Many of the movable components on cranes and
attachments are moved by wire rope. Wire rope is a
complex machine, composed of a number of precise
moving parts. The moving parts of wire rope are
designed and manufactured to bear a definite
relationship to one another to have the necessary
flexibility during operation.
Wire rope may be manufactured by either of two
methods. If the strands, or wires, are shaped to conform
to the curvature of the finished rope before laying up,
the rope is termed PREFORMED WIRE ROPE. If they
are not shaped before fabrication, the wire rope is
termed NON-PREFORMED WIRE ROPE. The most
common type of manufactured wire rope is preformed.
When cut, the wire rope tends not to unlay and is more
flexible than non-preformed wire rope. With non-
preformed wire rope, twisting produces a stress in the
wires; therefore, when it is cut or broken, the stress
causes the strands to unlay.
Figure 6-33.Composition of wire rope.
When the wire is cut or broken, the almost
instantaneous unlaying of the wire or strands
of the non-preformed wire rope can cause
serious injury. This situation is apt to occur
especially to someone who is careless or not
familiar with this characteristic of the rope.
Composition of Wire Rope
Wire rope is composed of three partswires,
strands, and core (fig. 6-33). A predetermined number
of wires of the same or different size are fabricated in a
uniform arrangement of definite lay to form a strand.
The required number of strands are then laid together
symmetrically around the core to form the wire rope.
WIRE.The basic component of the wire rope is
the wire. The wire may be made of steel, iron, or other
metal in various sizes. The number of wires to a strand
varies, depending on the purpose for which the wire
rope is intended. The number of strands per rope and
the number of wire per strand designate wire rope.
Thus a 1/2-inch 6 x 19 rope has six strands with
nineteen wires per strand. It has the same outside
diameter as a 1/2-inch 6 x 37 rope that has six strands
with thirty-seven wires (of a smaller size) per strand.
STRAND.The design arrangement of a strand is
called the construction. The wires in the strand may be
all the same size or a mixture of sizes. The most
common strand constructions are Ordinary, Seale,
Warrington, and Filler (fig. 6-34) as follows:
ORDINARY construction wires are all the same
Figure 6-34.Common strand construction.