Mechanical Engineering and Production Technology

Saimaa University of Applied Sciences
Faculty of Technology, Lappeenranta
Degree Programme in Mechanical Engineering and Production Technology
Georgy Olenin
Design of hydraulic scissors lifting platform
Thesis 2016
2
Abstract
Georgy Olenin
Design of hydraulic scissors lifting platform, 41 pages
Saimaa University of Applied Sciences
Faculty of Technology Lappeenranta
Degree Programme in Mechanical Engineering and Production Technology
Thesis 2016
Instructor: Principal Lecturer Seppo Toivanen, Saimaa University of Applied
Sciences
The goal of this study was to apply the knowledge obtained from studying in the
university and solve the substantial task of creating a design of the hydraulic
scissors lifting platform.
For this purpose a research of literature and articles was made, that contain
missing information of the theoretical part of the problem. The data was mainly
taken from the internet, particularly from articles, digital copies of books and
scientific works in a related field. The results of this research are presented in
the first theoretical part of the thesis.
Then to verify the validity of the theory the practice work was accomplished.
The type of the platform and the design of the structure were selected. The selection of the material and calculations of the loads and stresses were performed and explained. As the result of the work the 3D model of the lift using
SolidWorks software was created.
Keywords: Hydraulic lift, scissors lift, lifting table, scissors calculations.
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Table of contents
List of abbreviations and symbols ……………………………………………………………..4
1 Introduction……………………………………………………………………………………..5
2 Classification of lifting platforms………………………………………………………….6
3 Advantage and application…………………………………………………………………7
4 Aims/Objectives of the study………………………………………………………………9
5 Principle of action …………………………………………………………………………….9
6 Actions for the maintenance of hydraulic scissors lift……………………………12
7 Main faults and methods of their elimination……………………………………….13
8 Material selection……………………………………………………………………………13
9 Calculations …………………………………………………………………………………..14
9.1 Force acting on the cylinder………………………………………………………..15
9.1.1 Lowest position …………………………………………………………………..15
9.1.2 Highest position…………………………………………………………………..20
9.2 Forces acting on the leg……………………………………………………………..25
9.2.1 Lowest position …………………………………………………………………..25
9.2.2 Diagrams……………………………………………………………………………27
9.2.3 Stresses calculations……………………………………………………………29
9.2.4 Highest position…………………………………………………………………..31
9.2.5 Diagrams……………………………………………………………………………35
9.2.6 Stresses calculations……………………………………………………………37
10 Conclusion…………………………………………………………………………………….38
11 A list of figures ……………………………………………………………………………….39
12 A list of graphs ……………………………………………………………………………….39
13 A list of tables ………………………………………………………………………………..40
14 References ……………………………………………………………………………………40
4
List of abbreviations and symbols
Sum of forces in X-axis
Sum of forces in Y-axis
Sum of moments
Allowable stress
Normal stress
Factor of safety
Yield strength
Allowable shear stress
Shear stress
Combined stress
Bending stress
M Maximum moment
y Dimension from the center to the top (half of the H)
B Width
H Height
CCW Counterclockwise
5
1 Introduction
The structure of this thesis is planned as follows: in the first part, the theory is
presented. It consists of several topics concerning overall of lifting tables of
scissors type, things that are needed for the design, principles of working, technical characterization and others.
The first part is needed to give a general concept of the subject and after that
comes the practical part which presents and explains how to perform the
knowledge. It contains the 3D model of the lift, calculations of the load, several
diagrams, charts, and stress calculations, which confirm the viability and validity
of the theory part.
Such a thesis structure was chosen as the most appropriate and suitable for the
chosen topic. It allows increasing knowledge by appealing to the literature and
adding an individuality of the author by making him solve an actual practical
problem using own approach.
The scissors elevator is an elevator with a system of levers and hydraulic cylinders on which the metal platform is capable of moving in the vertical plane. This
is achieved by using of linked, folding supports in a crisscross pattern, called
scissor mechanism.
The hydraulic lift was chosen as a subject of the thesis because it is a perfect
example of mechanical engineering field. This mechanism combines a result of
