Plow-, or plough-steel ropes are made of wires having an ultimate tensile strength of 220,000 to 250,000 lb. per sq. in. The breaking strength of a 6X19 hoisting rope of this grade and 1 in. in diameter is given as 38 T., or 11.18% more than that of an extra strong cast-steel rope of the same dimensions. Ropes of this grade are not generally recommended, except where it is necessary to have the maximum of tensile strength with the least weight of rope, or where it is necessary to employ a rope of much greater strength but of the same diameter. The first necessity will arise when hoisting through extremely deep shafts; the second, where by reason of increased loads it becomes essential to have a stronger rope, but at the same time the diameter of the rope is fixed by the size of existing drums, sheaves, etc. Plow-steel ropes are extensively employed for logging lines, dredge and wrecking ropes, ballast unloading ropes, quarry ropes, etc.

Extra, special, or improved plow-steel ropes are made of wires having an ultimate tensile strength of from 240,000 to 300,000 lb. per sq. in. A rope of this grade of the size cited before has a breaking strength of 45 T., or about 11.84% more than an ordinary plow-steel rope of the same dimensions. The comments upon standard plow steel ropes apply as well to ropes of this grade.

CONSTRUCTION OF WIRE ROPES

Wire ropes consist of a number of strands, each composed of the same number of single wires twisted around a hemp or wire core or center to form a single rope. The hemp core adds practically nothing to the strength of the rope but, being saturated with lubricant, tends to prevent rusting of the wires and, being soft, acts as a cushion for the individual strands, thus reducing internal friction and wear. A wire core adds largely to the internal friction and consequent wear of rope as the strands rub upon the wire center; increases the weight; and, while adding about 10% to the strength, reduces the flexibility in a marked degree, at the same time adding 10% to the cost. Manufacturers, whose judgment should be final, recommend ropes with wire cores only for standing lines, such as the guy ropes of derricks, etc., because they lack the flexibility demanded of running ropes (those used for hoisting, haulage, etc.), and because of their much greater internal wear in bending around drums, sheaves, and the like.

FIG. 1

Lay of Ropes.-The lay of a rope is the direction of the twist of the strands composing it. Ropes are either right or left lay, the former being the ordinary construction as shown in Fig. 1 where the strands are bent to the right. The left-lay construction is shown in Fig. 2.

The term lay is also used to describe the direction of twist of the individual wires composing the strands in a rope. Thus, in Fig. 1, while the rope is right lay (strands twisted to the right), the strands are left lay, the single wires being twisted to the left. Similarly, in Fig. 2, while the rope is left lay, the strands are right lay.

FIG. 2

Finally, the term lay is used to designate the pitch of the rope; that is, the rate at which the strands twist or, what is the same thing, the ratio that the length of strand required for one complete turn bears to the diameter of the rope. In ordinary rope making, the lay or (better) pitch of the wires varies from 2.5 to 3.5 times the diameter of the rope, and that of the strands from 6.5 to 9 times the diameter of the rope. The lay exerts an important influence upon the life of a rope. For the same kind and size of rope, the shorter the lay or pitch, the greater the flexibility and elasticity, but the less the strength. This falling off in the strength, due to the shortening of the pitch, is brought about by the nicking, or cutting, of one wire by another, which is naturally less when the ropes cross one another at a long angle (long pitch) than when they cross at a sharp angle (short pitch). In practice, ropes are commonly classified as ordinary-lay or regular-lay ropes, and as Lang lay or universal-lay ropes. In the ordinary lay ropes, which are shown in Fig. 1 and Fig. 2, the wires in the strands are twisted in the opposite direction from that of the strands in the rope, while in Lang lay ropes, shown in Fig. 3, the single wires and the strands are twisted in the same

direction. Lang lay ropes may be either right or left twist, and their price is the same as that of ordinary-lay ropes.

The principal advantages of the Lang lay are that, the wires and strands being twisted in the same direction, the surface of the rope is smoother, the outside wires do not so soon become worn as a much longer surface of each wire is exposed to wear, and, the wires being straighter, these ropes are somewhat more flexible. The disadvantages of

Lang lay ropes are a tendency to untwist, rendering them unsuited for hoisting except where guides are used; they can be spliced to ropes of ordinary-lay only with difficulty; and when the wires break, the loose ends are very troublesome, because a much greater length of each wire is exposed than in ordinary-lay ropes. Under careful inspection, a regular-lay haulage

FIG. 3

rope may be used for some time after a few of its wires are broken here and there throughout its length, except when a dangerous risk would be incurred by so doing. The Lang lay ropes are commonly used for haulage, particularly where grips are used to attach the cars to the ropes, and are sometimes used for hoisting, but only where the cage works in guides.

HOISTING ROPES

ROUND ROPES

6X19 Ropes.-Ropes used for hoisting through shafts are round or flat and in either case may be of uniform or tapering section. Round ropes of uniform section, are practically the only ones used in American mines. The

standard American hoisting rope, shown in Fig. 1, is composed of 6 strands of 19 wires each (114 wires) wrapped around a hemp center. It is frequently spoken of as a 6X19 rope. These ropes are commonly made of cast

steel or, where greater strength is required, extra strong cast-steel. The diameter of sheave recommended for use with a 1-in. rope of this type is variously given at 4 to 4.5 ft.

