This is a special study on simple pulley and pulley block and their Practical Applications. I,from KUET , Khulna , Bangladesh

1. i
Study of different types of simple pulleys and pulley blocks and their
applications in actual practice.
By
Group – A1(01)
AntuDatta (1205001)
Zulfikar Habib Khan (1205003)
Md. Shariful Islam (1205004)
SudipSaha (1205005)
Asibul Islam Sohel (1205006)
The special works submitted in partial fulfillment of the requirements for the
2nd
Year, ME 2210, in
Department of Mechanical Engineering
Khulna University of Engineering & Technology
Khulna 920300, Bangladesh
February 2015

2. ii
Acknowledgements
All the praises to the almighty who makes authors capable to complete the special work
successfully. The authors are very much indebted to their course teachers Md.Helal-An-
Nahiyan,Assistant professor of department of Mechanical Engineering, Khulna University of
engineering & technology, Bangladesh, and DipayanMondal, Assistant professor of
department of Mechanical Engineering, Khulna University of engineering & technology,
Bangladesh, for their wise inspiration to do such extraordinary special work. The authors
express the heart- felt respect to them for their proper guidance and all kind of support to
perform and complete this special work.
The authors are extremely grateful to the department of mechanical engineering Khulna
University of engineering & technology, Bangladesh, to provide such a good opportunity to
do the experimental work and for providing all other supports. Long live department of
mechanical engineering Khulna University of engineering & technology, Bangladesh. May
ALLAH bless both of the course teachers.
Authors

3. iii
Abstract
It is very important to study about the simple machines i.e. Simple pulley and pulley block
and measure the mechanical advantage, efficiency of simple pulley and pulley block. It has a
great influence in practical life from ancient time to present era. The simple pulley and pulley
block are both basic simple machine which are frequently used our everyday life.
The purposes of this paper work is to verify the law of machine that is “effort will increase
with load linearly”, determine the Mechanical Advantage of a simple combination of fixed
and movable pulleys, and to investigate the mechanical characteristics of a set of pulley
blocks which has three sheaves in the upper block and two sheaves in the lower block. From
different test variation of effort with load is investigated and respective mechanical
advantages & efficiencies are measured. Finally, comparing the results obtained in the
present experiment with the standard values it can be said that the performance of the
constructed apparatus is satisfactory.

4. iv
Contents
Page
Acknowledgement i
Abstract ii
Contents iii
List of tables iv
List of figures v
Nomenclature vi
CHAPTER I Introduction 1
1.1 Simple machine 1
1.2 Pulley 1
1.3 Components of pulley 2
1.4 How pulley works 2
1.5 Pulley blocks 5
1.6 Application of pulleys 7
1.7 Application of pulley blocks 8
CHAPTER II Methodology 9
2.1 simple pulley 9
2.2 Pulley block 10
CHAPTER III Data 11
3.1 Experimental data 11
CHAPTER IV Result and Discussion 12
4.1 Result 12
4.2 Graph 12
4.3 Discussion 14
CHAPTER V Conclusion and Reference 15
5.1 Conclusion 15
5.2 Reference 16

5. v
List of Tables
Table No. Description page
3.1.1 Data for comparison of load and spring balance 11
3.1.2 Determination of mechanical advantage of simple pulleys 11
3.1.3 Determination of mechanical advantage of pulley blocks 11
4.1.1 Mechanical advantage of simple pulleys 12
4.1.2 Mechanical advantage and efficiency of pulley blocks. 12

6. vi
List of Figures
Table No: Description Page
1.1 Simple machines 1
1.2 Fixed and movable Pulley. 1
1.3 How pulleys work with one wheel. 3
1.4 How pulleys work with two wheels 4
1.5 How pulleys work with four wheels 4
1.6 How pulley Blocks Work 5
1.7 How pulley Blocks Work 6
2.1 Experimental setup for determination of M.A. & 9
Efficiency of simple pulley and pulley block
4.2.1 Variation of effort with load for Pulley Block 12
4.2.2 Variation of mechanical advantage with load
For Pulley Block 13
4.2.3 Variation of efficiency with load for Pulley Block 13

7. vii
Nomenclature
W: Load
P: Effort
M.A: Mechanical Advantage
V.R: Velocity Ratio
E: Efficiency
N: Newton

