FLEET ANGLE.The fleet angle is formed by
running wire rope between a sheave and a hoist drum
whose axles are parallel to each other (fig. 6-48). Too
large a fleet angle can cause the wire rope to climb the
flange of the sheave and can also cause the wire rope to
climb over itself on the hoist drum.
SIZES OF SHEAVES.The diameter of a
sheave should never be less than 20 times the diameter
of the wire rope. An exception is 6 x 37 wire for which
a smaller sheave can be used, because it is more
drums, sheaves, and blocks used with wire rope should
be placed to avoid reverse or S-shaped bends. Reverse
bends cause the individual wires or strands to shift too
much and increase wear and fatigue. For a reverse
bend, the drums and blocks affecting the reversal
should be of a larger diameter than ordinarily used and
should be spaced as far apart as possible.
SEIZING AND CUTTING.The makes of wire
rope are careful to lay each wire in the strand and each
strand in the rope under uniform tension. If the ends of
the rope are not secured properly, the original balance
of tension will be disturbed. Maximum service is not
obtainable because some strands can carry a greater
portion of the load than others can. Before cutting steel
wire rope, place seizing on each side of the point where
the rope is to be cut.
Figure 6-48.Fleet angle relationship.
Figure 6-49.Seizing wire rope.
A rule of thumb for determining the size, number,
and distance between seizing is as follows:
The number of seizing to be applied equals
approximately three times the diameter of the
Example: 3 x 3/4-inch-diameter rope = 2 1/4
inches. Round up to the next higher whole number and
use three seizing.
The width of each seizing should be 1 to 1 1/2
times as long as the diameter of the rope.
Example: 1 x 3/4-inch-diameter rope = 3/4 inch.
Use a 1-inch width of seizing.
The seizing should be spaced a distance equal to
twice the diameter of the wire rope.
Example: 2 x 3/4-inch-diameter rope = 1 1/2
inches. Space the seizing 2 inches apart.
A common method used to make a temporary wire
rope seizing is as follows (fig. 6-49):
Wind the seizing wire uniformly, using tension on
the wire. After making the required number of turns, as
shown in step 1, twist the ends of the wires
counterclockwise by hand, so the twisted portion of the
wires is near the middle of the seizing, as shown in step 2.