TELEPHONE LINE WIRE SPACING PROBLEMS 223 



of the spacers important from the standpoint of mitigating contacting 

 were tested. These related to the length of the spacer between wires. 

 It was not known whether this distance should be equal to, less than 

 or greater than the spacing between the wires of a pair at the crossarm. 

 The first tests indicated that when this distance was 3^ inch greater 

 than the wire spacing, there was a tendency for the pair to roll and 

 the wires to twist around each other. Later tests were confined, 

 therefore, to spacers with a distance between the wires the same as 

 the spacing or 3^ inch less. The data obtained in the natural wind 

 tests on wire arrangements where discs and spacers were used are 

 given in Table I. 



The efTect of insulating discs was to increase the threshold velocities 

 over those for similar arrangements without discs by about 5 to 20 

 miles per hour. The 4-inch diameter disc has some advantage over 

 the 3-inch diameter disc. Three discs per span or even two discs 

 give results somewhat better than those obtained with a single disc 

 but the gain is relatively slight. 



The spacer which holds the wires in the center of the span the 

 same distance apart as the spacing at the crossarm, in general, increased 

 the threshold velocities about 10 to 30 miles per hour for pairs with 

 wire spacings of 3 and 4 inches at equal sags and suspended in spans 

 of 160 and 260 feet over comparable arrangements of unequipped 

 wires. No information is available for the case where the wires of a 

 pair have unequal sags. 



The data for the 160-foot span give some comparison between the 

 efTectiveness of discs and spacers. In the case of wires spaced 3 

 inches with one 4-inch diameter disc, contacts occurred at a threshold 

 velocity of 35 miles per hour while the comparable figure for the 

 spacer was 55 miles per hour. 



Abstract Conclusion 



In these tests typical toll telephone wires were placed in spans of 

 100, 130, 160 or 260 feet with sags of 4 to 45 inches (depending upon 

 the span length and temperature) and with horizontal spacings between 

 the wires of a pair of 3, 4, 6, 8 or 12 inches. It was found that during, 

 the absence of glaze the wind velocities normal to the line when 

 swinging contacts began to occur increased with the wire spacings and 

 also with span lengths (if wire tensions were increased so as to maintain 

 a given sag) and decreased when the sag was increased. An empirical 

 equation based upon this relation and the data (Table I) has been 

 developed for the case of wires at equal sags. As a brief example of 

 the results, in the case of a 130-foot span, it was found that wires 



