Handbook of Railroad Construction; For the use of American engineers. / Containing the necessary rules, tables, and formulæ for the location, construction, equipment, and management of railroads, as built in the United States.

by George L. Vose

FROGS.

290. When one line of rail crosses another, a contrivance called a frog is used; see figs. 141 and 142.

Fig. 141.

That the wheel may run smoothly from a to c, fig. 141, the rail b f must be cut at D, and the rail a c must be cut at the same point. Cutting the two gives the form shown in the figure, and further developed in fig. 142.

In order that the flange of the wheel shall not leave the line a c, when at the break D, the guard rail m m is used to confine the opposite wheel. It should be placed at a distance of two inches from, and parallel with, the main rail g g, from opposite six inches below the frog point at s, to six inches above the shoulder at s′. From the ends of the parallel line n n the guard rail should gently curve away at both ends. Thus the wheel will be gradually brought into the right line, kept so until the break in the rail is passed, and finally easily released. To place and maintain the guard rail in the right position, it is well to put both it and the main rail into a double chair, which is spiked to the sleeper.

Fig. 142.

The form and dimensions of the cast-iron frog depends upon the angle at which the cutting rails cross, and upon the size of the wheel tire.

To draw the frog, proceed as follows:—