368 BELL SYSTEM TECHNICAL JOURNAL 



b. Select another point {di , Pj) about half way toward the origin from 

 (</2,P2). See Fig. 1.4.2. 



c. Calculate 



Pi ,2 P'. 



2 -f 2 



1 "2 

 «! "2 



-¥^1 



'^O = ^2 ^2 (1.6.1) 



-^1 



and 



di di 

 di — di 



(1.6.2) 



d. Using the known weight, W2 , of the packaged item, the specified height 

 of drop h, and ko and r from (1.6.1) and (1.6.2), calculate B, do and Go from 

 (1.5.2), (1.5.3) and (1.5.5). Then calculate the maximum acceleration Gm 

 and maximum displacement dm from (1.5.6) and (1.5.4) or find their values 

 from Figs. 1.5.1 and 1.5.2. 



Example: A large vacuum tube, weighing 22.5 lbs, was packed in a 7" x 

 Iz" X 15" carton which was supported on corrugated cardboard spring pads 

 in a 10^" X 11|" x 18|" carton. The latter was, in turn, packed in 28 pounds 

 of excelsior in a 25" x 25" x 30" carton. The tube is rated at 50g and the 

 package is intended for a drop of three feet. 



A rod was inserted through a hole cut through the three cartons to the 

 tube. Load was applied to the rod and the displacement of the tube was 

 measured. The data obtained were 



The data are plotted in Fig. 1.6.1. The resulting curve is suitable for 

 classification as either Class B or Class C cushioning. Considering it, for 

 the present, as Class B, we take P2 = 22.5 X 50 = 1225, and from the curve, 

 di = 1.9 inches. Also, from the curve, take di = 1 inch and Pi = 365 



