Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 114

for specific tensile forces above S/d 2 [ 70 N/mm 2 , as can be seen in Fig. 2.26 . For
that the constants are

c 1 ¼ 0 : 058
c 2 ¼ 0 : 269
c 3 ¼ 0 : 00853 :

2.4.2.5 Conditions for Calculations with Rope Twist

The results of the calculations are valid on the condition that

• the wire rope is at both ends fixed in a termination so that the relative motion of
wires and the strands are prevented strictly
• the twist angle x \ 360/100d for ropes with fibre core FC
\ 180/100d for ropes with steel core IWRC

according to the measurement limits in Feyrer and Schiffner ( 1986 / 1987 )

• and in case that the angle between the chord of the rope bow and the horizontal
b F \ 90, the result of the calculation is nearly valid on the condition that the
sag of the rope bow is small.

2.4.3 Rotary Angle of a Load Hanging on Two or More Wire
Rope Traces

A load hanging on wire ropes will be rotated by the rope torque. The rotary angle
u of the load will be derived for two or more traces from the same wire rope.
Following Unterberg ( 1972 ), who has made the first derivation, the bottom sheave
of a crane will be taken as example, Fig. 2.28 . Out of the energy W for lifting the
bottom sheave and the load when the bottom sheave turns, he found for the reverse
moment

M rev ¼ dW

r 1 r 2 sin u
h 0 2 r 1 r 2 ð 1 cos u Þ

p

du ¼

Q tot : ð 2 : 78 Þ

Q is the force from the mass of the load and the bottom sheave. The meaning of
the other symbols can be taken out of Fig. 2.28 .
With the presupposition that the height h 0 is much bigger than the distances r 1
and r 2 between the wire rope traces and the load rotary axis, the reverse moment is
(with the rope weight force G rope )