1) Introduction A jack is a great option in a vehicle for many reasons. Itcould be used for as simple as a tire change on the roadside, or carrying outmaintenance on the vehicle from home. The jack is used to ensure the vehicle islifted to a suitable height, so work can be carried out. The purpose of thejack is to lift a heavy object or a vehicle in this scenario. As safety is akey aspect, when a heavy object is being lifted there are a few things that areneeded 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, thecondition of the jack and the vehicle should be checked in terms of no damageto the jack and any corrosion or weak spots on the vehicle. After, suitable research acquired the scissor jack is proneto failure due to certain aspects. The aim of the project is to improve ordevelop a way to reduce the number of scissor jacks failing. This report willinclude some background research to understand what scissor jacks are used forand how they are operated. The key topic is the causes of failure for thescissor jacks. Also, some aspects include lack of use and corrosion.
Some jackshave been used incorrectly, for example many scissor jacks have markings andstickers to represent the weight, some of these don’t which mean that when anincorrect jack is used for the wrong vehicle it cannot withstand the weightwhich results in failure.Many manufactures provide breakdown tools with their vehiclessuch as jacks, wheel braces and spare wheels. This report will be discussingsome aspects of research that has been carried out with regards to safety. The report will also cover some advantages and disadvantagesof certain jacks to recognise various jacks are needed in different sectionsaround a vehicle. Furthermore, alternative designs have been provided to comprehendthat there are innovative designs evolving which are reducing the cost in theproduction, ease of use and mainly to be safer. The materials for each jackwill be provided to initialise the sequences of development in the material.Finally, the testing procedure will be carried out along with the methodologyof how each step will be taken with regards to the jack testing.
Fig 2.0 2) Literature ReviewScissor Jacks’The firstautomobile jack was patented in 1918 by Miller Falls Automobiles in MillerFalls, Massachusetts’. Scissor jack is used to lift heavy objects, or amore 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 orjust to lift a heavy object around the workshop. The average small jacks such asthe 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 liftingcapacity. Scissor car jacks use manual force for lifting whereas some useelectrical powered motor to do the lifting. The scissor jacks have a slot whereit fits onto the sill of the vehicle to enable it to lift. Some scissor jacksare designed to be only lifted from the sills and some can be lifted from otherplaces. A scissor car jack is designed by bolting pieces of metal elements intoa kite shape with hinges and a screw connecting the opposite sides of thediamond. When the screw is turning with the spanner/hook it will raise thediamond or lower it depends on the direction of the turn. The scissor jackcomes as a standard feature for majority of the vehicles, as a kit with thespare will and various other accessories.
However, large vehicles such astrucks and high clearance vehicles with integrated jacks or heavy-duty jacksdue to the size and weight. This jack operates by transferring rotationalmotion into linear, so this means the turning of the screw causes expansion orcontracting of the kite shape, which then translates to an upward force ordownward, when the jack is placed between solid grounds and jacked to thevehicle chassis or sill.OperationWhen the screw section is turned, two ends of the diamondmove closer together. This occurs due to the gears/ threads of the screw arepushing the arms, the size of force is being applied is multiplied. Not muchforce is required when the crank/hook is turning the gears yet the action thatis being caused results in the brace arms to slide together. This procedurehelps the arms extend upwards to lift the object/vehicle. UsageThe uses of the scissor jack can be simple as changing awheel 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 stands will need to be 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) DesignThe scissorjack head varies from different shapes and designs, the scissor jack is mainlyused for jacking up from the sill of the vehicle.
However, as said above thatsome users avoid jacking up from weak structures due to rusty sills or a weakstructure. To avoid jacking up from the sills or to prevent the vehicle fromsliding, some research has been done to overcome these issues. One of theways is to re-design the head of the scissor jack, create a claw head whip gripagainst certain objects or an adjustable head which can be adjusted to theusers need. This will be universal, so it can be jacked up from the sills manyother places. The floor of the scissor jack will need to be improved so itcan prevent the vehicle from sliding.
This can be done by having a rubber floorpad for the jack or the structure of the floor can be re-designed. Fig4.5Another improvement could be, having the scissor jack headsscrew into the jack so they can be used for more than one option. By having thehead of the scissor jack screwed into the jack, it will improve the structureof the jack.
The rubber pad canalso 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 step is tocreate some drawings to get a visual idea of the design.Progression of scissor jacks Scissor jack (Mechanical) The scissor jack todayis well-known jack used daily when needed.
They are the cheapest out of all thejacks. Vehicle manufactures use this jack into their vehicles as a standardfeature 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’tneed maintaining as much as the hydraulic jack due to it being a mechanicaldevice. These jacks restrict lifting certain vehicles up due to the weight.Furthermore, as people got lazy a new jack was invented which was an electricscissor jack powered by a motor.
