Motorized Sccissor Lift

MAJOR PROJECT
ON
“MOTORIZED SCISSOR LIFT”
SUBMITTED IN THE PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF THE
DEGREE OF
BACHELOR OF TECHNOLOGY
(Mechanical Engineering)
19 May 2018
SUBMITTED BY:
MOHIT SINGH (14303)
ARVIND RATHORE (14309)
GOURAV MITTAL (14352)
SHAMBHU SHARAN KUMAR (14379)
Under the Guidance of
Dr. Sunand Kumar
PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
NATIONAL INSTITUTE OF TECHNOLOGY, HAMIRPUR (H.P.)

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CANDIDATE’S DECLARATION
We hereby certify that the work which is being presented in the B.Tech Major Project-1
Report entitled “Motorized Scissor Lift”, in partial fulfillment of the requirements for the
award of the Bachelor of Technology in Mechanical Engineering and submitted to the
Department of Mechanical Engineering of National Institute of Technology Hamirpur HP is an
authentic record of our own work under the supervision of Dr. Sunand Kumar Professor of
Mechanical Engineering Department.
The matter presented in this project report has not been submitted by us for the award of
any other degree of this or any other Institute/University.
Mohit Singh (14303) Gourav Mittal (14352)
Arvind Rathore(14309) Shambhu Sharan Kumar (14379)
This is to certify that the above statement made by the candidate is correct to the best of my
knowledge.
Date:
Dr. Sunand Kumar
(Project Guide)
Professor
MED

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ACKNOWLEDGEMENT
The writing of this dissertation has been assisted by the generous help of many people. We
feel that we were very fortunate to receive assistance from them. We wish to express our
sincere appreciation to them.
First and foremost, we are indebted to our project guide, Dr. Sunand Kumar, Professor,
Mechanical Engineering Department), NIT Hamirpur Himachal Pradesh who has been very
supportive at every stage of our project work. We wish to express our utmost gratitude to
him for his invaluable advice and patience in reading, correcting and commenting on the
drafts of the project report and, more importantly, for his generosity which We have received
throughout our entire project work.
Finally, we are particularly indebted to our dearest parents/guardians as without their
generous assistance and love; this project work could never have been completed.

iii
`
ABSTRACT
Scissor lifts (Aerial work platforms in general) are generally used for temporary, flexible
access purposes such as maintenance and construction work or by firefighters for emergency
access, which distinguishes them from permanent access equipment such as elevators. They
are designed to lift limited weights. The contraction of the scissor action can be hydraulic,
pneumatic or mechanical (via a lead screw or rack and pinion system).
The main objective of scissor lift is to save time required in building platforms or temporary
lifts. Once the lift is constructed according to requirement, much time is saved. Its portability
can enable the workers to use it at various working areas whenever needed.
Considering the cost of lift, it is suitable and more productive than making temporary platforms
at construction sites with help of bamboo sticks or other materials. Maintenance cost is almost
negligible as only lubrication is required for components.

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List of Tables
Table 3.1 Values of Fx, Fy, Rx1, Ry1 Corresponding to (ϴ)………………………………….41
Table 4.1 Lead Screw model>Static Structural >Loads……………………………………. 43
Table 4.2 Lead Screw model>Static Structural >Solution > Results………………………..45
Table 4.3 Table Screw MildSteel > Isentropic Elasticity……………………………………46
Table 4.4 Sprocket model>Static Structural >Loads………………………………………...46
Table 4.5 Sprocket model>Static Structural >Solution > Results…………………………...48
Table 4.6 Sprocket Mildsteel > Isentropic Elasticity………………………………………..49
Table 4.7 Links Loads……………………………………………………………………….49
Table 4.8 Links Results……………………………………………………………………...51
Table 4.9 Table Loads……………………………………………………………………….52
Table 4.10 Table model>Static Structural >Solution > Results……………………………..54
Table 4.11 Chain Link Loads………………………………………………………………..55
Table 4.12 Chain Link Results………………………………………………………………57
Table 6.1 Observation and Results…………………………………………………………..60
Table 7.1 Cost of Material…………………………………………………………………...62
Table 7.2 Miscellaneous cost………………………………………………………………...62

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List of Figures
Figure 2.1 Scissor Jack………………………………………………………………………..8
Figure 2.2 Bottle Jack…………………………………………………………………………9
Figure 2.3 Hydraulic jack……………………………………………………………………..9
Figure 2.4 Nomenclature of Square Thread…………………………………………………12
Figure 2.5 Nomenclature of Trapezoidal Threads…………………………………………..13
Figure 2.6 ACME Threads…………………………………………………………………..14
Figure 2.7 Multiple Threaded Screw………………………………………………………...15
Figure 2.8 Nomenclature of Power Screw…………………………………………………..16
Figure 3.1 Link Inclination………………………………………………………………….37
Figure 3.2 Lead Screw Loading applied at Bottom…………………………………………38
Figure 3.3 FBD of Link……………………………………………………………………..39
Figure 4.1 Lead Screw………………………………………………………………………42
Figure 4.2 Lead Screw Strain……………………………………………………………….43
Figure 4.3 Lead Screw Total Deformation………………………………………………….44
Figure 4.4 Lead Screw Equivalent Stress…………………………………………………...44
Figure 4.5 Sprocket Strain…………………………………………………………………..46
Figure 4.6 Sprocket Equivalent stress……………………………………………………….47
Figure 4.7 Sprocket Equivalent Strain……………………………………………………....47
Figure 4.8 Sprocket Total Deformation……………………………………………………..48
Figure 4.9 Links Strain………………………………………………………………………49

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Figure 4.10 Links Equivalent Strain…………………………………………………………50
Figure 4.11 Links Total Deformation……………………………………………………….50
Figure 4.12 Links Equivalent Stress………………………………………………………...50
Figure 4.13 Table Strain…………………………………………………………………….51
Figure 4.14 Table Equivalent Stress………………………………………………………...52
Figure 4.15 Table Total Deformation……………………………………………………….53
Figure 4.16 Table Equivalent Strain…………………………………………………………53
Figure 4.17 Chain Link Strain……………………………………………………………….55
Figure 4.18 Chain Link Total Strain…………………………………………………………56
Figure 4.19 Chain Link Total Deformation………………………………………………….56
Figure 4.20 Chain Link Equivalent Stress…………………………………………………...57
List of Graphs
Graph 2.1 Coefficient of Friction and Lead Angle…………………………………………..17
Graph 2.2 Efficiency Vs Helix Angle………………………………………………………..18
Graph 6.1 Input Power Vs Angle (ϴ)………………………………………………………..60
Graph 6.2 Torque Vs Angle (ϴ)…………………………………………………………………...61
Graph 6.3 Output Power Vs Angle (ϴ)…………………………………………………………...61

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CONTENT
S.NO. TOPICS PAGE NO.
Candidate’s Declaration i
Acknowledgement ii
Abstract iii
List of Table iv
List of Figure v
List of Graphs vi
1. Introduction 1
2. Literature Review 2-20
2.1 Various developments in Lifting Devices 4
2.1.1 Lever
2.1.2 Screw Thread
2.1.3 Gears
2.2 Necessity of Jack 5
2.3 Types of Load Lifting Devices 6
2.3.1 Artificial Lifting Devices
2.3.2 Portable Automotive Lifting Devices
2.4 Types of Jacks Used Today 7
2.4.1 Scissor Jack
2.4.2 Bottle Cylinder Jack
2.4.3 Hydraulic Jacks
2.5 Operational conditions of a screw jack 10
2.6 Power Screw 10
2.6.1 Application
2.6.2 Advantages
2.6.3 Disadvantages
2.7 Forms of Threads 12
2.7.1 Square Threads
2.7.1.1 Advantages of Screw Threads
2.7.1.2 Disadvantages of Screw Threads
2.7.2 Trapezoidal Threads 13
2.7.2.1 Advantages of Trapezoidal Threads
2.7.2.2 Disadvantages of Trapezoidal Threads
2.7.3 ACME Threads
2.8 Designation of Threads 14
2.8.1 Multiple Threaded Power Screw
2.9 Terminology of Power Screw 16
2.10 Self Locking Screw 17
2.11 Efficiency of Locking Screw 18
2.12 Necessity / Application of Scissor Lift 19

