MECHANICAL.) Small cotton ropes are used extensively in textile mills for small machine drives. Rope is used on the farms for hoisting, hauling, harness and many other uses. Rope is used in building and engineering projects construction. In the home also it has many applications.
The useful life of rope depends on the quality of the rope, and on the care and treatment it receives. To give the best service, it must be made of high grade raw material, selected with a thorough knowledge of what the rope is to do. It must be so made that every strand will be of even tension. It must be properly treated with a lubricant which will at once preserve and lubricate. There are three general sources of damage which will shorten the life of rope; first, mechanical injury, such as bending over too sharp a pulley, second, damage from chemicals, such as acids, and third, damage from climatic or other con ditions of storage, such as moisture or dry rot. It should be stored in a cool dry place with air circulation. (J. S. McD.) In addition to the heavy rope there are many varieties of cord and twine made by means of the preparing, spinning and doubling machines. The fishing industry takes many different types for lines and nets, while the variety of cord and twine for other industrial and for household purposes is almost unlimited.
All yarn from long vegetable fibre is more or less rough as it leaves the spinning frame, even after two or more threads have been twisted together. It is therefore necessary, for many uses, to impart a polish to the cord or twine. Special machines are used for this purpose. Bobbins of yarn, equal to the number required, and depending upon the capacity of the machine, are placed in a bank or creel, and the ends are collected and passed under a roller which is immersed in hot starch. The yarns be come saturated with this starch, but, as they emerge from the starch-box, the superfluous starch is removed by passing the yarns between two rollers. The yarns now pass over a series of drying cylinders and polishing rollers, and are finally rewound by the same machine on to other bobbins. This machine is termed
a bobbin-to-bobbin polishing machine. In some cases the hot drying cylinders are replaced by a system of hot-air drying.
The finished yarns are now made up by machinery into hanks, balls or cheeses, according to which happens to be the best state for future use and for transport.
2. It occupies less space than belt driving, and the slip is not so great.
3. The turning movement is better; machines therefore run more steadily and production is increased.
4. Shafts may be run at higher speeds.
5. Greater range of drives; anything from 10 ft. to over 8o ft., and much greater distances when carrier pulleys are used.
6. The drive is usually obtained by a number of ropes; if one should break, the rope may be removed and the machinery run, in most cases, until stopping-time.
The number of ropes to be used depends upon the power to be transmitted; upon the sectional area of the ropes, and upon the surface speed of the driving pulley. The speed of the rope may vary from 2,000 ft. to 6,000 ft. or over per minute. In some few exceptional cases 6o ropes have been used on one pulley; the number usually varies between 15 and 4o. (See POWER TRANS MISSION : Mechanical.) The foregoing refers exclusively to ropes made from fibrous yarns ; metallic ropes appear under the heading WIRE ROPE.
See T. Woodhouse and P. Kilgour, Cordage and Cordage Hemp and Fibres (1919) ; Robert Chapman, A Treatise on Rope-making (1868); H. R. Carter, Modern Flax, Hemp and Jute Spinning and Twisting (1925) ; P. J. Stopford, Cordage and Cables (1925) ; • "U.S. Government Master Specifications for Rope Cotton," Bureau of Standards Cir. 326, (1927).