APPENDIX A.

ROPE-MAKING.

IN rope-making, the fibres of hemp, not averaging more than three and a half feet in length, must necessarily be overlapped among themselves and compressed together so as not to be drawn apart. The required compression is given by twisting, the fibres being continuously drawn out together, from a bundle, in the right quantity to produce the required size of thread or yarn. Yarns are then combined by twisting, and form a strand; three or four strands, by twisting, form a rope, and three or four ropes, a cable. These successive steps, in each of which the twist is reversed, cause the strain to be more equally diffused among the fibres than it would be if these were laid together in sufficient quantity at once and twisted, and moreover, the alternating directions given to the twist in the several operations, cause the different portions to bind upon themselves, and form a permanently firm bundle. The fibres only once twisted, make but a loose bundle, which, though decidedly stronger than the same quantity made into a hard-twisted rope, is not so durable nor so well adapted to the ordinary purposes of rope.* The actual loss in strength, by twisting, as found by trial, is about onethird the full strength of the fibre; its loss in length, from the same cause, being also one-third.

Rope is made in long buildings called rope-walks, and the process may be described briefly as follows:

Hemp, the material commonly used, is first hackled, or combed out, to remove the dust and tow. The hackle consists of a strong board, holding in a vertical position long steel prongs sharply pointed and polished. The hackling is done by hand.

The "preparation machines" prepare the hemp still further for spinning into yarn by a finer process of hackling. First is the "spreader," a machine having two endless chains fitted with gill-bars and gill-pins (steel teeth), which combs or straightens out and evens the fibres. The spreader is fed with the hackled hemp at one end, and throws it out in a "sliver" from the other. From the spreader the sliver is passed through two or more "drawing-frames," by which it is drawn down still more, and the fibres still further combed out straight, the size of the sliver being reduced at each step. The drawing-frame is similar to the spreader, but has only one chain. The sliver is now passed to the spinner, where it is spun into yarn, and at the same time reeled upon a bobbin. A recent improvement in the spinner, tubes the yarn, rendering it smoother and more even than any process yet devised, leaving little to be desired in the manufacture of rope. The yarn is spun right-handed. The size of the yarn varies according to the kind of rope for which it is intended. Forties-so-called because forty yarns will just fill a half-inch tube-are for the finer kinds of rope; twenties, requiring twenty to fill the tube, are for cables, hawsers, etc. From the spinning-room the bobbins containing the yarn are taken to the tar-house, where they are placed in frames conveniently arranged with reference to the tar-box. This is a long box filled

The wires which compose the cables of the East River Suspension Bridge (N. Y.) are not "laid-up," or twisted, but are run straight and bound together.

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with tar kept during the operation of tarring at a temperature of 220° F. by means of steam heaters. The yarns are led from the bobbins in the frame through two or more guide-plates working in a vertical plane over the tar-box, and convenient for lowering into the tar; thence to the farther end (between metal rollers, which press out and return to the box the superfluous tar) on to a

large wooden drum to cool them; through fair-leaders, and finally to a fresh set of bobbins, where they are wound up with the utmost regularity.

Rigging is so much exposed to moisture and heat that hemp would soon decay if not protected. Tar, though really injurious in its effects upon the hemp fibre, has been found indispensable to its general preservation. The weight of

Fig.B.

the yarn is increased from sixteen per cent. to twenty per cent. by the amount of tar required.

The bobbins containing the tarred yarn now go to the laying-ground, for hauling down, or making into strands. The layingground, where the rope is laid up, occupies the entire length of the rope-walk. The yarns for the strands, generally three in number, are led from the bobbins, in Fig. A, through holes bored in concentric circles in the frame, Fig. B, thence through a tube adapted to the size of the strand,

and attached to a hook on the end of a spindle in a movable machine like a car, called the former, Fig. C.

There is a plate, tube and hook for each strand; and the number of yarns to a strand is regulated by the size of the intended rope. All being ready, the machinery is put in motion, when the former is drawn down the walk, and the yarns, as they are hauled through the tubes, are formed into left-handed strands. Closing the strands is the next step, for which two machines are used. The lower one-the layer-lays up or closes the rope, and is movable; the upper one, which keeps the proper twist in the strand while laying, is stationary. Each strand being secured to its proper spindle, the machinery is put in motion and the strands hardened. A press attached to the layer prevents too much drawing up as the strands shorten by the additional twisting. After hardening, the strands are placed together on a central spindle of the layer and closed, a top inserted between them preventing too rapid closing. The top is a wooden cone with grooves cut to hold the strands, while tails of soft rope attached to it, by being applied to the rope as it is made, still further prevent, by the additional friction, the too rapid closing of the rope. The layer makes two revolutions to one of the upper machine. The skill of the ropemaker consists in knowing how to gear his preparation machines so as to draw a clean and uniform sliver; in giving the proper degree of twist to the yarn and strand; and in regulating the amount of hardening and the speed of the top in closing.

The foregoing process gives right-handed, tarred rope of three strands, or plain-laid rope. If the yarns are not tarred we should have white rope.

In the manufacture of manilla rope the first step in the foregoing description, hackling by hand, is omitted as being unnecessary; the manilla is oiled to enable the harsher fibre to pass the more readily through the preparation machines, and the yarns are not tarred, excepting when large hawsers are made, in which case the outside yarns are passed through the tar trough before laying up.

Twelve-flyer machine for forming strands. A, heart; B, bobbins; C, top and tube; D, draw-off drum; E, bobbins for large sizes: F, bobbins for small sizes. Wire Rope may be made either of forty-nine coarse wires or one hundred and thirty-three fine wires, put in six strands, and seven or fourteen "hearts." To make a one-inch fine wire rope, fill the bobbins of a "six-flyer" machine similar to Fig. D, with what is known as No. 8 wire, Birmingham gauge. And