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3. Proposed Work 21-41
3.1 Proposed Prototype 21
3.2 Design of Components 21
3.3 Details of Components 23
3.4 Working Principle 24
3.5 Technical Parameters (Prototype) 25
3.6 Drafting and 3D Model 25
3.6.1 Isometric View
3.6.2 Front View
3.6.3 Side View
3.6.4 Assembly Drawing
3.6.4.1 Chain Link
3.6.4.2 Lead Screw
3.6.4.3 Scissor Link
3.6.4.4 Sleeve
3.6.4.5 Trunnion Bar
3.6.4.6 Upper Table
3.7 General Calculations 37
4. Ansys Analysis 42-57
4.1 Lead Screw 42
4.2 Sprocket 46
4.3 Links 49
4.4 Table 52
4.5 Chain Link 55
5. TimeLine 59
6. Observation and Calculation 60-62
7. Cost Involved 63
8. Risk Management 64
9. Advantages and Disadvantages 65
10. Feasibility Study 66
11. Future Scope 67
12. Conclusion 68
References 69

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CHAPTER:1 INTRODUCTION
Any vehicle-mounted device, telescoping or articulating, or both, which is used to position
personnel is called aerial device. Any aerial device used to elevate personnel to job sites above
ground including extensible boom platforms, aerial ladders, articulating boom platforms and
vertical towers is called aerial lift. A mobile supported scaffold which can be powered or
unpowered is portable and caster or wheel-mounted is called scissor lift. Aerial scissor lifts
pose a serious safety hazard if not used properly. Scissor lifts are the elevating platforms that
can be raised or lowered to various heights. The platform can be positioned horizontally
beyond the base. These lifts are increasingly being used in various industries because they are
mobile and provide workers access to elevations to perform required tasks.
A scissor lift is a type of platform which moves in vertical direction. The mechanism
incorporated to achieve this function is the use of linked, folding supports in a criss-cross 'x'
pattern, known as a pantograph. The upward motion is achieved by the application of pressure
to the outside of the lowest set of supports, elongating the crossing pattern, and propelling the
work platform vertically upwards. The platform may also have an extending 'bridge' to allow
closer access to the work area (because of the inherent limits of only vertical movement.
The operation of the scissor action can be obtained by hydraulic, pneumatic or mechanical
means (via a lead screw or rack and pinion system). Depending on the power system employed
on the lift, it may require no power to enter 'descent' mode, but rather a simple release of
hydraulic or pneumatic pressure. This is the main reason that these methods of powering the
lifts are preferred, as it allows a fail-safe option of returning the platform to the ground by
release of a manual valve.

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Chapter: 2 Literature Review
Screw type mechanical jacks were very common for jeeps and trucks of World War II vintage.
For example, the World War II jeeps (Willys MB and Ford GPW) issued the "Jack,
Automobile, Screw type, Capacity 1 1/2 ton", Ordinance part number 41-J-66. These jacks,
and similar jacks for trucks, were activated by using the lug wrench as a handle for the ratchet
action to the jack. The 41-J-66 jack was carried in the jeep's tool compartment. Screw type
jacks continued in use for small capacity requirements due to low cost of production to raise
or lower the load. A control tab is marked up/down and its position determines the direction of
movement and with no maintenance. The virtues of using a screw as a machine element, which
is essentially an inclined plane wound round a cylinder, was first demonstrated by Archimedes
in 200BC with his device used for pumping water.
There is evidence of the use of screws in the Ancient Roman world but it was the great
Leonardo da Vinci, in the late 1400s, who first demonstrated the use of a screw jack for lifting
loads. Leonardo’s design used a threaded worm gear, supported on bearings, rotated by the
turning of a worm shaft to drive a lifting screw to move the load.
People were not sure of the intended application of his invention, but it seems to have been
relegated to the history books, along with the helicopter and tank, for almost four centuries. It
is not until the late 1800s that people have evidence of the product being developed further.
With the industrial revolution of the late 18th and 19th centuries, came the first use of screws
in machine tools, via English inventors such as John Wilkinson and Henry Maudsley. The most
notable inventor in mechanical engineering from the early 1800s was undoubtedly the
mechanical genius Joseph Whitworth, who recognized the need for precision as important in
industry.
While he would eventually have over 50 British patents with titles ranging from knitting
machines to rifles, it was Whitworth’s work on screw cutting machines, accurate measuring
instruments and standards covering the angle and pitch of screw threads that would most
influence our industry today.
Whitworth’s tools have become internationally famous for their precision and quality and
dominated the market from the 1850s. Inspired young engineers began to put Whitworth’s
machine tools to new uses. During the early 1880s in Coati cook, a small town near Quebec, a

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24- year-old inventor named Frank Henry Sleeper designed a lifting jack. Like da Vinci’s jack,
it was a technological innovation because it was based on the principle of the ball bearing for
supporting a load and transferred rotary motion, through gearing and a screw, into linear
motion for moving the load. The device was efficient, reliable and easy to operate. It was used
in the construction of bridges, but mostly by the railroad industry, where it was able to lift
locomotives and railway cars.
Arthur Osmore Norton, spotted the potential for Sleeper’s design and in 1886 hired the young
man and purchased the patent and then Norton jack was born. Over the coming years the
famous Norton jacks were manufactured at plants in Boston, Coati cook and Moline, Illinois.
Meanwhile, in Alleghany County near Pittsburgh in 1883, an enterprising Mississippi river
boat captain named Josiah Barrett had an idea for a ratchet jack that would pull barges together
to form a tow. The idea was based on the familiar lever and fulcrum principle and he needed
someone to manufacture it. That person was Samuel Duff, proprietor of a machine shop.
Together, they created the Duff Manufacturing Company, which by 1890 had developed new
applications for the original Barrett Jack and extended the product line to seven models in
varying capacities.
Over the next 30 years the Duff Manufacturing Company became the largest manufacturer of
lifting jacks in the world, developing many new types of jack for various applications including
its own version of the ball bearing screw jack. It was only natural that in 1928, The Duff
Manufacturing Company Inc. merged with A.O. Norton to create the Duff-Norton
Manufacturing Company.
Both companies had offered manually operated screw jacks but the first new product
manufactured under the joint venture was the air motor-operated power jack that appeared in
1929. With the aid of the relatively new portable compressor technology, users now could
move and position loads without manual effort. The jack, used predominantly in the railway
industry, incorporated an air motor manufactured by The Chicago Pneumatic Tool Company.
There was a clear potential for using this technology for other applications and only 10 years
later, in 1940, the first worm gear screw jack, that is instantly recognizable today, was offered
by Duff-Norton, for adjusting the heights of truck loading platforms and mill tables. With the
ability to be used individually or linked mechanically and driven by either air or electric motors
or even manually, the first model had a lifting capacity of 10 tons with raises of 2′′ or 4′′.