8. 1
Chapter I:
Introduction
1.1 Simple Machine:
A machine is an invention that makes work easier. A simple machine increases the
strength of a push or a pull (a force), or the distance of a movement, to complete a task
easily. With a nutcracker you increase the force from your hand to crack a hard nut. A
long fishing rod increases the distance moved by your arm to cast a line. Some simple
machine are: lifting devices-lever system, screw jack, pulley, pulley block. [1]
Weston differential chain block etc.
Fig.1.1: Simple machines.
1.2 Pulley: A pulley is a simple machine which is useful for lifting things. It reduces the
effort required to raise a load. It consists o f a wheel with a groove
through which a string or rope runs. The rope has a load on one end and
someone or something pulling at the other end.
1.2.1 A simple fixed pulley is one which enables you to pull down
while the load goes up (e .g. a pulley on top o f a flagpole for hoisting a
flag to a height). It requires the same force, but it is easier to pull down
(i.e. in the same direction as gravity) than to pull up.
1.2.2 A moveable pulley does not change the direction o f a force, but it
lets you use less force to lift a load. But you must pull the rope a longer
distance than the load moves.
There are more complicated pulley systems (mixture of fixed and
movable pulleys) which enable you to lift quite heavy loads with a
Fig.1.2: Fixed and movable Pulley

9. 2
small effort. These are used on building sites, in shipyards, on sailing ships to lift heavy sails.
The more pulleys you have, the easier it is to move heavy loads. [2]
1.3. COMPONENTS OF PULLEY:
Drum or shell, Diaphragm plates, Shaft, Locking elements, Hub, Lagging, Bearing
assemblies.
1.3.1. Drum or shell: The drum is the portion of the pulley in direct contact with the belt.
The shell is fabricated from either a rolled sheet of steel or from hollow steel tubing
Diaphragm.
1.3.2. Plates: The diaphragm or end disc of a pulley is circular discs which are fabricated
from thick steel plate and which are welded into the shell at each end, to strengthen the drum.
1.3.3. Shaft: The shaft is designed to accommodate all the applied forces from the belt and /
or the drive unit, with minimum deflection. The shaft is located and locked to the hubs of the
end discs by means of locking elements.
1.3.4. Locking Elements: These are high-precision manufactured items which are fitted over
the shaft and into the pulley hubs. The locking Elements attach the pulley firmly to the shaft
via the end plates.
1.3.5. Hubs: The hubs are fabricated and machined housings which are welded into the end
plates.
1.3.6. Lagging: It is sometimes necessary or desirable to improve the friction between the
conveyor belt and the pulley in order to improve the torque that can be transmitted through a
drive pulley.
 1.3.7. Bearing assemblies: Bearings support the rotating shaft and hence the pulley.
Which enable the mass of the pulley assembly plus the belt tension forces to be
transmitted for the supporting pulley structure. [3]
1.4 How pulleys work
1.4.1 One wheel
If you have a single wheel and a rope, a pulley helps you reverse the direction of your lifting
force. So, as in the picture below, you pull the rope down to lift the weight up. If you want to
lift something that weighs 100kg, you have to pull down with a force equivalent to 100kg. If
you want to raise the weight 1m into the air, you have to pull the loose end of the rope a total
distance of 1m at the other end. (Incidentally, although the kilogram is a unit of mass, not
force, it's okay to talk about a force equivalent to a given mass because masses generally

10. 3
convert to forces in the same way. Read more about thus in our article on weights and
balances.) [4]
Fig.1.3:How pulleys work with one wheel.
1.4.2 Two wheels
Now if you add more wheels, and loop the rope around them, you can reduce the effort you
need to lift the weight. Suppose you have two wheels and a rope looped around them, as in
the figure below. The 100kg weight is now effectively supported by two sections of the same
rope (the two strands on the left) instead of just one (ignoring the loose end of the rope you're
pulling with), and this means you can lift it by pulling with a force of just 50kg—half as
much! That's why we say a pulley with two wheels, and the rope wrapped around it this way,
gives a mechanical advantage (ME) of two.
Mechanical advantage is a measurement of how much a simple machine multiples a force.
The bigger the mechanical advantage, the less force you need, but the greater the distance
you have to use that force. The weight rises 1m, but now we have to pull the loose end of the
rope twice as far (2m). How come? To make the weight rise 1m, you have to make the two
sections of rope supporting it rise by 1m each. To do that, you have to pull the loose end of
the rope 2m. Notice that we can also figure out the mechanical advantage by dividing the
distance we have to pull the rope by the distance the weight moves.[5]

