins:...
or, later, the pantograph
Pantograph (rail)
A pantograph for rail lines is a hinged electric-rod device that collects electric current from overhead lines for electric trains or trams. The pantograph typically connects to a one-wire line, with the track acting as the ground wire...
, a folding metal device that presses a wide contact pan against the overhead wire. While more complex than the trolley pole, the pantograph has the advantage of being almost free from dewiring, being more stable at high speed, and being easier to raise and lower automatically. Also, on double-ended trams, they eliminate the need to manually turn the trolley pole when changing direction. The use of pantographs (or bow collectors) exclusively also eliminates the need for wire frogs (switches in the overhead wiring) to make sure the pole goes in the correct direction at junctions.
Apart from heritage streetcar
Heritage streetcar
Heritage streetcars or heritage trams are a development of the heritage railways that are becoming popular across the world. As with modern streetcar systems, the vehicles are referred to as trams or tramcars in the United Kingdom, Australasia and certain other places , but as streetcars or...
lines, very few tram/streetcar systems worldwide continue to use trolley poles on vehicles used in normal service. Among the largest exceptions are the streetcar systems of Toronto, Ontario
Toronto streetcar system
The Toronto streetcar system comprises eleven streetcar routes in Toronto, Ontario, Canada, operated by the Toronto Transit Commission , and is the largest such system in the Americas in terms of ridership, number of cars, and track length. The network is concentrated primarily in downtown and in...
; Philadelphia (the "Subway-Surface" lines and route 15); Riga, Latvia
Rigas Satiksme
Rīgas Satiksme is a limited liability company of Riga municipality which operates public transport and vehicle hire in the Latvian capital Riga and its surrounding areas. The organisation's principal activities involve the operation of the city's 476 buses, 354 trolleybuses and 267 trams. It is...
, Kolkata (formerly Calcutta), India
Calcutta Tramways Company
The Calcutta Tramways Company Limited is a West Bengal, India government-run company which runs trams in Kolkata and buses in and around Kolkata...
and Alexandria, Egypt. Smaller systems still using trolley poles for regular service include Hong Kong Tramways
Hong Kong Tramways
Hong Kong Tramways is a tram system in Hong Kong and one of the earliest forms of public transport in Hong Kong. Owned and operated by Veolia Transport, the tramway runs on Hong Kong Island between Shau Kei Wan and Kennedy Town, with a branch circulating Happy Valley...
, the Daugavpils, Latvia system
Daugavpils Tramway
Daugavpils Tramway , the tram system of the Latvian town of Daugavpils, was opened on 5 November 1946 with a Russian broad-gauge trackage . An uncommon characteristic of this system is the use of trolley poles for current collection....
, and Rio de Janeiro
Rio de Janeiro
Rio de Janeiro , commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th...
's Santa Teresa Tramway.
These systems and a few others worldwide retain use of trolley poles, even on new streetcars, in order to avoid the difficulty and expense of modifying long stretches of existing overhead wires to accept pantographs. Trams or light rail
Light rail
Light rail or light rail transit is a form of urban rail public transportation that generally has a lower capacity and lower speed than heavy rail and metro systems, but higher capacity and higher speed than traditional street-running tram systems...
cars equipped with pantographs normally cannot operate on lines with overhead wiring designed for trolley-pole collection. It is possible to construct overhead wiring that is capable of accommodating both trolley poles and pantographs, but such designs are more expensive to maintain and are generally seen only in cities where modern streetcars or light rail cars share tracks with preserved historic cars.