F T ra n sf o F T ra n sf o

PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c

Rope drive design

The rope drives are widely used where a large amount of power is to be transmitted, from one
pulley to another, over a considerable distance.
The ropes drives use the following two types of ropes :
1. Fibre ropes, and 2. *Wire ropes.
Fibre ropes
The ropes for transmitting power are usually made from fibrous materials such as hemp,
manila and cotton. When the hemp and manila ropes are bent over the sheave, there is some
sliding of the fibres, causing the rope to wear and chafe internally. In order to minimise this
defect, the rope fibres are lubricated with a tar, tallow or graphite. The hemp ropes are
suitable only for hand operated hoisting machinery and as tie ropes for lifting tackle, hooks
etc. The fibre ropes operate successfully when the pulleys are about 60 metres apart.
Advantages of Fibre Rope Drives
1. They give smooth, steady and quiet service.
2. They are little affected by outdoor conditions.
3. The shafts may be out of strict alignment.
4. The power may be taken off in any direction.
5. They give high mechanical efficiency.
Wire Ropes
When a large amount of power is to be transmitted over long distances from one pulley to
another (i.e. when the pulleys are upto 150 metres apart), then wire ropes are used. The wire
ropes are widely used in elevators, mine hoists, cranes, conveyors, hauling devices and
suspension bridges. The wire ropes run on grooved pulleys but they rest on the bottom of the
*grooves and are not wedged between the sides of the grooves. Indian companies producing
wire rope: Indian wire rope Corporation, Bharat Wire Ropes Ltd., usha martin etc. The world
largest rope is 5½ inch in diameter, 337 tonnes and is 4,000 metres long

Materials
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c

The wire ropes are made from cold drawn wires in order to have increase in strength and
durability. It may be noted that the strength of the wire rope increases as its size decreases. The
various materials used for wire ropes in order of increasing strength are wrought iron, cast steel,
extra strong cast steel, plough steel and alloy steel. For certain purposes, the wire ropes may also
be made of copper, bronze, aluminium alloys and stainless steel
Advantages of wire ropes
The wire ropes have the following advantages as compared to fibre ropes.
1. These are lighter in weight,
2. These offer silent operation,
3. These can withstand shock loads,
4. These are more reliable,
5. These are more durable,
6. They do not fail suddenly,
7. The efficiency is high, and
8. The cost is low.
Construction of Wire Ropes
The wires are first given special heat treatment and then cold drawn in order to have high
strength and durability of the rope. The steel wire ropes are manufactured by special machines.
First of all, a number of wires such as 7, 19 or 37 are twisted into a strand and then a number of
strands, usually 6 or 8 are twisted about a core or centre to form the rope
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c

Classification of Wire Ropes

According to the direction of twist of the individual wires and that of strands, relative to each
other, the wire ropes may be classified as follows :
1. Cross or regular lay ropes. In these types of ropes, the direction of twist of wires in the strands
is opposite to the direction of twist of the stands, as shown in Fig. 20.8 (a). Such type of ropes
are most popular.
2. Parallel or lang lay ropes. In these type of ropes, the direction of twist of the wires in the
strands is same as that of strands in the rope, as shown in Fig. 20.8 (b). These ropes have better
bearing surface but is harder to splice and twists more easily when loaded. These ropes are more
flexible and resists wear more effectively. Since such ropes have the tendency to spin, therefore
these are used in lifts and hoists with guide ways and also as haulage ropes.
3. Composite or reverse laid ropes. In these types of ropes, the wires in the two adjacent strands
are twisted in the opposite direction, as shown in Fig. 20.8 (c). Note: The direction of the lay of
the ropes may be right handed or left handed, depending upon whether the strands form right
hand or left hand helixes, but the right hand lay ropes are most commonly used.

Designation of Wire Ropes

The wire ropes are designated by the number of strands and the number of wires in each strand.
For example, a wire rope having six strands and seven wires in each strand is designated by 6 × 7
rope.
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c

D-19: Select a wire rope for a vertical mine hoist to lift a load of 60 kN from a depth 300
metres. A rope speed of 500 metres / min is to be attained in 10 seconds.
Solution. Given : F = 60 kN = 60 000 N ; Depth = 300 m ; v = 500 m/min ; t = 10 s
1. Rope type selection:
From Table 13.2, rope of type 6 × 19 is selected.
2. Design load
From Table 13.9, we find that the factor of safety for mine hoists from 300 to 600 m depth is 7.
Since the design load is calculated by taking a factor of safety 2 to 2.5 times the factor of safety
given in Table 13.9, therefore let us take the factor of safety as 15.
Design load for the wire rope = 15 × 60 = 900 kN
3. Rope dimensions:
From Table 13.2, we find that the breaking strength of 6 × 19 rope made of wire with tensile
strength of 1863 MPa is 972 kN for 41 mm rope diameter .
From Table 13.1, we find that for a 6 × 19 rope,
Diameter of wire, dw = 0.063 d = 0.063 × 41 = 2.6 mm and
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c

