This jack is operated by turning the handle in a clockwise direction. The action of the screw then makes the load rise (Cleghorn, 2010). A research was carried out on the weights of most family cars to determine the maximum weight the jack can lift. The average weight of a family car according to the research is about 1660kg, much of this weight being on the engine side, about two thirds. The jack will support a load of up to 610kg. With a safety factor of 1.63, the maximum lift of the jack can be determined as follows:Maximum lift * how much weight = 610×1.63 = 994, which is approximately 1000kg at maximum lift.
The effort, which is applied through the handle in a circular manner, will greatly depend on the user. Women have found it a little hard to use due to the force required to turn the handle when the jack is under a load. In its performance, the jack is put under the vehicle in a fixed position within a minute. This, therefore, reduces the overall set up time required in case of a minor break down like wheel change. It has a height slightly less than 120mm making it very easy to be positioned under the vehicle. For most family cars, the clearance with the ground is about 120mm, this, therefore, means that the jack can be comfortably fixed under most family cars without straining it. With ram plunger as main components, this jack can provide a lift of up to 160mm off the ground making it very suitable for the intended group of vehicles. Typical jacks use a screw of pitch 4mm and handle of about 150mm, which translates to a speed of up to 100mm/s for toggle jacks depending with the amount of torque applied to the handle (Khurmi & Gupta, 2008). The jack is slightly less than 120mm; hence this is the height you need before you start jacking up. The minimum height to lift a car will be -120mm and the maximum being 160mm. The cost of manufacturing this jack is slightly less than $20 and this is reflected in its market price of about $20-$50 making it one of the most affordable in the market among products in its category. Since it uses a screw mechanism, it has got a great mechanical advantage, which means less amount of effort is required actually to lift large amounts of loads. With an efficiency of about 28%, this is one of the best jacks in its category. The users of this jack can be assured of their safety as it is self-locking. This means that the jack can rest comfortably under the load without the fear of getting trapped under the load (Hannah & Stephens, 1984). The screw cannot move backwards under in circumstances unless the user decides to do it. It weighs about 2.5-5kg, a very decent weight to carry around in most cars. Its maintenance mainly involves checking the conditions of the screw that wear out with time and also oiling.
For a screw jack, the mechanical advantage is given the distance through which the handle is turned divided by the height through which the load is raised.
M.A = Distance through which effort is appliedHeight moved the load = 2πdh
The velocity ratio can be given by the distance round the effort circle divided by the pitch of the screw.
V.R = Distance round the effort cirlePitch of the screw = 2πdP
Efficiency of a screw jack is the ratio between the input efforts applied at the handle to the amount of weight lifted. If p is the effort applied and w is the weight lifted then, efficiency will be given as η = PW which is in the range of 28%
The weights of screw jacks vary depending on the application. However, car jacks are much lighter and weigh about 5-7kg.
Auto hydraulic jack uses hydraulic oil, which is incompressible to transmit the effort power. It uses two pistons, with smaller piston acting on the bigger one to lift the load. The mechanical advantage of this jack is given as load/effort.
M.A = LoadEffort
The velocity ratio is given by, area of larger piston/area of smaller piston
V.R = Area of larger pistonArea of smaller piston
Its efficiency can be calculated as (output force/input force)×100
η=Force outputForce input×100%, which is in the range of 25-30%
The sizes of hydraulic jacks also vary according where they are used. They are generally much heavier than screw jacks. They can weigh up to 10kg In conclusion, for someone looking to buy a jack for their cars, I strongly recommend the toggle car jack. This car jack offers a lot more for the users in terms of safety, cost, size and maintenance while still outperforming other jacks such as the hydraulic car jack.
References
Brar, J. S., & Bansal, R. K. (2006). A Textbook Theory of Machines (in S.I. units): [for degree, U.P.S.C. (Engg. Services), A.M.I.E. (India)]. Bangalore, India: Laxmi Publications
Cleghorn, W. L. (2010). Mechanics of Machines. New York: Oxford University Press.
Gupta, B. V. R. (2011). Theory of Machines: Kinematics and Dynamics. New Delhi: I. K. International Pub. House.
Hannah, J., & Stephens, R. C. (1984). Mechanics of Machines: Elementary Theory and Examples. London: E. Arnold.
Khurmi, R. S., & Gupta, J. K. (2008). Theory of Machines: [a textbook for the students of B.E. / B. Tech., U.P.S.C. (Engg. Services) ; Section 'B' of A.M.I.E. (I)]. Ram Nagar, New Delhi: Eurasia Pub. House.
