INTRODUCTION
Background
A car jack is a device that lifts vehicles off the ground so that maintenance and repair can be carried out underneath the car. Available car jacks, however, are manually operated. They require much laborious physical effort on the part of the user. Such jacks present problems for the handicapped and elderly.
Aim of the design
The aim of this study is to deliver a high an efficient car jack to the end user. This project has been motivated by the need to determine whether the introduction of automation and keen material selection in a jack saves time and improves on its performance and to what extent does operating it remotely reduce accidents and make it safer for users. These results will incorporate into the final design.
- Clients brief and research of the problem domain.
The clients expect a car jack that is safe, easy to use, fast, and portable (relatively light). Minimal maintenance requirements, precision in positioning, heavy duty, uniform lifting speed, ease of installation, low noise levels, long life, corrosion resistant, safely self-locking property, small/compact in size (GILLIS, 1991). It is justifiable to undertake this design study because the product will be directly and immediately be consumed by the society.
The different operation procedures of the different jacks provide the different challenge to the users (GILLES, 2012).
- PDS (product design specification) for a suitable car jack
- The load to lifted by the car jack is estimated as
Research types / weight of cars.
The average weight of the various family cars is 1660 kg. Two thirds of the total car weight is on the engine side, and it is shared by two tyres, therefore, the maximum load that the jack will hold will be 610 kg (KEROUAC, 1995).
Max lift – how much weight to lift = 610×1.63 = 1000 Kilograms
1.63----safety factor
- Performance: The jack should be fixable in position under the vehicle within one minute; this means that there is reduced set up time and overall time of changing a tyre.
- Size: The jack should be slightly less than 120mm in height so as to be easily positioned under the vehicle because the minimum clearance for the common family size cars is 120mm. It should provide a total lift of about 160mm from the ground. Therefore, the ram plunger and the saddle should be able to rise by more than 10mm. Therefore, it should be more than 10mm.
How high you need to before you start jacking up. = 120 mm high because the jack is slightly less than 120 mm in height.
Minimum height to lift the car – 120 mm
Maximum height- 160 mm
- Cost: Manufacturing charge is less than $20.
- Quantity: Mass produced to satisfy the available market, therefore, it should have minimal steps of production and utilize the minimum of skilled labor.
- Maintenance: Minimal maintenance to save on money. Characteristics like automatic oiling, rigid body and strong parts will reduce need for regular maintenance
- Finish: Corrosion resistant material parts to ensure continued usability in diverse environments for longer life.
- Production methods and materials: The material used for fabrication was mainly steel plates and iron rods. The jack is to be batch produced; therefore, it should have few production steps.
- Weight – Maximum of four kilograms. This is combined with lower cost to go with the reduced weight.
Mass of jack: - 4 kilograms
3. IDEA GENERATION USING ENGINEERING PRINCIPLES.
According to (ERJAVEC, 2010) it is evident that the customers requires a car jack that is cheap, self locking, reliable, long lasting, and corrosion resistant. The client’s needs are listed and potential interventions explained
- Full or semi automation of the car jack to make it easy to use. - Employment of gears and DC motors that would be switch controlled. Gear would serve in speed reduction and torque capacity increase.
- Safety of the jack is determined by its ability to self lock. The used screw will be self locking, when the friction angle will be greater than helix angle or if the coefficient of friction is greater than tangent of helix angle i.e. μ or tan φ > tan α. The screw would also ensure to a uniform loading speed to avoid impulse force on the car body.
- Weight of maximum four kilograms for easier portability. This would require selection of light, strong frame and body material. An example would be using cats iron for the body.
- Cost – The cheapest design will be selected.
DESIGN STAGE
- SELECTING A PLAN SOLUTION
. In this section, the four designs will be analyzed for operation and possible selection for final design.
- Bottle neck Hydraulic car jack
- Wedge type car jack
- Automatic toggle jack
- Automated Screw jack
DESIGN ANALYSIS
- AUTOMATED SCREW JACK
The improvements to make in the screw jack will be based on the client’s requirements.
http://grabcad.com/library/screw-jack--46
Materials and Manufacturing process
According to (Gray, 2007) the casting process will be used to manufacture the frame, cast iron will be used. This ensures power of the body. FG200 cast iron with UTS of 200N/mm2 is preferred because it contains carbon precipitate to form graphite flake, graphite is soft and, therefore, helps in resisting the compressive load.
Screw
Selected 22 mm diameter to 100mm (Square power screw) and 24mm diameter to 100mm (for trapezoidal power screws). A small applied force is used to raise or lower a larger load. The screw will be used to provide strength, and it should resist wear, 25c12s14 unalloyed free cutting steel is selected 0.25% carbon, and 0.14% sulphur, 1.2% manganese with a tensile strength of 560 N/mm2.
Bevel gearing and Dc geared motor- Automation of the screw jack plane is made through the introduction of a motorized Dc motor and bevel gearing.
Toggle switch- to stop or start the screw jack operation at any desired point.
Cost and Materials analysis
Maintenance practices
- Topping up or replacement of oil in the gear box.
- Oiling the moving parts
- Brushing off metal chips from screw
- Replacement of broken or bent handle
- AUTOMATED BOTTLE NECK HYDRAULIC CAR JACK
This is an analysis of the current hydraulic jack around the client’s demands. It is slow in operation, since it is manual and it is not also safe (Gilles, 2012). This proves a hard task especially to the handicapped people who are unable to perform this task. The Jack is also pressured dependent and, therefore, depends on the maintenance of pressure to self lock.
(Gilles, 2012)
Therefore the following interventions are recommended for this jack
Gear - a simple reduction gear train and a crank operation to control the lift of the jack. In this project I aim for the following;
Controlling the jack remotely.
