Design and analysis of scissor jack final report 8 sem (1)
- 1. DESIGN AND Analysis OF SCISSOR JACK Presented by:- Rahmatullah 16MEB203 Muzeer Ahmad 16MEB366 Mohd Tayyab 16MEB314 Under the supervision of Dr. Najeeb ur Rahman
- 2. Introduction -what is scissor jack -what is the purpose Types of jack Nomenclature Components Study of selected parts of Scissor Jack -Power Screw -Trunion -top & bottom arm -top & bottom plate Calculation of Scissor Jack Static Analysis of Scissor Jack Outline
- 3. A mechanical device which is used to lift heavy vehicles, partially or fully in the air for breakdown and maintenance. Components of scissor jack are • One power screw • Two fixed nuts • Four links which is connected to nuts • Eight pins used to fixed that four links • Two rings provided at screw end and • load platform supported by upper two links. Introduction What is scissor jack ? What is the purpose ? • Used to lift up the cars while changing the tires during an emergency. • To raised and lowered Heavy equipment • By using it maintenance can be performed
- 5. Top plate Power screw Bottom link Bottom plate Rivets Trunion Nomenclature
- 6. Components a. Frame(top and bottom arm top and bottom plate) b. Power screw c. Rivets d. Trunion a. Frame: • The entire frame of the scissor jack consists of links (top and bottom), • Top frame • Base frame • The frame is manufactured by sheet metal processes and forming by medium carbon steel.
- 7. b.Power screws:(Component) A power screw is a mechanical device used for converting rotary motion into linear motion and transmitting power Applications: The main applications of power screws are as follows: 1.To raise the load, e.g. screw-jack, scissor jack. 2.To obtain accurate motion in machining operations, e.g. lead-screw of lathe, 3.To clamp a work piece, e.g. bench vice 4.To load a specimen, e.g. universal testing machine.
- 8. Types of screw threads used in power screws are 1. Square threads: Power transmission in either direction Maximum efficiency and minimum efforts. Employed in screw jacks and clamps 2. Acme threads: Modification of square thread Efficiency is lower than square threads Easily manufactured 3. Buttress Thread: Used when large forces act along the screw axis in one direction only. High efficiency . Ease of cutting like acme threads. Strongest thread of all Forms of Threads:
- 9. • A rivet is a permanent mechanical fastener. • Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. • On installation the rivet is placed in a punched or pre-drilled hole, and the tail is upset, or bucked (i.e. deformed) • It is more reliable. c. Rivet:(Component) d. Trunion: • same as nut is a threaded fastener for joining two threads.
- 10. Scissor jacks advantages: a. The jack is light and compact. b. Making it easy to lift any size vehicle. c.The jack’s lightweight design makes it user friendly for people of all strengths and physical abilities. d. A scissor jack will not suddenly “leak” and drop down like some hydraulic jacks. e.The precision of these jacks allows for extremely precise lifting capabilities. Stress Calculations: On screw, there are mainly 6 types of failures.They are as follows:- I) For screw body Tensile failure Buckling failure Twisting failure II) For screw thread Crushing failure Bending failure Shear failure
- 11. Scissor Jack design for some specific range of weight up to 2000 kg of cars as some of them mention below s.no company Name of car Varient/model Gross weight(kg) 1 Audi Audi R8 1895 2 Ford ford Freestyle freestyle 1210 3 Maruti Suzuki swift AMT ZDI Plus (Diesel) 1405 4 Maruti Vitara Breza ZDi Plus AMT Dual Tone (Diesel) 1680 5 Toyota Glanza V CVT (Petrol) 1360 6 Tata Tiago Z plus 1200 7 Renault Duster E KVN(Diesel) 1349
- 13. Design Calculations: 1)power screw: Material Selected -Medium carbon steel Length of each arm = L1 =L2 =L3 =L4=170mm Length of the power screw = (w1+w2+w3) = 380mm w1= w3 = 160 mm, w2 = 60 mm Maximum lift of the jack = (h1+h2) = 310 mm q is the angle made by link with horizontal when jack is at its lowest position cos (q) = 160/170 = 19.74˚.Let the weight of car =2 ton,then weight acting on rear axle= 40%2ton=800kg,therefore weight on front axle=60%2ton=1200kg, weight on each wheel of front axle=600 kg. W = (load * g) = (600*10) = 6000 N The tensionT acting on the power screw is shown in the above Fig
- 14. Formula Used- Total tension = 2*T = W/tan (q) Let dc be the core diameter of the screw. But load on the screw is Load = (π/4)* dc 2* st So, 2*T = W/tan (q) = (π/4)* dc2*st Outer diameter, do=dc + P Mean diameter, d = do – P Check for self-locking tan (a) = Lead/π*d; a=helix angle Lead L = 2*P; since the screw has a double start square thread. tan (a) = 2*p/π*d
- 15. Coefficient of friction; μ = tan (f) = 0.20 Condition for self locking f > a Effort required to support the load = 2*T tan (f+a) Torque required to rotate the screw = effort *d/2 = 16*T/ (π* dc 3) But tensile stress st = 2*T/ (π/4) * dc 2 st max = st/2 + ((st/2)2+ 2 ) Maximum shear stress max = ((st /2)2+2 ) If the maximum stresses st max and max within the safe limits, the design of double started square threaded screw is satisfactory.
