196 BELL SYSTEM TECHNICAL JOURNAL 



At the outset of this study, considerable thought was given to a 

 theoretical determination of the limiting factor or the chance of two 

 parallel wires contacting in the wind, but with little success. Difficulty 

 was encountered in taking into consideration some of the factors 

 involved, principally the gusty nature of the winds to which a pole 

 line is frequently subjected. There was evolved out of this attack, 

 however, a theory embodying the movements of a single suspended 

 wire in wind. This theory, which was presented in a previous article,^ 

 contributed to the general knowledge of wire movements in wind and 

 gave information on the equilibrium position of a span of wire in a 

 steady wind and the movements of the wire about this position with 

 gusts of wind superimposed on this steady wind. This theory is 

 referred to later. 



As important as this theory is, it did not solve the problem of 

 determining the chances of two parallel wires swinging together in 

 natural winds. Consideration was also given to the possibility of 

 obtaining this information through tests of model lines in a wind 

 tunnel. While the problem of meeting the requirements of dynamic 

 similarity in these model tests did not appear to offer serious trouble, 

 the problem of simulating natural wind conditions did present diffi- 

 culties of major proportions. The line of approach finally adopted 

 was a full scale test of variously spaced and arranged wires on lines 

 erected at a location especially selected for its unusual exposure to 

 natural winds. 



This site which is in the township of Chester, New Jersey, is about 

 950 feet above mean sea level. It is the highest point for many miles 

 in every direction and is particularly well exposed to the prevailing 

 winds which are northwest in this locality. 



Provision of Test Facilities 



On this site there was first erected a six span line, referred to herein 



as Line 1, in a direction as nearly perpendicular to the prevailing 



northwest winds as the contour of the ground would permit without 



excessive pole heights at the extremities. The span between poles 



was 130 feet, the Bell System standard length for heavy open wire 



lines, except at the ends where two poles were set a few feet apart in 



line for convenience in testing. Figure 1 gives a view of the line and 



Fig. 2 the special end construction. This arrangement made it 



possible to include span lengths of 130 and 260 feet in any test.. The 



latter span length was obtained by attaching the wires to the lower 



^ "Motion of Telephone Wires in Wind," D. A. Quarles, Bell System Technical 

 Jourfial, April 1930. 