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2.1 Various Developments in Lifting Devices
1. Levers
2. Screw threads
3. Gears
4. Wheels and axles
5. Hydraulics
2.1.1 Levers
Use of the lever gives the operator much greater lifting force than that available to a person
who tried to lift with only the strength of his or her own body. Types of levers are first, second
and third order.
2.1.2 Screw thread
A screw is a mechanism that converts rotational motion to linear motion, and a torque to a
linear force. The most common form consists of a cylindrical shaft with helical grooves or
ridges called threads around the outside. The screw passes through a hole in another object or
medium, with threads on the inside of the hole that mesh with the screw's threads. When the
screw is rotated relative to the stationary threads; the screw moves along its axis relative to the
medium surrounding it for example rotating a wood screw forces it into wood. In screw
mechanisms, either the screw can rotate through a threaded hole in a stationary object, or a
threaded collar such as a nut can rotate around a stationary screw. Geometrically, a screw can
be viewed as a narrow-inclined plane wrapped around a cylinder.
2.1.3 Gears
The jack will lift a load in contact with the load platform when the power screw is rotated
through its connecting gear with the pinion gear when connected to the motor, plugged to the
automobile 12V battery source to generate power for the prime mover (motor), which transmits

5
its rotating speed to the pinion gear meshing with the bigger gear connected to the power screw
to be rotated with required speed reduction and increased torque to drive the power screw. The
power screw rotates within the threaded hole of its connecting members in the clockwise
direction that will cause the connecting members to be drawn along the threaded portion
towards each other during a typical load-raising process. During the typical load raising
process, the jack will first be positioned beneath the load to be lifted such that at least a small
clearance space will exist between the load platform and the object to be raised. Next power
screw will be turned so that the load platform makes contact with the object and the clearance
space is eliminated. As contact is made, load from the object will be increasingly shifted to the
load platform and cause forces to be developed in and transmitted through lifting members and
connecting members. The force transmitted through the connecting members will be
transferred at the threaded bore to the lead Acme threads, there within. A switch button
connected to the motor is used to regulate the lifting and lowering process.
2.2 Necessity of Jack
In the repair and maintenance of automobiles (car), it is often necessary to raise an automobile
to change a tire or access the underside of the automobile. Accordingly, a variety of car jacks
have been developed for lifting an automobile from a ground surface. Available car jacks,
however, are typically manually operated and therefore require substantial laborious physical
effort on the part of the user. Such jacks present difficulties for the elderly and handicapped
and are especially disadvantageous under adverse weather conditions. Furthermore, available
jacks are typically large, heavy and also difficult to store, transport, carry or move into the
proper position under an automobile. In addition, to the difficulties in assembling and setting
up jacks, such jacks are generally not adapted to be readily disassembled and stored after
automobile repairs have been completed. Car jacks must be easy to use for women or whoever
had problem with the tire in the middle of nowhere.
In light of such inherent disadvantages, commercial automobile repair and service stations are
commonly equipped with large and hi-tech car lift, wherein such lifts are raised and lowered
via electrically-powered systems. However, due to their size and high costs of purchasing and
maintaining electrically-powered car lifts, such lifts are not available to the average car owner.

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Engineering is about making things simpler or improving and effective. Such electrical
powered portable jacks not only remove the arduous task of lifting an automobile via manually
operated
jacks, but further decrease the time needed to repair the automobile. Such a feature can be
especially advantageous when it is necessary to repair an automobile on the side of a roadway
or under other hazardous conditions. There also reports on car jacks which lead to a serious
number of accidents.
A specified jack purposed to hold up to 1000 kilograms, but tests undertaken by Consumer
Affairs has revealed that is fails to work after lifting 250 kilograms and may physically break
when it has a weight close to its 1000 kilograms capacity. Whilst no injuries have been reported
to date, Ms. Rankine has expressed concerned about the dangers associated with the use of a
vehicle jack that does not carry the weight it is promoted to hold. Tests have proven that the
jack has the property to buckle well under the weight it is promoted to withstand, and it doesn’t
meet the labelling or performance requirements of the Australian Standard for vehicle jacks.
2.3 Types of load lifting devices
1. Artificial Lifting Devices (ALD)
2. Portable Automotive Lifting Devices (PALD)
2.3.1 Artificial Lifting Devices
1. Hydraulic pumping system
2. Electric Submersible Pumps
3. Gas lifts
4. Hybrid gas lifts
2.3.2 Portable Automotive Lifting Devices
1. Hydraulic hand jacks
2. Transmission jacks
3. Engine Stands
4. Vehicle support stands

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5. Upright type mobile lifts
6. Service jacks
7. Wheel dollies
8. Swing type mobile lifts
9. Scissor type mobile lifts
10. Auxiliary stands
11. Automotive ramps
12. High rich supplementary stands
13. Fork lift jacks
14. High reach fixed stands
15. Vehicle transport lifts
16. Cranes
17. Lever
18. Hydraulic ram
19. Block and tackle
20. Wedge
21. Escalator
2.4 Types of Jacks Used Today
2.4.1 Scissor Jack
Scissor jacks are mechanical devices and have been in use since 1930s. A scissor jack is a
device constructed with a cross-hatch mechanism, much like a scissor, to lift up a vehicle for
repair. It typically works in a vertical manner. The jack opens and folds closed, applying
pressure to the bottom supports along the crossed pattern to move the lift. When closed, they
have a diamond shape. Scissor jacks are simple mechanisms used to handle large loads over
short distances. The power screw design of a common scissor jack reduces the amount of force
required by the user to drive the mechanism. Most scissor jacks are similar in design, consisting
of four main members driven by a power screw. A scissor jack is operated simply by turning
a small crank that is inserted into one end of the scissor jack. This crank is usually "Z" shaped.
The end fits into a ring hole mounted on the end of the screw, which is the object of force on
the scissor jack. When this crank is turned, the screw turns, and this raises the jack. The screw

8
acts like a gear mechanism. It has teeth (the screw thread), which turn and move the two arms,
producing work. Just by turning this screw thread, the scissor jack can lift a vehicle that is
several thousand pounds. A scissor jack has four main pieces of metal and two base ends. The
four metal pieces are all connected at the corners with a bolt that allows the corners to swivel.
A screw thread runs across this assembly and through the corners. When opened, the four-
metal arms contract together, coming together at the middle, raising the jack.
Fig 2.1 Scissor Jack
When closed, the arms spread back apart and the jack closes or flattens out again. A scissor
jack uses a simple gear drive to get its power. As the screw section is turned, two ends of the
jack move closer together. Because the gears of the screw are pushing up the arms, the amount
of force being applied is multiplied. It takes a very small amount of force to turn the crank
handle, yet that action causes the brace arms to slide across and together. As this happens the
arms extend upward. The car's gravitational weight is not enough to prevent the jack from
opening or to stop the screw from turning, since it is not applying force directly to it. If a person
applies pressure directly on the crank, or lean his weight against the crank, the person would
not be able to turn it, even though his weight is a small percentage of the cars.
2.4.2 Bottle (Cylinder) Jack
Bottle screws may be operated by either rotating the screw when the nut is fixed or by rotating
the nut and preventing rotation of the screw. Bottle jacks mainly consist of a screw, a nut, thrust

9
bearings, and a body. A stationary platform is attached to the top of the screw. This platform
acts as a support for the load and also assists it in lifting or lowering of the load. These jacks
are sturdier than the scissor jacks and can lift heavier loads. In a bottle jack the piston is vertical
and directly supports a bearing pad that contacts the object being lifted. With a single action
piston, the lift is somewhat less than twice the collapsed height of the jack, making it suitable
only for vehicles with a relatively high clearance.
Fig 2.2 Bottle Jack
2.4.3 Hydraulic Jacks
Fig 2.3 Hydraulic Jacks
Hydraulic jacks are typically used for shop work, rather than as an emergency jack to be carried
with the vehicle. Use of jacks not designed for a specific vehicle requires more than the usual
care in selecting ground conditions, the jacking point on the vehicle, and to ensure stability
when the jack is extended. Hydraulic jacks are often used to lift elevators in low and medium
rise buildings.

