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Zig zag to cross the outer dyke on the "railway serving the island of "Nordstrandischmoor off the "German "North Sea coast
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"Darjeeling Himalayan Railway, a "UNESCO "World Heritage site, with 6 full zig zags and 3 "spirals
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Zig zag of the Cecina-Volterra railway[it]

A "railway zig zag, also called a switchback, is a method of climbing steep gradients with minimal need for "tunnels and heavy earthworks.[1] For a short distance (corresponding to the middle leg of the letter "Z"), the direction of travel is reversed, before the original direction is resumed.[2] Not all switchbacks come in pairs, in which case the train may need to travel backwards for a considerable distance.

A location on railways constructed by using a zig-zag alignment at which trains have to reverse direction in order to continue is a reversing station.[3]

One of the best examples is the "Darjeeling Himalayan Railway, a "UNESCO "World Heritage site railway in India, that has six full zig zags and 3 "spirals.[4]

Contents

Advantages[edit]

Zig zags tend to be cheaper to construct because the grades required are discontinuous. Civil engineers can generally find a series of shorter segments going back and forth up the side of a hill more easily and with less grading than they can a continuous grade which has to contend with the larger scale geography of the hills to be surmounted.

Disadvantages[edit]

Zig zags suffer from a number of limitations:

Hazards[edit]

If wagons in a freight train are marshalled poorly, with a light vehicle located between heavy ones (particularly with "buffer couplings), the move on the middle road of a zig zag can cause "derailment of the light wagon.[6]

Examples[edit]

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The switchback between Tanballyŏng and Malhwiri

References[edit]

  1. ^ Raymond, William G. (1912). "Railway Engineering" (Google books). In Beach, Frederick Converse. The Americana: A Universal Reference Library, Comprising the Arts and Sciences, Literature, History, Biography, Geography, Commerce, Etc., of the World. 17. New York: Scientific American Compiling Department. Retrieved 3 January 2010. High mountain levels … may be tunneled … but … may be reached by one of several methods adopted to secure practical grades: (1) Zig-zag development … (2) Switchback development … (3) Spirals or loops … 
  2. ^ Raymond 1912. "Switch-back development … necessitating the use of switches at these ends and the backing of the train up alternate stretches."
  3. ^ Jackson, Alan A. (2006). The Railway Dictionary (4th ed.). Stroud: Sutton Publishing. p. 285. "ISBN "0-7509-4218-5. 
  4. ^ "Mountain Railways of India". UNESCO World Heritage Centre. Retrieved 2006-04-30. 
  5. ^ "The Zig-Zag Deviation". "The Dubbo Liberal and Macquarie Advocate (NSW : 1892–1927). NSW: National Library of Australia. 5 December 1908. p. 4. Retrieved 17 February 2013. 
  6. ^ "The Railway Accident on the Zig-zag". "Bathurst Free Press and Mining Journal (NSW : 1851–1904). NSW: National Library of Australia. 10 April 1895. p. 3. Retrieved 19 February 2013. 
  7. ^ "Historical and Archaeological Assessment of Proposed Cycleway, Near Thornleigh Quarry, Via De Saxe Close, Thornleigh (Berowra Valley Regional Park), N.S.W." (PDF). The construction of the railway siding and zig-zag to the quarry and also Hall’s Camp were associated with Amos & Co, who won the contract to build the section of railway from Strathfield to Hawkesbury River. Edward Higginbotham & Associates PTY LTD. March 2002. Retrieved 19 November 2017. 
  8. ^ "Bang rdsskisser SVJ/HFJ". www.ekeving.se. 
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