TRACKWORK 



243 



FORMULAS AND CALCULATIONS 

 Radius and Lead of a Turnout for Stub Switches. Let 



RN, Fig. 4, be the main track and QP the turnout. Let Q 

 be the point of switch and K the point of frog. If a stub 

 switch is employed, the main-track rails will be securely spiked 

 along YB and LD; the parts BG and DV of these rails will be 

 movable, so that they may be bent outwards to meet the turn- 

 out rails W and Z. Here, then, the ends B and D are the heels 

 of the switch, and G and V are the toes. The head-block is 

 underneath G and V. 



In order to lay out a turnout when the frog angle is given, 

 it is necessary to find the radius r, in terms of the frog angle, 

 and the distance KB 

 from the point of frog 

 to the heel of switch, 

 which distance is called 

 the lead and is desig- 

 nated by L. 



The formulas for r 

 and L are: 



and 



In these formulas g 

 denotes the gauge. The 

 standard gauge of track 

 is 4 ft. 8i in. = 4.708 ft. 



The following table, some parts of which are calculated 

 from the foregoing formulas, can be used in laying out a turn- 

 out with a stub switch. The frog number, which is usually 

 given, is stated in the first column; the corresponding frog 

 angle in the second column; and the lead, or BK, Fig. 4, in 

 the third column. Then follow columns containing the 

 chord QT, Fig. 4, which is equal to 2r sin F; the radius of the 

 turnout; the corresponding degree of curve, which is equal to 



- ; the length I of switch rails AB, Fig. ], obtained by the 



FIG. 4 