11. 4
Fig.1.4: How pulleys work with two wheels.
1.4.3 Four wheels
Okay, what if you use four wheels held together by a long rope that loops over them, as in the
picture below? You can see that the 100kg weight is now hanging from four sections of rope
(the ones on the left, ignoring the loose end of the rope you're pulling with). That means each
section of rope is supporting a quarter of the total 100kg weight, or 25kg, and to raise the
weight into the air, you have to pull with only a quarter of the force—also 25kg. To make the
weight rise 1m, you have to shorten each section of the rope by 1m, so you have to pull the
loose end of the rope by 4m. We say a pulley with four wheels and the rope wrapped around
like this gives a mechanical advantage of four, which is twice as good as a pulley with two

12. 5
ropes and wheels. [5]
Fig.1.5: How pulleys work with four wheels.
1.5. Pulley block: Pulley blocks are widely used to lift heavy loads when only "manpower"
is available and are sometimes used in conjunction with motorized lifting tackle. By using
"fixed" and "movable" pulleys it is possible to gain a Mechanical Advantage. To develop this
principle further, this experiment shows that by using multiple pulley blocks the Mechanical
Advantage can be increased.
To achieve this condition and thereby lift heavy loads using little effort, it is necessary to
have a ‘fixed’ pulley block containing 3 pulleys (or 3 ’sheaves’) at the top .The rope is tied to
the lower frame; passes alternately around the top and bottom pulleys and finally over the top
pulley and becomes the pulling ropes . Because of friction in the pulleys, stiffness in the
ropes, the weight of the lower pulley block, etc. the effort (p) required to lift the load (W) will
in fact be greater than W/5, and this will be shown in the experiment. [6]
How a Block and Tackle Works:
If you have ever looked at the end of a crane, or if you have ever used an engine hoist or a
come-along, or if you have ever looked at the rigging on a sailboat, then you have seen a
block and tackle at work. A block and tackle is an arrangement of rope and pulleys that
allows you to trade force for distance Understanding the Block and Tackle.
In this figure, if you are going to suspend the weight in the air then you have to apply an
upward force of 100 pounds to the rope. If the rope is 100 feet (30.5 meters) long and you
want to lift the weight up 100 feet, you have to pull in 100 feet of rope to do it. This is simple
and obvious.
Now imagine that you add a pulley to the mix. [7]
Does this change anything? Not really. The only thing that changes is the direction of the
force you have to apply to lift the weight. You still have to apply 100 pounds of force to keep
the weight suspended, and you still have to reel in 100 feet of rope in order to lift the weight
100 feet.
The following figure shows the arrangement after adding a second pulley:

13. 6
Fig.1.6: How pulley Blocks Work.
This arrangement actually does change things in an important way. You can see that the
weight is now suspended by two pulleys rather than one. That means the weight is split
equally between the two pulleys, so each one holds only half the weight, or 50 pounds (22.7
kilograms). That means that if you want to hold the weight suspended in the air, you only
have to apply 50 pounds of force (the ceiling exerts the other 50 pounds of force on the other
end of the rope). If you want to lift the weight 100 feet higher, then you have to reel in twice
as much rope 0- 200 feet of rope must be pulled in. This demonstrates a force-distance
tradeoff. The force has been cut in half but the distance the rope must be pulled has doubled.
The following diagram adds a third and fourth pulley to the arrangement:
Fig.1.7: How pulley Blocks Work.

14. 7
In this diagram, the pulley attached to the weight actually consists of two separate pulleys on
the same shaft, as shown on the right. This arrangement cuts the force in half and doubles the
distance again. To hold the weight in the air you must apply only 25 pounds of force, but to
lift the weight 100 feet higher in the air you must now reel in 400 feet of rope.
A block and tackle can contain as many pulleys as you like, although at some point the
amount of friction in the pulley shafts begins to become a significant source of resistance.
1.6. Application of pulleys:
There are huge applications of simple pulley. Some these are given bellow:
1.6.1. Elevators use multiple pulleys in order to function.
1.6.2. A cargo lift system that allows for items to be hoisted to higher floors is a pulley
system.
1.6.3. Wells use the pulley system to hoist the bucket out of the well.
1.6.4. Many types of exercise equipment use pulleys in order to function.
1.6.5. Construction pulleys are used in order to lift and place heavy materials.
1.6.6. Curtains at a theatre are moved using pulley systems that pull the curtains apart.
1.6.7. Blinds on windows operate using a pulley system to move the blinds up and down. You
pull the cord on the blinds and the pulley system causes the blinds to open or close.
1.6.8. Flagpoles use pulleys in order to hoist the flag up or to bring it down. You pull the
string on the pulley and the flag runs up or down the pole.
1.6.9. Clotheslines can use pulley systems in order to make it easier to pull clothes toward the
user.
1.6.10. Pulleys can be used to place birdfeeders high in trees or on poles, and then to pull
them down when they need to be refilled or removed.
1.6.11. Roofers may use pulleys in order to hoist all of the shingles up on to the roof instead
of attempting to carry them.

