Cords are extensively useful for various purposes of domestic life, but more particuarly in the rigging of ships; in which case they are, according to their size, called cables, or rotes, to which we refer. Hence, the manufacture of these articles has become an object of considerable importance.
In the common way of making cordage, it has been found, that, by being twisted too tight, ropes were rendered incapable of raising weights beyond a certain proportion, and that, from the friction occasioned by their inelasticity, they were neither very durable, nor always safe. Various means have been devised to obviate this defect, and several patents have lately been granted, from which we select the following.
In July 1792, Mr. James Mitchell, of Poplar, andBlackwall, Middlesex, obtained a patent for a method of manufacturing cordage on a scientific principle. It apparently consists in subdividing the twists or cylindrical parts of ropes, or cordage, and giving them a peculiar turn, so as to make them blend and unite; and also to operate in such a manner that the component parts act. in spiral di-rections, similar to parallels. By this mode, the yarns all bear together, so that the cordage acquires an increased degree of tension, as well as a greater power of resisting fluids and friction, and also a more uniform elasticity.
A patent was also granted, in January 1798, to Mr. W. Chapman, of Newcastie-upon-Tyne, for a new method of manufactur-ing ropes or cordage. The patentee describes his invention to consist in placing those parts that separately twist the rope and strands (each of which contains a number of yarns twisted together) at a certain determinate distance. By such means, the process of twisting is not completed through the whole length at once, but only in the intermediate space. With this circumstance, the patentee combines a mode of twisting the cord or rope itself by an arbor or shaft, perforated either through? the whole or a part of its extent, and revolving round its own axis ; and which, at the same time, twists its several parts, by means of separate arbors or shafts, either perforated or otherwise, each of which performs a like revolution. Thus, not only the operation of twisting the cord or rope is effected, but also that of coiling it up, by the motion of the machine, while both time and length of ground are saved, which, according to the prevailing mode of making cordage, are uselessly occupied.
Another patent which we shall notice, is that granted in August 1799, to Joseph Huddart, of Islington, Esq. for an improved method of forming the strands in the machinery for manufacturing cordage. The leading principle of this invention is, to give the length of the yarns composing the strand, a certain ratio, in proportion to the hardness, or compression, with which the rope is intended to be laid, and thus to acquire a more equal distribution of the strain upon the yarns, than upon ropes made in the common way. This is effected,
1. By keeping the yarns separate from each other, and drawing them from revolving bobbins, in order to keep up the twist, while the strand is forming; 2. By passing the yarns through a register, which divides them by circular holes (Mr. Huddart says, circular shells of holes); the number in each being agreeable to the distance from the centre of the strand, and to the angle which the yarns make with a line parallel to it, that gives them a proper position to enter; 3. By a cylindrical tube, which compresses the strand, and maintains a cylindrical figure to its surface; 4. By a gauge, to determine the angle which the yarns in the outside shell make with a line parallel to the centre of the strand, when registering ; and, according to the angle made by the yarns in this shell, the length of all the yarns in the strand will be determined ; lastly, 5. By hardening up the strand, and thus increasing the angle in the outside shell, which compensates for the stretching of the yams, and compression of the strand. By attending to these directions, every yarn in the strand will bear a strain, when at the point of breaking: and, when laid into a rope, it will acquire additional strength.
Cord. - In June, 1801, a patent was granted to Mr. William Chapman, for the application of certain substances designed to preserve cordage; and which, being other with difficulty soluble, or totally insoluble in water, tend to render such ropes more durable, than has hitherto been practicable. The usual method adopted for this purpose, consists in boiling tar alone, till it be inspissated to a proper consistence ; but Mr. C. proposes to boil the tar in two or three different waters, till it be divested of its acid, and all the mucilaginous particles ; which, by the common process, remain in the liquid preparation ; and, by their speedy tendency to decomposition, frequently contribute to the decay of the ropes, at an earlier period than would naturally take place without such practice. He therefore adds a due proportion of suet, tallow, or any fixed oil, that has been deprived of extraneous matters, by similar boiling.