The motor may be powered by the vehicle battery or the battery can be incorporated in the system. An electric switch will be connected to the motor to control it from a distance.
Materials and their cost analysis
Maintenance practices
- Topping up or replacement of oil in the gear box.
- Oiling the moving parts
- Checking the hydraulic oil to ensure no seals.
- WEDGE TYPE CAR JACK
Given the advantages of wedge car jack and the customer’s requirements, we considered its design as a possible select design. The wedge type design has to be cheap, light, portable, and operated with minimum effort. It should also provide an appropriate lift with minimum effort.
Special improvements design emphasis was to be laid on the angle at which the various motions and components are to take. Automation of this jack will be made with the introduction of a 12 V DC motor (Erjavec, 2010).
(Erjavec, 2010).
Materials
- Body
- Sliding wedge
- Slotted screw
- Driving nut
- Handle
General equations for estimating the diameters and strength of the screws that should be used for lifting this equivalent car load are given. Substitute in the equations
P - μN1 Cos θ - N1 Sin θ - N2 = 0
μN1 Sin θ + N2 – N1 Cos θ = 0
N1 Sin α - μN3 – W = 0 N1 Cos α - N3 = 0
The client’s requirements are
Upright vertical lift head (α = 450)
Minimum length in the transverse direction (θ = 450)
Coefficient of friction – μ- (μ=0.2, contact between two metals)
Safety factor 1.5
W=7982 (vehicle load x 1.5)
Finding P = 5096N (point load on screw)
The critical load that can cause breaking of the screw
P=W (π E(D^4 – D^4 ))/256L
The diameters will be
Do = 35 mm and
Di = 30 mm
Cost estimation
Maintenance practices
- Topping up or replacement of oil in the gear box.
- Oiling the moving parts
- Cleaning of wedge, to remove metal chips on wedge
- Replacement of worn out handle.
- AUTOMATED TOGGLE JACK.
.
(Kerouac, 1995)
The operator turns the bar in a clockwise direction which makes it rise. When the screw lifts the load, the platform placed above it will similarly raise. According to (Kerouac, 1995) consider vertical direction to avoid buckling of links, the edges are assumed hinged; this allows the use of the Rankine-Gordon formula. The design load, is Pcr= F.O.S X F
Cost estimation
Maintenance practices
- Topping up or replacement of oil in the gear box.
- Oiling the moving parts
- Cleaning of foot to remove soil dirt
DESIGN COMPARISON AND SELECTION
Selecting the appropriate plan
Design analysis was done on the production cost of each design, its construction material availability, and potential for mass production
The automatic hydraulic jack is selected on the following Basis
The automatic hydraulic jack is selected. The design is selected on the advantage of lower cost, availability of production materials and ease of manufacturing the jack.
AUTOMATED BOTTLE NECK HYDRAULIC CAR JACK
The following is the design selected for fabrication, development and mass production.
(Erjavec, 2010), (Gilles, 2012).
Components
Motor
In this project, I will use a high torque mini12V D.C gear motor that runs at speed of 200 r.p.m. It is 100mm in length and 50mm diameter and has a spindle diameter of 8m
Crank action Analysis
The actual length of the con rod (l) depends on the ratio of l / r, given r is the crank radius. The smaller length will reduce the ratio l / r. which increases the angularity of the connecting rod that increases the side thrust of the piston rod. The greater length of the connecting rod will increase the ratio l / r. This decreases the angularity of the connecting rod. Hence, a compromise is made, and the ratio l / r is kept as 4 to 5.
For maximum efficiency, the diameter of the crank wheel should be equal to or slightly higher than the pumping piston stroke. The crankshaft length should also be slightly larger than the crank wheel diameter (Erjavec, 2010).
Piston stroke=50mm
Diameter of crank wheel=60mm
Length of connecting rod =60mm
Reduction gear ratio
The motor runs at speed of 200 r.p.m. We, therefore, use a reduction gear ratio of 3 to reduce the speed to 66.67 r.p.m (1.11≈1 revolutions per second). This will translate to a piston stroke of 1 per second (which is good enough). Therefore,
PCD of bigger gear =90mm
PCD of smaller gear=30mm
Centre distance =60mm
The motor spindle, which at its end is a small gear, and the axle that carries the larger gear and the crank will both are held and run the support frame by means of bearings. The crankshaft will be connected to the pumping piston using a coupling.
Conclusion
This project will help solve many car users’ problems especially the handicapped and make it safer for everyone’s use. It will also help save time in providing the needed service at a reduced effort.
The project has got a limitation in that, after lifting the load; one has to open the release valve manually to lower the load. However, this limitation can be improved provided there are more funds allocated to it but that will make it more expensive.
References
CAMBRIDGE EDUCATIONAL (FIRM). (2004). Auto shop safety. Lawrenceville, NJ, Cambridge Educational.
GILLES, T. (2012). Automotive service: inspection, maintenance, repairs. Clifton Park, NY, Delmar, Cengage Learning.
ERJAVEC, J. (2010). Automotive technology: a systems approach. Australia, Delmar Cengage Learning.
GILLIS, J. (1991). The car repair book: the essential consumer's guide to car repair: simple and straightforward information with step-by-step instructions and diagrams. New York, N.Y., HarperPerennial.
KEROUAC, J., & CHARTERS, A. (1995). The portable Jack Kerouac. New York, N.Y., U.S.A., Viking.
GRAY, M. E., & GRAY, L. E. (2007). Auto upkeep: basic car care, maintenance, and repair. New Windsor, MD, Rolling Hills Pub.
