Wire Ropes Under Bending and Tensile Stresses - Wire Ropes: Tension, Endurance, Reliability - page 241

3.2.3.7 Multi-layer Rope Spooling

A good overview of the problems occurring during multi-layer rope spooling onto
a drum is given by Verreet ( 2003 ) and his paper also includes many useful rec-
ommendations. Correct spooling can only be achieved with a well designed rope
drive with a grooved drum and a suitable wire rope.
Endurance tests with multi-layer rope spooling have been described by Briem
( 2002 ) and Weiskopf et al. ( 2005 ). The number of bending cycles for a wire rope
under multi-layer spooling N spool is always much smaller than the number of
bending cycles N for a wire rope running over a sheave or drum grooves.
Assuming the spooling has been done correctly, the ratio of both of these numbers
of bending cycles is the multi-spooling factor

f spool ¼ N spool
N

:

In the case of two-layer spooling, for the multi-spooling factor up to the first
outer strand breakage Briem ( 2002 ) found f spool and also for the rope discard factor
f spool,A (for different ratios of the tensile forces S and the minimum rope breaking
force F min )
S/F min 0.33 0.14 0.091 0.067

f spool 0.23 0.13 0.10 0.08

f spool,A 0.25 0.12 0.08 0.06

Weiskopf, Wehking and Vogel (2005) found global multi-spooling factors
between 0.02 and 0.09; mean 0.027. Their endurance tests were done by alter-
nating the spooling of the wire rope from the second layer to the third layer and
back again during each cycle. The results are shown in Fig. 3.52 .
From the test results from Briem ( 2002 ) and Weiskopf ( 2007 ) an endurance
factor f N3 can be derived in rough approximation

f N3 ¼ 0 : 005 þ 0 : 00085 S

d 2 :

This equation stands for compacted spiral round strand ropes, lang lay in good
quality bended on drums that are qualified for multil-layer rope spooling.

3.2.3.8 Rope Deflection

With Fig. 3.53 , Müller ( 1961 , 1966 ) published a first diagram describing the
influence of the deflection angle on the breaking number of bending cycles leading
up to the point where the rope breaks. For small deflection angles, the number of
bending cycles is very high because in this region the radius of the rope curvature