several main fields of engineering and at the same time, it is simple and accessible for understanding. The construction and load distribution represent statics
and strength of material subjects, the hydraulic cylinder and the control unit involve knowledge of hydraulic systems and automation. Material science is important for selection of a suitable material as well as knowledge of 3D modeling.
Also, scissors lift is an integral part of most of the workshops and building objects. The key advantage of lifts is that they even offer the best way to organise
a technological and industrial process. Besides, almost all lifts give the possibility to change the place of their installation without much effort, which is im-
6
portant in the frequently changing conditions in the production process these
days.
The need for the utilization of elevators is incredibly wide and it runs across
workshops, factories, labs, fixing of billboards, residential/commercial buildings
to repair street lights, etc. Expanded and less-efficient, the engineers may run
into one or more problems while using(Ritchikmikie 2011).
2 Classification of lifting platforms
To start something new it is needed to look at something that already exists. On
the design elevators can be divided into the following main types: permanent
and portable. The permanent elevators are: scissor raise platforms, track lifting
platform, launching and unloading platforms (Sinolifter.com 2011). An example
is on Figure 2.1.
Figure 2.1 Launching and unloading platform (southworthproducts.com
2016).
The portable elevators divided into: several mobile lifting platform, a couple of
tractor-lift platforms, improved car lifting platform, AC-DC dual-use working out
with a platform, self-elevating podium, crank-type raise platform, foldable arm lift
platform, packages cylinder lift platform, lightweight aluminium lift platform,
working out with height from 1-30 m. array(Sinolifter.com 2011) An example is
on Figure 2.2.
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Figure 2.2 Mobile lifting platform (Made-in-china.com 2016).
As the drive elevators divided into: electro-hydraulic, electromechanical, pneumatic hydraulic. As the lifting devices elevators divided into: chain, screw, telescopic, lever. As the picking-up devices elevators divided into: platform, frame,
and console. Stationary elevators are established in a defined place, frequently
without the special foundation on a flat surface of a floor and fastened by means
of anchor bolts or special pins. If the elevator is telescopic then for his installation is required the special basement is required(Stroytech-ms.ru 2016).
Elevators at which racks move belong to mobile. The main advantage of mobile
elevators is their mobility – a possibility to use serially on various posts and in
various technological zones of the enterprise(Stroytech-ms.ru 2016).
3 Advantage and application
The concept of a scissors lift with hydraulic power comes from Pascal’s law applied in car jacks and hydraulic rams which states that “pressure exerted anywhere in a conformed incompressible fluid is transmitted equally in all directions
throughout the fluid such that the pressure ratio remains the
same”(Hydraulicsonline 2013).
8
Since the emergence in the light of different cultural achievements, the individual tries to maximize their use to facilitate the work. Only a century ago, the society did not have the opportunity even to dream about what is already openly
available at present. The rough labor is replaced by technology, for example
lifting mechanisms.
“A scissor lift elevator is a vertical transportation cab which is raised and lowered from underneath, somewhat like a traditional hydraulic elevator, except
that instead of a hydraulic cylinder the extendable mechanism is a folding lattice
of crisscrossed beams similar to a pantograph. The entire mechanism extends
upward when pressure is applied to the lowest members.”(Standards.phorio.com 2013).
On Figure 3.1 below general examples of scissors elevators can be seen.
Figure 3.1 General examples (sv-e.com 2013).
People use a huge number of different lifts. The aim is also different, some are
used in some situations while others are for a totally different environment. For
example, there is an electro-hydraulic scissors elevator — quite a small device
allowing to lift hundreds of kilograms of freight on a height of tens of meters.
Thus, in particular, the hydraulic scissor hydraulic lift has been used successfully to electrical and other works on the heights of about 2-3 floors. Also, it allows
making work at a greater height than tens of meters.
9
Also, lifts of this type could also be applied to other conditions, such as daily
