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BELL SYSTEM TECHNICAL JOURNAL 



velocity equivalent to this angle was termed the accelerated method 

 threshold velocity or the velocity at which contacting begins. It is, 

 therefore, not necessarily the minimum angle or velocity at which the 

 wires can be made to contact but the minimum angle or velocity at 

 which the wires will contact for each of five consecutive trials in 

 practically still air. 



i 



Fig. 13 — Apparatus for the accelerated test. 



In order that the contacts recorded by the accelerated method 

 should be comparable in definition to those recorded by the natural 

 wind method, the wires used in the accelerated test were connected 

 to the same recording apparatus as was used in the natural wind tests. 



From the results obtained through the use of the accelerated 

 method of test an empirical equation was developed for the case of a 

 pair of wires with equal sags. This equation (6) is given in Appendix 

 II. The comparable empirical equation (5) for natural winds, referred 

 to above, is also given in Appendix II. With these two equations 

 it is possible to determine the expected natural wind threshold velocities 

 of a wire arrangement through the use of the accelerated method of 

 test. An equation (7) for this use, which was obtained from the 

 above two equations (5) and (6), is also given in Appendix II. 



While empirical equations were developed only for the case of a 