15. 8
1.6.12. A crane is a type of pulley that is used in construction.
1.6.13. Engines utilize a pulley system in order to work.
1.6.14. Fans with chains are utilizing a pulley system in order to be turned on and off.
1.6.15. A bulldozer is an example of use of a pulley system.
1.6.16. Pulleys are utilized regularly in oil derricks.
1.6.17. Pulleys can be used to extend ladders.
1.6.18. Sails on sailboats are raised and lowered using pulleys.
1.6.19. Garage doors raise and lower utilizing a pulley system.
1.6.20. Rock climbers use pulleys to help them to climb.
1.6.21 Timing belts in cars are examples of pulleys.
1.6.22. Escalators utilize pulley systems to function.
In all of these examples, a cable system works in order to make lifting easier or to make
moving items easier. Pulleys are essential to being able to move and lift very heavy or large
items. The simple principle behind pulleys makes these one of the most effective tools in
existence. [8]
1.7.Application of pulley Block:
1.7.1. Marine use, such as boat lift personal watercraft, Boat cradle, boat rigging, boat docks,
commercial fishing
1.7.2. Gates and Overhead Door use, in such uses as a hangar, barn or workshop.
1.7.3. Sporting and athletic equipment, including basketball goals, batting cages, volleyball
stands and various netting retrieval, such as for volleyball, soccer or tennis)
1.7.4. Commercial use, such as lighting, communication towers, flag pole manufacturing,
drapery cleaning and geological uses.
1.7.5. Suspension use for various wire(s), such as for airlines and cording for machinery that
has a traveling bed or component.
1.7.6. Portable towers and signage that must be lifted to an upright position.
1.7.7. Field use, such as in farming, logging, oil fields, and ranching.

16. 9
1.7.8. Manufacturing use, such as awnings and shades, conveyors, cranes and hoists, machine
welding shops, tool and die, wire rope or sling, foundries, scaffolding, material handling and
lifting.
1.7.9. Entertainment use, such as for movie sets, stage production, stage and theater rigging.
1.7.10. Transportation use, including aircraft and airport applications, automotive lifts, hanger
doors, locomotive washing tunnels or vehicle hard top lifts.
1.7.11. Zoos; Animal use, such as animal transportation, zoo cages and zoo cage doors. [8]
Chapter II:
Methodology
2.1: Simple pulley:
Secure the mounting panel in the vertical position. Place one adjustable hook (P6) in hole
(9K) & the other in hole (7J) & secure with nuts. Slide the hook up to give the shortest
length. Place one pulley (P12) in hole (B1) & the other in whole (10D) & secure with nuts
(P1). Hang the spring balance (P8) on the right hand adjustable hook. Place both looped
ends of the cordon the spring balance ring and use the cord ‘double’. Zero the spring
balance.

17. 10
Fig 2.1: Experimental setup for determination of M.A. & Efficiency of simple pulley and
pulley block.
2.1.1: TEST 1
Arrange the apparatus as shown in the diagram. Add 1.9N to the weight hook (P10) to give a
total weight of 2N (i.e. including the .1N weight hook) on the cord & record the weight
shown on the spring balance. Add weights to give loads of 3,4& 5N.
2.1.2: TEST 2
Arrange the apparatus as shown in the fig. 1. This time use a single cord & repeat as for
TEST (1).
2.1.3: TEST 3
Weight the pulley block (P15) & record its weight. Arrange the apparatus as shown in fig. 2
with the pulley block (P15) ‘Threaded’ on to the cord. Repeat with loads as for TEST 1 ,
recording the weight shown on the spring balance due to the loads of 2,3,4 & 5N applied to
the pulley block.
2.1.4: TEST 4:
Arrange the apparatus as shown in Fig. 3. By applying loads as in TEST (3), find the effort
(P) in each cast to just raise the load (W). (The total load (W) will be the applied weight
including the weight hook, plus the weight of the pulley block). Compare the reading of the
spring balance with the effort (P).

