The with its broad base and direct attachment to the cross ties, would seem to have the advantag-e, in this respect, of the chair-rail, with its narrow base and indirect form of fastening. The ease with which the flange-rail may be secured to the sleeper with fastenings of the simplest kind is another notable advantage in its favor; there is also a decided gain in economy in the case of the flange-rail in dispensing with the chairs. These advantages have been deemed sufficient to induce the almost uni versal adoption of the flange-rail in Continental Europe and America.
The keved in chairs, was at one time in general use in France, but it has been removed and the flange-rail substituted, with its simpler mode of fastening. In Great Britain the chair-rail, in the form of either the doubled-headed rail (,o/. 24, figs. 13, 1,5) or the bull-headed rail, is in common nse; to a limited extent, however, the flange-rail is in Ilse in Ireland. The advantages claimed for the double-headed rail are that it may be turned or reversed when the head is worn; that, the mode of fastening being less rigid than that of the flange-rail, it causes less dis turbance of the superstructures; and that it involves less labor for mainte nance. Of these alleged advantages, the first named appears to be the only one of any importance. On the other hand, the under side of the reversible rail is liable to be indented by hammering against its seat, unless the precaution is taken to cushion the blow of the wheels transmitted by passing loads, and the mode of securing the rail in the chair by means of wooden keys does not altogether prevent the " creeping " or longitudinal displacement of the rail.
The A'ail, according to Mr. D. K. Clark, is the form in use in the majority of the railway lines of England and Scotland, and pos sesses all " the advantages of the donble-headed rail, except that, like the flange-rail, it is not reversible." Lacking the element of reversibility, the advantages of the bull-headed rail are questionable, and its very general use in the United Kingdom, notwithstanding, is not readily explained.
SII7e anal Weight qf dimensions of rails vary considerably according- to the traffic weight they are to bear. In English practice, according, to Clark, doubled-headed and bull-headed rails " are rolled to a weig,dit of from eighty-two to eightv-six pounds per yard; the heads are made from 21/, to inches wide; the webs are from to tylif, of an inch in thickness, and the height of the rail varies from 51/1. to inches." The usual length is 3o feet. The weig,ht of rails on standard-gauge rail roads in the United States will vary from sixty to eig,hty pounds per yard. The common practice is to employ rails of from sixty to sixty-five pounds per yard. Thirty feet long- and 4 inches ltig,11 are -usual dimensions. Rails
weighing as ninch as one hundred pounds to the yard are in use on certain English roads where the traffic is unusually heavy, and also to a limited extent in the United States (Pennsylvania Railroad).
adapting rails to curves, rail-bending machines of various forms are employed. Plate 24 (figs. 2oa, b) exhibits a machine for this purpose. In this the ends of the rail are drawn down bv means of levers. Fig-nre 21 exhibits a rail-bending machine with adjustable rollers. Hydraulic machines for the same purpose are in COM T11011 use.
The are of cast iron, weighing from thirty to fifty pounds and having a width of from 43! to 8 inches. The rails are secured in place in the chairs by means of keys of hard wood (oak) or iron, and fregnently are supported on cushions of hard wood placed on the chairs, which afford an elastic bearing for the rail. This arrangement not only contributes to the smooth running of trains, but also prevents the indentation of the lower head of the rails. Such modes of support are seen in Fig-ures and 15. As above remarked, the use of the chair-rail is confined princi pally to Great I3ritain, the general verdict of railway engineers being- that it is a cumbrous and expensive expedient without any notable offsetting ad vantages.
Rail Conned/oils: order to prevent the vertical or hori zontal displacement of the rails at the joints from the weight of passing trains, the ends of contiguous rails are firmly united by so-called " fish plates" and angle-plates of iron or steel of various forms. This mode of union is seen in Figures 17 and IS. A typical form of fish-plate is shown in Fig-nre 12. Figure 25c exhibits the very powerful fish-plate joint of the Hartwich rail. These devices consist of two parallel iron or steel plates placed within the side-channels of the rail and firmly fastened to the latter and to each other by bolts and nuts (of which there are two to each rail end) passing throng-1i the web of the rail. These plates are commonly rolled in long bars, which are afterward cut off in proper lengths, usually 2 feet, and the weight of the complete joint, including- bolts and tints, is about twenty ponnds. The sharp undercut rail-head (fig. 12) is more favorable for this form of fastening than the sloping form (fig. 16), since the former offers a better bearing-snrface and makes a stronger joint. To give greater vertical stiffness to the joint, the fish-plates are in some cases carried down along- the lower member of the rail, and occasionally are turned tinder it (clip fish-plates).