TRACKWORK 241 



Switches. There are two kinds of switches, which differ 

 in the arrangement and form of switch rails, namely, the stub 

 switch and the point switch. In the stub switch, Fig. 1, a part 

 of each main-track rail is bent over to connect with the side 

 track. In the point switch, Fig. 2, the outer rail DV of the 

 main track is spiked rigidly $o the ties; the opposite rail EA'U, 

 lying partly in the main track and partly in the side track, 

 is also firmly spiked. These two rails are immovable. The 

 two switch rails BA and CD are planed to thin edges at A 

 and D. The ends B and C of these rails are the fixed ends or 

 heels; the thin edges at A and D are the toes. The head-block 

 is at H, and the head-rod at g. 



The point of the center line at which the turnout begins is 

 called the point of switch. In Figs. 1 and 2, W is the point 

 of switch. In stub switches, the point of switch is midway 

 between the heels; in point switches, it is midway between the 

 toes and above the head-block. 



Frogs and Guard-Rails. A frog is a combination of rails so 

 arranged that the broad tread of the wheel will always have a 



FIG. 3 



surface on which to roll, and that the flange of the wheel will 

 have a channel through which to pass. A frog is shown in 

 position on the track at K, Fig. 1, and a larger plan of the part 

 at ab, Figs. 1 and 2, is shown in Fig. 3. 



The wedge-shaped part akb of the frog is called the tongue 

 of the frog, and its point k is called the actual point of frog. 

 The actual point of frog is somewhat shortened and rounded. 

 The intersection c of the outside edges ac and be of the tongue 

 is called the theoretical point of frog. When the point of frog 

 is referred to, the theoretical point is usually meant. The 