loading and unloading work in warehouses. The scissor lift perfectly meets the
needs for certain warehouse facilities, mainly because of the fact that above the
lifting platform it has a lack of any mechanisms. This is complemented by access from all four sides, which gives the opportunity to use it for loading of objects on the top shelves of warehouse racks.
A distinctive feature of an electro-hydraulic scissor lift in comparison with other
analogues is the low price due to the use of a relatively simple design. A special
lifting platform is driven by a simple metal structure with levers that look like
scissors connected with others in a long chain. As a lifting force is used electrohydraulic mechanism for driving a pair of scissors in motion(sv-e.com 2013).
In addition, a scissor lift is suitable for use in situations, where movement of
other types of lifts is limited. This capability makes this type of lift particularly
versatile and convenient. A platform with load is movable not only vertically, but
also on the meter to the side, as is for example available on some models. This
feature is highly convenient in situations in the workplace where there is no
possibility to put the basis of lift exactly under the desired object(sv-e.com
2013).
4 Aims/Objectives of the study
The goal of the study is to design the hydraulic scissors lift to lift up to a height
of 1.2 meters and with the carrying capacity of 700 kilograms. The driving
mechanism of the lift must be a hydraulic cylinder. Calculations of the inner
stresses must be done and a 3D model must be created. It is also necessary to
choose the material.
5 Principle of action
The general view of the elevator is presented on Figure 5.1. The elevator with
the electro-hydraulic drive is performed for placement on the floor. The elevator
is intended for lifting objects with the weight of hundreds and thousands of kilograms from the floor to the height of 1 meter.
10
Figure 5.1 General view of lift (hydraulicscissorslift.com 2016).
There are two options for installing the lift on the floor or on the level with the
floor. The standard is to place the remote control for the lift to the left at a distance of 1 m. If necessary, the location of the control panel at the other distance
needed lengthening of the hydraulic drive.
The main technical capabilities (Garant-techservice.ru 2016):
1. The automatic device for blocking of mechanisms for safe work in any
situation;
2. The valves which are switching when hydraulic actuators are damaged;
3. Valve for control of speed of lowering;
4. The electro-hydraulic device for stopping the lowering in case of destruction of the basis of the elevator;
5. Electrically the switched-on device for protection of legs of the user;
6. The self-greased hinges.
The scissors lift has a table surface where the weight can be placed. The rising
of a platform is carried out due to work of a hydraulic cylinder. The management
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of the elevator is carried out by the control panel which has four buttons: the
main switch, lowering, rise, and blocking. As rising speed uniform and slow (on
average 30 mm per second), physics behavior of the elevator corresponds to a
static case(Garant-techservice.ru 2016).
The technical characteristics of the lift are shown in Table 1:
Loading capacity, kg 700
Height of rise, mm 1260
Rise time, sec. 40
Lowering time, sec. 40
Initial height, mm 125
Mass, kg 70
Power supply, volt 220
Table 1 Technical characteristic of the lift
On Figure 5.2 the main components of the lift are shown:
1. Hydraulic Cylinder
2. Leg
3. Table-top
4. Supporting tube 1
5. Supporting tube 2
6. Base plates
7. Top plates
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Figure 5.2 Main components
6 Actions for the maintenance of hydraulic scissors lift
Installation of the equipment:
Requirements for the floor:
1. The elevator has to be installed on a floor maintaining loading in 1.5 kN.
2. The minimum area for installation of the elevator of 1.3Ñ…0.7 m;
3. The floor has to maintain loading not lower than 1,3 kg/cm ²;
It is necessary to be convinced that the voltage in an electricity circuit corresponds to the elevator supply voltage. If the voltage does not comply it is necessary to rebuild circuit(Garant-techservice.ru 2016).
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7 Main faults and methods of their elimination
Main information about faults and methods of their elimination is presented in
table 2(Garant-techservice.ru 2016).
Type Possible reasons Method
Lift does not work Сylinder malfunction Remove cylinder, disassemble, and conduct