10
A hydraulic jack uses a fluid, which is incompressible. Oil is used since it is self-lubricating
and stable. When the plunger pulls back, it draws oil out of the reservoir through a suction 10
check valve into the pump chamber. When the plunger moves forward, it pushes the oil through
a discharge check valve into the cylinder. The suction valve ball is within the chamber and
opens with each draw of the plunger. The discharge valve ball is outside the chamber and opens
when the oil is pushed into the cylinder [9]. At this point the suction ball within the chamber
is forced to shut and oil pressure builds in the cylinder. For lifting structures such as houses
the hydraulic interconnection of multiple vertical jacks through valves enables the even
distribution of forces while enabling close control of the lift.
In a floor jack a horizontal piston pushes on the short end of a bell crank, with the long arm
providing the vertical motion to a lifting pad, kept horizontal with a horizontal linkage. Floor
jacks usually include castors and wheels, allowing compensation for the arc taken by the lifting
pad. This mechanism provides a low profile when collapsed, for easy manoeuvring underneath
the vehicle, while allowing considerable extension.
2.5 Operational Considerations of a screw jack
1. Maintain low surface contact pressure Increasing the screw size and nut size will reduce
thread contact pressure for the same working load. The higher the unit pressure and the higher
the surface speed, the more rapid the wear will be.
2. Maintain low surface speed. Increasing the screw head will reduce the surface speed for the
same linear speed.
3. Keep the mating surfaces clean Dirt can easily embed itself in the soft nut material. It will
act as a file and abrade the mating screw surface. The soft nut material backs away during
contact leaving the hard dirt particles to scrap away the mating screw material.
4. Keep heat away. When the mating surfaces heat up, they become much softer and are more
easily worn away. Means to remove the heat such as limited duty cycles or heat sinks must be
provided so that rapid wear of over-heated materials can be avoided.
2. 6 Power Screw
A power screw is a mechanical device used for converting rotary motion into linear motion
and transmitting power. A power screw is also called translation screw. It uses helical

11
translatory motion of the screw thread in transmitting power rather than clamping the machine
components.
2.6.1 Applications
The main applications of power screws are as follows:
1. To raise the load, e.g. screw-jack, scissor jack,
2. To obtain accurate motion in machining operations, e.g. lead-screw of lathe,
3. To clamp a work piece, e.g. vice, and
4. To load a specimen, e.g. universal testing machine.
There are three essential parts of a power screw i.e., screw, nut and a part to hold either the
screw or the nut in its place. Depending upon the holding arrangement, power screws operate
in two different ways. In some cases, the screw rotates in its bearing, while the nut has axial
motion. The lead screw of the lathe is an example of this category. In other applications, the
nut is kept stationary and the screw moves in axial direction. Screw-jack and machine vice are
the examples of this category.
2.6.2 Advantages
Power screws offer the following advantages:
1. Power screw has large load carrying capacity.
2. The overall dimensions of the power screw are small, resulting in compact construction.
3. Power screw is simple to design
4. The manufacturing of power screw is easy without requiring specialized machinery. Square
threads are turned on lathe. Trapezoidal threads are manufactured on thread milling machine.
5. Power screw provides large mechanical advantage. A load of 15 kN can be raised by
applying an effort as small as 400N. Therefore, most of the power screws used in various
applications like screw-jacks, clamps, valves and vices are usually manually operated.
6. Power screws provide precisely controlled and highly accurate linear motion required in
machine tool applications.
7. Power screws give smooth and noiseless service without any maintenance.
8. There are only a few parts in power screw. This reduces cost and increases reliability.

12
9. Power screw can be designed with self-locking property. In screw-jack application, self-
locking characteristic is required to prevent the load from descending on its own
2.6.3 Disadvantages
The disadvantages of power screws are as follows:
1. Power screws have very poor efficiency; as low as 40%. Therefore, it is not used in
continuous power transmission in machine tools, with the exception of the lead screw. Power
screws are mainly used for intermittent motion that is occasionally required for lifting the load
or actuating the mechanism.
2. High friction in threads causes rapid wear of the screw or the nut. In case of square threads,
the nut is usually made of soft material and replaced when worn out. In trapezoidal threads, a
split- type of nut is used to compensate for the wear. Therefore, wear is a serious problem in
power screws.
2.7 Forms of Threads
There are two popular types of threads used for power screws viz. Square, I.S.O metric
trapezoidal and Acme threads.
2.7.1 Square Thread
The square thread form is a common screw thread form, used in high load applications such as
lead screws and jackscrews. It gets its name from the square cross-section of the thread. It is
the lowest friction and most efficient thread form.
Fig 2.4 Nomenclature of Square Thread
2.7.1.1 Advantages of square threads

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The advantages of square threads over trapezoidal threads are as follows:
1. The efficiency of square threads is more than that of trapezoidal threads.
2. There is no radial pressure on the nut. Since there is no side thrust, the motion of the nut is
uniform. The life of the nut is also increased.
2.7.1.2 Disadvantages of square threads
The disadvantages of square threads are as follows:
1. Square threads are difficult to manufacture. They are usually turned on lathe with single-
point cutting tool. Machining with single-point cutting tool is an expensive operation compared
to machining with multi-point cutting tool.
2. The strength of a screw depends upon the thread thickness at the core diameter. Square
threads have less thickness at core diameter than trapezoidal threads. This reduces the load
carrying capacity of the screw.
3. The wear of the thread surface becomes a serious problem in the service life of the power
screw. It is not possible to compensate for wear in square threads. Therefore, when worn out,
the nut or the screw requires replacement.
2.7.2 Trapezoidal Threads
Trapezoidal thread forms are screw thread profiles with trapezoidal outlines. They are the most
common forms used for lead screws. They offer high strength and ease of manufacture.
Fig 2.5 Nomenclature of Trapezoidal Thread
2.7.2.1 Advantages of Trapezoidal Threads
The advantages of trapezoidal threads over square threads are as follows:

14
1. Trapezoidal threads are manufactured on thread milling machine. It employs multipoint
cutting tool. Machining with multi-point cutting tool is an economic operation compared to
machining with single point-cutting tool. Therefore, trapezoidal threads are economical to
manufacture.
2. Trapezoidal thread has more thickness at core diameter than that of square thread. Therefore,
a screw with trapezoidal threads is stronger than equivalent screw with square threads. Such a
screw has large load carrying capacity.
3. The axial wear on the surface of the trapezoidal threads can be compensated by means of a
split-type of nut. The nut is cut into two parts along the diameter. As wear progresses, the
looseness is prevented by tightening the two halves of the nut together, the split-type nut can
be used only for trapezoidal threads. It is used in lead-screw of lathe to compensate wear at
periodic intervals by tightening the two halves.
2.7.2.2 Disadvantages of Trapezoidal Threads
The disadvantages of trapezoidal threads are as follows
1. The efficiency of trapezoidal threads is less than that of square threads.
2. Trapezoidal threads result in side thrust or radial pressure on the nut. The radial pressure or
bursting pressure on nut affects its performance.
2.7.3 ACME Thread
There is a special type of thread called acme thread as shown in Fig. Trapezoidal and acme
threads are identical in all respects except the thread angle. In acme thread, the thread angle is
29° instead of 30°.The relative advantages and disadvantages of acme threads are same as those
of trapezoidal threads. There is another type of thread called buttress thread. It combines the
advantages of square and trapezoidal threads. Buttress threads are used where heavy axial force
acts along the screw axis in one direction only.
Fig 2.6 ACME thread
2.8 Designation of Threads
There is a particular method of designation for square and trapezoidal threads. A power screw
with single-start square threads is designated by the letters ‘Sq’ followed by the nominal

