Online Encyclopedia

ROPE AND

Online Encyclopedia
Originally appearing in Volume V23, Page 715 of the 1911 Encyclopedia Britannica.
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ROPE AND ROPE-MAKING. All varieties of cordage having a circumference of an inch or more are known by the general name of " rope." Twisted cordages of smaller dimensions are called cords, twines and lines, and when the sectional area is still smaller, the article is known as thread or doubled yarn. All these varieties of cordage are composed of a number of separate yarns, each of which is made from some kind of textile fibre by preparing and spinning machinery. The number of separate yarns which ultimately form the rope or cord depends upon the fineness of the yarn, and also upon the circumference of the finished article. From thread and fine twine upwards the whole art of manufacture is that of twisting together fibres and yarns; but the comparative heaviness and coarseness of the materials operated on in rope-making render necessary the adoption of heavy machinery and modified processes which clearly define this manufacture as a distinct calling. The modern trade of rope-making is again divided into two distinct branches dealing with vegetable fibres and metallic wire. Many different vegetable fibres are used for rope-making, but for the combined qualities of strength, flexibility and durability, none can compete with the common hemp, which is consequently the staple of the rope-maker. Cotton ropes are, however, much more flexible, and in addition are strong and durable; they are, therefore, much preferred for power transmission in textile and other works. Manila hemp is a fibre of remarkable tenacity, of unapproached value for heavy cordage, but too stiff for small cords and twines. After these in utility come Sisal hemp of Central America (Agava Sisalana), Phormium hemp of New Zealand (Phormium tenax) and Sunn hemp of the East Indies (Crotalaria juncea)—all fibres of great strength, and largely used by rope-makers. Jute (q.v.) of India (Corchorus capsularis and C. olitorus) is now largely used by rope-makers on account of its cheapness. When used alone it is deficient in strength and durability, but when used in conjunction with proper proportions of hemp it makes a very satisfactory and useful rope. Among fibres more rarely seen in rope-works are Jubbulpore hemp (Crotalaria tenuifolia), boxstring hemp (Sanseviera zeylanica), and other hemps of the East Indies, plantain fibre (Musa paradisica), and agave fibre (Agave americana) of America. Coir and many other fibres are used, but principally in the localities of their production. A rope is composed of a certain number of " strands," the strand itself being made up of a number of single threads or yarns. Three strands laid or twisted together form a " hawser-laid " rope, and three such hawsers similarly laid make a " cable-laid " rope or " cable." A " shroud-laid " rope usually consists of four strands laid around a central strand or core. The prepared fibre is twisted or spun to the right hand to form yarn; the required number of yarns receive a left-hand twist to make a strand; three strands twisted to the right make a hawser; and three hawsers twisted to the left form a cable. Thus the twist in each operation is in a different direction from that of the preceding one, and this alternation of direction serves, to some extent, to preserve the parallelism of the fibres. The primary object of twisting fibres together in a rope is that by mutual friction they may be held together when a strain is applied to the whole. Hard twisting has the further advantage of compacting the fibres and preventing, to some extent, the penetration of moisture when the ropes are exposed to water; but the yield of rope from a given length of yarn diminishes in proportion to the increase of twist. The proper degree of twist given to ropes is generally such that the rope is from three-fourths to two-thirds the length of yarn composing it. Rope-walk Spinning.—The sequence of operations in this method of working is as follows: (r) hackling the fibre; (2) spinning the yarn; (3) tarring the yarn when necessary; (4) forming the strands; (5) laying the strands into ropes. Hackling differs but slightly from the hand-hackling process used in the preparation of flax. The hackle board consists of a wooden block studded with strong, tapered and sharp-pointed steel prongs. A series of such hackle boards is used in the progressive hackling operation, the prongs diminishing in size and being more closely set together. For the commoner kinds of ropes, however, hackling through the coarsest board is found to be sufficient, while in most other cases two hacklings are adopted. The hackler takes up a handful or " streak "1 of hemp from the bundle, wraps one end firmly round his hand, and with his fingers distributes a little oil over the hemp. The oil softens the material, keeps the hackle pins in good condition, and facilitates generally the splitting up of the fibre as the streak is drawn through the pins. In the first place, only the ends of the streak are hackled; they are dashed into the pins and drawn through them in order to separate the fibres and to lay them parallel; but as the operation proceeds a gradually increasing length of the streak is thrown on and drawn through the pins. The process is indeed very similar to the combing out of a head of human hair. When half the length of the streak is thoroughly combed, the other half is treated in precisely the same manner. The hackled streak is then weighed, doubled up to prevent any entanglement, and laid aside for the process of spinning. During the hackling process a large quantity of comparatively short fibres are retained in the pins; the longest of these are separated, and the remainder used for tow yarns. The above description refers entirely to hand hackling; machine hackling of hemp is very similar to flax hackling. The spinning is done in what is termed the " rope-walk," and from the nature of hand-spinning, and the length of the rope required, it is necessary that this walk should be from 300 to 400 yds. in length. It is sometimes completely covered in with walls and roof; at other times only a roof is built; while in exceptional cases the whole of the walk, with the exception of a small hut at each end, is without shelter of any kind. The operation of spinning is very important, as the weight of the yarn and the appearance of the finished product depend upon