RAILS AND THEIR FASTENINGS.
Early Forms of first rails were made of east iron, and con tinued in use until Birkenshaw of Bedlington, Durham (England), made the first rolled rail of wrought iron, the metal, while hot, being-, passed between grooved rollers of the required pattern. The cast-iron rails had several disadvantages. They could not be made in lengths exceeding or 2 yards, and they possessed so little elasticity that they were readily broken, not only by concussion, but also where the support of the sleepers was insufficient. The first rolled rails—the " fish-bellied " pattern, laid in cast-iron chairs—were modelled after those of east iron. Robert Ste phenson is believed to have been the earliest to introduce (about 1838) rolled rails of uniform cross-section. These were at first supported upon longi tudinal sleepers, but the plan was soon abandoned in favor of the cross-tie system, now almost universally employed.
ana' Steel rolled rail of wroug,Tht iron WaS decidedly superior to the cast-iron rail, and, its length and weight being increased to conform to the progressive increase in the weight of locomo tives and trains, it served its purpose passably well for thirty years. Within the past twenty years, however, there has been an enormous growth of railroad traffic. To accommodate this, the power and weight of locomotives have been materially augmented to enable them to draw heavier trains, the average speed has been raised, and powerful mechanical appliances have been introduced to permit of the quick stopping of the trains. Consequently, the wear of the rails has been greatly increased, and, had not the development of the Bessemer steel process, proceeding coincidently with the growth of railway traffic, made it possible to produce rails of much greater power to resist wear than the rolled-iron rail, the railway systetn, as Mr. D. K. Clark forcibly puts it, " would have broken down under the enormous growth of traffic." At the present time iron rails have practically gone out of use, and upon all the principal railway lines of Europe and America, Bessemer (and to a slight extent, also, open hearth) steel rails have taken their place. How completely this statement may be verified by American practice will appear from the fact that dur ing the year ISS7, out of the total production of 2,139,64o tons of rails, 2,119,049 tons were of steel, and only 20,591 tons of iron.
The life of a steel rail is commonly estimated to be six times that of an iron rail of the same weight. This is an understatement, as there are
many situations (in and about stations, in yards, etc.) where, under the weight of the ponderous freight-engines employed in shifting and making up trains, a steel rail will outwear fifteen or twenty rails of iron, which latter would be so badly battered and laminated as to require replacement after one or two years of service, the steel rail in the same period exhibit ing little, if any, signs of wear.
respect to the form of the rail and the mode of fastening, the following general types may be recognized—namely, the chair-rail, almost universally nsed on the British railways (1/. 24, Jig.
in which the rail is supported in cast-iron chairs on cross-ties of wood or other material; the longitudinal-sleeper (or stringer) system (fig. 9), in which the rail is continuously supported: restricted, at present, to tram ways or street railways in cities; the flange-rail system (fig. 17), with a broad-base rail secured directly to cross-ties: in general use in Germany, France, and elsewhere in Europe, and universally in the United States and Canada; and the metallic permanent way, in which the superstructure is entirely of iron (figs. in use to a limited extent in various Euro pean countries.
The Forms of Rails that have been devised are legion, but it will suffice to refer to those only that have come into general use. These are (1) the flat, or street-car, rail (fig. 9c); (2) the bridge, or Brunel, rail (fig. n); (3) the single-headed chair-rail (fig. 14); (4) the double-headed chair rail (fig. 13); (5) the broad-base rail (fig. 12), called variously the flange rail, T-rail, Stevens, or •Vignoles rail; (6) the Barlow rail (fig. 24). At the present time the flange-rail and the chair-rail (single and double headed) are the two forms that are nearly universally employed, and these alone need to be considered in connection with the question of the most advan tag-eous form of rail. The strain to which a rail will be subjected is that resulting not only from the vertical pressure of the load, but also from a lateral pressure, usually from the swaying of the moving- load from side to side. The rail, therefore, in addition to a sufficient cross-section to with stand the first strain, must have sufficient lateral stiffness to withstand the second.