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Rope Data

Flexibility

Apart from Locked Coil & specialised constructions too complicated to detail here, our standard constructions in their approximate order of flexibility are :-
Construction For 26mm Diameter Rope
Strands Construction Outer Wire diameter % of solid bar
6x7 (6/1) 2.75 mm 47
6x8 (7/s) 2.75 mm 57
6x15 (7/7/1) 2.50 mm 49
6x17 (8/8/1) 2.26 mm 49
6x22 (9/12/s) 2.26 mm 56
6x23 (10/12/s) 2.11 mm 56
6x19 (9/9/1) 2.05 mm 49
6x21 (10/5+5F/1) 1.90 mm 50
6x19 (6&6/6/1) 1.84 mm 50
6x12 (12/Fibre) 1.66 mm 29.5
6x25 (12/12/s) 1.64 mm 56
6x19 (12/6+6F/1) 1.64 mm 50
6x19 (12/6/1) 1.64 mm 45.5
17x7 (6/1) 1.64 mm 52
8x19 (9/9/1) 1.63 mm 43.5
6x24 (15/9/Fibre) 1.54 mm 41
6x28 (15/12/s) 1.53 mm 56
6x36 (14/7&7/7/1) 1.44 mm 50
6x37 (15/15/6/1) 1.40 mm 50
6x29 (17/11/s) 1.37 mm 56
8x19 (12/6+6F/1) 1.31 mm 44.5
6x41 (16/8&8/8/1) 1.28 mm 50
34x7 (6/1) 1.23 mm 53
6x37 (18/12/6/1) 1.18 mm 45.5
6x61 (24/18/12/6/1) 0.92 mm 45.5

Rope Calculations

The following section contains calculations, which use the symbols detailed below.
Symbols used in Formulae Units
WT = Total load Kgf
WS = Static load Kgf
WD = Dynamic load Kgf
WB = Bending load Kgf
WR = Suspended rope weight
(unit rope weight x rope length)
Kgf
WL = Rope end load Kg
g = Acceleration due to gravity m/s2 (9,81 m/s2)
a = System acceleration m/s2
x = Elastic stretch mm
d = Rope diameter mm
E = Apparent Modulus of Elasticity Kgflmm2
A = Nominal Cross sectional area of rope mm2
L = Rope length m

Stretch

Two types of stretch occur. Constructional (or permanent stretch) and Elastic Stretch (or load stretch)
Constructional Stretch
This occurs due to the wires within the rope bedding in. The rate and degree of constructional stretch varies accordingly to the type of rope, how heavily and how often it is loaded and how much it is bent.
Any rope will tend to stretch more when it is new. The rate of stretch will decrease throughout its useful life, although the rate of stretch might increase again as the rope starts to wear out at the end of its life.

Total constructional stretch is difficult to predict. The tables below offers a guide as to what should be expected.
Stranded Ropes
Fibre Core
Load Typical F of S % Stretch
Light 10 : 1 0.25
Medium 5 : 1 0.50
Heavy 3 : 1 0.75
Steel Core As above ½
Many bends As above x2
Single Strand Ropes
(Locked Coil, Spiral Strand, etc)
These generally stretch 0.25% in total.
Reducing Constructional Stretch - Prestressing and Prestretching
By cyclically loading any rope, the above constructional stretch can be reduced and in some cases almost eliminated. By removing the construction stretch and applying the working load to the rope, accurate measurements can be marked onto the rope to enable accurate fixing of terminations either before or after installation. Latch & Batchelor are able to offer this service. Please contact our Technical Department for more details.

Elastic Stretch

This is stretch induced by a change in rope end load. A reasonably accurate guide to elastic stretch can be calculated from:

x = WL x 103 EA

The rope will increase in length by x when the load W is applied and decrease in length by x when the load W is removed.

Apparent Modulus of Elasticity - E

Ropes are not truly elastic, but can be regarded as so when applied loads are within normally accepted ranges.

Values for E for various constructions of rope are listed below.
They are for guidance only.
Apparent Modulus of Elasticity
(Kgslmm2)
6 x 7 Fibre Core 6300
6 x 7 Steel Core 7000
6 x 19 Fibre Core 6000
6 x 19 Steel Core 6500
6 x 36 Fibre Core 5500
6 x 36 Steel Core 6000
Multistrand ropes 5500
1 x 7, 1 x 19, 1 x 36 10000
Locked Coil Hoist 10000
Half Locked Guide 12500
Spiral Strand 12500

Calculation of Rope Loads

Static Load
Usually used when considering factors of safety, tread pressures, etc.

Static Load = weight of suspended rope + weight of rope end load (conveyance, payload, attachments, etc)
WS = WR + WL

Factor of Safety = Minimum breaking load/Static load
FOS = (MBL ÷ WS)

Dynamic Load
This is the increased value of the static load due to acceleration. As the rope is elastic, the rope end load may oscillate, increasing the rate of acceleration. A factor of 1.5 is therefore applied to the Mean rate of acceleration to account for this :-

Dynamic load = Static load x 1.5 x rate of acceleration / gravitational constant

WD = (WS x 1.5 x a ) ÷ g

Bending Load
This is the additional load induced in the outer wires of the rope as they are bent over a sheave or drum. This load increases with outer wire diameter but decreases with larger drum or sheave diameters,

Bending Load = Outer Wire Dia x Cross Section of Rope Area x Apparent Modulus of Elasticity ÷ Drum or sheave dia

WB = (d x A x E) ÷ D

where E is obtained from values on Page, A is the nominal cross sectional area of the rope

A = x (rope diameter2) ÷ 4

Total Load
This is used as a guide to help choose suitable ropes or design suitable winding systems. Experience has shown that if the total load is over 25% of the actual breaking load of a rope, it is likely to suffer premature fatigue of the wires within the rope.

