Wire Ropes Under Bending and Tensile Stresses - Wire Ropes: Tension, Endurance, Reliability - page 318

Spiral round strand rope 34 9 7 + WSC, bright, lubricated, W = 0.904 kg/m
Nominal rope diameter d = 15 mm
Sheave diameter D = 20d, cast iron
Roller bearings with sliding seals

Constants:
For the rope force loss that is greater in not more than 10 % of the cases, using
the data from Table 3.20 , the constants c tot are
c 0tot = 04.14 + 1.5 1.73 + 5/15 = 7.07 and
c 1tot = 0.294 + 1.5 0.031 + 0.075 = 0.416
Rope efficiency for one sheave:
With these constants, according to ( 3.106 ) the wire rope efficiency is lower in
not more than 10 % of the cases for the specific tensile force S/d 2 = Q/(z
d 2 ) = 164 Nmm -2 for the rope running over one sheave

20 1 : 33 ¼ 0 : 9914 :

7 : 07
164 þ 0 : 416

g 90 ¼ 1

Efficiency of the rope drive:
According to ( 3.111 ), the efficiency for the rope drive—once again it is lower in
not more than 10 % of the cases—is

8 1 0 : 9914 8

1 g tot90 ¼ 0 : 9914 2

1 0 : 9914 ¼ 0 : 9538 :

The rope efficiency for one sheave and for a rope drive can be calculated with the
help of the Excel-program ''WIRKUNG2.XLS''.

3.5.3 Lowering an Empty Hook Block

For lowering an empty hook block, the weight force of the empty hook block
should be greater than the weight force of the hanging wire rope (between the
drum and the first sheave) and the resistance forces from the wire rope efficiency.

Fig. 3.87 Rope drive of a
crane, Z = 6 and n = 2

S A

S Z S 5 S 4 S 3 S 2 S 1

Q