15
diameter and the pitch expressed in millimetres and separated by the sign ‘x’. For example, Sq
30 x 6
It indicates single-start square threads with 30mm nominal diameter and 6mm pitch.
Similarly, single-start I.S.O metric trapezoidal threads are designated by letters ‘Tr’ followed
by the nominal diameter and the pitch expressed in millimetres and separated by the sign ‘x’.
For example, Tr 40x7 It indicates single-start trapezoidal threads with 40mm nominal diameter
and 7mm pitch.
2.8.1 Multiple Threaded Power Screws
Multiple threaded power screws as shown in Fig 3.4 are used in certain applications where
higher travelling speed is required. They are also called multiple start screws such as
doublestart or triple-start screws. These screws have two or more threads cut side by side,
around the rod.
(a) (b) (c)
Fig 2.7Mupltiple Threaded Screw (a) Single Start (b) Double Start (c) Triple Start
Multiple-start trapezoidal threads are designated by letters ‘Tr’ followed by the nominal
diameter and the lead, separated by sign ‘x’ and in brackets the letter „P‟ followed by the pitch
expressed in 15 millimetres. For example, Tr 40 x 14 (P7)
In above designation,
Lead=14mm pitch=7mm
Therefore, No. of starts =14/7=2
It indicates two-start trapezoidal thread with 40mm nominal diameter and 7mm pitch. In case
of left handed threads. The letters ‘LH’ are added to thread designation. For example,
Tr 40 x 14 (P7) LH

16
2.9 Terminology of Power Screw
The terminology of the screw thread is given in Fig 3.5:
Fig 2.8 Nomenclature of a Power Screw
1. Pitch: The pitch is defined as the distance, measured parallel to the axis of the screw, from
a point on one thread to the corresponding point on the adjacent thread. It is denoted by the
letter ‘p’.
2. Lead: The lead is defined as the distance, measured parallel to the axis of the screw that the
nut will advance in one revolution of the screw. It is denoted by the letter ‘L’. For a single-
threaded screw, the lead is same as the pitch, for a double-threaded screw, the lead is twice that
of the pitch, and so on.
3. Nominal diameter: It is the largest diameter of the screw. It is also called major diameter.
It is denoted by the letter ‘do’.
4. Core diameter: It is the smallest diameter of the screw thread. It is also called minor
diameter. It is denoted by the letters ‘dc’.
5. Helix angle: It is defined as the angle made by the helix of the thread with a plane
perpendicular to the axis of the screw. Helix angle is related to the lead and the mean diameter
of the screw. It is also called lead angle. It is denoted by α.

17
2.10 Self Locking Screw
It can be seen that when Ф < α, the torque required to lower the load is negative. It indicates a
condition that no force is required to lower the load. The load itself will begin to turn the screw
and descend down, unless a restraining torque is applied. This condition is called
“overhauling” of screw.
When Ф > α, a positive torque is required to lower the load. Under this condition, the load will
not turn the screw and will not descend on its own unless effort P is applied. In this case, the
screw is said to be “self-locking”. The rule for self-locking screw is as follows: “A screw will
be self-locking if the coefficient of friction is equal to or greater than the tangent of the helix
angle”.
Graph 2.1 Graph Between coefficient of friction and lead angle
Therefore, for a self-locking screw the following conclusions can be made 1. Self-locking of
screw is not possible when the coefficient of friction (μ) is low. The coefficient of friction
between the surfaces of the screw and the nut is reduced by lubrication. Excessive lubrication
may cause the load to descend on its own.
2. Self-locking property of the screw is lost when the lead is large. The lead increases with
number of starts. For double-start thread, lead is twice of the pitch and for triple threaded screw,

18
three times of pitch. Therefore, single threaded is better than multiple threaded screw from
self-locking considerations. Self-locking condition is essential in applications like scissor jack.
2.11 Efficiency of Self-Locking Screw
The output consists of raising the load. Therefore, Work output = force x distance travelled in
the direction of force = W x L
The input consists of rotating the screw by means of an effort P.
Work input = force x distance travelled in the direction of force = P x (π d)
The efficiency η of the screw is given by,
η = Work output/ Work input
= W x L/ P x (π d)
= (W/P)* tan (α)
= tan (α)/tan (Ф +α)
From the above equation, it is evident that the efficiency of the square threaded screw depends
upon the helix angle α and the friction angle Ф. The following figure shows the variation of
the efficiency of square threaded screw against the helix angle for various values of coefficient
of friction. The graph is applicable when the load is lifted.
Graph 2.2 Graph between Efficiency and Helix angle
Following conclusions can be derived from the observation of these graphs,
1. The efficiency of square threaded screw increase rapidly up to helix angle of 20°.
2. The efficiency is maximum when the helix angle between 40 to 45°.
3. The efficiency decreases after the maximum value is reached.

19
4. The efficiency decreases rapidly when the helix angle exceeds 60°
5. The efficiency decreases as the coefficient of friction increases.
There are two ways to increase the efficiency of square threaded screws. They are as follows:
1. Reduce the coefficient of friction between the screw and the nut by proper lubrication
2. Increase the helix angle up to 40 to 45° by using multiple start threads.
However, a screw with such helix angle has other disadvantages like loss of self-locking
property.
2.12 Necessity / Application of scissor lift
1. Vehicle loading and docking operations
2. Mobility impaired access (see below)
3. Work positioning and ergonomic handling
4. Load positioning (e.g. when integrated into conveyor systems)
5. Materials positioning in machine feeding applications
6. Pallet and roll cage handling
7. Furniture upholstery
 There are three main types of aerial work platforms: boom lifts, scissor lifts, and
mechanical lifts. They can be operated with hydraulics, pneumatics, or mechanically
via screws or a rack-and-pinion system. They are either unpowered units, requiring an
external force to move them, self-propelled with controls at the platform, or mounted to
a vehicle for movement.
 The aerial work platform invention is widely credited to John L. Grove, who was an
American inventor and industrialist. However, even before JLG’s first model, a
company called Selma Man lift introduced a model in 1966.

20
 As for John L. Grove, after selling his previous business, Grove Manufacturing, in 1967
he and his wife headed out on a road trip. During a stop at the Hoover Dam, Grove
witnessed two workers electrocuted while working on scaffolding. Through this “tragic
event” John Grove saw a large untapped market for a product that could put workers in
the air more safely to perform construction and maintenance tasks.
 When Grove returned home from his trip, he formed a partnership with two friends,
bought a small metal fabrication business, and began designing concepts for the aerial
work platform. The company was named JLG Industries Inc., and with the aid of 20
employees it released its first aerial work platform in 1970.
 Aerial work platforms eventually began being designed with a variety of additional
features. Many are now equipped with electrical outlets, compressed air connectors,
and various other adaptations for tools.

21
CHAPTER:3 PROPOSED WORK
3.1 Proposed Prototype
The machine consists of a lead screw, gear and pinion, shaft in a slot and the lift scissors
(X linkages). Rotation of pinion attached to shaft of motor drives the system., the gear gets
driven by the rotating pinion. The lead screw rotates and this drives the main scissor
mechanism at its bottom linkage.
Thus, the rotary motion to pinion is converted into reciprocating / linear motion by using a gear
which moves the table.
2.2 Design of Components
Fixtures must always be designed with economics in mind; the purpose of these devices is
to reduce costs, and so they must be designed in such a way that the cost reduction outweighs
the cost of implementing the fixture. It is usually better, from an economic standpoint, for a
fixture to result in a small cost reduction for a process in constant use, than for a large cost
reduction for a process used only occasionally.
Most fixtures have a solid component, affixed to the floor or to the body of the machine and
considered immovable relative to the motion of the machining bit, and one or more movable
components known as clamps. These clamps (which may be operated by many different
mechanical means) allow work pieces to be easily placed in the machine or removed, and yet
stay secure during operation. Many are also adjustable, allowing for work pieces of different
sizes to be used for different operations. Fixtures must be designed such that the pressure or
motion of the machining operation (usually known as the feed) is directed primarily against
the solid component of the fixture. This reduces the likelihood that the fixture will fail,
interrupting the operation and potentially causing damage to infrastructure, components, or
operators.

