537 



A frame of this construction was, of coiirse, good for only one shot. 



Partly in an effort to avoid constant replacement of frames, and 

 partly due to a presentiment that a foreign object so close to the 

 charge might be affecting the results, a second type of wooden frame, 

 shown in Figvire 11 was soon put into use. The charge in this case was 

 positioned by twine tied between it and the sides of the frames. 



Position 

 of gauge 



Figure 11. Second Frsune Type. 



By an \3nfortxinate coincidence, the damage recorded by the gauges 

 vrtien mounted on this frame was the same, within experimental error, as 

 that obtained with the cross frame, and it was concluded that the frame 

 in neither case had ajiy significant effect on the damage gauge results, 

 peirticularly since the primary interest was in comparing other explosives 

 relative to a standard explosive (THT) . However, because the second type 

 frame seemed to be an improvement in technique, it was retained in use 

 although frames of this type also were almost invariably destroyed by a 

 single shot. 



Another experiment which led to the belief that the method of 

 mounting the gauges had little effect on damage was the following. In 

 order to determine whether an increase of inertia of the damage gauges 

 would increase the damage, several cheurges varying in weight from 0.8 

 to k.2 lbs. were fired at steel diaphragms at distances of 36 and k8 in. 

 The weight of each gauge, weighing 30 lbs. normally, was successively 

 increased by 15, 30, and 50 lbs. In no instance was there an increase 

 in damage to the diaphragm until the charge and distances were such that 

 the diaphragm was damaged more than 80^ of the maximum damage possible 

 without ruptiire. Beyond 80^ of maximum depression, doubling the weight 

 of the gaxige (total weight 60 lbs.) increased the damage by 3%- 



