Scissor Jack Design ProjectGE 410 Fall 2005 Jim Ramirez David Hettinger Instructor: Hall 12/05/2005 ii . The power screw design of a common scissor jack reduces the amount of force required by the user to drive the mechanism. Most scissor jacks are similar in design. is made of the common c-shape. The manufacturability of the proposed scissor jack lowers the cost of production. This eliminates the need for machined power screw sleeves. consisting of four main members driven by a power screw. Each member. a unique design of a scissor jack is proposed which is very easy to manufacture. In this report.ABSTRACT Scissor jacks are simple mechanisms used to drive large loads short distances. which connect the four members and the power screw together. including the power screw sleeves. . 11 Appendix B: Calculations and Assumptions for Components 2. 9 Conclusions and Recommendations………………………………………………………. 6. 5 Table 1: Design Criteria……………………………………………………………………. Bevel Gears & Screw Jacks Linear Guides & Rails Ballscrews www.wmh-trans..pvp-software.. and 8……………… 12 Appendix C: Calculations and Assumptions for Components 3 and 7……………………. 4.de GD&T & Tolerance Analysis Leading Edge Training. iii Introduction………………………………………………………………………………… 4 Proposed Design…………………………………………………………………………… 5 Figure 1: Labeled Scissor Jack Design……………………………………………………. 13 Appendix D: Calculations and Assumptions for Components 1 and 5……………………... 14 Appendix E: Calculations and Assumptions for Component 9……………………………. i Abstract…………………………………………………………………………………….uk best italian brands direct elevators supplier spare parts.com PVP Software Online-Calculations and Software for Engineers and Designers www. 16 Appendix G: . ii Table of Contents…………………………………………………………………………. Books & Software – Get it Right!™ AdvancedDimensionalManagement... 15 Appendix F: Calculations and Assumptions for All Pins…………………………………. 10 Appendix A: Drawings……………………………………………………………………...co.Ads by Google WMH Leadscrews & Gears Racks . Consulting.liftexport.special projects www.com TABLE OF CONTENTS Title Page…………………………………………………………………………………. Calculations and Assumptions for Crank Handle…………………………… 17 Appendix H: ANSYS Force Analysis……………………………………………………. Our goal in this project is to design an efficient scissor jack capable of raising a 2000lb load.. scissor jacks allow us to raise vast loads using only a fraction of the force ordinarily needed. The design itself has gone through multiple stages of development.. and operate with a factor of safety of n = 2 using standard mechanical design methods for all components. We have taken several possible failure modes into account and are confident that our design is efficient and safe. With the power to magnify input forces. . the jack will be manually operated and have at least 7 inches under load. 18 iv Introduction The most basic scissor jack design is truly engineering at its finest. have a removable crank handle. As a screw-driven mechanical system. The design will be transportable and storable. Members 1 through 8 are all primarily cshapes with ideal pin connections. four connection members. The following is a summary of the design features for our proposed scissor jack. . All members are 50 ksi strength steel with the exception of the rubber grip on the crank. a power screw and a crank.Proposed Design Summary The scissor jack design. consists of four main lifting members. shown in Figure 1. The power screw is single threaded with a collar at the member 3 connection. Members 1 and 5 both have additional details to account for the contact surfaces. Details of the design specifications and failure criteria can be found in the attached appendices. The lifting members are greater in length and are subjected to compression. The bending moment from the power screw creates tension on the inner edge of the sleeve and compression on the outside edge. The web of the members is cut out near the pin connections to allow proper serviceability of the scissor jack at its maximum and minimum heights. The flanges of the channels are to wrap around the flanges of the sleeve members. . Tension along flanges on the inside prevents the possibility of localized bucking in the flanges from compressive forces. Lifting member flanges on the outside of the sleeve flanges is to compensate for slenderness ratio by increasing the moment of inertia of the lifting members. This is so the flanges are subjected to tension instead of compression. Members 4 and 6 have ideal gear connections to balance the load between the left and right side.Main Lifting Members: These members are made from simple c-shapes. Sleeve Members: The sleeve channels are to open inwards as shown in Figure 2. Figure 2: Orientation of Sleeve Channels to Prevent Localized Buckling. Additionally. shown in Figure 3. the threaded sleeve section is to have additional thread surface area. These additional threads safely transmit the stress from the power screw to the . The collar transmits the stress safely to the c-shape. The primary raising method is through the power screw’s hook coupling which is common to most scissor jacks. The Power Screw: The Power Screw is single threaded with a collar on the side in contact with Member 3. The collar on the power screw doubles as a bolt with a hexagonal head. The collar is assumed to be frictionless and the power screw has been designed to be selflocking. Member 5 has an attached plate atop to provide sufficient contact area. Figure 3: Addition to C-Shape to Provide Adequate Threaded Area. The criteria are organized by failure mode with the applicable members identified. Design Criteria The design checks used in the design of the scissor jack are summarized in Table 1. Contact Members: The members that make contact with ground and the service load are members 1 and 5 respectively.sleeve. Incorporated into our proposed design is an option for a secondary raising method. In a situation where the main hook coupling becomes inoperable. Threading the thickness of the web of the channel would not be sufficient for reasonable power screw diameters. a standard socket wrench can be used on the hexagonal nut to raise the mechanism. This addition is only made on the threaded sleeve section and not on the collared sleeve section. This causes stress concentrations which can damage the underside of a car. Member 1 has additional flanges to provide a stable base for the mechanism while servicing the load. Most scissor jacks have ridges which lower the area of contact. Table 1: Design Checks for Different Failure Modes of Members . . Since only c-shapes are utilized. however. Also. Unique to our design. . is the manufacturability of our design. which is much simpler. Similar to others. when compared to similar scissor jack designs that perform equally as well. bulk material can be more efficiently purchased and used. Therefore.Conclusion and Recommendations Our proposed design is similar to common scissor designs in some aspects. our proposed design is recommended for its manufacturability and lower cost. less machining is required since there are no complex sleeves for the power screw. Only simple attachments which can be welded on are proposed. our proposed design can safely raise a load of 2000 lbs to the required heights with relative ease on the user. but also advantageous in others. Appendix A: Drawings Note: All Drawings are in Inches . . . . . . . . . . **See ANSYS printouts in Appendix H: All force analysis support can be found there *See “Appendix C Support” for supporting calculations (not computer-generated) . . . . . Appendix H: ANSYS Force Analysis Note: Power Screw is composed of members 9 and 10 in ANSYS repor .