PLOW STEEL wire rope is unusually tough and strong. This steel has a tensile strength (resistance to lengthwise stress) of 220,000 to 240,000 psi. This wire rope is suitable for hauling, hoisting, and logging.

IMPROVED-PLOW STEEL wire rope is one of the best grades of wire rope available, and most, if not all, of the wire rope you will use in your work will probably be made of this material. It is stronger, tougher, and more resistant to wear than either plow steel or mild-plow steel. Each square inch of improved-plow steel can stand a strain of 240,000 to 260,000 psi.

Measuring Wire Rope The size of wire rope is designated by its diameter. The true diameter of a wire rope is considered as being the diameter of the circle that will just enclose all of its strands. Both the correct and incorrect methods of measuring wire rope are shown in figure 1-5. Note, in particular, that the CORRECT WAY is to measure from the top of one strand to the top of the strand directly opposite it. Use calipers to take the measurement; if calipers are not available, an adjustable wrench will do. To ensure an accurate measurement of the diameter of a wire rope, always measure the wire rope at three

Figure 1-4.- Two types of wire rope.

a 1/ 2-inch-diameter wire rope. Using the formula above, you would solve the problem as follows:

SWL = (1/ 2) 2 x 8 SWL = 2 tons

Figure 1-5.- Correct and incorrect methods of measuring wire rope. places on a six-stranded, and four places on an eight-stranded wire rope. Use the average of the three measurements as the diameter of the wire rope. Safe Working Load The term safe working load (SWL), as used in reference to wire rope, means the load that you can apply and still obtain the most efficient service and also prolong the life of the wire rope. Most manufacturers provide tables that show the safe working load for their wire rope under various conditions. In the absence of these tables, you may apply the following rule-of-thumb formula to obtain the SWL: SWL (in tons) = D 2 x 8 This particular formula provides an ample margin of safety to account for such variables as the number, size, and location of sheaves and drums on which the wire rope runs and such dynamic stresses as the speed of operation and the acceleration and deceleration of the load, all of which can affect the endurance and breaking strength of the wire rope. Remember this formula is a general computation, and you should also consider the overall condition of the wire rope.

In the above formula, D represents the diameter of the rope in inches. Suppose you want to find the SWL of WIRE-ROPE ATTACHMENTS Wire rope can be attached to other wire ropes, chains, pad eyes, or equipment by splicing, which is permanent, or by any of a number of wire-rope attachments. These include sockets and wire-rope clips. In general, these attachments permit the wire rope to be used with greater flexibility than would be possible with a more permanent splice. The attachments allow the same wire rope to be made up in a variety of different arrangements. 

Clips A temporary eye splice may be put in wire rope by using clips. A single clip (fig. 1-6) consists of three parts: U-bolt, saddle, and nuts. The correct and incorrect methods of applying these clips to wire rope are shown in figure 1-6; the second incorrect method shown is the most common. Notice that the correct way is to apply the clips so that the U-bolts bear against the bitter end; that is, the short end of the wire rope. If the clips are attached incorrectly, the result will be distortion or mashed spots on the live end of the wire rope. After a wire rope is under strain, tighten the clips again. On operating wire ropes, tighten the clips daily and inspect the wire ropes carefully at points where

Figure 1-6.- Use of wire-rope clips.

there are clips. Pay particular attention to the wire at the clip farthest from the eye, as vibration and whipping are heaviest here and fatigue breaks are likely to occur. To obtain maximum strength in the temporary eye splice, use the correct size and number of wire clips. The size is stamped on the saddle between the two holes. A rule of thumb for determining the number of clips required for various sizes of wire rope is to multiply the diameter of the wire rope by 3 and add 1. Stated as a formula, this means

3D + 1 = number of clips. For example, if the wire rope has a diameter of 1 inch, determine the number of clips as follows:

(3 x 1) + 1 = 4 clips In case the answer contains a fraction, then use the next largest whole number. For example, suppose you

want to find the number of clips for a wire rope 1/ 2 inch in diameter. Using the formula, the answer would be 2 1/ 2 clips. You simply use the next whole number to get the correct answer.

You should space the clips properly to provide a good hold on the wire rope. You can determine the correct distance between the clips by multiplying 6 times the diameter of the wire rope. Where D is equal to

Figure 1-7.- Wire-rope bends and couplings.

Figure 1-8.- Wire-rope fittings.

the diameter, 6 x D = DISTANCE BETWEEN CLIPS. Here, as in determining the number of clips, if the answer contains a fraction, use the next whole number. You should inspect and tighten wire-rope clips at regular intervals. Also, after comparatively long use, remove the clips and examine the wire rope for broken wires. If any are present, remove the damaged part and make a new attachment.