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BELL SYSTEM TECHNICAL JOURNAL 



whip displacement. It is also observed that the large relative displacements 

 occur when the frequency of the system is smaller than the pulse frequency. 



After the transient has passed, the relative steady-state displacement, 

 which is of course equal to the absolute, obtains large values too. 



From Fig. 5 we note that a maximum of 1.5 is reached for the triangular 

 whip and up to 1.7 times for the sine whip (see Fig. 7) at a frequency of 

 approximately | of the whip. Apparently even larger displacements 

 across the mount occur after the transient has disappeared. 



This is illustrated in Fig. 11 for the same systems as in Fig. 10. 



As (f increases, which means if the frequency of the system increases with 

 respect to the pulse frequency, the displacements across the mounts diminish, 



0.5 



1.5 2.0 2.5 3.0 



Pulse length (interval) 

 natural period of system 



3.5 



4.0 



4.5 



Fig 

 cosine 



9 — Maximum amplitude as a function of frequency ratio-steady state shifted 

 whip. 



while on the other hand the acceleration increases as will be shown later ( ee 

 equation 39). 



From this it seems advantageous to select a natural period of the system 

 at least twice that of the pulse frequency. 



The relative displacements are limited by practical considerations, such 

 as available space between cabinets and bulk head, cable connections, per- 

 sonnel safety and others. 



In the design of Bell Telephone Laboratories radar equipment, the rela- 

 tive displacement has been held to one-half inch, and the natural frequency 

 in the neighborhood of 35 to 40 cycles per second or a period of 25 to 30 m.s. 



The average of the heaviest shock administered to this type of equipment 

 has a peak amplitude of 1.5 inch and a time interval of approximately 60 m.s. 



From Fig. 5, we find that under these conditions a maximum relative dis- 