the necessary repairs.
Leaks in the joints of
hydraulic tubes
Loose connections Tighten the coupling
nuts. Loosen the nuts
and adjust the tip end of
the tube to tighten the
nut.
The stock does not
create the necessary
pressure
Easing tightening sleeves
cylinders.
Maladjustment of the safety valve
Tighten bolts, adjust the
spool valve.
Leak under a hydraulic
cylinder cover
Weakening of an inhaling
of bolts or wear of laying of
a cover
Tighten coupling bolts
or turn off nuts of a
cover and replace laying.
The pump does not
develop pressure
Malfunction of the pump Replace the pump new
Table 2 Main faults and methods of their elimination
8 Material selection
Depending on a component and tasks that this component performs the selection of a certain material is founded. Different parts of the mechanism take different load and stress because they carry out different functions. It is important
14
to use an individual approach to select a material for every part. It impacts on a
total efficiency and benefit received from each detail and best properties which
can give different materials. Thus, it is necessary to allocate the main parts of a
design and to explain features of each of them separately.
The main interest is made by the legs of the lift, the greatest part of loading is
shared between them and they are a basic element of the assembly. It means
that the material of which they are made has to be capable of maintaining this
load. This part is subjected to a normal force which might cause buckling and
shear force which cause bending, which possibly cause bending deformation or
even braking of the part. Then such properties as strength, hardness, and stiffness are needed. An appropriate material for these purposes is structural steel,
more precisely the S355 steel.
The second basic element of a design is the cylinder. From the technical point
of view, it acts as a bar with pinned ends. It is subjected to direct compressive
force which leads to bending and buckling load in the rod. Also, there exists the
internal pressure of the fluid, which causes circumferential and longitudinal
stresses all around the wall thickness. Thereby the cylinder must have such
properties as strength, toughness, ductility and hardness. An appropriate material is mild steel.
There are also such components as top plates and base plates. The top plates
take the load caused by a weight of lifting goods. The main needed property
here is strength and the selected material is mild steel. The base plates are
subjected to the weight of the load and scissors mechanism itself – cylinder and
legs, hence, hardness and stiffness are required. Mild steel is appropriate.
9 Calculations
The calculations of forces, stresses, and reactions of the structure play the most
important role in the design because on the result of these calculations and its
correctness depends stability, safety and successful work of the whole mechanism. The lifting table is a dynamic mechanism, but the speed of acting is relatively low, so this fact can be neglected and this system can be concerned as
15
static. Then only two positions are needed to be considered, they are the initial
position when the lift is lowered and just lying on the floor, and the highest position, when the mechanism lifted a weight on the highest possible distance. In
these two positions, the highest reactions and internal forces are observed. In
all the other positions the results will be between the two mentioned above.
9.1 Force acting on the cylinder
9.1.1 Lowest position
While calculation it is important to understand the behavior of the structure. For
this, the simplified picture is used to focus on the main acting forces. Here is the
free body diagram on Figure 9.1
Figure 9.1 Free body diagram for the initial position
As it can be seen on Figure 9.1, A and D are roller supports and B and C are
pin supports, point O is also a pin joint between two legs of the lift. Force W is
applied as the weight of the load and it is acting in the middle of the table, dimension “d” shows it. Also in the other plane which is not shown, the weight is
supposed to be as well in the middle. When the force acting on the middle or
shared over the table, it is transmitted equally to A and B supports. The “Wlegs”
is the load caused by a weight of the legs, it is also acting in the middle, but only
in the initial position. Also, the total incoming forces must be equal to the total
out coming, which means that whatever is happening inside the system the sum
of reactions Dy and Cy would be equal to the weight. Then vertical reactions of
D and C are half of the weight of the main load plus the weight of legs.

