DYNAMICS OF PACKAGE CUSHIONING 



377 



5. Enter, on Line 5, the dimension / (inches). For a package to have 

 the same spring rate in all directions, ( = Xo\/2 is a necessary con- 

 dition. 



6. Enter, on Line 6, the value chosen for b. As b becomes greater than 

 zero, the stiffness of the whole suspension increases for a given stiff- 

 ness of individual springs. The reverse happens for b less than zero. 



Fig. 1.8.2 — Tension spring package design curve. Equation (1.8.2). 



7. Calculate Xo/^. 



8. Enter Fig. L8.1 with xo/^ and find \/c. 



9. Calculate L = h/iVc^m). 



10. Enter Fig. L8.2 with L and find N. 



n. Calculate K = (W2GJ^)/(2kN). This is the initial spring rate of the 

 suspension in the direction of Xo . 



12. Calculate/ = 3.13 (K/Wi)^ This is the natural frequency of vibra- 

 tion (cycles per second) of the suspension for small amplitudes in the 

 ^0 direction. This should not be close to the natural frequency of 



