'ROPE MAKING. A rope is a combination of fibres of hemp, or other materiel, so arranged as to form a flexible and tenacious cord or baud ; retaining, as far as possible, their collective strength. The name rope is generally confined to the larger descriptions of cordage, such as exceed an inch in circumference ; though the principles of formation are much the Slialle for cordage of every size.
If the fibres, used by the ropemaker were of sufficient length, the most effectual way of obtaining their united strength would be to Lay them side by side, fastened together at each end, so as to form a bundle or skein ; but, as the fibres of hemp do not, on an average, exceed Rite entanglement is produced by twisting, which causes the fibres to compress each other ; and it not only enables .the ropemnaker to produce cordage of any required length, but also, by making the rope hard and compact, increases its durability, and enables it to resist the penetration of water, which would rapidly impair its strength. While however some degree of twist is absolutely essential to.the cohesion of a rope, any twist beyond that which simply prevents the fibres being drawn out without breaking, is injurious. A skein of fibres, or a rope, may be twisted so hard that any further attempt at twisting would break it ; and such a skein will evidently have no power to support a weight, each fibre being already strained to the utmost extent that it will bear. In fact, whatever force is exerted by any fibre in compress ing the rest, may be considered the same as a weight hanging on that fibre, and must be subtracted from its absolute strength before its useful effect can be ascertained; the available strength of a rope being the remainder of the absolute strength of its component fibres after deducting the force exerted in twisting them.
Were a rope to be formed by simply twisting together, in one direc tion, the whole of the fibres of which it is composed, there would be nothing to prevent its =twisting as soon as left to itself. It is there , fore necessary to twist the fibres in comparatively small portions, and so to combine these into a rope that the tendency to untwist in one part may counteract the like tendency in another. Thus the same force which would cause the component parts, if separate, to become loose or untwisted, is employed, when they are combined into a rope, to keep the whole firm and compact. This is illustrated in fig. 1, which may be considered as the unravelled end of a cablet or small cable. Tho cablet a may be untwisted into three smaller
ropes, b; untwisting either of these in the opposite direction, we find it to consist of three smaller ropes, c; each of these may be untwisted into several small strings, d ; and each of these consists of several distinct fibres of hemp, e. Thus several fibres form a yarn, several yarns a strand, three strands a rope, and three ropes a tablet.
With fig. 2 as an illustration, we may briefly describe the hand method of rope-making. The first process consists in twisting the hemp into thick threads, called rope-yarns. This process, which resembles ordinary spinning, is performed with various kinds of machinery. The common mode of spinning rope-yarns by hand is per formed in the rope-ground, or rope-walk, an enclosed slip of level ground COO feet or more in length. As many of the operations of a ropery would be impeded by wet weather, or by the unchecked heat of the sun, it is not unusual to cover the walk with a slight roof. At one end of this ground a spinning-wheel is set up, which gives motion by a band to several small rollers or whirls. Each whirl has a small hook formed on the end of its axis next the walk. Each of the spinners is provided with a bundle of dressed hemp, laid round his waist, with the bight or double in front, and the ends passing each other at his back. He draws out a sufficient number of fibres to form a rope-yarn of the required size ; and, after slightly twisting them together with his fingers, he attaches them to the hook of a whirl. The whirl being now set in motion by turning the wheel, the skein is twisted into a rope-yarn ; the spinner walking backwards down the rope-walk, sup porting the yarn with one hand, which is protected by a wetted piece of coarse cloth or flannel, while with the other be regulates the quan tity of fibres drawn from the bundle of hemp by the revolution of the yarn. The degree of twist depends on the velocity with which the wheel is turned, combined with the retrograde pace of the spinner. Great care is necessary in this operation to make the yarn of uniform thickness, and to supply the hemp equally from both sides of the bundle ; because, if a considerable body of hemp be supplied to a yarn that is becoming too thin, it will not combine perfectly with it, but will form a loosely connected wrapper ; and any irregularity in the last• mentioned particular will cause the fibres to bear the strain unequally.