ROPEWAYS AND CABLEWAYS.) Types of Ropes.—Since wire for rope manufacture can be drawn in all sizes it is possible to make ropes of almost any de gree of flexibility that may be required. This is necessary since wire rope, to bend around sheaves and drums, must possess flexi bility as well as strength and ductility. A great number of con structions of rope have been developed to meet service require ments. Ropes composed of large wires, few in number, are least flexible; whereas ropes composed of a great number of wires are most flexible. Many different arrangements of wires are also pos sible. It is customary to use galvanized wire in the construction of ropes to protect them from corrosion ; however, in some in stances, corrosion resisting steels are also being used. The follow ing summary of wire rope constructions covers the principal types in general use : A. Ropes made of 6 strands of 7 wires each are most frequently used as hauling topes when the sizes of drums and sheaves per mit. When galvanized, this type of rope is also used for ships' standing rigging as required by Lloyd's, and the American Bu reau of Shipping regulations.
B. Ropes made of 6 strands of 19 wires each are used for general hoisting and mine work.
C. Special flexible ropes made of 6 strands of 37 wires each are used for overhead travelling cranes and for service where drums and sheaves are comparatively small.
D. Ropes made of 8 strands of 19 wires each strand, containing a larger hemp core than is used in the case of ropes of 6 strands, are very flexible and are used on elevators and for light duty in other places.
E. Ropes made of 6 strands of 25 wires each, the centre wire of which is triangular, are known as flattened strand wire ropes and are used for general hoisting purposes. This construction possesses greater external surface to take care of wear. It is also made of 6 strands of 7 wires each; but this construction produces less flexible rope. This type of rope, on account of higher cost, is less frequently used.
F. Tiller rope is a compound rope consisting of 6 ropes, each composed of 6 strands, each strand containing 7 wires. This is the most flexible standard rope made and is used for hand rope on elevators, steering rope on small boats and for similar duties.
G. Rope made of 6 strands, each strand containing 12 wires ar ranged around hemp, a total of 7 hemp cores in all, is used as a flexible rope for mooring ships and for similar purposes. It is usually galvanized to conform to Lloyd's and the American Bureau of Shipping requirements.
H. Rope made of 6 strands of 24 wires each, arranged around a hemp core—making a total of 7 hemp cores—is a still more flexible rope for hawsers and mooring lines. It is usually gal vanized to meet the requirements of Lloyd's and the American Bureau of Shipping.
J. Ropes made in the customary manner but having each strand wrapped with Marlin, known as Marlin-clad ropes, are used for cargo hoists, oyster dredging, mine planting, etc. They usually contain 5 strands, each strand composed of 19 wires.
K. Track strands, sometimes called smooth coil strands, made of 7, 19, 37, 61, and 91 wires or more, are used as track cables for tramways and cableways.
L. Locked coil cable, made of an inner series of wires, round in cross section, surrounded by intermediate layers of wires in key shape and having outside wires that lock into position, is largely used as track cable for overhead tramways and cable ways. In some countries this type is also used by collieries for winding ropes.
M. Non-spinning or non-rotating rope ordinarily made of 18 strands, each strand containing 7 wires, is constructed with the inner layer of strands left lay and the outer layer of strands right lay, thus producing a wire rope which will not twist when a load is raised or lowered on a single part of such rope.
N. Wire rope slings for handling heavy loads are made in a great variety of sizes and designs. The more common form of sling, known as a bridle sling, is made with 2, 3, or 4 ends with differ ent fastenings on the ends for attaching to loads.
The diameter of drums and sheaves for best results should be not less than 42 times the rope diameter for 6 x 7 rope, 34 times for 18 x 7 rope, 3o times for 6 x 19 rope, 18 times for 6 x 37 rope, and 21 times for 8 x 19 rope. Proportionately larger sheaves and drums will increase the rope life.
Wire is produced by passing rods through tapered conical dies until the diameter is reduced to the required size. Several heat treatments are necessary to enable wire to be reduced in diame ter by drawing. This wire is tested and graded for strength, bend ing, and torsion qualities, and is then ready for rope making. Rope manufacture starts with winding wire on to spools which are put into a machine known as a stranding machine which, by rotation, assembles the requisite number of wires into a strand. Six large reels or spools of strands are again twisted around a core of hemp or wire in a large machine known as a layer. The finished rope is wound on reels or into coils for shipment. Various sizes and types of machines are required to produce the different sizes of rope. These machines operate at speeds ranging from 3o to 2,000 revolu tions per minute.