224 BELL SYSTEM TECHNICAL JOURNAL 



spaced 12 or 8 inches were practically free from swinging contacts in 

 wind velocities below about 70 miles per hour, wires spaced 6 inches 

 contacted at velocities around 50 miles per hour and wires spaced 4 

 or 3 inches contacted at the more common velocities of 30 or 40 

 miles per hour. 



In the absence of glaze, when the wires of a pair were at unequal 

 sags, about 3 inches difference in the 130-foot spans and about 6 

 inches in the 260-foot spans, there was in general a somewhat greater 

 tendency toward contacting in the shorter spans and a lesser tendency 

 in the longer ones than when the wires were at equal sags. 



When glaze was on the wires their action was more erratic and 

 swinging contacts were more general and occurred at lower wind 

 velocities than when glaze was not present. 



Regarding the theory ^ relating to the equilibrium position of a 

 suspended wire in a steady wind, tests were conducted at Chester, 

 New Jersey, in which the displacements of a copper wire were photo- 

 graphed in natural winds. It was found that there was general 

 agreement between the angle of deflection of a wire as determined by 

 this theory for a given steady wind and the angle obtained experi- 

 mentally in a comparable natural wind. 



The experimental substantiation of this relationship led to the 

 development of an accelerated method for a quick and economical 

 preliminary classification of various wire arrangements. This method 

 was useful in selecting from among several similar arrangements the 

 most promising ones for test in natural winds. An empirical equation 

 based on the data obtained by the accelerated method for the case of 

 equal sags was developed for expressing the relationship between 

 accelerated method wind velocity, span length, wire spacing and sag. 

 By combining this equation with that developed from the natural 

 wind data a third equation was obtained which was used in determining 

 expected natural wind threshold velocities from the accelerated method 

 results. 



In regard to the anti-contacting devices included in the study with 

 the wires spaced 6 inches and less, it was found that: 



1. A 4-inch diameter insulating disc placed at the approximate center 

 of the span on one wire of the pair increased the normal wind 

 velocities at which contacting began by 5 to 20 miles per hour 

 over those for the same arrangements unequipped. The use 

 of three discs per span or even two gave an improvement over 

 the use of one but the gain was relatively slight. 



^ Loc. cit. 



