Fig. 76. Grooved Rail.
Fig. 77. Shanghai T-Rail and Joint.
Common T-Rail. The T-rail used by steam railroads is known as the A. S. C. E. standard T-rail, because it follows the standard dimensions recommended for T-rails by the American Society of Civil Engineers. A standard 65-pound T-rail of this kind is shown in [Fig. 78]. Other weights of this rail have the same relative proportions. Such a rail is used for interurban roads, and for suburban lines in streets where there is no block paving. The high rails are used to facilitate paving with high paving blocks.
Fig. 78. Standard A. S. C. E. Rail and One Joint Plate.
Track Support. The greater portion of track is laid on wooden ties. These ties, in the most substantial wooden tie construction, are 6 inches by 8 inches in section, and 8 feet long. They are spaced two feet between centers. Sometimes smaller ties, spaced farther apart, are used in cheaper forms of construction; but the foregoing figures are those of the best construction known in American railway practice. In paved streets, ties are usually employed, although sometimes what is known as “concrete stringer” construction is used instead of ties to support the rails. A strip of concrete about 12 inches deep is laid under each rail, and the rails are held to gauge by ties or tie rods placed at frequent intervals. Sometimes the concrete is made a continuous bed under the entire track. In most large cities the concrete foundation is used under all paving; and consequently, when concrete is used instead of ties to support the rails, this concrete is simply a continuation of the paving foundation. Where ties are used, they are laid sometimes in gravel, crushed stone, or sand, although frequently, in the largest cities, they are embedded in concrete. Sometimes this concrete is extended under the ties, and sometimes it is simply put around the ties.
Ballast. A ballast of gravel, broken stone, cinders, or other material which is self draining and which will pack to form a solid bed under the ties, should be used to get the best results under all forms of tie construction, whether in paved streets or on a private right of way, as on an interurban road. Of course, if concrete is placed under the ties, the gravel or rock ballast is not necessary. If ties are placed directly in soft earth, which forms mud when wet, they will work up and down under the weight of passing trains, and an insecure foundation for the track will be the result.
Joints. The matter of securing a proper joint for fastening together the ends of rails so as to make a smooth riding track without appreciable jar or jolt when the wheels pass a joint, has been given much study by electric railway engineers. A section through an ordinary bolted angle-bar joint is shown in [Fig. 75]. This joint is formed by bolting a couple of bars, one on each side of the rails. The edges of these bars are made accurately to such an angle that they will wedge in between the head and base of the rail as the bolts are tightened; hence the name angle bars. This is the form of joint generally used on steam railroads and on electric roads in exposed track, or in track where the joints are easily accessible, as in dirt streets. In paved streets, the undesirability of tearing up the pavement frequently to tighten the bolts on such joints, has led to the invention of several other types, which will be described later. Nevertheless very good results have been obtained in recent years with bolted joints laid in paved streets where care has been given to details in laying the track, and where the joints have been tightened several times before the paving is finally laid around them.