TRACKWORK 



249 



the main track. The degree of curve of the center line of 

 the turnout and the lead BK are found as follows: 



Rule I. Take from the table for a stub switch, or from the table 

 for a point switch, the value of the degree of curve corresponding 

 to the given frog number. Add this to the degree of curve of 

 the main track. The sum is the degree of curve of the turnout. 



Rule II. Take the value of 

 the lead from the table for a stub 

 switch, or from the table for a 

 Point switch, corresponding to the 

 given frog number. This will be 

 the value of the desired lead BK, 

 Fig. 7. 



CONNECTING CURVES 



A connecting curve is a curve 

 introduced to connect a turn- 

 out with a side track. Thus, 

 in Fig. 8, the two parallel 

 straight tracks are connected 

 by the turnout ME and the 

 curved track ED. The values 

 of n and g, and the distance a, 

 usually taken as 13 ft., must be 

 known; then the radius r' = OiD 



= OiE, and distance KT may be computed by the formulas 

 r' = 2 (a-g) 2 

 a i 



FIG. 8 



and 



KT-- 



XL 



L is the lead PK of the turnout, and, in such cases as this, 

 is always to be taken from the table for a stub switch, even 

 when the point switch is inserted, because in deriving the for- 

 mula for KT, QK and ME are assumed to be circular arcs. 