18. 11
2.2: Pulley block:
Secure the mounting panel in the vertical position. Insert the support screw (P5) through
whole (K9) and secure with nut (P1). Take the set of pulley blocks (EX10) and place the hole
in the three sheaves (P1). Do not tighten this nut as the pulley blocks should hang freely.
Place the adjustable pulley (P13) in hole (F11) and adjust so that it is in line with the free end
of the cord. Secure the adjustable pulley with nut (P1). Make sure that the cord is correctly in
the groove on all five pulleys and then hang one weight hook (P10) from the hole in the lower
pulley block and the other on the free end of the cord which should pass around the right
hand side of the adjustable pulley.
2.2.1: TEST 1
Place a weight of 1.9N (making a total of 2N including the 0.1N weight hook) on the lower
pulley block. Add weights to the other weight hook so that the weight is sufficient to just
raise the load (W). RECORD the effort (P) to raise the load (W).
REPEAT for total loads (W) of 4, 6, 8 and 10N, finding the effort (P) in each case.
Chapter III
Experimental Data
3.1: Experimental data:
Table: 3.1.1: Data for comparison of load and spring balance.
Obs Test -1 Test-2
W (N) Spring
Balance(N)
W (N) Spring Balance(N)

19. 12
1 2.1 2.1 0.6 0.45
2 3.1 2.5 1.6 1.00
3 5.1 4.1 2.6 1.35
Table: 3.1.2: Determination of mechanical advantage of simple pulleys.
Obs W(N) P(N) Spring
balance(N)
Deviation M.A
1 1.4 0.6 0.6 0.2 2.33
2 2.4 1.2 1.1 0.1 2.0
3 3.4 1.8 1.6 0 1.89
Table: 3.1.3: Determination of mechanical advantage of pulley blocks.
obs W(N) P(N) M.A V.R E=
.
.
∗
100%
1 1.6 0.6 2.67
5.22
51.49%
2 2.1 0.70 3.0 57.47%
3 2.6 0.88 2.95 56.5%
4 3.6 1.19 3.03 58.00%
5 4.1 1.4 2.93 56.13%
Chapter IV
Result and Discussion
4.1: Result
Table: 4.1.1: Mechanical advantage of simple pulleys.
W(N) 1.4 2.4 3.4
M.A 2.33 2.00 1.89

20. 13
Table: 4.1.2: Mechanical advantage and efficiency of pulley blocks.
W(N) 1.6 2.1 2.6 3.6 4.1
M.A 2.67 3.00 2.95 3.03 2.93
E(%) 51.49 57.47 56.50 58.00 56.13
4.2: Graphs:
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.5 1 1.5 2 2.5 3
P(N)
W (N)
Fig 4.2.1: variation of effort with load for Pulley Block

21. 14
2.65
2.7
2.75
2.8
2.85
2.9
2.95
3
3.05
0 1 2 3 4 5
M.A
W (N)
Fig 4.2.2: variation of mechanicaladvantagewith load for…
51
52
53
54
55
56
57
58
59
0 1 2 3 4 5
E(%)
W (N)
Fig 4.2.3: variation of efficiency with load for Pulley Block

22. 15
4.3: Discussion:
Experimental investigation and performance determination was done in this special work. For
different load mechanical advantage and efficiency for simple pulley and pulley blocks
determined. Then variation of effort, mechanical advantage, and efficiency with load were
shown graphically.
From effort vs. load graph (fig: ) it is clear that with increase of load effort also increase
linearly. Thus law of machine verified.
From mechanical advantage vs. load graph (fig:) it is seen that mechanical advantage varies
with load according to second degree curve. There is some deviation with ideal mechanical
advantage vs. load graph.
From efficiency vs. load graph (fig:) it is seen that efficiency varies with load according to
second degree curve. There is some deviation with ideal efficiency vs. load graph.

23. 16
Chapter V
Conclusion
Conclusion:
Simple pulley and pulley block both deserve great importance in mechanical engineering.
Pulley is one of six simple machines used to lift weights. Pulleys are assembled to form
a block and tackle in order to provide mechanical advantage to apply large forces. Pulleys are
also assembled as part of belt and chain drives in order to transmit power from one rotating
shaft to another. . They are always in touch in our practical life.

24. 17
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