- 16. POWER SCREW
- 17. Trunion Material Selected Cast iron Let n be the number of threads in contact with the screw assumed that load is Uniformly Distributed over the cross section area of the nut. Allowable Bearing pressure between the threads (Pb) = 16N/mm2. Pb = (2*T)/((π/4)*(do2-dc2)*n) Nut thickness = n*p Width of Nut b =1.5*do Pins in Nut Design calculations Let d1 = diameter of pins in the nuts Since Pins are in double shear stress Load on pins = W/2 = 2*(π/4)*d21*
- 18. Trunion
- 19. Top Arm Material selected Medium carbon Steel Design calculations σt = σyt/F.S σc = 1.25*σt Cross section area (A) Moment of Inertia Ixx , Iyy Radius of Gyration Rx, Ry Rankine’s constant (a) =1/7500 Ends are hinged (Leff = L) Pcr rankine crippling load in vertical plane σc= crushing stress Pcr = (σc*A)/ (1+a*(L/ Ry)2) Pcr in horizontal plane Pcr = (σc*A)/(1+a*(L/2*Rx)2) If Buckling load is more than Design load the dimensions of the link safe.
- 20. Top Arm
- 21. Bottom Arm
- 22. Top Plate Material used Medium carbon Steel Design calculations Moment, M = (p*l)/4 Z = (b*h2)/6 σb = M/Z If The permissible stress for Medium carbon steel is greater than σb. The top plate design is safe
- 23. Top Plate
- 24. Bottom Plate
- 26. Scissor Jack Final Render Image
- 27. STATIC ANALYSIS OF SCISSOR JACK
- 31. CONCLUSION In this project, a scissor jack is modelled in SOLIDWORKS and a structural analysis of scissor jack with a force of 6000 N is also performed in SOLIDWORKS software. The Resultant Displacement, Equivalent Strain and Von-mises stress of the scissor jack is analyzed. From the results, it is observed that the Resultant Displacement, Equivalent Strain and the Von-mises stress of the scissor jack are within the limits. Therefore, modelled Scissor Jack is safe to use and has long life. In future scope, different types of jacks can be modelled by taking different materials and by giving different loading conditions for structural analysis.
- 32. References: Design Data Handbook for mechanical engineers, K. Mahadevan. Mechanical Engineering Design Joseph Edward, Shigley. Mechanical Design Engineering Handbook, Peter R. N. Childs. Materials Selection in Mechanical Design, Michael F. Ashby. Detailed Mechanical Design: A Practical Guide, James G. Skakoon. INPRESSCO-GERNAL ARTICLE; E-ISSN2277-4106, AUTOMATED CAR JACK. Academia.edu/6167889/Modification_of_the_Existing_Design_of_a_Car_Jack. http://en.wikipedia.org/wiki/Jackscrew Powerjacks.com/downloads/Design%20Guides/PJLMPT-02/S1-Screw-Jacks PJLMPTDG- 02.pdf Design and fabrication of motorized automated object lifting jack; IOSRJEN.ISSN (e):2250- 3021. http://www.ijceronline.com/papers/Vol4_issue07/Version-1/A0470101011.pdf IOSR Journal of Engineering (IOSRJEN) www.iosrjen.org, ISSN (e): 2250-3021, ISSN (p): 2278-8719, Vol. 04, Issue 07 (July. 2014), ||V1|| PP 15-28.
- 33. THANKS!!