it. A description of spinning and laying as per-formed by the aid of the hand-wheel will perhaps be the best means of giving an idea of this useful branch of manufacture. The front and end elevations of one variety of spinning-wheel are shown in figs. i and 2. The apparatus is fixed to some convenient part of the' building, or to special supports. The wheel A, which is turned by hand, and always in the same direction, communicates motion to the rotating hooks or " whirls " B, C, D and E by means of a listing band or strap F. The arrangement of the listing shows clearly that the hook E will revolve in the opposite direction to hooks B, C, and D. The spinner takes two streaks of the hackled hemp, wraps them round his waist with the ends at his back, and keeps the fibre in position by adjusting his apron partly round it. From the middle of the streak—that is, midway between the two ends —he takes hold of a quantity of fibre and hangs it on to one of the ' See note in the article on JUTE for variations of spelling. hooks B, C or D ; the assistant at the wheel begins to turn, and thus a certain amount of twist is imparted to the material between the spinner and the hook. The spinner now walks backwards down the walk, drawing out the fibre with his left hand and adjusting it with his right. A piece of flannel or woollen cloth held in his right hand aids in the formation of the thread and protects his fingers from the rough fibre. In some cases two threads are spun simultaneously; when this is done, two of the hooks, say B and C, are used at the same time. Since the revolutions of the hook divided by the length of yarn spun give the amount of twist per inch or foot, it follows that the ratio of the walking pace of the spinner to the revolutions of the wheel A should be constant, otherwise the yarn will not be uniform. The spinner calls to the assistant when there is any irregularity in speed, or when, from any cause, he is obliged to stop walking. At convenient intervals in the length of the walk, and projecting from posts, are short horizontal bars; the top of each bar is provided with wires or pegs to form a number of vertical partitions something like a very coarse comb. As the spinner proceeds down the walk, he throws the spun yarn into one of these partitions, thus relieving himself of the weight and keeping the yarn off the ground. When a sufficient length of yarn has been spun, he breaks off the fibres and fastens the yarn to a convenient peg or hook until he has spun a sufficient number (usually three) to form a small rope or cord. The person at the wheel hangs these three yarns one on each of the three hooks B, C and D, while the spinner attaches the other ends to a revolving hook termed a " looper." All is now ready for " laying " the yarns. For small cords, this may be done, with or without a " top." This top is a conical-shaped piece of hard wood provided with three equidistant grooves which merge towards each other at the thin end, and into which the yarns are laid. The thick end of the top is nearest the wheel, so that the yarns may be kept separate on that side. As the hooks twist the three threads, the spinner goes up the walk with the top; the twist in the yarns causes the looping hook to revolve in the opposite direction to the other hooks, and thus it twists the three threads in the opposite direction to the original twist. Fig. 3 shows one form of top, the three yarns being shown in distinctive marks so that the path of each may be more easily followed by the reader; a plan of the thick end of the top appears to the left of the figure. If four yarns of strands are required, the top would contain four grooves, as well as a hole through the centre to admit of a core when such a thing is required. As soon as the spinner, who carries the top, arrives at the wheel, the assistant takes the yarns off hooks B, C and D (figs. I and 2), and puts them all on hook E. The other ends of the strands are removed from the looper and attached to a block of wood called a " drag." The wheel is then rotated as before, which puts more twist into the cord. While this operation, which is termed hardening, proceeds, a shrinkage in the length of the cord takes place, and the drag is consequently drawn up the walk. The drag, however, holds the cord taut, and serves to retain the twist which is imparted by the hook E. If the strands require tarring before they are laid, they are separately taken off the hooks, after they have been spun, and tied at both ends to pegs to keep them taut until a sufficient number has collected to be conveniently handled at the tarring tank. The tar is heated to about 220° F., and the strands are then passed through it at a speed not greater than 15 ft. per minute. Before emerging from the tank, the strands pass between squeezing rollers which remove all superfluous tar. In a short time the strands are dry, while in the space of a few days the tar is hard enough to allow the strands to be formed into ropes. Such is, in general, the hand process of forming ropes when they are composed of only three or four single yarns. It very often happens, however, that a number of single yarns are required to form each strand of the rope. The single yarns may be spun by hand, as described above, or by machinery. In the former case a group of yarns is usually termed a " haul," while the machine-spun yarns are formed into what is known as a " warp " or " chain." In any case, the group of yarns is stretched down the rope-walk, at each end of which is a " jack " twister. A few of the yarns taken from the group—the number depending upon the size of the yarn and also upon the required diameter of the strand—are then placed on a hook of the jack twister and twisted together. When three such strands are made they are laid into a rope in a similar manner to that explained above. A simple form of hand jack twister is illustrated in figs. 4 and 5. The wheel A gears with pinions B on the shafts of the hooks or whirls, and this imparts the necessary motion to the latter. At the other end of the walk is a similar machine which moves upon rails as the twist is put into the strands. When the hooks are empty, pinions B and wheel A (fig. 4) are out of gear, but those hooks carrying yarn are drawn out, as shown at C, until the pinion B gears with wheel A, when the hooks are rotated. The C
End of Article: ROPE AND
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ELIHU ROOT (1845– )
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