TRACKWORK 245 



formula 1= V*(2r-0 ; and the distance Ka, Fig. 1, or cw, Pig. 3. 

 With different forms of frogs, this distance varies; the engineer 

 should therefore measure it for the different frogs he uses, 

 as it is necessary in determining the length of spiked rail Aa, 

 Fig. 1. 



Turnout Dimensions for Point Switches. Let MN, Fig. 5, 

 be the center line of the main track and MJ that of the turnout. 

 Let BA and CD be the two switch rails whose fixed ends, or 

 heels, are at B and C, and whose toes are at A and D. These 



FIG. 5 



rails are usually of a uniform length of 15 ft., except for the 

 sharpest curves. 



The center line MIJ will, when a point switch is used, have 

 a somewhat different position from that which it has when 

 a stub switch is employed. In the stub-switch turnout, the 

 rails A'TU and DCK are bent to a uniform curve between 

 M and J; in a point switch, the outer rail is made up of a straight 

 part DC, which is the switch rail, and a curved part CE, which 

 is tangent to DC at C. On this account, the lead A'K is less 

 with a point switch than with a stub switch. 



Since point switches are used on the main line where very 

 accurate work is required, it is necessary to take account of 

 the fact that the short frog rails are not curved, the part EE' 

 of the rail being straight. 



