Page:The New International Encyclopædia 1st ed. v. 20.djvu/692

* WIBE BOPE. 590 for all purposes for which fibre ropes have been employed, and for many purposes they have dis- placed fibre ropes entirely. For most kinds of ■wire ropes steel is the metal employed, but other metals can be twisted into rope equally well, and such rope is made in limited quantities for spe- cial purposes. Steel wire rope is referred to alone in the statements which follow. _ To ex- plain the construction of wire rope it is essen- tial to note first that it is composed of two or more units called strands, and second, that each strand is composed of two or more units or wires. Rope-makint? consists, therefore, first in making the individual strands, and second in combining these strands into rope. In ordinary rope — spe- cial forms of rope will be considered later — the wires forming the strand are twisted together to the left ; for running ropes nineteen wires usu- ally form a strand, and for standing ropes seven wires form a strand. To make the rope, sis strands are twisted together to the right. The reason for using a greater number of wires for running rope is that rope which works over pulleys' nuist be flexible, and the greater the number of component wires is, the more flexible is the rope. Ropes for certain purposes are made with as many as 400 wires. Flexibility is also increased bv twisting the strands around a WIRE-WOUND GUN. evenly, as it comes on a number of wires instead of the single one nearest the periphery of the rope. The strength of wire rope varies, of course, with the strength of the material from which tlie wire is made, and it is usually about 10 to 15 per cent, less than the aggregate strength of the component wires. Flat wire STANDING ROPE (seven-wire strands around hemp core). centre core of hemp, and in some instances by also twisting the wires of each strand around a hemp core. The length of twist or the lay adopted in rope depends upon the diameter of the wires employed and upon the size of the rope. Broadly speaking, the lays in strands vary from six to twelve inches. Short-laid ropes are more flexible than those with a comparatively long lay. It has just been stated that round-wire ropes of ordinary construction have the com- posite wires of their strands twisted in one direction, while the strands forming the rope are closed the opposite way about. In 1S80 Mr. G. Craddock, an Englishman, introduced a con- PATENT LOCK COIL WIRE ROPE. struction of roping known as 'the Lang lay,' in which the wires forming the strands and the strands comjiosing the rojje are all laid in the same direction. Ropes of this type have been extensively used for running or winding piir- poscs. In recent years many special forms of wire ropes have been invented. They are gen- erally made of wires of special section designed to interlock with each other, and increased strength and wearing capacity may be secured by having the strands so woven as to form a flat surface which will take up the wear more PATENT FLATTENED STRAND WIRE BOPE. ropes are now little used; they were generally formed of four, six, or more round ropes of alternate lays sewn together by wires in a zig- zag direction. The earliest form of wire rope was the 'selvagee' construction, in which several wires were laid parallel to each other and wound with fine wire; such ropes are still used for sus- pension bridi;e cables. The manufacture of wire rope appears to have originated in Germany about 1821; in this year ropes of the 'selvagee' type were made for the Geneva Suspension Bridge. Shortly after- wards formed or stranded wire ropes were made and utilized. Wire rope manufacture in England dates from about 1838; in that year R. S. Kewall, of Dundee, invented a rope-making machine, and later he established a wii'e rope works. From this origin the vast wire rope industry of Great Britain, and afterwards of the United States, was developed. Wire rope is now made alto- gether by machinery. The machines used are all built on the same principle, although they vary in form and arrangement and in their capacity. To understand the principle of a wire rope ma- chine, picture a large wheel free to revolve on a horizontal axle. At regular intervals on the side of the wheel rim, assume spools or reels of wire to be attached, so that they revolve with the wheel. If now we carry the free end of the wire on each wheel through a hole in a block of metal placed in line with the axle, and some distance away from the wheel, we have a crude form of rope-making machine, since by revolving the wheel the wires leading from the reels are twisted together at the metal block or head. Generally separate machines are used for twist- ing the wires into strands and for twisting the strands into rojie. but some machines accomplish both ]U'OCOsses simultaneously. , full descrip- tion of wire rope making is given in J. B. Smith's ir/»<'.- Us Mamifacture and Uses (New York, ISOl). WIRE-TAILED BIRDS OF PARADISE. See liiitii III I'AiiAulSE. WIRE-WORM. The larva of any one of the click-beetles of the family ElateridiP. (See CurK-BKETLE: Ei.ATKRin.K.) The name is also sometimes iip]i!iod to certain small myriapods. WIRE-WOUND GUN. See Ordnance; Gu.N'S, X.WAL.