1) Introduction A jack is a great option in a vehicle for manyreasons. It could be used for as simple as a tire change on the roadside, orcarrying out maintenance on the vehicle from home. The jack is used to ensurethe vehicle is lifted to a suitable height, so work can be carried out. Thepurpose of the jack is to lift a heavy object or a vehicle in this scenario. Assafety is a key aspect, when a heavy object is being lifted there are a fewthings 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 usethe condition of the jack and the vehicle should be checked in terms of nodamage 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 ofscissor jacks failing. This report will include some background research tounderstand what scissor jacks are used for and how they are operated. The keytopic is the causes of failure for the scissor jacks. Also, some aspectsinclude lack of use and corrosion.
Some jacks have been used incorrectly, forexample 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 thewrong vehicle it cannot withstand the weight which results in failure.Many manufactures provide breakdown tools with theirvehicles such as jacks, wheel braces and spare wheels. This report will bediscussing some aspects of research that has been carried out with regards tosafety.
The report will also cover some advantages anddisadvantages of certain jacks to understand various jacks are needed indifferent sections around a vehicle. Furthermore, alternative designs have beenprovided to understand that there are innovative designs evolving which arereducing the cost in the production, ease of use and mainly to be safer. Thematerials for each jack will be provided to initialise the sequences ofdevelopment in the material. Finally, the testing procedure will be carried outalong with the methodology of how each step will be taken with regards to thejack testing. Fig 2.0 2) Background of jacks The first diamond shape jack was built by Mr Joseph LaFrance (1920). Ascissor jack is used to lift heavy objects, or a more specific object will be avehicle. The most generic form of jacks is; floor jacks or garage jacks, whichare used so that maintenance can be performed on vehicle or just lifting aheavy object around the workshop.
The average small jacks such as scissor jacksare usually fixed for a maximum lifting capacity around 1.5-3 ton. Industrialjacks use greater loads, so they will have a lot more lifting capacity. Scissorcar jacks use manual force for lifting whereas some use electrical poweredmotor to do the lifting. The scissor jacks have a slot where it fits onto thesill of the vehicle to enable it to lift. Some scissor jacks are designed to beonly lifted from the sills and some can be lifted from other places.
A scissorcar jack is designed by bolting pieces of metal elements into a kite shape withhinges and a screw connecting the opposite sides of the diamond. When the screwis turning with the spanner/hook it will raise the diamond or lower it dependingon the direction of the turn. The scissor jack comes as standard feature formajority of vehicle as a kit with the spare will and various other accessories.However, large vehicles such as trucks and high clearance vehicles withintegrated jacks or heavy-duty jacks due to the size and weight. This jackoperates by transferring rotational motion into linear, so this means theturning of the screw causes expansion or contracting of the kite shape, whichthen translates to an upward force or downward, when the jack is placed betweensolid grounds and jacked to the vehicle chassis or sill.OperationWhen the screw section is turned, two ends of thediamond move closer together. This occurs due to the gears/ threads of thescrew 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 theaction that is being caused results in the brace arms to slide across andtogether.
That procedure helps the arms extend upward to life theobject/vehicle. UsageThe uses of the scissor jack can be simple as changinga wheel on a car due to a puncture. Also, it can be used on a flat surface towork on a vehicle at home, for example changing some brake pads, oil change andvarious other components on a vehicle that need changing can be done. It ishighly recommended with any vehicle jack that an axle stand will need to putunderneath for safety reasons. Scissor jacks are a standard feature in somecars and can be bought for around £10/15.
Scissor jacks are the ones thattypically come in a vehicle’s boot kit in case of an emergency. These jacksbenefit because they don’t take up much space can be stored in the trunk of avehicle also they don’t require any additional maintenance. 3) Causes of failure SlidingOne of the common reason of this jack is prone tofailure is because of the head of the jack.
The head is shaped as a sphere, sowhen the jack is lifted elsewhere apart from the sills, due to not being stablethe vehicle begins to slide. To overcome this problem the jack head will haveto be re-designed or a polymer can be used above the head prevent the jack fromsliding. A rubber pad can be used to prevent the car from sliding; this willfirmly grip the structure of the vehicle. Some vehicles have soft sills whichmean users will prevent jacking up from these sorts of areas.
