Rail gauges & rail sections Railway Engineering


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Rail gauges & rail sections Railway Engineering

  2. 2. RAIL GAUGES The gauge of a railway track is defined as the clear minimum perpendicular distance between the inner faces of the two rails. 2
  3. 3. RAIL GAUGES Following are the factors affecting the choice of a gauge: 1. Traffic Condition: If the intensity of traffic on the track is likely to be more, a gauge wider than the standard gauge is suitable. 2. Development of Poor Areas: The narrow gauges are laid in certain parts of the world to develop a poor area and thus link the poor area with the outside developed world. 3
  4. 4. RAIL GAUGES 4. Speed of Movement:  The speed of a train is a function of the diameter of wheel which in turn is limited by the gauge.  The wheel diameter is usually about 0.75 times the gauge width and thus, the speed of a train is almost proportional to the gauge.  If higher speeds are to be attained, the B.G track is preferred to the M.G or N.G track. 4
  5. 5. RAIL GAUGES 3. Cost of Track:  The cost of railway track is directly proportional to the width of its gauge.  If the fund available is not sufficient to construct a standard gauge, a metre gauge or a narrow gauge is preferred rather than to have no railways at all. 5
  6. 6. RAIL GAUGES 5. Nature of Country:  In mountainous country, it is advisable to have a narrow gauge of the track since it is more flexible and can be laid to a smaller radius on the curves.  This is the main reason why some important railways, covering thousands of kilometers, are laid with a gauge as narrow as 610 mm. 6
  7. 7. RAIL GAUGES The different gauges can broadly be divided into the following four categories: 1) Broad Gauge: width 1676 mm to 1524 mm or 5’6” to 5’0” 2) Standard Gauge: width 1435 mm and 1451 mm or 4’-8⅟2” 3) Metre Gauge: width 1067 mm, 1000 mm and 915 mm or 3’-6”, 3’-33/8” and 3’-0” 4) Narrow Gauge: width 762 mm and 610 mm or 2’-6” and 2’-0”. 7
  8. 8. RAILS The high carbon rolled steel sections, which are laid end-to-end, in two parallel lines over sleepers to provide continuous and leveled surface for the trains to move and for carrying axle loads of the rolling stock are called rails. 8
  9. 9. RAILS Functions of the rails: To provide continuous and level surface for the movement of trains with minimum friction with steel wheels of the rolling stock; Provide strength, durability and lateral guidance to the track; Transmit the axle loads to sleepers which transfer the same load to the underlying ballast and formation; Bear the stresses developed due to heavy vertical loads, breaking forces and temperature variance.9
  10. 10. RAILS Types of rails: 1. Double Headed Rails 2. Bull Headed Rails 3. Flat-footed Rails 10
  11. 11. RAILS 1. Double Headed Rails:  This type of rail consists of three parts – upper table, web, and lower table;  Both the upper and lower tables were identical;  They were introduced with the hope of doubling the life of rails;  When the upper table was worn out, the rails can be reversed in the chair and thus, the lower table can be brought into use; 11
  12. 12. RAILS However, this idea soon turned out to be wrong because it was observed that long contact with chairs made the surface of lower table very rough and smooth running of trains was then impossible. Thus, these rails are nowadays practically out of use; 12
  13. 13. RAILS 2. Bull Headed Rails:  These rails consist of head, web and foot and are made of steel;  The head is larger than the foot and the foot is designed only to properly hold the wooden keys with which the rails are secured to chairs; 13
  14. 14. RAILS The two cast-iron chairs are required per each sleeper when these rails are adopted. These rails are extensively used in England and in some parts of Europe. 14
  15. 15. RAILS 3. Flat-footed Rails: In this type of rail, the foot is spread out to form a base; This form of rail was invented by Charles Vignoles in 1836 and hence, these rails are sometimes known as Vignoles rails; At present, about 90% of the railway track in the world is laid with this form of rails. 15
  16. 16. RAILS 16 Advantages: i. Chairs: No chairs are required in this form of rails. The foot of the rail is directly spiked to the sleepers. This fact makes them economical. ii. Stiffness: This form of rail is stiffer, both vertically and laterally than the bull-headed rail of equal weight. Especially on curves, the lateral stiffness of rails is very important. iii. Kinks: This form of rail is less liable to develop kinks and it maintains a more regular top surface than the bull-headed rails.
  17. 17. RAILS iv. Cost: The flat footed rails are found to be cheaper than the bull-headed rails. v. Load Distribution: The flat footed rail distributes the train load over a great number of sleepers. This results in greater track stability. 17