Therefore as a guide to achieve a satisfactory fatigue life :-

Total Load = (x 100 < 25) ÷ Breaking Load

This, of course, does not take into account the effects of wear, corrosion and other factors that can affect fatigue and rope life.

Total Load = Static Load + Dynamic Load + Bending Load

WT = WS + WD + WB

Recommended Minimum Drum and Pulley Diameters

Rope Drum
Locked Coil Winding Rope 1 120
Haulage Rope 1 60
Engineering Rope 6x19 1 24
Engineering Rope 6x24 & 17x7 1 22
Engineering Rope 6x37 & 34x7 1 19
Lift Ropes 6x12/6 x 6/1 1 40
Lift Ropes 8x9/9/1
Lift Ropes 6x9/9/1 1 47

General Engineering Data

Manufacturing Tolerances
Rope Diameter :
Engineering ropes: +4% / +5%
Lift ropes
- up to 10mm dia. Incl. +6% / -2% (+4% / -0% at 10% MBL)
- over 10mm dia. +5% / -2% (+3% / -0% at 10% MBL)
Small ropes:
- 2 & 3 mm dia. +7% / -1%
- 4 & 5 mm dia. +6% / -1%
- 6 & 7 mm dia +5% / -1%
Rope length:
- up to and Incl. 400m +5% / -0%
- over 400m +20% m for each 1000m or part thereof -0%
- Locked Coil Ropes Refer to British Coal Specifications
Conversion Factors
Length in x 25.4 = mm x 0.03937 = in
ft x 0.3048 = m x 3.28 = ft
mile x 1.60934 = Km x 0.62137 = mile
Area in2 x 645.16 = mm2 x 0.00155 = in2
ft2 x 0.0929 = m2 x 10.7639 = ft2
Volume in3 x 16.387 = cm3 x 0.06102 = in3
ft3 x 0.028317 = m3 x 35.3147 = ft3
ft3 x 28.3161 = litre x 0.035316 = ft3
Mass lb x 0.453592 = Kg x 2.20462 = lb
UK ton x 1.01605 = tonne x 0.984207 = UK ton
lb/ft x 1.488 = Kg/m x 0.672 = lb/ft
Force lbf x 0.453592 = Kgf x 2.20462 = lbf
Kgf x 9.80665 = N x 0.101972 = Kgf
UK tonf x 9.96402 = kN x 0.100361 = UK tonf
Stress Kgf/mm2 x 9.80665 = N/mm2 x 0.101972 = Kgf/mm2
lbf/in2 x 0.00689476 = N/mm2 x 145.04 = lbf/in2
tonf/in2 x 1.57488 = Kgf/mm2 x 0.634969 = tonf/in2
hbar x 0.1 = N/mm2 x 10.0 = hbar
MPa x 1.0 = N/mm2

Relevant Specifications

References have been made to various specification where breaking loads, weights etc apply.
Only relative items are quoted, for full details reference should be made to the appropriate standard.
British Standards
Number Date Title
236 1968 Stranded wire ropes for mine hoisting
302 1987 Stranded steel wire ropes
443 1982 Testing zinc coatings on steel wire
461 1970 Bordeaux connections
462 1983 Wire rope grips
463 1958 Sockets for wire ropes
464 1958 Thimbles for wire rope
525 1973 Fibre cores for wire ropes
643 1970 White metal ingots for capping steel wire ropes
970 1983 Part 4: Valve steel
2763 1982 Round carbon steel wire for wire ropes
4429 1987 Rigging screws and turn buckles for general engineering, lifting
purposes and pipe hanger applications
5281 1975 Ferrule - secured eye terminations for wire ropes
6210 1983 Safe use of wire rope slings for general lifting purposes
6570 1986 Selection, care and maintenance of steel wire ropes
7035 1989 Socketing of stranded wire rope
MA29 1982 Steel wire rope and strand for yachts
British Coal Standards
Number Date Title
175 1968 Wire ropes for mineral haulage and manriding
176 1968 Stranded wire ropes for winding
186 1970 Locked coil winding ropes
366 1968 Round strand wire ropes for mineral haulage
367 1968 Triangular strand wire ropes for mineral haulage
368 1968 Wire ropes for manriding haulage
386 1968 Wire ropes for use with coal-cutters and other coal face machinery
388 1970 Half-Locked coil guide rope
461 1965 Sockets, zinc cone and tail strand units
International Standards
Number Title
ISO 7595 Socketing procedures for wire ropes - Molten Metal
ISO 7596 Socketing procedures for wire ropes - Resin Socketing
Other Sources Of Reference
Federation of Wire Rope
Manufacturers of Great Britain
Tables of weights and breaking loads for steel wire ropes
British Coal Ropeman's Hand Book
British Coal Guidance for the resin capping of wire ropes
Latch & Batchelor Ltd Guide to Locked Coil rope repair
Guidance notes on the capping of steel wire ropes
For more information with reference to specification or products please feel free to contact us.





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