Aerodynamic Analysis of Car body with Aerodynamic Devices to Improve Performance
Y Link Presentation - Senior Design
1. A New Design for Improving Suspension Performance Y-Link Control Arm and Cross Member Project Jesse Parnell Matthew Etter Advisor: Dr. Ahmed Soliman University of North Carolina at Charlotte 1
2. Outline Problem Statement Design Goals Techniques to Measure Success Measures of Performance Articulation Ride Quality Possible Solutions Justification of Design Design Risk and Mitigation Conclusion 2
3. The Problem The Original Equipment Manufacturer (OEM) suspension design on the 84-01 Jeep Cherokee features a limited suspension travel due to short Lower Control Arm (LCA) design This design causes the LCA to limit axle movement As a result there exists binding in the suspension and steering linkage Due to the wide angle of rotation the force components that are reflected on the chassis are high 3
4. The Problem Picture 1: Illustrates OEM style upper and lower control arms http://www.off-road.com/jeep/cherokee/2001/10_oct/longarm/Stock_Arms.jpg Figure 1: Created in Visio to compare OEM arc radius to long arm arc radius 4
5. Design Goals Increase articulation and suspension travel A quantifiable increase in articulation Improve ride quality Reduce the road roughness felt by vehicle occupants Increase strength over OEM Adjustable for alignment The system must include a means for adjustment Increased ground clearance Compare measurements of factory design to improved design Completely bolt-on design with simple integration This design modification should be easily integrated 5
7. Articulation Measurement Ramp Travel Index (RTI) Ability to measure vehicles axle articulation Typical 20 degree ramp standard Current RTI score for Jeep Cherokee with 4.5” lift is 647 Figure 2: How to calculate RTI score using 20 degree ramp Picture 2: Measuring Jeep Cherokee with 4.5” lift on RTI 7
22. Data will be collected in similar fashion to compare ride quality after buildFigure 3: Screen Shot of iPhone accelerometer application 8
23. Accelerometer data Plot 1: Accelerometer impact data of standardized bumps using iPhone application 9
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25. Justification Simplified single arm design Increased ground clearance Enhanced protection Improved ride comfort Extended articulation 11
26. Proposed Design Figure 4: Proposed Y-link Control Arm modeled in Solidworks Dual function of Y-link control arm as upper and lower control arm Increased ground clearance Adjustable for alignment purposes Longer than factory LCA, increasing articulation 12
27. Risk and Mitigation Bent style introduces stresses Simulate stresses using Ansys Vehicle stability Factory sway bar will provide stability Coil spring float Retaining straps to maintain spring position 13
Introduce our selves, Dr. Soliman and our project with an overview of project (what is fits)
This is the outline for the presentation and what topics are coveredProblem statement – what the problem is and what is coversDesign modifications – what we plan on changing and gain in doing this projectTasks – Things to be done in order to determine our successMeasure of performance – Items that will determine if the project was a successPossible solutions – Different ideas that were generated in order to accomplish our goalsJustification of design – Why we chose the solution we didDesign – Our design to accomplish our goalRisk and Mitigation – Things that could be a bump or “show stopper” during the project
This is the problem that we are occurring. Due to the relatively short length of the OEM control arms with a lifted Jeep the axle is limited to a relatively short range of motion before binding. Along with its short range of motion the road harshness is transmitted more directly though the LCA due to its angle relative to horizontal.
This slide illustrates the problems due to the length of the OEM arms and the height of the vehicle. As you can see from the picture 1 even with the weight of the vehicle on the springs the angle of the control arms are relatively steep, creating binding in the suspension and steering. Figure 1 illustrates that with a longer arm the amount of suspension travel due to horizontal distance is greatly increased over the OEM control arm. Figure 1 also shows an indicated force from the road and its relative resultant forces that are transmitted directly into the chassis.
This is what the proposed design will accomplish. A measureable increase in axle articulation, droop and improved ride quality. While the system will be easily integrated with a bolt-on design with the ability to be adjusted for alignment of axle location but caster angle.
Here are the tasks that will have to be achieved in order to measure our products worth and that it is acceptable. The systems’ simulated stresses will be assessed by Ansys and stress analysis. Also to evaluate the systems articulation it will be post measured using a Ramp Travel Index RTI for short, along with re-analysis of accelerometer data used to measure ride quality.
