a - Wire

b - Strand

c - Center

d - Wire Rope

What Is Wire Rope?

DEVELOPING the thought of last month's article -- "Wire Rope -- A Machine," we conclude that wire rope is a highly complex machine -- a fact that is little appreciated by the average user. For example, we can take standard "Blue Center" Steel, and is a distinctive hoisting rope, which is 6 x 19 construction, and find that this rope is made up of 114 separate and distinct steel wires, each of these wires specified and drawn to a size held generally within .001''. When it is considered that each of these wires is in contact at three or more points, and comparing these bearing surfaces with the bearing surfaces of machines. it will be seen that this is a complex mechanism, and it should be appreciated as such.

There are five standard grades of Wire Rope in general use; namely, iron, cast steel, extra strong cast steel, plow steel and improved plow steel. To this list we add "Blue Center Steel" a distinctive Roebling Product. There are of course other grades of wire fabricated into rope, of which products for aircraft are a good example but we are dealing here with the general grades best known to users.

While wire rope is furnished in all of these grades, it is nevertheless true that the increasingly severe requirements make it necessary to use only the stronger ones, and in fact the best quality possible to obtain, in order to assure customers of economical average service with safety.

In each of the grades mentioned there are a great number of constructions of rope which can be, and are furnished, although naturally these constructions divide themselves into four general classifications that cover most of the wire rope in use. The standard constructions are 6x7, which is sometimes spoken of as coarse lay; 6x19, or flexible and 6x37 together with 8x19, or extra flexible. There are of course many variations from these constructions which call for different numbers of wies in the strands and sometimes different numbers of strands in the rope. The majority of these, however, have generally been accepted as falling within these four general classifications.

6x7 Construction 6 Strands, 7 Wires to Strand
6x19 Construction 6 Strands, 19 Wires to Strand

	6x37 Construction 6 Strands, 37 Wires to Strand
	8x19 Construction 8 Strands, 19 Wires toStrand

Before further discussing wire rope construction, however, let us first consider the individual wires that enter into the rope. They are called "wires" both before and after the rope is fabricated. The correct number of wires of a proper size are laid together to form strands. The proper number of strands are then laid together around the center, which may be hemp, strand or an independent wire rope, and this forms the rope with which we are familiar, and which is in use on so many varied installations.

We refer to wire, strand and center, merely in an attempt to establish the correct terms for wire rope, because so many times strands are spoken of as wires and, vice versa, wires are spoken of as strands.

Wire rope can be made either "right lay" or "left lay." Most of the wire rope furnished, however, is "right lay." This means that the strands composing the rope are laid around the center in the direction that causes them to form a right hand spiral. This can probably be better understood by referring to a right-hand screw thread. The strands in a right lay rope will advance along, and around the axis of the rope, in the same manner as do the threads in standard right-hand screw. Another way of expressing this would be to note the direction of rotation of the strands around the rope as you follow the strand from a point near to you to a point farther away. If this direction of rotation is clockwise, it is a right lay rope. Left lay would naturally be the reverse. In other words, the strands form a left-hand spiral in the rope. Since right lay is the standard lay, this is always furnished, unless left lay is definitely specified on the order.

Wire rope is furnished either Regular Lay or Lang Lay. Regular Lay wire rope is one where the wires in the strands and the strands in the rope are laid in opposite directions. That is, the lay of the wire in the strands in a right lay rope would be "left lay" in making a Regular Lay wire rope. Naturally a left lay Regular Lay rope would have the wires in the strands laid "right lay." Regular Lay is the standard type of construction and, unless otherwise specified, is furnished on orders for wire rope.

What is known as "Lang Lay" rope is also made Right Lay or Left Lay; however, right lay is more frequently used. In this construction the wires in the strands, and the strands in the rope, are laid in the same direction, or, in other words, the wires in the strands of a right lay Lang Lay rope would be laid "right lay." This particular type of rope is slightly more susceptible to abuse and, therefore must be handled with greater care, and should be used only where it is especially recommended.

Wire rope is generally furnished "bright'" that is, the rope is made of bare steel wires with no coating other than that used, and formed, as part of the lubrication for the wire drawing operation. Most of the rope in use is of this finish or grade. Galvanized wire rope has a wide variety of uses. In this type of rope, all of the wires are coated with pure zinc, which forms a protection against corrosion. It is called "galvanized wire rope" to distinguish it from bright rope. Wire rope is also furnished "tinned," but this finish represents only a small percentage of the wire rope in use.

The most satisfactory material for making wire rope is carbon steel, although many other metals are used: some of which are copper, bronze, stainless steel and various alloys.

Next month we will discuss the construction of Wire Rope.

Regular Lay Right Lay
Regular Lay Left Lay

	Lang Lay Right Lay
	Lang Lay Left Lay