Homework answers / question archive / Table of Contents Problem Statement & Introduction………

Table of Contents Problem Statement & Introduction………

Writing

Share With

Table of Contents Problem Statement & Introduction………...……………………….………...……………2 ? Functions and Constraints Design & Approach………………………….………….…….………….….……………...3 ? Outlines ? Budgets Testing Plan & Results………………………………………....………………..............4-7 ? FEA ? Real-Case Scenario Design Changes……....……………………………………..…………………...………8-9 ? Beta Revision Appendix……………………………………………………….....………………..…...10-17 ? ? ? ? Figures BOMs Units Miscellaneous Problem Statement & Introduction Most of today's standard automobile portable jack systems by themselves are unstable and unreliable. The use of hydraulic fluids to lift a car seems inadequate as it requires huge maintenance, extremely expensive to maintain, and could possibly lead to death. The use of hydraulic fluid pumps requires daily maintenance and flush after a few months of use. This uncertainty creates an unsafe condition when doing long, heavy maintenance. In addition, specialty cars need a low-profile lift system to get underneath the lift point of a car. Not only do we want to design a portable lift system that will fix those issues, but also versatile and affordable enough for most DI-Y consumers. Functions Lift 1500 lbs. Constraints Need Lock Bar in place before working underneath the car All Electric Lift System Need to lift the Lock Bar up before retracting Adjustable Lift Support Slow actuator extension and retraction 1 Safety Bar to Support Weight Low-Profile Actuator will only lift the car and not provide much support after the lift Under 8” height Design & Approach The lab instructor decided that we should design the top and bottom rack, including the Lock Bar, without the electrical components. The manufactured portion of the design also provides the most feedback and will provide possible iterations that will need to be made. Since those are the main functions of our assembly and the most critical parts of our design, we set up the manufacturing approach and methods below: ? ? ? ? Outlines Cut top and bottom racks using a 45 degree angle cutter With the same angle cutter, cut short brackets to connect the racks together. ? Use calipers to measure the ends to the holes. Use the drill press to make 0.5 in. holes on the racks. ? Use Tap to make the hole. ? Use ? drill bit to make the hole. ? Use ½ drill bit to make the hole. ? Use the chamfer to make the hole smooth. Welded the racks together. ? 45 angle degree weld. 2 ? Assemble the parts together with screws and nuts. ? Run Finite Element Analysis. ? SolidWorks ? Test the assembly in a real-case scenario. ? Lift system on the whole assembly. Budgets Our total budget for the materials were: $490(See Appendix: BOMs). We ordered the parts on February 15th, 2021 and received the parts on March 14th, 2021. Since Metal Depot was the cheapest, we ordered our raw materials there. Our raw materials are mainly hot-rolled steels in square and rectangle shapes. We bought pins and nuts from Ace Hardware. Testing Plan & Results Our testing plan originally required physical testing of our two critical components, our top rack and Lock Bar. We were unable to complete any physical testing methods in-house because of lack of available resources and of safety concerns. Our product is meant to experience loads of up to 1500 lbs., which can be dangerous amounts of force in an unprepared testing area. Thus, In this section, finite element analysis will be provided, along with real-case scenario testing outside of the school zone with top and bottom rack assembled, including the Lock Bar. Finite Element Analysis The analysis shows that while the Lock Bar should be able to handle the full load associated with the product, the top rack will fail in a worst case scenario. The Lock Bar will only deflect 0.0026 in. total. This was a non-linear mechanical analysis that was made to ensure that the Lock Bar would not fail due specifically to buckling. As this is a long thin member, buckling is the most likely cause of failure for this critical component. 3 This picture displays the result of the stress analysis. The analysis shows that the highest stress on this model is less than 3,000 psi, which is a much lower stress than the yield strength of the material. These two analyses together confirm that the Lock Bar should not fail due to buckling in compression. The top rack analysis shows that the rack will fail in multiple scenarios. The first scenario is with the Lock Bar not installed with 1500 lbs. on one point. This is the worst case scenario for the product in which a vehicle tilts onto a single outer edge of the lift and the Lock Bar is not installed to help support the load. This picture of the deformation shows that the rack will displace almost 4 in. under the load that is being applied to it. This is a lot of deformation and could lead to injury for users should it occur. This shows the highest stress area in the bearing surfaces at more than 77,000 psi. The yield strength for this material is 72,000 psi. These areas will yield, and this will cause the end of the top rack to sink permanently to the loaded side. The ultimate strength for this material is 87,000 psi, so at least the failure should not be catastrophic. 