A more economical method of securing permanent construction is by the use of .a. concrete beam or stringer under the rail. This method of construction is illustrated in Fig. 46. The concrete stringers are usually made of Portland-cement concrete from 9 to 12 inches in depth and 12 to 18 inches in width The rails are commonly held in place by iron ties, to which the base of the rail is bolted, as shown in figure. Fre quently light angle-bars are used for ties, but various other sections have also been employed for which special advantages are claimed. Spacing rods between the webs of the rails may also be employed as shown in Fig. 45, but these rods are objectionable in a block pavement on account of the difficulty of paving be tween them. The ties are usually spaced about ten feet apart.
In some instances, where concrete beams are used under the rails, ties are omitted altogether and the base of the rail is spiked directly to the concrete or bolted through the concrete beam to plates below. This latter method has been carried out at Rochester, N. Y., with entire success, no difficulty being experi enced in holding the rails in position. In construct ing such track the rails are usually laid on temporary ' wooden ties spaced ten or twelve feet apart and brought to line and grade, after which the concrete beams are placed and the wooden ties removed.
Form for Rails. The rails in common use for street-railway track are divided into two general classes: tee rails, as commonly used on steam roads, and girder rails, in which the head is .so formed as to afford a channel for,.the flanges of the wheels and ad mit of the pavement being laid close against the rail. on both sides.
Tee rails differ considerably in their details and weights and are often modified for street service by making them of greater depth than is usual for steam road service. These rails are shown in Figs. 42 and 43. The upper surface varies from 2 to 3 inches in width and is usually made convex, the section being frequently circular, of radius 8 to 20 inches. As used for street railways, these rails vary from 4 to 7 inches in height. In using the smaller depths it is necessary, except for very thin paving surfaces, that the rails be supported on chairs or stringers to give room for pav ing over the cross-ties, and deeper sections are there fore more commonly used. The six-inch depth is fre quently employed and is sufficient with an asphalt or brick pavement, the ties, if used, being embedded in the concrete foundation.
The disadvantage of the tee rail consists in the fact that the pavement cannot come against the rail on the inside of the track, as it has no groove for the wheel flange. The pavement must therefore either be low ered under the rail-flange or a groove be left between the head of the rail and the pavement. The first method, shown in Fig. 42, is ordinarily the best con struction, as the pavement is set firmly against the rails and there are no exposed edges to cause rapid wear, but it is objectionable on account of the impact of crossing in dropping from the rail, and because it tends to hold the wheels of vehicles in the track. The second method is accomplished by using a thin block or a filling of concrete under the head of the rail and paving against this filling, as is usual when stone-block pavement is employed between the rails, or when a toothing of stone blocks or bricks is employed with an asphalt pavement. For brick pavements special bricks are sometimes molded to fit against the rails, leaving a groove for the wheel-flanges, as shown in Fig. 43. Difficulty has sometimes been met in the use of these bricks on account of their tendency to tilt when the car-wheel flanges press down any dirt or small gravel which may fall into the groove, unless they are very firmly bedded next the rail. Tee-rail construction is very commonly preferred by railway companies, as giving a better road for operation. It affords cheap construction, has little tendency to be come clogged with dirt, and will usually be avoided by the ordinary traffic of the street, not affording good channels for the wheels of vehicles.
Girder rails are divided as to form of head into center-bearing, side-bearing, and grooved. They vary, as commonly used, from 6 to 9 inches in height, and each type is subject to several variations in form.
The center-bearing rail is shown in Fig. 47. It is the most objectionable of any of the forms in .use, there being two channels, one on each side of the head, thus offering a double obstruction to traffic and causing greatly increased wear to the pavement. It is of advan tage to the traffic of the railway because it does not retain dirt, and where streets are not kept in good condition cleanses itself, which is particularly important on electric roads in which the rail is used as a current conductor. Its objectionable features, however, prevent its use in most places.