Wire Ropes Under Bending and Tensile Stresses - Wire Ropes: Tension, Endurance, Reliability - page 297

• For pull drives B A30 C 2
• For lifting appliances B A30 C 8
• For lifting appliances with loads probably moving over persons B A30 C 15.
For lifting appliances containing dangerous loads or even persons, additional
safety methods and installations are required, see Table 3.7 .

3.4.5.3 Optimal Rope Diameter

The optimal wire rope diameter is the diameter at which the wire rope reaches an
optimum for the number of bending cycles with a given tensile force S and a given
sheave diameter D. If the wire rope diameter is smaller or bigger, the wire rope
endurance is reduced.
According to Sect. 3.2.7 , the optimal rope diameter is
For simple bendings

q

D S

p

d opt ; sim ¼ c 0 ; sim ð 3 : 73a Þ

For combined fluctuating tension and bendings

q

D

p

d opt ; com ¼ c 0 ; sim S equ ð 3 : 73b Þ

and for reverse bendings

q

D S

p

d opt ; rev ¼ c 0 ; rev : ð 3 : 73c Þ

In ( 3.73 ), S is set in N and d and D in mm. The constants c 0 —listed in
Table 3.19 —are calculated according to Sect. 3.2.7 for the discarding number
The constants for eight strand ropes are also valid for six strand ropes of
bending cycles. For the breaking number of bending cycles, the constants are a
little greater.
For rope drives with different numbers of loading elements w i , during one
working cycle a common optimal rope diameter can be calculated

d opt ¼ w sim

d opt ; sim þ w com d opt ; com þ w rev d opt ; rev

P w : ð 3 : 95 Þ

To be cost-effective, the wire rope diameter should not be bigger than the optimal
rope diameter. Using a rope diameter bigger than the optimal one has the disad-
vantage of getting lower rope endurance for higher costs. The maximum of the
number of bending cycles is rather flat which means that with only a minor deviation