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1. Minimum winding diameter
The minimum winding diameter for the rope is determined by checking the relationship:
D ≥ H * d
D is the winding diameter on pulleys, drums or compensating pulleys measured to the axis of the rope. The unit is millimeter (mm).
H is a coefficient depending upon the mechanism group, see Table T.22.214.171.124.1.
d is the nominal diameter of the rope. The unit is millimeter (mm).
Note: Please see the previous article for wire rope selection.
Table T.126.96.36.199.1. Values of H
|Mechanism group||Drums||Pulleys||Compensating pulleys|
Note: By formula has been used to determine a minimum rope diameter from which in turn the minimum diameters for drums and pulleys have been determined, a rope of diameter greater than the minimum calculated diameter can be used with these latter diameters, provided that the diameter of the rope used does not exceed the minimum diameter by more than 25 % and that the pull in the rope does not exceed the value S used for calculating this minimum diameter.
2. Radius of the bottom of the groove
The useful life of the rope depends not only on the diameter of the pulleys and drums, but also on the pressure exerted between the rope and the groove supporting the rope.
The winding ratios above are given on the assumption of a radius of supporting groove r where :
r = 0.53 * d
d being the nominal diameter of the rope.
3. Rope fixing device
Rope attachments must be so designed as to withstand a tensile force 2.5 times the maximum tensile force S without showing permanent deformation.
The device attaching the rope to the drum must be of such a design that, taking account of the friction of the turns which remain around the drum, the sum of the frictional and fixing forces withstands a tensile force 2.5 times the maximum tensile force S.
The coefficient of friction between the rope and the drum used in the calculations shall be :
when the rope is completely unwound from the drum, at least two complete turns of rope must remain on the drum before the rope end attachment.