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EXPANSION IN LONG RAILS

Experiments have been conducted on rails up to 1 mile long. These rails are fixed by means of the resistance of the fishplates, sleeper fastenings, and sleepers themselves embedded in the ballast; thus, for a 75 degrees F temperature variation above and below the temperature at which the rail was laid, a total force of about 61.3 tons (137,800 lb) is brought into play for a 96-lb rail, and the tendency to push the rail ends away from the center of the rail is resisted, and contained within the rail in the form of compressive stress (or with the tendency to contraction, tensile stress). The prevention of a rail from expanding or contracting causes an internal stress of 195 lb per sq. in. for each 1 degree F change in temperature. To minimize these high internal stresses, it is customary to lay long rails at the mean average annual temperature, and thus reduce the tendency of the rail to buckle, if the fastenings should become weakened. One of the great difficulties with long rails, apart from the practical limitations provided by transport, is that the opening up of the track can be done only at approximately the same temperature as that at which the rail was laid. The London Transport railways has used sliding expansion joints at the ends of the long sections. this expansion joint enables the keys to be knocked out, and any tendency toward expansion or contraction which may be imprisoned in the rail can exhaust itself at each end before further operations are begun.

  • Corporate Authors:

    Temple Press Limited

    161-166 Fleet Street
    Longon EC4,   England 
  • Publication Date: 1949-2-11

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Filing Info

  • Accession Number: 00037883
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Dec 4 1994 12:00AM