FORCES OF OBLIQUE WINDS ON TELEPHONE WIRES 597 



Here, F„ (the normal component of wind force) is measured in pounds 

 per foot of wire. The diameter {D) of the wire is in inches and the 

 actual wind velocity {V) is in miles per hour. This is the familiar 

 equation for the force of normal winds with the addition of the term, 

 cos^ a. 



Values of the constant {K) found for each value of the actual 

 velocity (F) and angle are given in Table I (0.104-inch wire) and 

 Table II (0.165-inch wire). The arithmetical averages {X) of the 

 constants for angles up to and including 60° and for angles up to and 

 including 80° in the case of each \elocity {V) are also given in these 

 tables. As in the case of normal winds and as indicated by equation 

 (6) K varies with the product of v^elocity and wire diameter {VD). 



4 5 6 7 8 9 10 II 12 13 

 VD IN MILES PER HOUR AND INCHES 



Fig. 6 — Values of the Constant iK) in Equation F„ = Kiy co?, oi)'^D for variations 

 of the angle (a) of wind direction from normal — range, 0° to 60°, inclusive. 



The relation between the average constant {K) for angles up to and 

 including 60° and the product of velocity and wire diameter {VD) is 

 summarized in the accompanying Fig. 6. 



While our interest was centered mainly in evaluating the normal 

 force of an oblique wind as stated above, some consideration has been 

 given to the tangential force of an oblique wind and the variability of 

 the angle between the normal and resultant wind forces. 



The tangential forces of the oblique winds were determined by 

 equation (3). Curves, for both sizes of wire, of tangential forces 

 plotted against the angle a are given on Figs. 7 and 8 for all velocities 

 (30 to 90 m.p.h.) used in the tests. The tangential force, of course, is a 

 relatively small quantity as compared to the normal force. For this 



