TRACKWORK 247 



In computing the dimensions of a point-switch turnout, 

 the usual data are the length AB = DC of the switch rail, 

 the angle CDP between the outer switch raU and the 

 main rail. This angle is called the switch angle, and will be 

 represented by 5. The frog number or the frog angle must 

 also be known, as well as the length of the straight part EE'. 

 It is then required to determine the radius OI of the center 

 line of a turnout whose outer rail shall be tangent to the switch 

 rail DC at C and to the frog rail EE 1 at E, and to find the lead 

 A'K of this turnout. 



The formulas for computing these quantities are so com- 

 plicated that, in practice, tables giving the various dimensions 

 of point switches are always employed. 



The accompanying table contains all the dimensions neces- 

 sary for laying out a point switch when the frog number is 

 known. It contains the frog angle, the switch angle CDP, 

 Fig. 5, the lead A'K, the radius 01 of the center line of the turn- 

 out, the degree of curve of this center line, the cfrord JI, the 

 length AB = CD of the switch rails, and the length KE = Ka 

 of the straight frog rail. 



FIG. 6 



Turnouts from the Outer Side of a Curved Track. A turnout 

 from the outer side of a curved track is shown in Fig. 6. The 

 radius DE = R of the main track, Fig. 6, the frog angle F, or 

 frog number n, and the gauge g are usually known; from these 

 the lead BK = L, and the radius Oe = r of the center line of the 