Below is an incident where a scissor jack was used andslid of the vehicle. ‘Hesaid he had jacked the passenger’s side tire off the ground with a scissorjack, and was looking to “find a good jack stand point.” The car shifted abit’, David Tracy 2016 This articlesuggests that a scissor jack was used incorrectly and caused major injury tothe user. Fig3.0Non-slip materialThejack 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 theforce opposing motion. One type of friction is static friction.
The lower thestatic friction, the easier it is to make an object start moving. Fig3.5 Safety of the operationChocks- wheelchocks can be used to prevent the vehicle from rolling. The chock fits in frontand behind the wheel, this is made from a thick polymer. As, the vehicle isbeing lifted from one side using the scissor jack the load is increasing on theopposing side which can surge the vehicle to roll. The vehicle must be put intogear as well as handbrake must be applied.Surface- Asthe scissor jack is lifted the diamond shape turns into a tall rectangle.
Thisbecomes a down fall because it has higher chances of toppling over. The surfaceof the ground must be flat because the jack will start to slide depending onthe slope of the surface.Stands- Withany type of lifting operation whether it’s a vehicle or a heavy object axlestands are a must.
They are placed on the chassis of the vehicle during lift orthe load of the jack can be released onto the stands for safetyprecautions. 4) Testing/Methodology The testing consists of three sections. The firstsection is Ansys; the scissor jack will be simulated on the software. A 3Dmodel will need to be made on computer aided design or even on ansys. Once this isdone the file will be converted onto ansys to enable it to run. The jack willgo through the testing procedure which will involve a load being set, whichwill represent the weight of a car.
On the jack, certain points must be fixedduring 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 jackmaterial and various other aspects. The results gained such as stress, strain,fatigue and fracture can then be noted so they can be used later forvalidation.Some drawings will be made to interpret modern designskeeping in consideration the scissor jacks.
Each part of the jack will then be analysed todetermine each component weak point. Calculations will be carried out for eachcomponent individually. The weakest component will then be modified to overcomeits weakness to enable a strong structure.
As the main goal is to analyse a scissor jack, thematerial and shape will be taken under consideration. The next test will involve an actual jack beingtested. A hydraulic press will apply a load to the scissor jack. This is likethe ansys test where the load will represent the wright of a vehicle and pushedagainst the car. The procedure will be carried out with various loads torepresent various vehicles. At a point,the jack will have fractured or have some signs of fatigue in the material.
Theresults gained from the jack will be then calculated to support the ansys. The final test is hand calculations; these willvalidate both tests by getting comparable results. If the results are differentthis means, there is a problem between the three tests.So far, the 3D model of the scissor jack has beenmade. It will now need to go through the ansys procedure for the finite elementanalysis. The first material that will be used for the test will be structuralsteel 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 correlationbetween both the materials when a load is applied.The tests the four materials will determine if thefinal project design will be from aluminium or steel.
The rough of idea of the3d model will be then improved. 5) Materials Structural steelAny jack that is made acquires components made fromsteel, they may have been assembled with an aluminum structure, but steel isrequired for the fixings, pins and many other components. ‘While aluminum tends to win out on weight, steel jacks tend toacquire out on cost. Steel jacks are normally always a tiny bit more expensiveon ordinary for a graded capacity than aluminum jacks. This is because theweight economies, aluminum jacks are normally promoted as superior solutions’. Matt Seals 2017. The development of scissorjack 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 beincreased by the addition of alloys such as manganese, niobium and vanadium.
However, these alloy additions can also adversely affect other properties, suchas ductility, toughness and weldability. The properties of steel also include thestrength and reliabilities of the material. Aluminium Alloy (Alternative)The key features of aluminium are that, it is verylight in weight and it is one of the materials that don’t rust.
The focus ofhaving a floor jack made from aluminium is to decrease its weight. As previousjacks, were made from steel and they are very heavy to carry and move around aworkshop. Steel is a much denser material than aluminium which implies that iftwo identical sized blocks of these materials measured in weight, steel wouldweigh more.Many people misunderstand the strength of aluminium.This is due to the misconception of aluminium being soft and weak in variousproducts. ‘The truth is that dependingon the grade of aluminum and the process by which a part is manufacturedaluminum parts can be every bit as strong as steel’. Matt Seals 2017 This material is used in a lot ofproducts floor jacks, jack stands, or airplanes made all from aluminum’. Thespecific weight of aluminium is roughly around 2.
