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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.
When the bow collector was first conceived by German inventor Ernst Werner von Siemens in the late 1880s, American inventor Frank J. Sprague of Virginia had just patented his trolley pole system of current collection from an overhead wire. To avoid contravening this patent, the Siemens company was forced to design its own, unique form of current collection, namely the bow collector. The bow collector was first used by the Siemens electric company in its early electric tramcars in either the late 1880s or early 1890s. The Hobart electric tramway system - the first of its kind in the Southern Hemisphere, opened in 1893 - used Siemens cars with very early bow collectors. Many other continental European and some British tramway systems, including Leeds and Glasgow, also used this method.
The bow collector is one of the simplest and most reliable methods of current collection used on tramways. The very earliest versions were simply very heavy-gauge wire or steel bars bent into a rectangular shape and mounted long-side-down on the tramcar roof. The collector was then raised by a spring, so that its top edge would press against the wire above. That top edge is made of a 1-inch (or more) wide steel rod, machined to have a bow-shaped cross section; that cross-section inspired the name. This bow-shaped rod is referred to as the 'collector plate', and in later models may be up to several inches wide, positive polarity are collected by the bow while the other polarity are at the rails, these are for safety purposes. Unlike many trolley poles, the bow collector does not normally have a revolving base (an exception was in Rome, where the entire assembly could be revolved), but is rather fixed centrally to the tramcar's roof.
After 1900, the simple framing methods mentioned above were gradually replaced by more complex and sophisticated methods, but the general mode of operation remained the same. The changes of design are most noticeable on systems where both double- and single-deck cars were used on the same system. Single deck trams usually have tall and lightly constructed collectors with complicated frames to support the heavy cast-steel collector plate, while double-deck cars usually have heavier collectors with less complicated frames.
To maintain good electrical contact, the bow collector must exert quite strong pressure on the wire above, and so a complex system of springs or weights are put into use to ensure good electrical contact. The wire itself has to be tensioned and kept as flat as possible, a requirement shared for both bow collectors and pantographs.
The steel rails on the tracks act as the electrical return.
Properly the bow collector should be mounted in such a way so that the top edge of the collector plate would rise several inches above the wire when the collector frame is standing straight up. Thus the collector usually leans opposite to the direction of travel; when the time comes to travel in the opposite direction, the collector must be swung over. To allow this to happen, the overhead wire must be raised by several inches at places where the bows are swung over, such as terminals and turn-outs. This operation is usually achieved by ropes and pulleys. The collector is folded down to a horizontal position when the car is not in use.
Some early cars had no means to swing the bows over. It was thought that this would happen automatically when the tramcar started travelling the other way, but collectors such as these were a failure.
Most Soviet trams (of which some are still in use in the USSR's successor states) had no means to swing the bows over. These trams were "single-ended", and not designed to travel both ways. Some trams, such as the KTV-55-2 tram, had two bow collectors to handle both directions.
The bow collector has fewer moving parts than the trolley pole, but is heavier and sometimes more complicated to construct. The construction of overhead wires for bow collectors is simpler than trolley pole wiring. As bow collectors do not have revolving mountings, the collector cannot jump off the wire or follow the wrong one at intersections, as trolley poles sometimes do. Thus overhead 'frogs' and guides for trolley poles are not necessary with bow collectors. Bow collectors are, however, much noisier than trolley poles.
The overhead wires for bow collectors are stretched tighter than for trolley poles, and straight sections are 'staggered', that is, the wire does not run completely straight down the centreline of the track, but rather zig-zags slightly across a small distance. This distributes wear across the bow collector's collector plate, and extends the collector's life. Overhead wires also are 'staggered' for pantographs, so systems may replace bow collectors with pantographs on the trams without modifying the overhead.
In addition to some vintage tramways, bow collectors are still used in some tram systems in the former Soviet Union, e. g., in Kazan, Minsk, and Dzerzhinsk.
On the Isle of Man, the Snaefell Mountain Railway's implementation is unusual in that the overhead wire is slack and free to hang in a catenary. Hopkinson bow collectors are used, to avoid problems with trolley poles in high winds on the mountainous route [1] – the Snaefell line also uses a Fell rail for braking. Each car has two rigidly vertical bow collectors, with a slack wire above them making contact under its own weight. The collectors are not quite tall enough to make contact with the wire at its suspension points. They are far enough apart, relative to the pole spacing, so that while one is out of contact with the wire the other is mid span and making good contact. The collectors can only be lowered by unbolting them at roof level, whilst the power is off. This inability to isolate them easily hampered fire fighting when car 5 caught fire in 1970.[ citation needed ]
Similar collectors were also used at first on the nearby and slightly earlier Manx Electric Railway. They gave trouble initially with poor contact and so the slack wire system was developed. A tensioned wire usually gave a good contact but broke contact when the collector passed the pole. Slackening the wire and deliberately lifting it up clear of the collector at the poles allowed its weight to give a reliable contact over the other collector, spaced to be at the midpoint between poles. A revised collector was in use within the first few years, by 1900. A small hinged bow frame was placed on top of the fixed uprights, giving a sprung contact. [2] Bow collectors did not last though and were replaced with trolley poles.