22
Fixtures may also be designed for very general or simple uses. These multi-use fixtures tend
to be very simple themselves, often relying on the precision and ingenuity of the operator, as
well as surfaces and components already present in the workshop, to provide the same benefits
of a specially-designed fixture. Examples include workshop vises, adjustable clamps, and
improvised devices such as weights and furniture. Each component of a fixture is designed for
one of two purposes: location or support.
Aerial Scissor Lifts comprises of eight components. There is no concrete design procedure
available for designing these components. The main components of the lift are Base plate,
Upper plate, lead screw, nut, links and pins. On the basis of certain assumptions, the design
procedure for each of the components has been described as follows:
3.6 Design of base plate:
The base plate in a scissor lift only provides proper balance to the structure. Considering the
size constraints, the dimensions of the base plate are taken as under. Also, it has been found
that not much of the stresses are developed in the base plate. It is responsible for the lift to
handle the total weight of the lift and the weight to be carried and also acts as carrier for the
hydraulic cylinder
1. Design of upper plate:
The upper plate in a scissor lift is used to place the load and transfer it to the links. The
designing of the upper plate is undertaken similar as the base plate. The upper plate has the
similar requirements as the base plate. Also, it has been found that not much of the stresses are
developed in the upper plate as well.
2. Design of scissor link:
The scissor link is responsible for the lift structure to move up and down.
3. Design of Bolts
The bolt is one of the important elements in the aerial scissor lift. The carries major stress
during static and dynamic conditions. The bolt is used to join two centers of the scissor links
which forms a fulcrum point for the two-scissor links.

23
4. Design of pin:
The pin is used to join the two-scissor links then they form a joint.
5. Design of Lead Screw
Lead Screw is used to convert Rotary motion into Vertical Motion.
6. Design of Sprocket
Two Sprockets are used in this Project. One is at the motor end and other on the axis of
Lead screw. They are used to transmit power from motor to lead screw.
7. Design of Guide Shafts
They are galvanized shaft which are used to guide link and carry weight.
8. Design of Link Bar
It is used to connect Two Scissor Bar.
9. Thrust Sleeve
Thrust sleeve used to slide on guide bars and carry thrust. These are made up of galvanized Steel.
10. Motor
Motor used in this project have a high torque and low RPM (30 Rpm).
3.3 Details of Components
S. no. Parameters Measurement
1. Radius of Guide Shaft 25 mm
2. Length of Guide Shaft 580 mm
3. Lead Screw Diameter 30 mm
4. Length of Links 430 mm
5. Width of links 25 mm
6. Height of Links 5 mm
7. Diameter of Motor sprocket 50 mm
8. Diameter of Lead Screw Sprocket 200 mm

24
9. Cross section of Upper Plate 922 mm X 572 mm
10. Cross section of Lower Plate 922 mm X 572 mm
11. Diameter of Thrust Sleeve 26 mm
3.4 Working Principle
As shown in image the motor is provided to provide clockwise rotational motion to the
sprocket. The rotational motion of the motor is transmitted to the rotational motion in the same
axis of sprocket as they are attached along the same axis. The rotational motion of the sprocket
is transmitted to the sprocket as rotational motion, but in an axis, which is perpendicular to the
axis of a sprocket. The sprocket rotates the shaft attached with it, which in turn rotates the
Sprocket in the same sense as the sprocket. The sprocket rotates in a clockwise direction which
moves the lead screw. The rotary motion of lead screw results in forcing the scissor lift in
upward direction. This upward motion is desired to raise the height of a load for any
application.
The opposite happens when the handle is rotated in anti-clockwise direction. The anti-
clockwise rotation of handle leads to the downward motion of scissor mechanism. This
downward motion is required when a load is to be lowered.

25
As the load increases the effort required to raise the load is also increasing.
3.5 Technical parameter (Prototype)
Lifting height 200 mm
Minimum height 300 mm
Length 1000mm
Breadth 500 mm
Net weight 20-25 Kgs
3.6 Drafting and 3D model
3.6.1 Isometric View

28
3.6.4 ASSEMEBLY DRAWING –
Front View

31
3.6.5 Component Drawings
3.6.5.1 Chain Link

37
3.8 Calculations
Link Design:
Assumptions-
 Max. Height (AC) = 500 mm
 30o
< θ < 75o
 Max. Angle (θ) = 75o
 Min. Angle (θ) = 30.0o
We’ve to find Length of Link (AB) =?
If we design the scissor for single stage: -
Fig 3.1 Link Inclination
In OO’A
sin 𝜃 =
𝑂′𝐴
𝑂𝐴
𝑂′
𝐴 =
𝐴𝐶
2
=
500
2
= 250 𝑚𝑚
𝑂𝐴 =
𝐴𝐵
2
𝜃

38
𝐴𝐵 = 430𝑚𝑚
Total length of material required (l′) = 4 × AB = 1720 mm
Fig 3.2 Lead Screw Loading Applied at Bottom

39
Fig: 3.3 FBD of Link
 Solution:
a. ∑ MB (CCW) = Ф =
w
2
x 2L x cos (ϴ) – Fy x L x cos(ϴ) – Fx x L x sin(ϴ)
b. ∑ Fx = Ф = Fx – Rx1
c. ∑ Fy = Ф = -
w
2
+ Fy + Ry1
d. ∑ MA (CCW) = Ф = -
w
2
x 2L x cos (ϴ) – Fy x L x cos(ϴ) + Fx x L x sin(ϴ)
e. ∑ Fx = Ф = - Fx – Rx2
f. ∑ Fy = Ф = -
w
2
- Fy + Ry2
6 Equations, 6 Unknown Variables
A. 0 =
w
2
x 2L x cos(ϴ) – Fy x L x cos(ϴ) – Fy x L x sin(ϴ)
Fy =
−
w
2
x 2L x cos(ϴ)
L x cos( ϴ)
+
Fx x L x cos(ϴ)
𝐿 𝑥 sin(ϴ)
𝑊
2
𝑊
2
ϴ ϴ

40
Fy = - w + Fx x Tan(ϴ)
D. 0 = -
w
2
x 2L x cos (ϴ) – Fy x L x cos(ϴ) + Fx x L x sin(ϴ)
Fx =
w
2
x 2L x cos(ϴ)
L x sin( ϴ)
-
Fy x L x Sin(ϴ)
𝐿 𝑥 cos(ϴ)
Fx =
𝑤
𝑇𝑎𝑛(ϴ)
−
𝐹𝑦
𝑇𝑎𝑛(ϴ)
By Substitution ( Eq. A into Eq. D)
Fx =
𝑤
𝑇𝑎𝑛(ϴ)
− (
− 𝑤
𝑇𝑎𝑛(ϴ)
−
Fx x Tan(ϴ)
𝑇𝑎𝑛(ϴ)
Fx =
𝑍 𝑤
𝑇𝑎𝑛(ϴ)
+ Fx
If, -Rx1 + Fy = 0 and Rx2 – Fx = Ф
Rx1 = Fx Rx2 = Fy
Therefore,
Fx = Rx1 = Rx2 =
𝑤
𝑇𝑎𝑛(ϴ)
A. – w + Fx x Tan(ϴ) = Fy
D.
𝑤
𝑇𝑎𝑛(ϴ)
−
𝐹𝑦
𝑇𝑎𝑛(ϴ)
= 𝐹x
Fy = - w + (
𝑤
𝑇𝑎𝑛(ϴ)
−
𝐹𝑦
𝑇𝑎𝑛(ϴ)
) x Tan(ϴ)
Fy = - Fy
Fy = Ф
For Calculating upward relations
F. Ф = -
w
2
- Fy + Ry2
w
2
= Ry2
C. Ф = -
w
2
- Fy + Ry1
w
2
= Ry1
In Conclusion
Rx1 = Rx2 =
𝑤
𝑇𝑎𝑛(ϴ)
Fx =
𝑤
𝑇𝑎𝑛(ϴ)
Ry1 = Ry2 =
𝑤
𝑧
Fy = 0