Scissorjack (Electrical)This jackis 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 fromthe jack connected into the vehicle’s cigarette lighter socket. The electricscissor jack is powered by 12-volt electricity provided directly from the car’scigarette 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 bemade on computer aided design or even on ansys.Ansys Once this is done thefile will be converted onto ansys to enable it to run.
The jack will go throughthe testing procedure which will involve a load being set, which will representthe weight of a car. On the jack, certain points must be fixed during the testto demonstrate that the jack is not moving as it’s under load. The test willbegin and create a set of results which depend on the jack material and variousother aspects. The results gained such as stress, strain.
Fatigue and fracture mustbe calculated so they can be used later for validation.DrawingsSome drawings will be made to interpret modern designskeeping in consideration the scissor jacks.Each part of the jack will then be analysed to determine eachcomponent weak points.
Calculations will be carried out for each componentindividually. The weakest component will then be modified to overcome itsweakness to enable a strong structure.As the main goal is to analyse a scissor jack, the materialand shape will be taken under consideration. TestingThe next test will involve an actual jack being tested. Ahydraulic press will apply a load to the scissor jack.
This is like the ansystest where the load will represent the wright of a vehicle and pushed againstthe car. The procedure will be carried out with various loads to representvarious vehicles. At a point, the jackwill have fractured or have some signs of fatigue in the material.
The resultsgained from the jack will be then calculated to support the ansys. CalculationsThe final test is hand calculations; these will validate bothtests 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. Itwill 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 test consists of four materials, this will determine ifthe final project design will be from aluminium, steel, mild steel and caststeel. The rough of idea of the 3d model will be then improved.5) Materials Structural steelAny jack that is made acquires components made from steel,they may have been assembled with an aluminum structure, but steel is required forthe fixings, pins and many other components.’While aluminum tends to win out on weight, steel jacks tend to acquire out oncost. Steel jacks are normally always a tiny bit more expensive on ordinary fora 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 scissorjacks 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 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 very light inweight and it is one of the materials that doesn’t rust. The focus of having afloor 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 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 isdue to the misconception of aluminium being soft and weak in various otherproducts. ‘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 and lacquer to improve its properties; make it standout from other jacks.This material is also recyclable which means that any scrapaluminium 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 between 70and 700 MPa. Aluminium doesn’t get brittle at low temperatures however itincreases its strength. Aluminium alloy can be attached to other aluminium productsor to various materials by the following methods: welding, brazing, soldering,bolting, riveting, clinching, crimping, clipping, adhesive bonding andslide-on, snap together or interlocking joints. Mild steel,and cast steel will go through material testing 6) 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, 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. 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 (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. £122.04 7) Causes of failure SlidingOne of the common reason of this jack is prone to failure isbecause of the head of the jack.
The head is shaped as a sphere, so when thejack is lifted elsewhere apart from the sills, due to not being stable thevehicle begins to slide. To overcome this problem the jack head will have to bere-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/weak sillswhich mean users will prevent jacking from these areas.Below is an incident where a scissor jack was used and slidof the vehicle.
‘He said hehad jacked the passenger’s side tire off the ground with a scissor jack, andwas looking to “find a good jack stand point.” The car shifted a bit’, DavidTracy 2016. This article suggests that a vehicle was jacked using ascissor jack and slid off. Fig3.
0 Wear & Tear Safety of the operationChocks- wheel chocks can be used to prevent the vehicle fromrolling. The chock fits in front and behind the wheel, this is made from athick polymer. As, the vehicle is being lifted from one side using the scissorjack the load is increasing on the opposing side which can surge the vehicle toroll. The vehicle must be put into gear as well as handbrake must be applied.Surface- As thescissor 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- With anytype of lifting operation whether it’s a vehicle or a heavy object axle standsare a must. They are placed on the chassis of the vehicle during lift or theload of the jack can be released onto the stands for safety precautions. 8) Current Progression Research- a scissorjack has been chosen to analyse and recognise the causes of failure.
The designand strength will be analysed so alternative materials alternative materialscan be used. The scissor jack is a mechanical device that is failing a lot morethan other jacks. The research includes different jacks that have been developingover time. The research has created the foundation of the project, by providingsome information on the scissor jack. The background information helps thereader understand what the report is about. Ongoing CAD- A 3D modelhas been designed to represent the scissor jack. The jack is consists of 6parts. The design of the scissor jack is to get a rough idea also it will beused on Ansys to gain some results.
Completed Jack- The physical testing involves a jack being tested on apress. A scissor jack has been brought for the testing. Designoptions – A few design options have been developed regarding thescissor jack head, the shape and the material.
The standard 3d design will go through Ansys first to see the resultsand then the improved design will be tested. 9) Further Plan/Objectives Ansys- As the 3Dmodel is made, the testing will need to be done to see the maximum stress andstrain. Deadline: 18th January Jacktesting- 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 jackcannot withstand the load.
This procedure will result in fracture which willthen 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
