294 



LOGGING 



The back-spiking crew is followed by the surfacing gang who 

 level up the roadbed with ballast, dig or open drainage ditches 

 alongside of the track, adjust the gauge, raise the outer rails on 

 curves, and perform any work necessary to put the road in a 

 condition for operation. On main lines a large amount of sur- 

 facing may be done, but on spurs it is limited. 



Speed, Miles per Hour 

 5 10 15 20 



Fig. 84. 



Diagram showing the Customary Elevation of the Outer Rail, in Inches, 

 for Various Degrees of Curvature. 



Roads which have sharp curves must have the gauge widened 

 to reduce the frictional resistance of the wheels against the rails. 

 It is customary to widen the gauge at least ^^g-inch for each 2^ 

 degrees of curvature in excess of 5 degrees. For example, the 

 gauge would be increased ^-inch for a 20-degree curve. The 

 extra width allowed is dependent chiefly on the width of the car 

 wheel treads. 



The centrifugal force of a train under speed tends to force the 

 wheels against the outer rail. This tendency increases with 



