Rotation Resistant Wire Rope
Rotation resistant wire rope is a special category (class) of wire rope designed to resist the tendency to spin or rotate under load. In general these ropes are used as single part lines, or in situations where operating conditions require a rope that will resist cabling in a multipart system. The essential nature of rotation resistant rope designs impose certain limitations on their application and necessitate special handling requirements not encountered with other rope constructions.
Rotation resistant wire rope is available in two general classifications:
1) Single layer-consisting of a single layer of three or four strands. Typically the strands support one another without a core member.
2) Multilayer strand (Multistrand)-consisting of two or more strand layers closed in opposing directions. Torsional forces generated by each layer of the rope counteract one another to minimize rotation.
The multistrand classification includes ropes with between eight and twenty outer strands. Table 1 of this manual describes some of the more commonly available rotation resistant multistrand rope classification. In addition to these, a wide variety of special multistrand ropes is available. See (Figure 9). It would be impractical to cover the specific features of each in this manual.
Figure 9. Cross sections of rotation resistant rope constructions.
In multistrand rotation resistant ropes the crossover points between strand layers are points of high stress concentration. Relative motion of the strands at these points results in accelerated deterioration of the internal components of the rope. Because of this design characteristic of the multistrand construction, care must be taken to avoid high loads with small diameter sheaves. Design factors less than five are not recommended.