Area of rope, A = 0.38 d 2 = 0.38 (41)2 = 638.78 mm2

Rope weight
From Table 13.1, we find that weight of the rope,
w = 0.0363 d2 = 0.0363 (41)2 = 61.02 N/m
Fr = 61.02 × 300 = 18306 N ...(Q Depth = 300 m)
Let us take D = 100 d = 100 × 41 = 4100 mm
4. Checking actual factor of safety
(a) during starting
FOS= Fu/ 2(F + Fr )+Fb
Bending stress, b = Er*dw/D = 52.6 MPa (equation 13.2, Taking Er = 83000 N/mm2) and the
equivalent bending load on the rope, Fb = b × A = 52.6 × 638.78 = 33600 N
Impact load during starting (when there is no slackness in the rope),
Fs = 2 (F + Fr) = 2(60000+18306) = 156612 N
Effective load on the rope during starting = F s + Fb = 190212 N
Actual factor of safety during starting = 972000/190212 = 5.11
(b) FOS during acceleration
We know that the acceleration of the rope and load, a = v / 60 t = 500 / 60 × 10 = 0.83 m/s 2
Additional load due to acceleration,
Fa = (F + Fr)*a/g = (60000+18306)*0.83/9.81 = 6026 N
Effective load on the rope during acceleration of the load (i.e. during first 10 seconds after
starting)
= F + Fr +Fb +Fa= 117932 N
Actual factor of safety during acceleration of the load =972000/117932 = 8.24
(c) During normal working:
We know that the effective load on the rope during normal working (i.e. during uniform lifting or
lowering of the load) = F + Fr +Fb =60000+18306+ 33600 = 111906 N
Actual factor of safety during normal working = 972000/111906 =8.6
Since the actual factor of safety calculated during starting is unsafe, therefore use double rope
system.
New actual FOS
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c

(a) During starting

Bending stress, b = Er*dw/D = 52.6 MPa (equation 13.2, Taking Er = 83000 N/mm2) and the
equivalent bending load on the rope, Fb = b × A = 52.6 × 638.78 = 33600 N
Impact load during starting (when there is no slackness in the rope),
Fs = 2 (F/2 + Fr) = 2(30000+18306) = 96612.2 N
Effective load on the rope during starting = Fs + Fb = 130235N
Actual factor of safety during starting = 972000/130235 = 7.46
(b) FOS during acceleration
We know that the acceleration of the rope and load, a = v / 60 t = 500 / 60 × 10 = 0.83 m/s 2
Additional load due to acceleration,
Fa = (F/2 + Fr)*a/g = (30000+2*18306)*0.83/9.81 = 4103.5 N
Effective load on the rope during acceleration of the load (i.e. during first 10 seconds after
starting)
= F/2 + Fr +Fb +Fa= 86032.3 N
Actual factor of safety during acceleration of the load =972000/86032.3 = 11.2
(c) During normal working:
We know that the effective load on the rope during normal working (i.e. during uniform lifting or
lowering of the load) = F/2 + Fr +Fb =30000+18306+ 33600 = 81928.8 N
Actual factor of safety during normal working = 972000/81928 =11.86
Since the actual factor of safety as calculated above are safe, therefore double rope of diameter
41 mm and 6 × 19 type is selected. Ans.
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c

or

Solution. Given : F = 25 kN ; Fr = 15kN, a=1 m/s2, D= 30d, FOS =6, u= 1800 MPa
1. From Table 13.2, rope of type 6 × 19 is selected.
2. The given factor of safety is 6. Since the design load is calculated by taking a factor of safety
2 to 2.5 times the factor of safety given, therefore let us take the factor of safety as 12.
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c

Design load for the wire rope = 40 × 12 = 480 kN

3. From Table 13.2, we find that the breaking strength of 6 × 19 rope made of wire with tensile
strength of 1863 MPa is 572 kN for 32 mm rope diameter .
4. From Table 13.1, we find that for a 6 × 19 rope,
Diameter of wire, dw = 0.063 d = 2.1 mm and
Area of rope, A = 0.38 d 2 = 389.2 mm2
5. Now let us find out the various loads in the rope as discussed below :
(a) Rope weight
Fr = 15 kN
(b) Bending load on rope
The minimum diameter of the sheave (D) may be taken as 30 times the diameter of rope ( d ).
D = 30 d = 960 mm
Bending stress, b = Er*d w/D = 175 MPa and the equivalent bending load on the rope,
Fb = b × A = 68110 N
(c) Load due to acceleration
The acceleration of the rope and load, a = 1 m/s2 Additional load due to acceleration,
Fa = (F + Fr)*a/g = (40000)*1/9.81 = 4077.5 N
6. Checking actual factor of safety
Effective load on the rope during acceleration of the load
F + Fr +Fb +Fa= 112187.5 N
Fu =A*1800 =700560 N
Actual factor of safety during acceleration of the load =700560/112187.5 = 6.24
Since the actual factor of safety as calculated above are safe, therefore a wire rope of diameter 32
mm and 6 × 19 type is satisfactory. Ans.
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c

FW -Filler Wire Strand Construction

SF-Seale Filler Construction
S -Seale Strand Construction
WSC -Wire Strand Core
W-Warrington
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c

fully locked wire rope: - A strand used as a rope and composed of one or two layers of Z-shaped
wires laid over layers of half lock coil and/or layers of round wires
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c
 F T ra n sf o F T ra n sf o
PD rm PD rm
Y Y
Y

Y
er

er
ABB

ABB
y

y
bu

bu
2.0

2.0
to

to
re

re
he

he
k

k
lic

lic
C

C
w om w om
w

w
w. w.
A B B Y Y.c A B B Y Y.c