7 g/cm3. Various treatments can be applied toaluminium such as paint lacquer to improve its properties and make it stand outfrom other jacks.This material is also recyclable which means that anyscrap aluminium can be reused to make a scissor jack. This process of recyclingrequires less energy and roughly 5 percent of the energy is used to produce theprimary metal. Furthermore, this material has a tensile strength between70 and 700 MPa. Aluminium doesn’t get brittle at low temperatures however itincreases its strength. Aluminium alloy can be attached to other aluminiumproducts or to various materials by the following methods: welding, brazing,soldering, bolting, riveting, clinching, crimping, clipping, adhesive bondingand slide-on, snap together or interlocking joints. Mild steel,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 amechanical device that is failing a lot more than other jacks. The researchincludes recent incidents relating to scissor jacks failing. The research hascreated the foundation of the project, by providing some information on the scissorjack. The background information helps the reader understand what the report isabout. Ongoing CAD- A3D model has been designed to represent the scissor jack. The jack is consistsof 6 parts.
The design of the scissor jack is to get a rough idea of thescissor jack also it will be used on Ansys to gain some results. Completed Jack- Thephysical testing involves a jack being tested on a press. A scissor jack hasbeen brought for the testing.
Designoptions – A few design options have been developed regardingthe scissor jack head, the shape and the material. The standard 3d design will go through Ansysfirst to see the results and then the improved design will be tested.Further Plan/Objectives Ansys-As the 3D model is made, the testing will need to be done to see the maximumstress and strain. Deadline: 18thJanuary Jacktesting- The next step after Ansys will be the testing of thejack; a load will be applied to the scissor jack and will increase till thejack cannot withstand the load.
This procedure will result fracture will thenwill be calculated. Deadline: 23rd January Calculations-The following will need to be calculated:Maximum Stress, Strain, fracture, crippling Deadline: 29thJanuary Materialtesting- The materials mentioned will be tested on the press todetermine which one will be used in the final design. Deadline: 23rdJanuary 7) Alternative Designs Type of Jack Features Pros Cons Price (Average) Bottle Jack Steel 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 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. This escalates a problem when standard vehicles need lifting and there isn’t enough clearance. £21.
99 Exhaust Air Jack PVC/Polyester 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 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 £23.00 Floor Jack Aluminium 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 carried out 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. £122.04 8) Scissor Jack Head The scissor jack head varies from different shapes anddesigns, the scissor jack is mainly used for jacking up from the sill of thevehicle. However, as said above that some users avoid jacking up from weakstructures due to rusty sills or a weak structure. To avoid jacking up from thesills or to prevent the vehicle from sliding some research has been done toovercome these issues. One of the waysis to re-design the head of the scissor jack into a claw or an adjustable headwhich can be adjusted to the users need.
This will be universal, so it can bejacked up from the sills and other strong structures. The floor of the scissor jack will need to be improvedso it can prevent the vehicle from sliding. This can be done by having a rubberfloor pad for the jack or the structure of the floor can be re-designed.
Fig4.5Another improvement could be, having the scissor jackheads screw into the jack so they can be used for more than one option. Byhaving the head of the scissor jack screwed into the jack, it will improve thestructure of the jack. The rubber padcan also be fitted over the jack head to prevent the vehicle from sliding.
Thehigher the jack is lifted there is a greater chances of the jack the jacksliding or falling. Some design ideas have been shown above, the next stepis to create some drawings to get a visual idea of the design.Progression of scissor jacks Scissorjack (Mechanical) The scissorjack today is well-known jack used daily when needed.
They are the cheapest outof all the jacks. Vehicle manufactures use this jack into their vehicles as astandard feature along with wheel braces and various other items. These jacksare small, so they can be carried around unlike trolley/floor jacks. They arevery easy and simple to use. These jacks don’t need maintaining as much as thehydraulic jack due to it being a mechanical device. These jacks restrictlifting certain vehicles up due to the weight. Furthermore, as people got lazya new jack was invented which was an electric scissor jack powered by a motor.
Scissorjack (Electrical)Thisjack is an improved version of the scissor jack. This jack is manufactured fromheavy duty steel; a motor has been added to the scissor jack which means lessmotion is required. The electric powered jack has equivalent properties to thenormal scissor jack however this is quicker to operate and has a remote tocontrol the lift. This jack operates by a wire from the jack connected intothe vehicle’s cigarette lighter socket.
The electric scissor jack is powered by12-volt electricity provided directly from the car’s cigarette lighter portwhich means that no extra power pack is needed.