1)  Introduction


A jack is a great option in a vehicle for many reasons. It
could be used for as simple as a tire change on the roadside, or carrying out
maintenance on the vehicle from home. The jack is used to ensure the vehicle is
lifted to a suitable height, so work can be carried out. The purpose of the
jack is to lift a heavy object or a vehicle in this scenario. As safety is a
key aspect, when a heavy object is being lifted there are a few things that are
needed to be taken under consideration. The surface of floor; flat surface,
smooth and not weak so the jack doesn’t sink in. When the jack is in use, the
condition of the jack and the vehicle should be checked in terms of no damage
to the jack and any corrosion or weak spots on the vehicle.

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After, suitable research acquired the scissor jack is prone
to failure due to certain aspects. The aim of the project is to improve or
develop a way to reduce the number of scissor jacks failing. This report will
include some background research to understand what scissor jacks are used for
and how they are operated. The key topic is the causes of failure for the
scissor jacks. Also, some aspects include lack of use and corrosion. Some jacks
have been used incorrectly, for example many scissor jacks have markings and
stickers to represent the weight, some of these don’t which mean that when an
incorrect jack is used for the wrong vehicle it cannot withstand the weight
which results in failure.

Many manufactures provide breakdown tools with their vehicles
such as jacks, wheel braces and spare wheels. This report will be discussing
some aspects of research that has been carried out with regards to safety.

The report will also cover some advantages and disadvantages
of certain jacks to recognise various jacks are needed in different sections
around a vehicle. Furthermore, alternative designs have been provided to comprehend
that there are innovative designs evolving which are reducing the cost in the
production, ease of use and mainly to be safer. The materials for each jack
will be provided to initialise the sequences of development in the material.
Finally, the testing procedure will be carried out along with the methodology
of how each step will be taken with regards to the jack testing.




Fig 2.0


2)  Literature Review

Scissor Jacks

‘The first
automobile jack was patented in 1918 by Miller Falls Automobiles in Miller
Falls, Massachusetts’. Scissor jack is used to lift heavy objects, or a
more specific object will be a vehicle. The most generic form of jacks is;
floor jacks which are used so that maintenance can be performed on vehicle or
just to lift a heavy object around the workshop. The average small jacks such as
the scissor are usually fixed for a maximum lifting capacity around 1.5-3 ton.
Industrial jacks use greater loads, so they will have a lot more lifting
capacity. Scissor car jacks use manual force for lifting whereas some use
electrical powered motor to do the lifting. The scissor jacks have a slot where
it fits onto the sill of the vehicle to enable it to lift. Some scissor jacks
are designed to be only lifted from the sills and some can be lifted from other
places. A scissor car jack is designed by bolting pieces of metal elements into
a kite shape with hinges and a screw connecting the opposite sides of the
diamond. When the screw is turning with the spanner/hook it will raise the
diamond or lower it depends on the direction of the turn. The scissor jack
comes as a standard feature for majority of the vehicles, as a kit with the
spare will and various other accessories. However, large vehicles such as
trucks and high clearance vehicles with integrated jacks or heavy-duty jacks
due to the size and weight. This jack operates by transferring rotational
motion into linear, so this means the turning of the screw causes expansion or
contracting of the kite shape, which then translates to an upward force or
downward, when the jack is placed between solid grounds and jacked to the
vehicle chassis or sill.


When the screw section is turned, two ends of the diamond
move closer together. This occurs due to the gears/ threads of the screw are
pushing the arms, the size of force is being applied is multiplied. Not much
force is required when the crank/hook is turning the gears yet the action that
is being caused results in the brace arms to slide together. This procedure
helps the arms extend upwards to lift the object/vehicle.



The uses of the scissor jack can be simple as changing a
wheel on a car due to a puncture. Also, it can be used on a flat surface to
work on a vehicle at home, for example changing some brake pads, oil change and
various other components on a vehicle that need changing can be done. It is
highly recommended with any vehicle jack that an axle stands will need to be put
underneath for safety reasons. Scissor jacks are a standard feature in some
cars and can be bought for around £10/15. Scissor jacks are the ones that
typically come in a vehicle’s boot kit in case of an emergency. These jacks
benefit because they don’t take up much space can be stored in the trunk of a
vehicle also they don’t require any additional maintenance.


3)  Design

The scissor
jack head varies from different shapes and designs, the scissor jack is mainly
used for jacking up from the sill of the vehicle. However, as said above that
some users avoid jacking up from weak structures due to rusty sills or a weak
structure. To avoid jacking up from the sills or to prevent the vehicle from
sliding, some research has been done to overcome these issues.

One of the
ways is to re-design the head of the scissor jack, create a claw head whip grip
against certain objects or an adjustable head which can be adjusted to the
users need. This will be universal, so it can be jacked up from the sills many
other places. 

The floor of the scissor jack will need to be improved so it
can prevent the vehicle from sliding. This can be done by having a rubber floor
pad for the jack or the structure of the floor can be re-designed.        Fig4.5

Another improvement could be, having the scissor jack heads
screw into the jack so they can be used for more than one option. By having the
head of the scissor jack screwed into the jack, it will improve the structure
of the jack.

