Fall hammer equipment

The impact sensitivity of energetic compounds is tested with a so-called fall hammer equipment. Samples are exposed to the impact of falling weights from variable heights... 

Equipment A Structural Integrity Tester having a 3.18 cm (1.25 in.) diameter hammer weighing 0.33 kg (0.73 lbs.) and having a free fall of 15.24 cm (6 in.) shall be used. This device is available from Associated Design and Manufacturing Company, Alexandria, VA 22314, as Part No. 125, or it may be fabricated to meet specifications. 

The first thing we used, Kurti recalls, was Dutch cloth, as I think it is called—a very fine copper gauze which has many hundreds of holes to the inch. The assistants hammered the holes even finer by hand. They tested the copper barrier not with hex but with a mixture of water vapor and carbon dioxide, in other words something much like ordinary soda-water —the first in an urgent series of experiments carried out through the summer and fall to study materials, pore size, pressures and other basic parameters preliminary to any equipment design. 

Steel apron conveyors or chain conveyors, though mechanically more elaborate and expensive than belt conveyors, are preferable for product removal from impact crushers and from hammer crushers not equipped with bottom grids. The reason is that the material discharged from the crusher falls with greater impact force on the conveyor than when a bottom grid limits the size and impact velocity of the pieces discharged. 

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