 

16
EF from Figure 9.1 is the hydraulic cylinder and here it is acting like a truss. It is
subjected a compression force, that means the cylinder acts with a certain force
to the points E and F. On Figure 9.2 it can be seen how this force P is decomposed into a Y and X components according to the axes. And as a result:

 

 

 

Figure 9.2 Force components at point E
Then the free body diagram is drawn for each leg separately on Figure 9.3. Fy
and Fx are the components of F force acting on the pin, it is better to decompose it right now because its value and direction are not known yet.
Figure 9.3 Free body diagram for each of leg separately
17
Also, it is needed to get the projections of the dimensions of the leg which will
be called “L”, the dimension between E and O is called “a”. The analogous result may be used for projection of CE, the dimension of which is “(L/2+a)” as
shown on Figure 9.4.
Figure 9.4 Projections of the leg

 

 

 

Then, using the diagram on Figure 9.3 it is needed to consider a balance of
forces in Y and X directions and also the balance of moments created by the
action of forces. It is done only for AC, but there will be an identical result on DB
because dimensions are the same.

 

 

 

 

 

 

 

 

 

18
Rotating around point C, CCW is positive direction:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rule from geometry:
(Tammertekniika 2012, p. 15). (1)

 

 

 

 

(2)
In this project, there was the following order of actions: first, based on the existing examples and approximate representation what has to be the elevator,
rough 3D model was drawn, which can be seen on Figure 9.5, to get the needed measurements and numbers with which calculations can be done. Then in
case if the model does not correspond to the necessary result it can be
changed in an appropriate way.
19
Figure 9.5 3D view of the lift
Having the 3D, the needed dimensions for further calculations can be obtained,
which can be seen on Figure 9.6.
Figure 9.6 Dimensions in the lowest position
20
According to the design there are the following measurements:
L = 1.300 meters
a = 0.244 meters
Mass of the load is 700 kg.
Mass of the legs is 67 kg.
= 5°
= 13°

 

 

 

 

9.1.2 Highest position
On Figure 9.7 the free body diagram for the highest position of the lift is shown:
Figure 9.7 Free body diagram for the highest position
21
d = 0.650 meters
AB = 0.529 meters

 

 

 

 

 

 

According to the behavior of the legs: for the free body
diagrams of the legs in the highest position which is shown on Figure 9.8. Calculations are done only for AC, but there will be an identical result on DB because dimensions are the same.
Figure 9.8 Free body diagram of legs in highest position
22

 

 

 

 

 

 

Rotating around point C, CCW is positive direction:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rule from geometry:
(Tammertekniikka 2012, p. 15).
23

 

 

 

 

(3)
The formula (3) can be used for calculating the force in the cylinder in any position where reactions Cy and Dy are not the same, it means that any position
except initial – lowest position, because in that position dimension between DC
is the same dimension as .
The needed dimensions for further calculations, can be seen on Figure 9.9.
Figure 9.9 Dimensions in the highest position
According to the design there are the following measurements:
L = 1.300 meters
a = 0.82 meters
Mass of the load is 700 kg.
Mass of the legs is 67 kg.
24
= 66°
= 72°

 

Graph 1 and table 3, show how force depends on the angle :
Graph 1 Cylinder force and angle
angle (deg.) angle (deg.) Force of Cylinder (N)
6 14 59751
11 17 45448
16 22 36019
21 27 30874
26 32 27867
31 37 26135
36 42 25281
41 47 25124
0
10000
20000
30000
40000
50000
60000
70000
0 10 20 30 40 50 60 70
Force (N)
Angle α (deg.)
Force of the cylinder
25
46 52 25602
51 57 26745
56 62 28679
61 67 31672
66 72 36254
Table 3 Cylinder force and angle
9.2 Forces acting on the leg
9.2.1 Lowest position
Now all needed forces are known. If , then P force equals to
the force F in the pin and as they are acting like counter forces, their values are
the same. Then it is necessary to find normal and shear forces acting on the leg
in order to be able to find stresses. For that all the forces must be projected
parallel to the axis of the leg, as shown on Figure 9.10, using the rules of geometry and components of the forces as it was done earlier.
Figure 9.10 Forces components parallel to the axis of the leg

