PRINCIPLES OF CONSTRUCTION. 95 



driving off moisture from it. For this reason the wires are 

 generally treated first this way whether they are to be indi- 

 vidually taped or not. The galvanising of the wires is very 

 important for the prevention of ruat, and there is no doubt that 

 a good coat of zinc greatly prolongs the life of the sheath. 

 Where the wires are to be individually taped, as described on 

 page 75, this process is next carried out, the tapes being also 

 impregnated with compound. The wires are then wound on 

 bobbins ready for the sheathing machines, which is done by 

 special machinery. 



The large shore-end machine (Fig. 44) is capable of sheath- 

 ing with wires up to 10mm. diameter (or No. 3/0 B.W.G ), 

 and is constructed to carry 18 bobbins, each holding about one 

 ton of wire. The bobbins, which are arranged in two sets, are 

 mounted on cast-steel frames or flyers between three large 

 revolving discs. Answering the purpose of the sun-and-planet 

 motion in the old vertical machines for laying the wires 

 without twist, the device is adopted of keeping the frames 

 carrying the bobbins in a constantly horizontal position as the 

 discs revolve. The frames are not fixed rigidly to the discs, 

 but liave end spindles passing through bushes in the same, 

 and as will be seen in the illustrations the spindles terminate 

 at the front of the machine in cranks dipping downwards, having 

 pins let into holes in a large ring. The latter revolves with the 

 discs, but on a centre lower than that of the discs by the distance 

 between centres of frame spindles and crank pins. The ring 

 keeps this relative position by the two rollers, one on each side 

 of the main bearing (of which one is seen in the engraving) which 

 bear on the inner surface of the ring ; thus the cranks dip con- 

 stantly downwards during the rotation of the machine, and 

 the frames are kept constantly horizontal. The three discs are 

 keyed to a large hollow shaft through which the core passes. 

 The shaft is of Whitworth compressed steel 28ft. long (coupled 

 in two lengths), 9in. external diameter, bored and turned all 

 over, and rests in an outer bearing at one end, as shown in the 

 engraving. This takes the weight of the first disc while the 

 two further discs run on rollers which are adjustable for 

 centering. The third disc is provided with holes equal to the 

 number of bobbins, through which the wires pass out to the 

 cable. Beyond this again is the small lay plate having the 