41
When W = 500 N
By assuming θ we get these values:
Table 3.1
Θ 30o
35 o
40o
45 o
50o
60o
Fx 866 714 596 500 419 288
Fy 0 0 0 0 0 0
Rx1 866 714 596 500 419 288
Ry1 250 250 250 250 250 250
*Values approximated to near values. All the forces are expressed in Newtons (N)

42
CHAPTER: 4 ANSYS ANALYSIS
4.1Lead Screw
Fig 4.1 : Lead Screw

43
TABLE 4.1 Lead Screw
Model (A4) > Static Structural (A5) > Loads
Object Name Fixed Support Force
State Fully Defined
Scope
Scoping Method Geometry Selection
Geometry 1 Face
Definition
Type Fixed Support Force
Suppressed No
Define By Vector
Magnitude 800. N (ramped)
Direction Defined
Results
Fig 4.2 Lead Screw Strain

44
Fig 4.3 : Lead Screw Total Deformation
Fig 4.4: Lead Screw Equivalent Stress

45
TABLE 4.2
Results
Object Name Equivalent Elastic Strain Total Deformation Equivalent Stress
State Solved
Scope
Geometry All Bodies
Definition
Type Equivalent Elastic Strain Total Deformation Equivalent (von-Mises) Stress
By Time
Display Time Last
Calculate Time History Yes
Identifier
Suppressed No
Integration Point Results
Display Option Averaged Averaged
Results
Minimum 7.8166e-016 mm/mm 0. mm 1.7668e-010 MPa
Maximum 1.0613e-004 mm/mm 1.2684 mm 26.584 MPa
Information
Time 1. s
Load Step 1
Substep 1
Iteration Number 1

46
MILDSTEEL
TABLE 4.3
MILDSTEEL > Isotropic Elasticity
Temperature C Young's Modulus MPa Poisson's Ratio Bulk Modulus MPa Shear Modulus MPa
2.6e+005 0.29 2.0635e+005 1.0078e+005
4.2 Sprocket
Fig 4.5 Sprocket Strain
TABLE 4.4
Model (A4) > Static Structural (A5) > Loads
State Fully Defined
Scope
Geometry 2 Faces 1 Face
Definition

47
Suppressed No
Define By Vector
Magnitude -70. N (ramped)
Results
Fig 4.6: Sprocket Equivalent Stress

48
Fig 4.7: Sprocket Equivalent Strain
Fig 4.8: Sprocket Total Deformation
Table 4.5
Object Name Total Deformation Equivalent Elastic Strain Equivalent Stress
State Solved
Scope

49
Geometry All Bodies
Definition
Type Total Deformation Equivalent Elastic Strain Equivalent (von-Mises) Stress
By Time
Display Time Last
Identifier
Suppressed No
Results
Minimum 0. mm 6.6925e-010 mm/mm 9.8705e-005 MPa
Maximum 9.8404e-004 mm 3.754e-005 mm/mm 7.5488 MPa
Time 1. s
Mild Steel
TABLE 4.6
Mild Steel > Isotropic Elasticity
Temperature C Young's Modulus MPa Poisson's Ratio Bulk Modulus MPa Shear Modulus MPa
2.05e+005 0.29 1.627e+005 79457
4.3 Links
Fig 4.9: Links Strain

50
TABLE 4.7
Loads
Object Name Fixed Support Force Force 2
State Fully Defined
Scope
Definition
Suppressed No
Define By Vector
Magnitude 875. N (ramped) 216. N (ramped)
Direction Defined
Results

51
Fig 4.10: Links Equivalent Strain
Fig 4.11: Links Total Deformation
Fig
Fig 4.12: Links Equivalent Stress
TABLE 4.8
Results
Object Name Total Deformation Equivalent Stress Equivalent Elastic Strain
State Solved

52
Scope
Geometry All Bodies
Definition
Type Total Deformation Equivalent (von-Mises) Stress Equivalent Elastic Strain
By Time
Display Time Last
Identifier
Suppressed No
Results
Minimum 0. mm 0.14537 MPa 7.6817e-007 mm/mm
Maximum 1.4194 mm 249.65 MPa 1.2249e-003 mm/mm
4.4 Table
Fig 4.13: Table Strain

53
TABLE 4.9
Loads
Object Name Fixed Support Fixed Support 2 Fixed Support 3 Force
State Fully Defined
Scope
Definition
Suppressed No
Define By Components
Coordinate System Global Coordinate System
X Component 0. N (ramped)
Y Component -500. N (ramped)
Z Component 0. N (ramped)
Results

54
Fig 4.14 : Table Equivalent Stress
Fig 4.15 : Total Deformation
Fig 4.16: Table Equivalent Strain

55
TABLE 4.10
Model (A4) > Static Structural (A5) > Solution (A6) > Results
State Solved
Scope
Geometry All Bodies
Definition
Results
Maximum 1.0641 mm 1.0485e-004 mm/mm 29.5 MPa
Minimum Occurs On Part 6
Maximum Occurs On Part 5 Part 1
4.5 Chain Link
Fig 4.17: Chain Link Strain

56
TABLE 4.11
Loads
State Fully Defined
Scope
Geometry 2 Faces
Definition
Suppressed No
Define By Components
Coordinate System Global Coordinate System
X Component 77. N (ramped)
Y Component 0. N (ramped)
Z Component 0. N (ramped)
Results
Fig 4.18: Chain Link Total Strain

57
Fig 4.19: Chain Link Total Deformation
Fig 4.20: Equivalent Stress
TABLE 4.12
Results
State Solved

58
Scope
Geometry All Bodies
Definition
Type Total Deformation Equivalent Elastic Strain Equivalent (von-Mises) Stress
By Time
Display Time Last
Identifier
Suppressed No
Results
Maximum 2.805e-004 mm 9.261e-005 mm/mm 16.569 MPa

59
CHAPTER: 5 TIMELINE
 January: We started the Project work in the month of January, firstly by doing the
Literature review. Giving consideration to all the theoretical concepts and scientific laws
before designing is a must to check the feasibility of an idea.
 February: After we had done review of all concepts and concerned study, we started
the design of our model in Solid Works 2016 and went through a number of iterations
before reaching the final dimensions. All the features were based on theoretical concepts
underlying the phenomenon.
 March: Prior to manufacturing analysis of the design was done, so that to predict the
behavior of the final model in actual conditions although it gives an approximate result
only but is very crucial to know safety and durability of design.
 April: In the month of April we started the manufacturing of the project. All the
materials were procured timely. The manufacturing was done in the Central Workshop
and took almost 5 weeks for completion.
 May: We finally took the practical observations for different weights up to 50Kgs and
measured behavior of components under varying conditions. The readings of currents,
angles and Power were taken and efficiency was calculated.

