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:—

Fig. 142 A.

Let a c b be the angle. Parallel with and two inches from b c draw d e, e being in a c produced. In the same manner fix the point g. At the width of the rail head (from 2¼ to 2½ inches) draw, parallel to a c, L 8. The point 8 is the limit to the solid steel. At double the rail width, or 4½ inches, draw, also, parallel to a c, 16. 6; 5. 6 is the limit of the flat steel, generally about half an inch in thickness. This is the least amount of steel allowable; it is best to steel the whole tongue, and all of that part of the wings acted upon by the wheels. The geometric point is generally very thin, and is omitted to a distance far enough back to make the point a third or half an inch wide, which is rounded off; e L and d k are made two and a half inches; as also f m and g n; k 10 and m 11 are made six or seven inches, and joined to d and f by a curve, abrupt at first, but afterwards more gentle. The distances, 5 a and 6 b must be such that a 9 is three and one eighth inches, (depending upon the breadth of rail base,) o m″ is from three to four inches. At the other end of the frog e h must be enough to make s t at least an inch, when e h and i g are from three to four inches; i m′ being, as at the other end, three or four inches. The steel plates N N are one half inch in thickness. The surface, N, is two inches above the bottom, M. The lower plate, M, is two inches thick. A B, C D, and E F are six or seven inches wide, and one inch thick. The spike holes 11
16 square, the spike being one half inch. The sharp edges, i g, e h, a c, b c, should be rounded off to fit the wheel at A, fig. 142 A. The surface of the tongue N 9 should be formed to a double incline to fit the wheel cone.

Note.—Fig. 142 A gives the shape and dimensions of the largest tires.

Another method of making a frog is to cut and weld the rails a and b of the track, as in fig. 143. The continuations of these rails are bent as shown in the figure.

Fig. 143.

The whole angle is placed upon a firm wooden bearing.

There is no weaker part of the track than the frog. To make up the strength at such places a heavy longitudinal timber twelve feet long will answer a good end.