RAILWAY ENGINEERING AND CONSTRUCTION. In railway engineering the railway track more than any other part of the railway machine had a crude beginning and has reached its present condition of ex cellence by a continuous series of improvements. In the first stages of construction, tracks of numerous designs were built, the chief thought of the builders being to secure a solid structure that would not allow the rails to spread. The track was of necessity relatively heavy and expensive in relation to the weight of the rolling stock and volume of traffic. Three kinds of rails were used, the one most generally employed consisting of strong wooden beams, surfaced with strap iron. The iron rails first used were cast and their length did not exceed three and one-half feet. Rolled rails were soon substi tuted for those of cast-iron and the length was increased to 15 feet, with a weight of about 40 pounds to the yard. Up to 1844 all rolled iron rails used in the United States were 15 feet in length. The T-rail now universally em ployed was not much used during the first 20 years of railroad construction. Since 1870 rolled steel has been used instead of iron and the weight of the rail has been steadily in creased to 110 pounds to the yard. One hundred pounds to the yard has become the standard upon tracks where traffic is heaviest. The standard length of rail has been maintained at 30 feet, but at the present time some track is being laid with rails 60 feet in length. Along with the improvements in the track, bridges and other structures have been strengthened to meet the necessities of the modern transportation methods.
The whole trend of modern engineering is toward constant increase in the search after and adoption of labor-saving appliances, on the one hand, and constant increase in the develop ment and elaboration of systems on the other. This is especially true in railway engineering, and an examination of recent subway, tunnel and bridge constructions and other engineering operations serve to point out the wonderful progress in engineering methods and the present easy accomplishment of former undertakings either abandoned or considered impossible.
Construction.—A perfect and safe track is complete in all respects when full bolted, full spiked, well ballasted, surfaced, lined and gauged. The best dirt ballasted track is made when laying it, by bedding the tics to a level surface on top before putting on the rails. If it is intended to ballast track with cinders, gravel or stone, as fast as it is laid, the tie bedding is omitted in order to have the full width of the grade upon which to deposit the ballast, but at the same time the ballasting should be kept well finished up to obviate the danger of spoiling the rails. When laying the rails care is taken to the proper space at the joints for expansion. Too much space at the joints must be avoided in .order to prevent the car wheels from battering the ends of the rails. The coefficient of expansion for steel is .0000065 of its length for each degree. For a rail 30 feet long and a difference of 100 degrees, or from 10° below zero to 90°, the amount to allow would be one-quarter inch. To take up the flow of the rail one-eighth inch must be added, making a total allowance of three-eighths inch. A steel rail expands or contracts 1-1()0,000 of a length under a load of one ton (2,240 pounds) per square inch. This is also its ex pansion under a rise of 15° of temperature: consequently, if a 30-foot rail is subjected to a rise or fall of 15°, it exerts a force of one ton per square inch if resisted. Where angle bar splices are used on joints the best method to hold steel and to keep it from creeping down grades or from running ahead enough to throw the track out of line or kink the rails, is to use the slot spikes in the splices. Short rails (less than 10 feet in length) should never be used in making connections except in cases where it is absolutely necessary to use short pieces of rail as at the ends of frogs, in the round house tracks, etc.