60
Chapter: 6 OBSERVATIONS AND CALCULATIONS
FL =
𝑤
𝑇𝑎𝑛 (θ)
x Tan (α+ Ф)
Where α = Helix angle
Ф = Friction Angle
Torque on Lead Screw
TL =
𝑤
𝑇𝑎𝑛 (θ)
x Tan (α+ Ф) x r1
Here α = tan-1
(
𝑙
𝜋𝑑
) = 3.030
Ф = tan-1(.74) = 36.50
r1= radius of lead Screw = 15 mm
We know that torque on lead Screw (T2) = Torque on bigger Sprocket (T2)
Torque on smaller sprocket
T3 = T2 x R3/R2
T3 =
𝑤
𝑇𝑎𝑛 (θ)
x Tan (α+ Ф) x r1 x R3/R2
Motor Rpm = 30 rpm
Motor Angular Speed (ɷ =
2𝜋𝑁
60
= 3.14 rad
Torque on Motor Shaft (T4)= Torque on bigger sprocket (T3)
Motor Output Power = T4 x ɷ
Motor Input Power = IV
Where V= 24 V
Efficiency =
𝑤
𝑇𝑎𝑛 (θ)
x Tan (α+ Ф)x r1x R3/R2
𝐼𝑉

61
Table 6.1 Observations and Results
Torque(Nm)
Power(Watt) Input
Up Down Mechanical
Power(Output)(Watt)
Angle
(θ)
30 3.35 53.52 51.84 10.53
35 2.76 52.32 47.52 8.67
40 2.30 45.6 45.36 7.23
45 1.93 45.12 43.68 6.07
50 1.63 38.16 42.24 5.12
60 1.12 29.28 39.6 3.50
70 0.70 31.92 38.4 2.21
75 0.51 32.16 35.04 1.62
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80
TorqueN/m
Angle (Degrees)
Graph 6.1 Variation of Input Power with Angle (θ)
up
Down

62
0
0.5
1
1.5
2
2.5
3
3.5
4
0 10 20 30 40 50 60 70 80
Graph 3.2 Variation of Torque with angle (θ)
0
2
4
6
8
10
12
0 10 20 30 40 50 60 70 80
Graph 6.3 Variation of Output Power with Angle(θ)
Torque(N/m)Torque(N/m)
Angle (Degrees)
Angle (Degrees)

63
CHAPTER:7 COST INVOLVED
Table 7.1 Cost of Materials
S.no. Parts/
Components
Invoice
no.
Invoice
Date
Quantity Rate
(INR)
Amount
(INR)
1. Shaft Ф25mm 419 05-04-18 9.9 feet 80/feet 792
2. M.S. Plate
5×40 mm
419 05-04-18 6.6 feet 70/feet 462
3. Square pipe
50×25 mm
419 05-04-18 4 feet 80/feet 320
4. Square pipe
25×25 mm
419 05-04-18 20 feet 80/feet 1600
5. M.S.Sheet 419 05-04-18 7 kg 50/kg 350
6. D.C.Motor
24v 30rpm
419 05-04-18 1 no. 2300 2300
7. Transformer
24v 6amp.
419 05-04-18 1 no. 900 900
8. sprocket
Ф160mm
419 05-04-18 1 no. 400 400
9. Chain 419 05-04-18 1 no. 150 150
10. Lead screw 419 05-04-18 1 no. 300 300
11. Wheels 419 05-04-18 4 no. 90 360
12. Total 7934
Table 7.2 Miscellaneous Costs:
Sr .no Details Cost
1 Fasteners 300
3 Painting 150
4 Transport 1000
Total 1450

64
CHAPTER:8 RISK MANAGEMENT
While operating scissor lift there are chances of sudden collapse of platform due to overload.
To eliminate this risk a locking system should be provided which can stop motion of linkages
when in locked position
In prototype as worm and worm wheel is used. It doesn’t rotate reversely unless it is operated
by handle.
The aerial lift program applies to all University owned or rented aerial platform and scissor
lifts designed to elevate personnel on a platform. It applies to the departments who own or rent
the equipment and the employees who use them. Parts of this program address the use of
forklifts that have been approved for the use of elevating personnel. Examples of aerial
platform lifts include vehicle (or trailer) mounted aerial lift/bucket trucks, vertical personnel
lifts, scissor lifts, articulating boom aerial lifts, and extendable/telescoping aerial lifts.
Training Requirement
To become authorized to operate an aerial lift, employees must successfully complete an initial
two-part training program: a classroom session and a specific lift hands-on familiarization
session. Employees will only be authorized to operate the make and model of aerial lift which
they received hands-on familiarization. However, if an employee has received classroom
training, they are permitted to be passengers in lifts operated by authorized employees.
Employees who have no need to operate an aerial platform lift but have a need to ride in a lift
may complete the classroom session and become authorized as a “passenger only.” Classroom
training for aerial lifts will eventually be transitioned into complyND.

65
CHAPTER:9 ADVANTAGES AND DISADVANTAGES
Advantages:
 The scissor lift has a unique mechanism which uses worm and worm wheel. This
mechanism provides a self-locking system which makes the scissor lift completely safe
for use.
 Unlike the hydraulic systems, this mechanism has to be driven to bring the platform back
down. This gives us the opportunity to use this lift as a machine part for accurate
elevation.
Disadvantages:
 Scissor lift occupies substantial floor space which makes it unsuitable for smaller
applications.
 Height of the elevation is limited.
 Effort required to lift material increases with increase in weight.
 Periodically lubrication is to be done for smooth working.

66
CHAPTER:10 FEASIBILITY STUDY
5.1 Economic feasibility
Considering the cost of lift it is suitable and more productive than making temporary platforms
at construction sites with help of bamboo sticks or other materials. Maintenance cost is almost
negligible as only lubrication is required for components.
5.2 Technical / operational feasibility
There is no need of external support for the platform as the linkages itself work as supporters.
Only single worker is required to operate the lift and thus it saves man power as compared to
temporary platforms which need labors while being construct.

67
CHAPTER:11 FUTURE SCOPE
As a development the web part of the arms can be replaced by stiffening ribs to reduce
the overall weight. The top and base plates can be made foldable to make the unit more
compact. Permanently mounted jacks on the vehicle can be developed so that tire
change can be completely automated. The design can be made more compact and
materials can be made lighter and low frictional contact.

68
CHAPTER: 12 CONCLUSIONS
In this project a prototype of power scissor jack which can be operated by a power gun has
been designed and fabricated. The jack has been designed to a pay load of 1000N. The salient
features of the present fabrication are elimination of human effort to operate the jack, through
a simple electrical device which can be actuated by a 24 V battery.All the elements of the jack
are fabricated in the machine shop. The assembly of the component can be achieved in 100
minutes. Another feature of the unit is provision of two trunnions on both the sides of the jack
to ensure jerk free operation. The elements which are useful are readily available commercially
for each and early replacement of failed components if required.

69
REFERENCES
[1] [1]http://powerjacks.com/about-us/powerjacks-what-we-do.php
[2]RS Khurmi, A text book of Machine Design, Eurasia publishing house
[3]Msmillar.hubpages.com/hub/The-Hydraulic-Jack
[4]Powerjacks.com/downloads/Design%20Guides/PJLMPT-02/S1-Screw-Jacks PJLMPTDG-02.pdf
[5]Scholarsresearchlibrary.com/EJAESR-vol1-iss4/EJAESR-2012-1-4-167-172.pdf
[6]INPRESSCO-GERNAL ARTICLE; E-ISSN2277-4106, AUTOMATED CAR JACK.
[7] Academia.edu/6167889/Modification_of_the_Existing_Design_of_a_Car_Jack.
[8]http://en.wikipedia.org/wiki/Jackscrew
[9]http://scholarsresearchlibrary.com/EJAESR-vol1-iss4/EJAESR-2012-1-4-167- 172.pdf
[10] http://www.duffnorton.com/productmenu.aspx?id=7898
[11] http://www.ehs.utoronto.ca/Assets/ehs+Digital+Assets/ehs3/documents/Lifting+
Devices+Standard.pdf
[12] Design and fabrication of motorized automated object lifting jack; IOSRJEN.ISSN (e):2250-3021.
[13] http://www.ijceronline.com/papers/Vol4_issue07/Version-1/A0470101011.pdf
[14] Module 7 Screw threads and Gear Manufacturing Methods,
http://nptel.ac.in/courses/112105127/31
[15] IOSR Journal of Engineering (IOSRJEN) www.iosrjen.org, ISSN (e): 2250-3021, ISSN (p): 2278-
8719, Vol. 04, Issue 07 (July. 2014), ||V1|| PP 15-28

Motorized Sccissor Lift

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