Wire Ropes, Elements and Definitions - Wire Ropes: Tension, Endurance, Reliability - page 51

Clearance between the round lay wires, approximation

Shitkow ( 1957 ) [in an other form Costello ( 1997 )] provided the following rela-
tively simple equation for the clearance in the cross-section perpendicular to the
strand axis with z W for the number of wires in the layer being considered

p
z W

d

s WQ ¼ 2 r sin r

cos 2 a þ tan 2

: ð 1 : 12 Þ

p
z W

p
z W

cos

Then the real clearance between the wires is

s W ¼ s WQ cos a : ð 1 : 12a Þ

Jenner ( 1992 ) found that these equations are sufficiently accurate for the lay
angles used in practice.

Calculation program:
The accurate clearance between the neighbouring round wires in a round strand
and the coordinates of the contour of the wire helix in the cross-section can be
calculated with the help of the Excel-program SPERRU2.XLS.

Example 1.2 Cross-section of a strand wire

Data:

Strand 1 + 6,
Wire diameter d = 1 mm; winding radius r = 1.055 mm; lay angle a = 20.

Results:

For an angle w = 30 the coordinates of a point of the cross-section contour are
according to ( 1.11 )
x = 0.2787 mm and y = 1.4804 mm.
The contact angle is ( 1.11a )

resp.u c ¼ 29 : 85 u c ¼ 0 : 5209 rad

with the parameter w c = 2.01383 rad
The contact radius is ( 1.11b )
r c = 0.9418 mm.
The clearance angle is ( 1.11c )
Du = 0.0054 rad Du = 0.31.

The clearance is (1 : 11d) clearance, approximation (1 : 12a) is

s W ¼ 0 : 0048 mm ; s W ¼ 0 : 0075 mm :