 The rubber pad can
also be fitted over the jack head to prevent the vehicle from sliding. The
higher the jack is lifted there is a greater chances of the jack the jack
sliding or falling.

Some design ideas have been shown above, the next step is to
create some drawings to get a visual idea of the design.

Progression of scissor jacks

Scissor jack (Mechanical)

 The scissor jack today
is well-known jack used daily when needed. They are the cheapest out of all the
jacks. Vehicle manufactures use this jack into their vehicles as a standard
feature along with wheel braces and various other items. These jacks are small,
so they can be carried around unlike trolley/floor jacks. These jacks don’t
need maintaining as much as the hydraulic jack due to it being a mechanical
device. These jacks restrict lifting certain vehicles up due to the weight.
Furthermore, as people got lazy a new jack was invented which was an electric
scissor jack powered by a motor.

jack (Electrical)

This jack
is an improved version of the scissor jack. This jack is manufactured from
heavy duty steel; a motor has been added to the scissor jack which means less
motion is required. The electric powered jack has equivalent properties to the
normal scissor jack however this is quicker to operate and has a remote to
control the lift. This jack operates by a wire from
the jack connected into the vehicle’s cigarette lighter socket. The electric
scissor jack is powered by 12-volt electricity provided directly from the car’s
cigarette lighter port which means that no extra power pack is needed. 

4)  Testing


The testing consists of three sections. The first section is Ansys;
the scissor jack will be simulated on the software. A 3D model will need to be
made on computer aided design or even on ansys.


 Once this is done the
file will be converted onto ansys to enable it to run. The jack will go through
the testing procedure which will involve a load being set, which will represent
the weight of a car. On the jack, certain points must be fixed during the test
to demonstrate that the jack is not moving as it’s under load. The test will
begin and create a set of results which depend on the jack material and various
other aspects. The results gained such as stress, strain. Fatigue and fracture must
be calculated so they can be used later for validation.


Some drawings will be made to interpret modern designs
keeping in consideration the scissor jacks.

Each part of the jack will then be analysed to determine each
component weak points. Calculations will be carried out for each component
individually. The weakest component will then be modified to overcome its
weakness to enable a strong structure.

As the main goal is to analyse a scissor jack, the material
and shape will be taken under consideration.


The next test will involve an actual jack being tested. A
hydraulic press will apply a load to the scissor jack. This is like the ansys
test where the load will represent the wright of a vehicle and pushed against
the car. The procedure will be carried out with various loads to represent
various vehicles.  At a point, the jack
will have fractured or have some signs of fatigue in the material. The results
gained from the jack will be then calculated to support the ansys.


The final test is hand calculations; these will validate both
tests by getting comparable results. If the results are different this means,
there is a problem between the three tests.

So far, the 3D model of the scissor jack has been made. It
will now need to go through the ansys procedure for the finite element
analysis. The first material that will be used for the test will be structural
steel and understand what effects it has on the design and any damage caused.

The test consists of four materials, this will determine if
the final project design will be from aluminium, steel, mild steel and cast
steel. The rough of idea of the 3d model will be then improved.

5)  Materials


Structural steel

Any jack that is made acquires components made from steel,
they may have been assembled with an aluminum structure, but steel is required for
the fixings, pins and many other components.
‘While aluminum tends to win out on weight, steel jacks tend to acquire out on
cost. Steel jacks are normally always a tiny bit more expensive on ordinary for
a graded capacity than aluminum jacks. This is because the weight economies,
aluminum jacks are normally promoted as superior solutions’. Matt Seals 2017. The development of scissor
jacks made from steel is improving to tick certain boxes such as price,
durability, ease of use and various other aspects. The strength of steel can be
increased by the addition of alloys such as manganese, niobium and vanadium.
However, these alloy additions can also adversely affect other properties, such
as ductility, toughness and weldability.  The properties of steel also include the
strength and reliabilities of the material.

Aluminium Alloy (Alternative)

The key features of aluminium are that, it is very light in
weight and it is one of the materials that doesn’t rust. The focus of having a
floor jack made from aluminium is to decrease its weight. As previous jacks,
were made from steel and they are very heavy to carry and move around a
workshop. Steel is a much denser material than aluminium which implies that if
two identical sized blocks of these materials measured in weight, steel would
weigh more.

Many people misunderstand the strength of aluminium. This is
due to the misconception of aluminium being soft and weak in various other
products. ‘The truth is that depending
on the grade of aluminum and the process by which a part is manufactured
aluminum parts can be every bit as strong as steel’. Matt Seals 2017 This material is used in a lot of
products floor jacks, jack stands, or airplanes made all from aluminum’.  The
specific weight of aluminium is roughly around 2.7 g/cm3.  Various treatments can be applied to
aluminium such as paint and lacquer to improve its properties; make it stand
out from other jacks.

This material is also recyclable which means that any scrap
aluminium can be reused to make a scissor jack. This process of recycling
requires less energy and roughly 5 percent of the energy is used to produce the
primary metal.