8X19 Ropes. Where extreme flexibility is required, ropes composed of 8 strands of 19 wires

each (152 wires) may be employed. From the tables given later, it will be noted that the maximum diameter of rope of this section commonly carried in stock is 1 in. as against 2

FIG. 2

in. for the 6X 19. Fig. 2 shows that the core is much larger in proportion to the area of metal than in a 6X19 rope of the same size and quality. Consequently, this rope is not so strong as a 6X19 rope of the same diameter

(24 T. as against 30 T. for 1-in. cast-steel rope) and is more liable to flatten out under heavy pressure. The diameter of sheave suggested for use with a 1-in. rope of this type is variously given as 2.5 to 3.25 ft.; materially less than that required for a 6X19 rope. Ropes of this class are recommended for derricks and similar work where small sheaves must be employed, but it should be noted that, so far as the working life of this type is

FIG. 3

concerned, the increased flexibility in a very considerable measure offsets its decreased strength.

6X37 Ropes. A form of very flexible rope that is not infrequently used in preference to the 8X19, is shown in Fig. 3; in this, the rope is composed of 6 strands of 37 wires each. As there is a much greater area of metal in proportion to the hemp core than in an 8X 19, the breaking strength of a 1-in.

FIG. 4

cast-steel rope of this type is given as 29 T., only 1 T. less than that of the standard 6X 19 rope and 3 T. more than the 8X19. The diameter of sheave suggested for this rope is the same as that for the 8X19;

viz., 2.5 to 3.25 ft. As the wires in this rope are, of necessity, smaller than those in a 6X19 rope of the same diameter, it is apparent that this type of rope is not so well adapted to withstand abrasion as those containing larger wires. This rope is employed where the bending strains are very great, as in logging operations, for use with electric cranes, etc. When galvanized, this rope is largely used for hawsers in towing, etc.

Non-Spinning Ropes.-Non-spinning hoisting rope, made by one of the leading manufacturers, is shown in Fig. 4, It is composed of 18 strands of 7 wires each (126 wires), 12 of the strands being laid in a reversed direction about 6 which, in turn, are laid about a hemp core. Because of the reversed directions in which the inner and outer sets of strands are laid, there is no tendency to twist and the rope is, thence, adapted to hoisting where the load is not raised between guides but

hangs freely as a bucket in shaftsinking. The rope is slightly more flexible than the standard 6X 19 rope and slightly stronger. However, it cannot be spliced.

In

(a)

(b)

FIG. 5

Flattened-Strand Ropes.-In order to present a larger and smoother wearing surface, and thus to increase the life of the rope, flattened-strand wire ropes have been devised. these ropes the strands have an elliptic, or triangular, cross-section, depending on the shape of the metal center of the strand, and the rope has either a hemp or a wire core. They are made either 5X 28 (5 strands of 28 wires each, or 140 wires) as shown in Fig. 5 (a), or 6X25 (6 strands of 25 wires each, or 150 wires) as shown in (b). These ropes are made of Swedes iron, and of cast-steel, extra strong cast-steel, and extra plow-steel. The breaking strength of a cast-steel rope of this make, 5X28, and 1 in. in diameter is given as 30 T., the same as that of the same size and kind round, 6X 19 standard rope. A 6X25 cast-steel rope of this type 1 in. in diameter is given as 33 T., which is greater than that of the corresponding 6X 19 round rope and nearly as great as that of an extra strong cast-steel rope. There is claimed for this rope greater flexibility, less liability of the wires becoming brittle, and freedom from all tendency to spin or kink; also that they maintain their form better than round ropes.

ropes.

FIG. 6

Seale Ropes.-A form of rope made by some manufacturers and used for hoisting, but possibly better adapted to haulage purposes, is shown in Fig. 6, as it is of the 6X19 type used in standard hoisting

This is known as Seale rope or Seale lay rope, and consists of 6 strands of 19 wires each, in which 9 large wires are twisted around 9 small ones, which in turn surround one of the larger size. This rope is intermediate in flexibility and ability to stand abrasion between the standard ropes of 7-wire (haulage) and 19-wire (hoisting) strands. This type of rope, on account of the large outside wires, will withstand heavy frictional wear and is used on slopes, planes, and cable

roads where the rope commonly drags, provided, however, that there are no bends of sharp angle to overstrain the outer wires. While there is more metal in the outer wires than in those of the standard rope, there is correspondingly less in the inner wires, and closer inspection of the outer wires is, therefore, necessary to prevent the rope being used too long. The price of these ropes is the same as the standard 6X 19 hoisting rope of the same grade.

FLAT ROPES

Flat ropes, Fig. 7, are composed of a number of loosely twisted ropes of four wires each and without hemp centers. The ropes, of alternately right and left lay, are placed side by side and are then sewed together with soft iron or annealed steel wire to form a single rope. The sewing wires, which vary in number from 8 to 12 pass through the centers of the individual ropes from side to side and often have to be renewed, as they naturally wear faster than the wires composing the rope

proper.

