TELEPHONE LINE WIRE SPACING PROBLEMS 213 



gustiness of natural winds it was apparent that the study would have 

 to be conducted on a statistical basis. The equilibrium position of a 

 span of wire in a steady wind can be defined by the angle between 

 the vertical plane through the supports and the plane of the suspended 

 wire. This angle is given by equation (1) in Appendix I. Briefly, 

 the problem was to determine this angle for a large number of cases 

 over the complete range of natural wind velocities experienced and 

 to determine the degree of agreement between these values and the 

 angle given by the theory for the corresponding steady wind velocities. 



A pair of 0.165-inch diameter hard drawn copper wires with a 

 lateral spacing of 16 inches was installed in a 260-foot span with the 

 supports at the same level. The two wires were maintained at equal 

 sags throughout this study. To prevent movements of the pole 

 supports four guys were used on each pole, three 120° apart attached 

 at about two-thirds the height above the ground and a head guy 

 attached at approximately the top of the pole. The wires were 

 approximately normal to the prevailing northwest winds and were 

 located in close proximity to and at approximately the same height 

 as the graphic recording anemometer and wind vane used in the wire 

 spacing study. A Pathe motion picture camera was modified to take 

 a continuous picture of a point (center of span) on each wire. The 

 camera was mounted rigidly directly under the wires at the center of 

 the span. A fine platinum wire was attached to the camera just 

 above the film to provide a fixed zero reference point on the film and 

 a mechanism was provided for synchronizing the wind velocity chart 

 and the motion picture film. 



With this equipment the wires were photographed when at rest, 

 with no wind present, and a number of pictures were obtained at 

 various wind velocities ranging from zero to approximately sixty 

 miles per hour. Figure 10 is a photograph of a section of film showing 

 the wire images and the reference line. Examination of the films 

 disclosed that except on rare occasions when the wind velocity was 

 low the wires were continually in motion and the point photographed 

 on each wire was represented by a wavy line. 



In most cases, during the occasions when the wires were being 

 photographed, the wind was approximately normal to the line. The 

 variation in the distance of each wire image on the film from the zero 

 reference line (with reference to the distance when the wires were at 

 rest) provided a means of determining the actual horizontal displace- 

 ment of the wires for any recorded wind velocity through the use of 

 the ratio of the actual spacing between the wires to the spacing between 

 the wire images on the film, equation (2), Appendix I. The angle of 



