252 



TRACKWORK 



In order to lay out a straight-track cross-over, it is only 

 necessary to compute the distance BE = B'E' t Fig. 10, in addi- 

 tion to the usual dimen- 

 sions of the two turnouts, 

 which may be done by 

 taking the lead L from the 

 stub-switch table and 

 applying the formula: 



BE 



2L-+(a-2g)n 

 4n 



FIG. 10 



The turnout Rm having 

 been put in place, the dis- 

 tance BE is laid off and the 

 heels B' and H ' of the second 

 turnout are located oppo- 

 site the point E. This 

 turnout is then laid out 

 as far as m', and finally 

 the straight rails KT and 



K'T are laid adjoining the ends of the two turnouts. 



The only modification of the work for a point switch arises 

 from the fact that the lead Kb = K'b' of the point switch is 

 less than that of the stub switch. The whole length of cross- 

 over is, for a point switch, 



be = 2L'-+(a-2g)n 

 Here L' is the lead taken from the table for point switches. 



LAYING OUT TURNOUTS 



To Lay Out a Stub Switch. Having decided on the position 

 of the end b. Fig. 11, of the frog rail, measure the total length 

 of the frog and deduct it from the length of the rail to be cut, 

 marking with red chalk on the flange of the rail the point at 

 which the rail is to be cut. From Fig. 3, 

 ch 



and 