 

 

 

 

 

 

 

 

 

 

26

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Now the free body diagram for one of the legs can be drawn as on Figure 9.11.
Figure 9.11 Free body diagram for the first leg in initial position
The same things are done for the second leg, where forces are the same but
directions are different. Reaction forces at the points D and B are the same. It is
shown on Figure 9.12.
Figure 9.12 Forces components parallel to the axis of the second leg
27

 

 

 

 

 

 

Now the free body diagram for the one of the leg can be drawn as on Figure
9.13.
Figure 9.13 Free body diagram for the second leg in initial position.
9.2.2 Diagrams
Now it is possible to draw a shear force diagram, a normal force diagram, and a
moment diagram. Then corresponding stresses can be calculated. The normal
force diagram, shear force diagram and bending moment diagram for both legs
are shown below on Figures 9.14 and 9.15.
”+” is for tension; ”-” is for compression:
28
Figure 9.14 Diagrams for the first leg in initial position
29
Figure 9.15 Diagrams for the second leg in initial position
9.2.3 Stresses calculations
Allowable normal stress for S355 steel:
Factor of safety is taken as 3 according to the safety standard ANSI MH29.1
(Ecoalifts.com 2016)

 

(4)

 

Allowable shear stress:
(5)
30

Actual stresses:
The highest normal stresses are between EO and FO, but the areas in the
points E and F are the smallest, so as it is not obvious where the stress is higher, it is needed to check them both. Multiplier “2” comes from the fact that there
are 2 symmetric legs supporting the table.
The width of the leg is 15 mm.
Point E:

 

 

 

 

 

 

 

 

(6)

Point F:

 

 

 

 

 

 

 

Bending stress

where

 

 

M – maximum moment
y – dimension from the center to the top (half of the H)
B – width
H – height
The diameter of the hole at point O – 22 mm.
31
Point O:

 

 

Point E:

 

 

Point F:

 

 

As it can be seen all the actual stresses are lower than allowable stresses, that
means that the current design is satisfactory and the structure is safe.
9.2.4 Highest position
In the other positions the formula for the force of the cylinder is different, and
reaction forces and internal forces are different and stresses are needed to be
revised. The second position is the highest possible point for the lift. But because of the geometry of the structure, the behavior of the forces is changed,
internal forces are not the same as in the first position, its nature (compression
and tension) is other.
Figure 9.16 shows the free body diagram of the first leg in the highest position.
32
Figure 9.16 Free body diagram for the first leg in the highest position

 

 

 

 

33

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The force of the pin is no longer a counter force for the cylinder, its direction and
magnitude is different now.

 

 

 

 

34
The same is done for the second leg as shown on Figure 9.17.
Figure 9.17 Free body diagram for the second leg in the highest position
;

 

 

;

 

 

same direction as
;
opposite direction to

 

 

35
9.2.5 Diagrams
The normal force diagram, shear force diagram and bending moment diagram
for both legs are shown below on Figures 9.18 and 9.19.
Figure 9.18 Diagrams for the first leg in the highest position
36
Figure 9.19 Diagrams for the second leg in the highest position
37
9.2.6 Stresses calculations

 

 

 

Actual stresses:
Point E:

 

 

 

 

 

 

 

Point F:

 

 

 

 

 

 

 

Point E:

 

 

