32 FOREST UTILIZATION 



top of the rail was shod with a strip of ^4-inch iron,, 

 the ends joined by hook and pin, and by hole and pin. 

 Steel sectional tracks of 2^-inch gauge are manufactured 

 by the C. W. Hunt Co., New York. The trucks used 

 have the wheel flange outside. Curves and switches are 

 ready made. Straight sections are 6 feet to 20 feet 

 long. 

 II. Stationary track. 



(a) Grade. A proper survey is very essential. For 



steep grades (over 7%) a soft rail is required. 

 Grades of 11% are feasible on straight track for 

 locomotives having eight drivers. 



High percentage for very short distance is, how- 

 ever, permissible. 



Logging roads in the South have grades running 

 up to 15% for uphill traffic, obtaining the neces- 

 sary impetus by a corresponding downhill grade. 

 The expense of maintaining the track and the 

 frequency of accidents render steep grades highly 

 expensive. 



The standard railroads have never over 4% 

 grade. 



(b) Curves. The minimum radius of curves depends 



on gauge of track; distance between axles of 

 front and hind trucks ; length of timber to be 

 carried and grade in the curve. Curvature is 

 measured by the subtended angle, the (secant) 

 chord of which is 100 feet. Standard railroads 

 do not allow of an angle exceeding 10%. 

 In curves, to relieve the increased friction, and, 

 further, to prevent the trucks from jumping the 

 track, owing to centrifugal force, three remedies, 

 are required : 



1. Lessened speed and reduced grade. 



In practice for standard gauge of 56^2 

 inches, for each degree of curvature the 

 grade is released by 0.02% ; for narrow 

 gauge by 0.03%. 



2. The outer rail is elevated for standard 



track by ^-inch for every degree of 

 curvature; -for 36-inch gauge (usual nar- 

 row gauge) by 1-3 inch for each degree 

 of curvature. 



3. The track is widened in curves by i-i5 



inch for every 2^2 degrees of curvature. 



(c) Rails. The form is usually the T rail. Grooved 



rails, flat rails, rails inclined toward center of 

 track etc. are freaks merely. In logging; rail- 



