How Is Rope Made?

Rope is a term applied to the larger dimensions of twisted fibers or steel wires. Fiber rope of smaller diameters up to approximately I em is usually regarded as cordage. Thread is composed of two or three twisted yarns and twine is made of a dozen yarns or so. Cord is made of three or more strands while string comes under the heading of cord or twine. The general method of manufacture is the same in all cases-the yarns are twisted together into strands and the strands twisted together to form the rope. A hawser-laid rope consists of three strands; a cable or cable-laid rope is composed of three such hawsers twisted together. A shroud-laid rope has a central strand with three or four strands twisted around it. Some cordage, and sometimes rope, is plaited to give greater flexibility. Various fibers have been used in rope-making, but sisal and manila are the most widely used. Hemp, jute, and coir are used to some degree locally.

Cotton is also used for ropes and cordage for certain applications such as driving wheels.

The processes of fiber rope-making involve hackling, to separate the fibers in the rather tangled 'raw' state and to lay them parallel to each other. After this the fibers are spun and then the ends are passed through holes in a register-plate, and as the machinery revolves the yarns are automatically twisted together into strands. A further extension of this process twists the strands together to form the rope. The advent of man-made fibers made a great impact on rope-making. Ropes of nylon, terylene, and polypropylene are being increasingly used for sporting and many industrial applications. The method of manufacture is very similar to that of natural fibers. Fibrillated polypropylene is being used to replace sisal for domestic and light industrial cordage. The low melting point of this fiber does cause some problems but allows the cordage to be cut and the ends sealed with hot wire cutters.

Wire rope is used for many industrial applications, on cranes, excavators, drilling rigs, for suspension bridges, aerial ropeways, and as a method of roof suspension.

The principles of wire rope-making are broadly similar to those of fiber rope manufacture in that high-tensile steel wires are twisted together to form strands which are further twisted together to form the rope.

Many types of constructions are available depending on the type of duty for which they are to be used. In general the greater the number of wires used, the greater is the flexibility of the rope. A development of great importance is pre-formed rope, in which the wires and strands forming the rope are, during the manufacturing process, given the exact helix which they take in the completed rope. There is far less internal stress with pre-formed rope and the rope has a longer life.

All fiber used in making ropes is generally called "hemp," but it may come from many different plants. The best rope material is the fiber of a plant called the abaca, which grows in the Philippines. This fiber is generally known as Manila hemp. It is easier to work with and stronger than other forms of hemp. The century plant of Mexico provides a material for making rope and so does coconut fiber. Rope can be made from cotton and flax fibers, but it is too expensive for general use.

Until the 19th century ropes were made entirely by hand on rope-walks. These were long, low buildings in which the ropemaker walked backward, step by step, unwinding the fibers from about his waist. At the upper end of the walk, a boy turned a wheel to which one end of the rope yarn was attached. This wheel kept twisting the yarn while it was being spun.

Today almost all rope is made by machinery. The fibers are passed through a series of machines called breakers, which look like steel combs. They comb the fibers out thoroughly, clean out the dirt, straighten out the snarls, and turn the rough mass of fibers into a "sliver." This is a straight, continuous ribbon of loose threads, equal in thickness. These slivers are sent to the spinning machines. Here they are twisted into yarn and the yarn is wound onto spools or bobbins.

The bobbins are mounted on a revolving disk. The yarn is put through a metal tube which presses the separate pieces together and as it comes out it is twisted together into a strand. Then the same process takes three or four of these strands and twists them together to make a rope.

Each time the fibers are twisted the twist is made in the opposite direction from the last one. In this way the different twists counterbalance each other and keep the rope from untwisting.