A tram is a type of urban rail transit consisting of a rail vehicle, either individual railcars or self-propelled trains coupled by a multiple unit, that runs on tramway tracks on urban public streets; some include segments on segregated right-of-way. The tramlines or networks operated as public transport are called tramways or simply trams/streetcars. Many recently built tramways use the contemporary term light rail.
A trolleybus is an electric bus that draws power from dual overhead wires using spring-loaded trolley poles. Two wires, and two trolley poles, are required to complete the electrical circuit. This differs from a tram or streetcar, which normally uses the track as the return path, needing only one wire and one pole. They are also distinct from other kinds of electric buses, which usually rely on batteries. Power is most commonly supplied as 600-volt direct current, but there are exceptions.
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 Manx Electric Railway is an electric interurban tramway connecting Douglas, Laxey and Ramsey in the Isle of Man. It connects with the Douglas Bay Horse Tramway at its southern terminus at Derby Castle at the northern end of the promenade in Douglas, and with the Snaefell Mountain Railway at Laxey. Many visitors take an excursion on the trams. It is the oldest electric tram line in the world whose original rolling stock is still in service.
The Snaefell Mountain Railway is an electric mountain railway on the Isle of Man in Europe. It joins the village of Laxey with the summit of Snaefell, at 2,036 feet (621 m) above sea level the highest point on the island. It connects with the Manx Electric Railway (MER) in Laxey. The line is 5 miles (8 km) long, is built to 3 ft 6 in gauge and uses a Fell Incline Railway System centre rail for braking on the steep gradients. It is electrified using overhead wires at 550 volts direct current, with bow collectors.
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.
The National Tramway Museum is a tram museum located at Crich, Derbyshire, England. The museum contains over 80 trams built between 1873 and 1982 and is set within a recreated period village containing a working pub, cafe, old-style sweetshop and tram depots. The museum's collection of trams runs through the village-setting with visitors transported out into the local countryside and back and is operated by the Tramway Museum Society, a registered charity.
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.
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 Saint-Étienne tramway is a tram system in the city of Saint-Étienne in the Rhône-Alpes (France) that has functioned continuously since its opening in 1881. The first tramway line was steam-operated and was opened by the Chemins de Fer à Voie étroite de Saint-Étienne (CFVE) on 4 December 1881, stretching for 5.5 km between La Terrasse and Bellevue. The CFVE took over the Compagnie des Tramways Électriques de Saint-Étienne lines and discontinued the use of steam in 1912.
A trolleytruck is a trolleybus-like vehicle used for carrying cargo instead of passengers. A trolleytruck is usually a type of electric truck powered by two overhead wires, from which it draws electricity using two trolley poles. Two current collectors are required in order to supply and return current, because the return current cannot pass to the ground since trolleytrucks use tires that are insulators. Lower powered trucks, such as might be seen on the streets of a city, tend to use trolley poles for current collection. Higher powered trucks, such as those used for large construction or mining projects, may exceed the power capacity of trolley poles and have to use pantographs instead. Trolleytrucks have been used in various places around the world and are still in use in cities in Russia and Ukraine, as well as at mines in North America and Africa. Because they draw power from the mains, trolleytrucks can use renewable energy sources – modern trolleytrucks systems are under test in Sweden and Germany along highways using diesel–electric hybrids to reduce emissions.
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.
A rubber-tyred tram is a development of the guided bus in which a vehicle is guided by a fixed rail in the road surface and draws current from overhead electric wires.
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.
The Cantono Frigerio system was an Italian electric power supply for trackless trolleybuses with two wires about 20 inches (50 cm) apart being contacted by a four-wheeled collector on a single trolley pole. In English publications it was often described as Filovia system although the Italian term filovia means literally wire way, i.e. a trolleybus line or a trolleybus system.
Stockport Corporation Tramways operated a tramway service in Stockport, England, between 1901 and 1951. It was preceded by a horse tramway from Levenshulme to Stockport, which opened in 1880, and was ultimately run by the Manchester Carriage and Tramways Company. A second independent horse tramway opened in 1890, running to Hazel Grove. In 1899 the Corporation bought the first line, electrified it, and leased it back to the operating company. Their powers to buy the Stockport and Hazel Grove Tramway, authorised by the same Act of Parliament, were not exercised until 1905.