Flat ropes may be made to order of any width to give any desired strength, but the width must, of necessity, be some multiple of the diameter of a single strand. They are made of the same grades of steel as round ropes and, under certain conditions present material advantages over the ordinary type. In very deep shafts

FIG. 7

round ropes have a tendency to twist and untwist, or to spin, something that flat ropes do not do. The width of the reel upon which a flat rope winds is very much less than that of the drum used for round ropes, and as the rope coils upon itself like a ribbon, it tends to equalize the load upon the engine, the effect being approximately the same as that produced by conical drums. Likewise, in hoisting, the rope is always in the same vertical plane, thus avoiding the wear that round ropes are subject to when wound on a drum. Flat ropes are not used in coal mines in the United States, owing to the comparatively shallow depths of the shafts, but are quite extensively used in the metal-mining districts, where vertical lifts of 2,000 ft. and over are common.

TAPER ROPES

Taper ropes, both round and flat, have been used in deep hoisting. Such a rope has its diameter or width reduced uniformly throughout its length by dropping a single wire at a time, or by decreasing the size of the wire used at regular intervals, so as to reduce the sectional area of the rope in proportion to the weight to be supported. The reason for using taper rope is as follows: When the load is at the bottom of the shaft, the upper part of the rope sustains both the load to be hoisted and the weight of the rope itself. As the rope is wound up, the load on the rope at the drum gradually decreases and, therefore, the size of the rope may be proportionately decreased. Owing to the difficulties of manufacture, taper ropes cannot be made as perfect as straight ropes and their cost is greater; furthermore, they cannot be used for haulage and other purposes when partly worn, as is the case with straight ropes.

HAULAGE ROPES

6X7 Ropes. For underground haulage and for the transmission of power, a rope of the section shown in Fig. 1, and either ordinary or Lang lay, is in

general use in American mines, to the practical exclusion of any other type. It is composed of 6 strands of 7 wires each (6 X 7) twisted around a hemp center. It is decidedly stiffer than a 6X 19 standard hoisting rope and requires larger sheaves, as will appear from the tables. Owing to the small number of wires (there are but 42 as against 114, 152, and 222, in the 6X 19, 8X 19, and 6X37 hoisting ropes) this

FIG. 1

rope should be used with a higher factor of safety than is employed with hoisting ropes, as the breaking of one or two wires materially reduces the strength of the rope. These ropes are made of Swedes iron and of the four grades or strengths of steel previously mentioned. As in the case of hoisting ropes, haulage ropes of iron require the use of deecidedly larger sheaves than do those of steel. Manufacturers recommend a sheave from 10.5 to 11 ft. in diameter for a 1-in. iron rope of this type as against a sheave 7 to 8 ft. in

diameter for a corresponding steel rope.

Flattened-Strand Ropes.-Flattened-strand rope, similar in general construction to the rope of the same name used for hoisting, is also employed for haulage. Ropes of this type are shown in Fig. 2 (a) and (b). The former shows the 5X9 (45 wires) rope very similar to the 5X28 hoisting rope of the same type. View (b) shows the 6X8 haulage rope, which is not unlike the 6X25 hoisting rope. The ultimate breaking strength of a 1-in., caststeel, ordinary, haulage rope is given as 31 T., and those of the 5X9, and 6X8, flattened-strand rope of the same diameter and material are 31 and 34 T., respectively. The diameter of sheave suggested for the standard 6X7 1-in. haulage rope is 7, and 5.75 ft. for either type of the flattened-strand rope. The comments made upon hoisting ropes of this type apply here.

(a)

FIG. 2

(b)

Seale Ropes.-Seale lay ropes are used to a certain extent for haulage and those of the Lang lay type are very commonly employed for the same purpose, as explained before.

ROPES FOR MISCELLANEOUS PURPOSES

Ropes for Cableways.-Many of the ropes described, and particularly the 6X7 Lang lay, are used for the track or supporting cable of what are variously known as cableways,

wire-rope tramways, aerial tramways, and the like. In this system of transportation, the materials to be moved are carried in buckets suspended from wheeled trucks, which are hauled

FIG. 1

by a lighter rope upon a fixed rope known as the cable, or track cable. Such cables are subject to extreme wear and to produce a rope having the maximum of wearing surface, what are known as locked-wire cables and locked-coil cables have been devised.

The locked-wire construction is shown in Fig. 1. The outside wires are drawn of such a shape as to interlock one with the other, making a smooth cylindrical surface for the carrier wheels to run upon. Ropes of this type have wire cores and are, consequently, stiffer than ordinary ropes of the same size;

FIG. 2

but as they are proportionally stronger for equal strengths there is probably not much difference in the stiffness of the two forms of construction. The advantages claimed for this rope are lessened wear, both on the part of the rope and on that of the wheels of the traveling carriage; absence of any tendency to twist and turn; and freedom from unraveling should any of the wires break.

The locked-coil construction is illustrated in Fig. 2. It differs from the preceding only in the smaller number and larger size of the wires, which makes it stiffer.