roXTACT AVF.T.DlXr; IX WIRE SPRIXn KKLAYS 



915 



? 0.08 



0.020 5:^ 



-0.8 -0.4 0.4 0.8 



ARC TIME IN MILLISECONDS 



0.010 

 



-0.010 

 -0.020 



5x 



Fig. 17 — Motion of contact during percussion welding plotted from measure- 

 ments on film. 



evidence of what occurred during the welding operation as could be re- 

 vealed \iy high speed motion pictures. Fig. 17 shows the kind of informa- 

 tion obtained from these films; notably the speed of approach, the 

 amount of burn-off, and the deflection of the comb ^^-ires back of the front 

 plastic block upon impact by the welding gun. 



In connection ^\ith a study directed toward a better understanding 

 of the mechanism of percussion welding undertaken by E. E. Sumner of 

 Bell Telephone Laboratories tests were made with an electro-capacitive 

 transducer, oscilloscope, and polaroid camera arrangement for the 

 purpose of recording variations in the velocity of the welding gun. The 

 characteristics of the current discharge during welding was recorded bj^ 

 another oscilloscope-camera setup. Burn-off was measured and broken 

 weld surfaces on the contacts were examined and photographed. These 

 tests pointed to the value of a parallel capacitor discharge circuit as a 

 solution to the arc duration variability problem. A commercial trial of 

 parallel capacitor circuits at Western Electric demonstrated the merit 

 of this type of circuit, which will be described in more detail later. 

 Calculations from the transducer traces indicated that the striking 

 force of the contact and contact holder upon impact with the comb \\ire 

 is less than seventy-five pounds. The welding gun was operated on a 

 reed mounting during Mr. Sumner's study. 



Early experimental work on percussion welding showed that small 

 gas pockets in the weld zone were causing weak welds. Nickel silver was 

 used at that time. Its component of easily volatilized zinc was sus- 

 pected of causing the trouble. Then various metals and alloys were tested 

 and silicon-copper was chosen for the A\ires in the comb. This alloy. 



