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 sinks 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. 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 understand various jacks are needed in different sections
around a vehicle. Furthermore, alternative designs have been provided to
understand 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.
2) Background of jacks
The first diamond shape jack was built by Mr Joseph LaFrance (1920). A
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 or garage jacks, which
are used so that maintenance can be performed on vehicle or just lifting a
heavy object around the workshop. The average small jacks such as scissor jacks
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 depending
on the direction of the turn. The scissor jack comes as standard feature for
majority of vehicle 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 across and together. That
procedure helps the arms extend upward to life 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 stand will need to 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) 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 sills which
mean users will prevent jacking up from these sorts of 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 scissor jack was used
incorrectly and caused major injury to the user. Fig3.0
needs a material that prevents the vehicle sliding of it, to achieve this; a
rubber pad must be fitted to the scissor jack. Friction is defined as the force
opposing motion. One type of friction is static friction. The lower the static
friction, the easier it is to make an object start moving.
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.
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
can then be noted 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 point. 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 second will be the improved version with aluminium and see the correlation
between both the materials when a load is applied.
The tests the four materials will determine if the final
project design will be from aluminium or steel. The rough of idea of the 3d model
will be then improved.
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
jack from steel is improving to gain 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 don’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
Many people misunderstand the strength of aluminium. This is
due to the misconception of aluminium being soft and weak in various 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 lacquer to improve its properties and 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
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.
and cast steel will go through material testing
6) Current Progression
Research- a scissor
jack has been chosen to analyse and improve the material properties, the design
and strength to reduce the number of failures. The scissor jack is a mechanical
device that is failing a lot more than other jacks. The research includes
recent incidents relating to scissor jacks failing. 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
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 of the scissor
jack also it will be used on Ansys to gain some results.
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.
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 fracture will then will
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
7) Alternative Designs
The max capacity of this jack is 10-ton
150mm stroke and an 80mm adjustment screw
230mm to 460mm lifting range
Strong a durable
Automatic safety overload valve
The bottle jack is small and compatible
It has a very high lifting
It can lift heavy objects and vehicles with ease due to its high
The bottle jack is small and can be stored anywhere and doesn’t take
The small base design of the bottle jack causes instability.
The bottle jacks can lift heavy item buts only to a certain height.
This escalates a problem when standard vehicles need lifting and
there isn’t enough clearance.
Exhaust Air Jack
Capacity: 4 tons, size: 58 x
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 manufacture
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
Racing style 1.5 tonne trolley jack
Low profile with dual pumps for a quicker lift
Fast access with front roller wheel
Lifting range is 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 procedure of work being
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.
8) Scissor Jack Head
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 into a claw 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 and other strong structures.
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
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. They are very easy
and simple to use. 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.
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.