98 SUBMAKINE CABLE LAYING AND REPAIRING. 



are cut squarely in a special wire cropper and clamped in the 

 jaws, care being taken to see that the two ends are in align- 

 ment Distance gauges are used to determine the amount by 

 which the ends of the wires of diflferent diameters project 

 between the clamps. The primary circuit is then closed by 

 means of a button switch on the top of the machine, and the 

 metal at the joint is almost instantaneously raised to a welding 

 heat. In this soft condition of the metal the spring at once 

 pushes the movable clamp closer to the fixed one, thus com- 

 pleting the weld by pressure, while at the same moment the 

 automatic switch operates and cuts off the current. All these 

 operations are automatically performed by the machine, and 

 are independent of the skill of the operator. Skilled labour is 

 unnecessary, and any intelligent lad can, with very little prac- 

 tice, manipulate the machine and produce perfectly satisfactory 

 welds. The small swelling or " burr " which is produced at the 

 weld by the pressure of the moving clamp, is easily removed 

 by hammering or filing. 



In all cases where steel with a high breaking strain is joined 

 by any process requiring heat, it has been found impossible to 

 retain the full strength of the unheated material at the joint, 

 and electric welding is no exception to this rule. By making 

 what is termed a " snap " weld, with a very short application 

 of the current (a quick cut-off and high spring pressure) good 

 results can, however, be obtained. In electrically welding 

 ordinary iron wires no difficulty is experienced, and the full 

 strength of the material is retained. 



The usual factory outfit for welding consists of a small 

 trolley on which are mounted the automatic electric welding 

 machine, a small block or anvil, a wire cropper and a small 

 vice ; while attached to the bottom of the trolley is a special 

 foot switch, to enable the operator to connect the primary 

 circuit of the welding transformer to the supply wires. 



Where no suitable supply of electric current is available a 

 separately-excited alternator is generally used, which supplies 

 alternating current at about 300 to 350 volts pressure to the 

 various shops where the welders are used, suitable wall attach- 

 ments being provided at convenient positions in each shop 

 to which the welding machines can be connected by means of 

 a removable plug and flexible cable. In this way one welding 

 machine may be made to serve a number of stranding or other 



