PEINCIPLES OF CONSTRUCTION. 



97 



Fig. 46 shows the form of electric welding machine supplied 

 by the Electric Welding Co. (Ltd.), of 28, Basinghall-street, 

 London, E.G., for welding iron, steel and copper wires, such 

 as are used in submarine cable work. The transformer is 

 mounted in a substantial cast-iron box, the ends of the secondary 

 circuit being brought out at the top and terminating in mas- 

 sive gun-metal platens. On the platens are mounted the clamps 

 for holding the work, one of which is stationary, while the 

 other is free to move in the direction of the fixed clamp, under 



Fig. 46. 

 the influence of a strong spiral spring. The strength of the 

 spring, and consequently the amount of pressure, may be varied 

 and adjusted according to the size and nature of the material 

 to be welded. An automatic switch is also provided on the 

 machine, with marked quadrant and set-screw to enable the 

 exact amount of upset on the weld to be predetermined. 



To operate the machine, the ends of the wires to be welded 



