Seitember I, 1907.] 



THE INDIA RUBBER WORLD 



365 



The Insulated Wire Manufacture 11. 



By a Practical Man. 

 HE testing department of a large insulated wire factory is ing compound 



_£ a most interesting as well as important place. Here the 

 novice becomes duly impressed with the fact that the 

 drudgery of manufacturing has an occult side. The very sound 

 of "ohm" and "megohm" gives him a creepy sensation. The 

 electrical engineer, however, is generally keenly alive to the 

 importance of his duties. He must put voltage on every coil 

 and try it out for good or ill. To aid him in locating defects he 

 uses a galvanometer. It contains a mirror less than an inch 

 square, which is suspended and adjusted to the mechanism by 

 means of very delicate wires which are sensitive to the slightest 

 variations in the electric current. In front of the galvanometer, 

 a few feet distant, is a scale designed for measuring the meg- 

 ohm resistance of insulation. Through the frame that sustains 

 this scale projects a small tube, so placed that the electric light 

 at one end shines through it directly upon the small mirror de- 

 scribed, and is reflected back upon the scale of measurements. 

 When a coil is to be tested it is connected with the galvanometer. 

 Immediately the current is turned on, its delicate mechanism 

 causes the little mirror to turn, and as it turns, the reflected light 

 travels along the scale and tells the operator the megohm re- 

 sistance. If tl.e coil is sound and strong, the light travels quickly. 

 If the insulation is poor, the light moves slowly and but a short 

 distance. 



The galvanometer, together with a lot of arithmetic, enables 

 the operator to figure the exact location of a defect in a wire 

 that has been twisted into a cable. For it must be understood 

 that when a cable is made from a number of insulated wires, 

 each wire, although separately tested, is again tested after having 

 been made a part of it. It is occasionally necessary to tear apart 

 a cable, that repairs may be made, and it is the province and priv- 

 ilege of an electrical engineer to locate the source of the trouble. 



Repairing defects in insulation is accomplished by cutting 

 away the rubber at the point where the electric current burned 

 through. The coil is placed upon a drum, and an end of the 

 wire carried to another drum, upon which it is bound as fast 

 as inspected and repaired. The first drum is connected with the 

 system by means of a weak current, and a circuit is established 

 through means of another wire, the end of which the repair man 

 carries in his mouth against his tongue. The wire that is being 

 rapidly unwound passes through his hand, and the instant a de- 

 fect in the insulation is reached, he receives a slight shock. Upon 

 cutting away the rubber about a defective spot, a strip of thin 

 rubber is wound about the place until, by degrees, it is built up 

 to the outside diameter of the insulation. These patches are 

 then carried in a sectional electric vulcanizcr and the wire again 

 tested as described. 



Once marked "O K" the wire is ready for immediate use in the 

 telegraph or telephone service, or for various combinations in 

 stranded conductors or cables. For some purposes two or more 

 such wires, before vulcanization, are twisted together and covered 

 with a cotton thread braided on, then run through the tubing ma- 

 chine to receive another cover of insulation, this in turn being 

 covered by a braid of cotton or silk. Orders frequently specify 

 that a number of small wires shall be twisted together before 

 being covered with insulation. They are called "stranded con- 

 ductors." Such a conductor receives the insulation coat in a tub- 

 ing machine in precisely the same manner as a single wire. Two 

 such conductors are sometimes twisted together, covered with a 

 cotton braid, and the whole saturated with a waterproof com- 

 pound. Again, two stranded conductors, insulated and twisted 

 together, have the space between tw-ists, so to say, filled in with 

 a jute yam or "lateral." This is then covered by a frictional 

 tape, and finally by a cotton braid, duly coated with waterproof- 



The braided cover for insulated wire serves the 

 double purpose of protecting the rubber cover from injury and 

 imparting a handsome finish. Cotton, silk and other threads are 

 used, in plain white, or brilliant red, greens, yellows, bronzes, and 

 combinations of colors, so applied as to create a figured design 

 in the cover. 



The braiding department of an insulating wire factory is an 

 interesting and noisy place, with its hundreds of whirring wheels, 

 and thousands of clicking shuttles. Braided covers are not, how- 

 ever, confined to use of thread. For larger insulation heavy 

 twines, jute and asbestos are used. 



This brings us to the consideration of cable manufacture. 

 Cables, by the way, are not necessarily submarine. They are 

 used in underground conduits, and suspended from telegraph 

 poles, in large buildings, shops, battle ships, and numerous other 

 situations. The finished outside diameter of cables ranges from 

 '/2 inch to 4 or more inches. One of the most interesting sights 

 in the cable department of an insulating factory is the application 

 of the cover. Cables are frequently made up of uncovered wires, 

 as many as 700-20 B & S being twisted together, and occasionally 

 much larger ones are made. Such a cable is wound upon a large 

 spool and placed in line with the tubing machine. Let us sup- 

 pose that all preliminaries are completed, i. c, a sufficient quantity 

 of insulating material at hand, the work of centering the metal 

 cable completed, 1. e., so adjusting it to the machine as to secure 

 a rubber insulation of even thickness. 



The word is given, the machine starts, and the end of the 

 metal cable is thrust into one side of the tubing machine head, 

 to immediately appear upon the other, rubber covered. There is 

 a dignity of movement in the slow unwinding of the grreat coil, 

 like a huge silver boa constrictor, diving into a hole after its 

 prey, to reappear transformed into one of the great modern 

 world wonders — an electric cable ! The steady, forceful on- 

 thrust of this prodigy of the mine and the forest, is impressive. 

 Here is no ordinary job. There must be no mistakes, no mis- 

 chance, no miscalculation. The "feed" must be "just so," sup- 

 plies of material continuous and uniform in quality. 



Three men are attending to the machine, three more are un- 

 coiling. The foreman, callipers in hand, is everywhere, the soul 

 of expert concern. The cable has now projected its huge bulk 

 along the carrying table where half a dozen men are protecting 

 it against possible abrasion. It is almost scorching hot, hence 

 it is no "cinch" to help it along. It reaches the great steel drum 

 that is to hold it, and slowly, with most delicate care, is helped 

 to make the first turn. In a half hour, perhaps, this part of the 

 work is done. The cable, coil upon coil, suspended in midair, 

 seems a sleeping monster. It is, however, but half completed. 

 Before it is ready for the vulcanizer it must have a strong coat 

 braided about it of hemp, or asbestos, or cotton. This will be 

 covered in turn by waterproof tape, and over that again an 

 armor of galvanized iron wire. 



Or, possibly, the specifications call for a cable with an armor 

 of lead. In such case the rubber insulation is first vulcanized 

 and then wound with tape. The lead armor is applied in the 

 following manner: on one side of an hydraulic press with appli- 

 ances for cable covering stands the smelter. It is elevated above 

 the floor level 3 or 4 feet, so a spout may convey its molten 

 contents to the chamber in the top of the press. This chamber 

 is like a huge cap on the top of the ram, and, in being lifted, 

 receives the end of a steel plunger that exactly fits into it. The 

 molten contents, therefore, of the cap must either check the 

 hydraulic pressure, or get out. This latter it promptly does, 

 covering the cable with a thick coat that looks like new silver, 

 as it slowly passes from the press. 



