Trolley pole
A trolley pole is a tapered cylindrical pole of
An early development of an experimental tramway in Toronto, Ontario, was built in 1883, having been developed by John Joseph Wright, brother of swindler 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 is no evidence about this. Likewise, Wright never filed or was issued a patent.[3]
Credit for development of the first working trolley pole is given to
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
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
On systems with
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 lines to 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.
Single- and double-pole usage
When used on a
Decline in usage on railways
All trolleybuses use trolley poles, and thus trolley poles remain in use worldwide, wherever trolleybuses are in operation (some 315 cities as of 2011[update]),.
However, on most railway vehicles using overhead wire, the trolley pole has given way to the
The trolley pole with a shoe at its tip is problematic for longer modern streetcars that draw more electricity than older streetcars. In Toronto, the
Apart from
Compatibility with pantographs
Trams or light rail cars equipped with pantographs normally cannot operate on lines with overhead wiring designed for trolley-pole collection. For this reason, 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.
However, the
Large portions of San Francisco's surface network are also set up to handle both trolley pole and pantograph operation in order to allow for compatibility both with Muni's current fleet of light rail vehicles (pantograph only), as well as Muni's historic streetcar fleet (trolley pole only).
Cultural references
Upon their introduction, trolley poles and the new electrical technology they represented were fascinating to writers, with their lightning-like sparks and power.
In January 1889, Boston introduced its first electric streetcars, which became so popular and noteworthy that poet Oliver Wendell Holmes composed a verse about the new trolley pole technology, and the sparking contact shoe at its apex:[11]
Since then on many a car you'll see
A broomstick as plain as plain can be;
On every stick there's a witch astride—
The string you see to her leg is tied.
In 1947, composer Samuel Barber wrote the now-classic orchestral and vocal piece Knoxville: Summer of 1915, based on the childhood reminiscences of James Agee. Partway through the composition, the singer refers to a noisy passing streetcar, with its overhead trolley pole and sparks:[12]
A streetcar raising into iron moan;
stopping;
belling and starting, stertorous;
rousing and raising again
its iron increasing moan
and swimming its gold windows and straw seats
on past and past and past,
the bleak spark crackling and cursing above it
like a small malignant spirit
set to dog its tracks;
See also
- Current collectors
- Bow collector
- Collector pole
- Contact shoe
- Pantograph (transport)
- Railway electrification system
References
- ^ Koebel, Romin (2005). "Boston Transit Milestones". MIT Open Courseware. Archived from the original on 2006-09-20. Retrieved 2012-08-01.
- ^ ISBN 0-89024-013-2.
- ^ "Patents of Invention and the Story of Canadian Innovation". Library and Archives Canada.
- ^ Middleton (1967), p. 67.
- ^ "Electric Trolley System". Massachusetts Institute of Technology. Archived from the original on 2006-09-13.
- ISBN 0-9622348-3-4.
- ISBN 978-0-7106-2954-8.
- ^ Munro, Steve (February 22, 2018). "Problems With Trolley Shoes on Flexity Cars". Steve Munro. Retrieved February 27, 2018.
- ^ Munro, Steve (September 12, 2017). "Pantographs Up On Harbourfront". Steve Munro. Retrieved October 2, 2017.
- ^ O'Neil, Lauren (May 15, 2018). "The TTC is rolling out a new type of streetcar technology". blogTO. Retrieved May 18, 2018.
Pantograph on Spadina, @bradTTC/@TTCStuart ... 1:15 PM - May 14, 2018 · 1 Spadina Crescent
- ISBN 0-8289-0173-2.
- ^ Redmont, Jane (6 February 2008). ""Knoxville, Summer 1915:" James Agee, Samuel Barber, Dawn Upshaw". Acts of Hope. Retrieved 2015-05-08.