As it can be seen all the actual stresses are lower than the allowable stresses,
that means that the current design is satisfactory and the structure is safe.
Bending stresses in point F and others are obviously too small, there is no need
for calculations.
38
10 Conclusion
The project was carried out successfully according to the project plan. The outcome of the hydraulic scissors lift design meets the objective of the project. As a
result, the project designed the electro-hydraulic parallelogram lift. The general
section described the classification, purpose and technical characteristics of the
lift, and the mechanism and operation principle of the designed lift.
In the design section, the lift calculation is done, where the forces acting in the
cylinder and emerging stresses in the system were calculated. A 3D model was
created.
After completed this project, I have gained some skills and knowledge in this
field. I have learnt many things in terms of utilizing engineering mechanisms in a
proper manner. Finally, the experience I have obtained throughout this project
will certainly help me to be a creative engineer in the future.
39
11 A list of figures
Figure 2.1 Launching and unloading platform (southworthproducts.com 2016)..6
Figure 2.2 Mobile lifting platform (Made-in-china.com 2016). ………………………..7
Figure 3.1 General examples (sv-e.com 2013)……………………………………………8
Figure 5.1 General view of lift (hydraulicscissorslift.com 2016). …………………..10
Figure 5.2 Main components…………………………………………………………………..12
Figure 9.1 Free body diagram for the initial position …………………………………..15
Figure 9.2 Force components at point E…………………………………………………..16
Figure 9.3 Free body diagram for each of leg separately…………………………….16
Figure 9.4 Projections of the leg ……………………………………………………………..17
Figure 9.5 3D view of the lift …………………………………………………………………..19
Figure 9.6 Dimensions in the lowest position…………………………………………….19
Figure 9.7 Free body diagram for the highest position………………………………..20
Figure 9.8 Free body diagram of legs in highest position…………………………….21
Figure 9.9 Dimensions in the highest position …………………………………………..23
Figure 9.10 Forces components parallel to the axis of the leg……………………..25
Figure 9.11 Free body diagram for the first leg in initial position…………………..26
Figure 9.12 Forces components parallel to the axis of the second leg ………….26
Figure 9.13 Free body diagram for the second leg in initial position. …………….27
Figure 9.14 Diagrams for the first leg in initial position………………………………..28
Figure 9.15 Diagrams for the second leg in initial position…………………………..29
Figure 9.16 Free body diagram for the first leg in the highest position…………..32
Figure 9.17 Free body diagram for the second leg in the highest position……..34
Figure 9.18 Diagrams for the first leg in the highest position ……………………….35
Figure 9.19 Diagrams for the second leg in the highest position…………………..36
12 A list of graphs
Graph 1 Cylinder force and angle ……………………………………………………………24
40
13 A list of tables
Table 1 Technical characteristic of the lift …………………………………………………11
Table 2 Main faults and methods of their elimination ………………………………….13
Table 3 Cylinder force and angle …………………………………………………………….25
14 References
1. Engineers Edge 2012. Scissor Lift Jack Review and Equations.
http://www.engineersedge.com/mechanics_machines/scissor-lift.htm.
Accessed on 1 March 2016.
2. Ecoalifts 2016. Scissor Lifts.http://www.ecoalifts.com/category/ScissorLifts/. Accessed on 1 March 2016.
3. Hydraulicsonline 2013. Pascal’s Law.
http://www.hydraulicsonline.com/hydraulic-principles. Accessed on 1
March 2016.
4. Hydraulicscissorslift 2016. Hydraulic Scissor Lift.
http://www.hydraulicscissorslift.com/hydraulic-scissor-lifts.php. Accessed
on 1 March 2016.
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6. Made-in-China 2016. Scissor Hydraulic Mobile Lifting Platform for Sale.
http://jnshanglong.en.made-in-china.com/productimage/CetxFowrMjRS2f1j00SszTMNkfHrpI/China-Scissor-Hydraulic-Mobile-Lifting-Platform-forSale.html. Accessed on 1 March 2016.
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http://standards.phorio.com/?t=definition&code=9598059865. Accessed
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13.Tammertekniika (Amk Publishing Ltd) 2012. Technical Formulas. 4th Revised Edition.

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