MOTION OF TELEPHONE WIRES IN WIND 



2,hl 



Some time will be required, however, before definite conclusions can 

 be drawn from the experimental work of this new laboratory. 



As an aid in the interpretation of the experimental results, certain 

 theoretical work has been done on the dynamics of a wire loop swinging 

 in the wind. It is this phase of the problem that is dealt with in this 

 article. 



In the first part of this discussion, the wire loop is treated as an 

 inelastic, rigid body.^ As it was later found that under the conditions 

 applying in our problem there was a considerable increase in the sag of 

 the wire due to the wind, an investigation was made of the magnitude 

 of the correction required when the elasticity of the wire is taken into 

 account, the results of which are given in the latter part of this article. 



Fig. 1. 



Consider an element of the wire, shown in Fig. 1 in cross-section, 

 swinging about axis 0, at a radius y. The wind is assumed horizontal 

 and transverse to the axis. The sag a is also assumed small compared 

 with the span length so that to a sufficient approximation the length 

 of the wire is equal to the length of the span and the surface of the wire 

 opposing the wind is independent of the angle of deflection {a) of the 

 wire in the wind. 



The velocity of the element of wire relative to axes fixed with respect 

 to the earth is ya. The wind velocity relative to the same coordinate 



^ An article entitled "The Behavior of Overhead Transmission Lines in High Winds " 

 by Professor E. H. Lamb, which appeared in the October 1928 Journal of the Institu- 

 tion of Electrical Engineers, gives an analysis of the inelastic, rigid loop problem which 

 has been followed in general outline in the present treatment. There is disagreement, 

 however, with one of the fundamental assumptions upon which Professor Lamb's 

 analysis is based and our formulae are therefore generally at variance with those 

 derived in his article. 



Mr. R. L. Peek, Jr. of Bell Telephone Laboratories, working independently, ar- 

 rived at results in agreement with those given in the present article. 



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