Side-bearing rails are shown in Figs. 44, 48, and 49. They are probably more commonly used than any other type of girder rail. The tram is from 2 to 3 inches wide and offers a smooth track for the wheels of vehicles, but it is difficult for a wheel to leave it and is extremely hard on the street traffic.
Pavements may be laid against the side-bearing rail as shown in Fig. 44, in which the surface of the pave; ment is at the same level inside as outside the track; or, as shown in Fig. 48, in which the pavement inside the track is brought even with the top of the tram of the rail. The first method leaves an exposed edge of the paving surface, which is commonly subject to rapid wear, while the width of tram is sufficient to per mit the wheels of vehicles to run in the grooves and to leave the track with difficulty.
Grooved rails are shown in Figs. 45, 46, 50, and 51. There are many variations in the form of groove and lip designed to meet varying conditions of use. The full-groove rail, shown in Fig. 41, has a groove in the head usually from an inch to an inch and a quarter in width; and when the pavement is made flush with the top of the rail it presents no obstruction to traffic of the street, and as the groove is too narrow to admit the wheels of vehicles it forms the most desirable track for use with smooth pavements. It can only, however, be used where pavements are kept clean and in good condition, as the groove is otherwise easily clogged with dirt, rendering the operation of the railway difficult and expensive. This disadvantage is greater in cold climates where snow and ice are common during winter.
For the purpose of lessening the clogging of the groove, the form of the grooved rail is sometimes modified by sloping the lip and widening the groove at the top, as shown in Fig. 46 or, as shown in Fig. 50, by making the lip of less height than the head of the rail, thus allowing the wheel-flange to clear the groove of dirt in passing. This latter form, however, has the effect of forming a track which retains the wheels of vehicles, as will any difference of elevation between the head of the rail and the pavement between the rails.
In Fig. 51 is shown a grooved rail with an exten Sion of the hp intended to form a track for wheels of vehicles with a view to reducing the wear of the pave ment which commonly takes place immediately inside the rails. When this lip is below the level of the rail
head it is subject to the same objection as the side bearing rail of forming a track which it is difficult for wheels to leave.
For paved streets, where the pavement is well kept, the grooved rail seems to be superior to any other, and is often required by municipal authorities, par ticularly in the larger cities. For unimproved streets or on macadam or earth roads the tee rail is usually considered preferable, and may usually be employed with no more injury to the street traffic than any of the others, while possessing the advantage of economy both in cost and operation to the railway.
Joints and Fastenings. The solid construction of track is a matter of importance upon paved streets, because of the difficulty and expense of getting at the track to make repairs, as well as because of the dis turbance to traffic when the pavement must be removed for this purpose. The rail-joints and tie-connections are therefore matters requiring particular attention. Where no chairs are used, the use of tie-plates to form a bearing for the rail upon the tie, and to hold it securely in place, is to be recommended, and will greatly aid in forming a rigid There are a number of forms in use which give good results. They should be arranged to clamp the rail firmly and present a good bearing upon the tie. When chairs are used, they, like the tie-plates, should clamp the rail firmly and give good bearing surface. They should also be well braced for stiffness against lateral bending.
Joints, in the case of track formed of rails laid directly upon the ties, or upon wooden stringers, are usually made by placing a plate or channel-bar upon each side of the web of the rail-ends to be joined and bolting through. The use of slightly curved channel-bars fitting against the flanges of the rail, as shown in Figs. 49 and 51, seems to give good results, the spring in the channels serving to prevent the loosening of the bolts. This is the most common method of making joints. Fig. 50 shows a pair of ribbed-joint plates as used for high rails, the center bearing serving to prevent the buckling of the plates or the bending of the rail at the ends.