Machinery's Handbook, 31st Edition
Wire Rope 2713 Flexibility: Wire rope that undergoes repeated and severe bending, such as in pass- ing around small sheaves and drums, must have a high degree of flexibility to prevent premature breakage and failure due to fatigue. Greater flexibility in wire rope is ob - tained by 1) using small wires in larger numbers; 2) using Lang lay; and 3) preforming, that is, the wires and strands of the rope are shaped during manufacture to fit the posi - tion they will assume in the finished rope. Resistance to Crushing and Distortion: Where wire rope is to be subjected to trans- verse loads that may crush or distort it, care should be taken to select a type of con- struction that will stand up under such treatment. Wire rope designed for such conditions may have 1) large outer wires to spread the load per wire over a greater area; and 2) an independent wire core or a high-carbon cold-drawn wound spring core. Standard Classes of Wire Rope.— Wire rope is commonly designated by two fig - ures, the first indicating the number of strands and the second, the number of wires per strand, as: 6 × 7, a six-strand rope having seven wires per strand, or 8 × 19, an eight-strand rope having 19 wires per strand. When such numbers are used as designa- tions of standard wire rope classes, the second figure in the designation may be purely nominal in that the number of wires per strand for various ropes in the class may be slightly less or slightly more than the nominal as will be seen from the following brief descriptions. (For ropes with a wire strand core, a second group of two numbers may be used to indicate the construction of the wire core, as 1 × 21, 1 × 43, and so on.) 6 × 7 Class (Standard Coarse Laid Rope): Wire ropes in this class are for use where resistance to wear, as in dragging over the ground or across rollers, is an important requirement. Heavy hauling, rope transmissions, and well drilling are common appli- cations. These wire ropes are furnished in right regular lay and occasionally in Lang lay. The cores may be of fiber, independent wire rope, or wire strand. Since this class is a relatively stiff type of construction, these ropes should be used with large sheaves and drums. Because of the small number of wires, a larger factor of safety may be called for.
Fig. 1d. 6 × 7 with IWRC
Fig. 1a. 6 × 7 with Fiber Core
Fig. 1c. 6 × 7 with 1 × 19 WSC
Fig. 1b. 6 × 7 with 1 × 7 WSC
As shown in Fig. 1a through Fig. 1d, this class includes a 6 × 7 construction with fiber core: a 6 × 7 construction with 1 × 7 wire strand core (sometimes called 7 × 7); a 6 × 7 construction with 1 × 19 wire strand core; and a 6 × 7 construction with independent wire rope core. Table 1 provides strength and weight data for this class. Two special types of wire rope in this class are: aircraft cord, a 6 × 6 or 7 × 7 Betha- nized wire rope of high tensile strength and sash cord, a 6 × 7 iron rope used for a variety of purposes where strength is not an important factor.
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online