4 With the Lock Bar installed the results look more promising for deformation of the top rack. It should be noted that this scenario is just a revision of the worst case scenario of a vehicle being allowed to fully tilt itself to one side of the lift. This is not the normal scenario for the use of this product. This shows that only one corner of the rack should deflect, and only by 0.03 in., which would seem like a favorable result. However the stress analysis shows some more alarming data. The usual scenario is the weight being distributed evenly across the top rack, which is where the mounting brackets would have been installed. In this stress analysis, there are some readings that exceeded the ultimate strength. These high values may be occurring because of singularities in the model that are artificially inflating these values, but physical testing to this system could be dangerous unless conditions are able to be heavily controlled. 5 In the product's normal and intended operation, the stresses stay below the yielding stress. This shows that the product will be able to fully handle all the loads associated with its normal operation. But it is important to test and develop this product with its worst case scenario being at the heart of its design. Real-Case Scenario 6 In a controlled environment outside of the school zone, we used a machine to lift different weights of 4130 Alloy steel onto our assembly, which includes the top and bottom racks assembled, including the Lock Bar. As you can see(See Appendix: Figures 1), our assembly held on fine. The testing material weighted: 291 lbs. Since it held up fine, we continued to test the assembly by adding the next weight. As you can see(See Appendix: Figures 2), our assembly held on fine. The testing material weighted: 772 lbs. Since it held up fine, we continued to test the assembly by adding the next weight. As you can see(See Appendix: Figures 3), our assembly held on fine. There were some movements, but nothing out of the sort to indicate buckling or tilting. The testing material weighted: 1545 lbs. Design Changes We had to make a new hole on the bottom rack, near the 45 degree angle cut. The drill bits we used made the hole on the 45 degree angle cut. We had to make a new hole an inch away from the previous hole and tested it in SolidWorks and it ran perfectly fine. 7 Beta Revisions The product will need to have some beta revisions done to it in order to create a more safe environment for customers. The failure in the test data for yielding and possibly worse case scenario is unacceptable for this product. Revisions that could be applied include thicker steel bars, changes in geometry, and materials. With thicker steel bars, the bearing surface area increases , which is where all the largest stress values are occurring.This increase in surface area spreads out the force on the bearings, lowering the stress values. This would be more expensive and also make the product less portable. Different materials could also be selected for the rack that have higher yielding and ultimate stress values, but this could be more expensive and affect the total weight of the product. Products with higher strengths sometimes require more machining effort and wear, which make the manufacturing process more expensive for a commercial product. For changes in geometry, the product could be shortened in an attempt to limit the bending moment experienced by placing the load on one side of the lift. This would make the lift lighter and use less material, so it would be a more than ideal solution to revising the product. The original design was made the length it was to give a wide base and increase stability of the product, but some shortening should not affect the stability greatly, while majorly decreasing the bending moment. Even a change in length of 2 in. can lower the torque by 3000 in.-lbs. Moving forward, this is the preferred revision to creating a more successful product, with possibly screening for more suitable materials to fabricate the racks. Along with the benefits of reducing bending moment, geometry changes will make the product more compact. When all the manufactured parts were put together, it was a bit too large to fit in smaller cars and would be more difficult to carry around than desired. By reducing length, the product will fit in more areas which in turn will make it more desirable in comparison to other similar products on the market. 8 The important aspect of this beta revision will be to secure a respectable safety factor in its worst case scenario. The product has to be built with this scenario in mind in order to prevent customer injury in the case of product misuse. Appendix Figures 1: 9 Figures 2: Figures 3: 10 BOMs 11 In. - Inch Units 12 Lbs. - Pounds Psi - Pound Per Square Inch Miscellaneous 13 14 15 16 17 Team Lift Problem Statement Most of today's standard automobile portable jack systems by themselves are unstable and unreliable. The use of hydraulic fluids to lift a car seems inadequate as it requires huge maintenance, extremely expensive to maintain, and could possibly lead to death. The use of hydraulic fluid pumps requires daily maintenance and flush after a few months of use. This uncertainty creates an unsafe condition when doing long, heavy maintenance. In addition, specialty cars need a low-profile lift system to get underneath the lift point of a car. Not only do we want to design a portable lift system that will fix those issues, but also versatile and affordable enough for most D-I-Y consumers. Function ? ? ? ? ? Lift 1500lbs All Electric System Adjustable Lift Support Safety bar for Support Low Profile Constraints ? Need Lock Bar in place before working ? Need to lift the lock Bar before retracting ? Slow actuator extension and retraction ? Actuator only lifts the car ? Under 8” height Design and Approach Materials ASTM A-36 Hot Rolled Steel ? ? Mild steel(