Furthermore, this material has a tensile strength between 70
and 700 MPa. Aluminium doesn’t get brittle at low temperatures however it
increases its strength.

Aluminium alloy can be attached to other aluminium products
or to various materials by the following methods: welding, brazing, soldering,
bolting, riveting, clinching, crimping, clipping, adhesive bonding and
slide-on, snap together or interlocking joints.


Mild steel,
and cast steel will go through material testing


6)  Alternative Designs






Bottle Jack

The max
capacity of this jack is 10-ton
150mm stroke
and an 80mm adjustment screw
230mm to
460mm lifting range
Strong a
safety overload valve

The bottle
jack is small, cheap & compatible
 It has a very high lifting capacity.
It can lift
heavy objects and vehicles with ease due to its high lifting capacity.
The bottle
jack is small and can be stored anywhere and doesn’t take much space

The small
base design of the bottle jack causes instability.
The bottle
jacks can lift heavy item buts only to a certain height.
escalates a problem when standard vehicles need lifting and there isn’t
enough clearance.


Exhaust Air Jack

Capacity:  4 tons, size: 58 x 75 cm
Weight:  4 tons:6.5kg
2 x
Protective mat sizes: 640mm x 670mm
5.6 meters
one-way air hose

Uses the
exhaust gases to full up the bag which lifts the vehicle.
Can lift
around 30 inches from the ground.
Cost less to

stay inflated
for as long as 45 minutes
car must be
started up during the procedure, consumption of fuel
Depending on
surfaces can pop the bag


Floor Jack

Racing style
1.5 tonne trolley jack
Low profile
with dual pumps for a quicker lift
Fast access
with front roller wheel
Lifting  (90-358 mm)

This enables
it to lift lowered vehicles.
The floor
jack is very simple to use due to the long pumping handle.
The floor
jack remains stable throughout the

The floor
jack has a low rate of lifting capacity. Cannot be carried around like the
other jacks
Takes a lot
of space due to its size.


Causes of failure



One of the common reason of this jack is prone to failure is
because of the head of the jack. The head is shaped as a sphere, so when the
jack is lifted elsewhere apart from the sills, due to not being stable the
vehicle begins to slide. To overcome this problem the jack head will have to be
re-designed or a polymer can be used above the head prevent the jack from
sliding. A rubber pad can be used to prevent the car from sliding; this will
firmly grip the structure of the vehicle. Some vehicles have soft/weak sills
which mean users will prevent jacking from these areas.

Below is an incident where a scissor jack was used and slid
of the vehicle. 

‘He said he
had jacked the passenger’s side tire off the ground with a scissor jack, and
was looking to “find a good jack stand point.” The car shifted a bit’, David
Tracy 2016. This article suggests that a vehicle was jacked using a
scissor jack and slid off.                                               


Wear & Tear








Safety of the operation

Chocks- wheel chocks can be used to prevent the vehicle from
rolling. The chock fits in front and behind the wheel, this is made from a
thick polymer. As, the vehicle is being lifted from one side using the scissor
jack the load is increasing on the opposing side which can surge the vehicle to
roll. The vehicle must be put into gear as well as handbrake must be applied.

Surface- As the
scissor jack is lifted the diamond shape turns into a tall rectangle. This
becomes a down fall because it has higher chances of toppling over. The surface
of the ground must be flat because the jack will start to slide depending on
the slope of the surface.

Stands- With any
type of lifting operation whether it’s a vehicle or a heavy object axle stands
are a must. They are placed on the chassis of the vehicle during lift or the
load of the jack can be released onto the stands for safety precautions. 


8)  Current Progression


Research- a scissor
jack has been chosen to analyse and recognise the causes of failure. The design
and strength will be analysed so alternative materials alternative materials
can be used. The scissor jack is a mechanical device that is failing a lot more
than other jacks. The research includes different jacks that have been developing
over time. The research has created the foundation of the project, by providing
some information on the scissor jack. The background information helps the
reader understand what the report is about.



CAD- A 3D model
has been designed to represent the scissor jack. The jack is consists of 6
parts. The design of the scissor jack is to get a rough idea also it will be
used on Ansys to gain some results.



Jack- The physical testing involves a jack being tested on a
press. A scissor jack has been brought for the testing.


options – A few design options have been developed regarding the
scissor jack head, the shape and the material. 
The standard 3d design will go through Ansys first to see the results
and then the improved design will be tested.












9)  Further Plan/Objectives


Ansys- As the 3D
model is made, the testing will need to be done to see the maximum stress and
strain.  Deadline: 18th January


testing- The next step after Ansys will be the testing of the jack;
a load will be applied to the scissor jack and will increase till the jack
cannot withstand the load. This procedure will result in fracture which will
then be calculated. Deadline: 23rd January


The following will need to be calculated:

Maximum Stress, Strain, fracture, crippling Deadline: 29th


testing- The materials mentioned will be tested on the press to
determine which one will be used in the final design. Deadline: 23rd



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