LATCH & BATCHELOR LTD

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

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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

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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

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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

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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.