Overview |
2017 Rear Suspension Design
2016 dual a-arm suspension (left) and 2017 three link suspension (right)
The 2017 three-link rear suspension was in part a product of my capstone project. The overall system design goals were to reduce weight by 20% (15 lbs), improve high speed stability, and reduce cost. The goal of this section is to catalog the complete process through design, fabrication, and full system assembly.
Part 1 |
Part 1: Rear Suspension Kinematics
In order to improve high speed stability and cornering speeds, the 2017 suspension was designed with a reduced toe change and increased longitudinal wheel travel. The shock mount direction was moved to improve response and drivetrain packaging. The results of the suspension height measurements were used to determine the ideal camber curves to maintain positive camber in hard low speed cornering.
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Rear suspension kinematic design
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Part 2 |
Part 2: Mechanical Design
The trailing arm is a weldment box construction which reduces weight through varying wall thicknesses and water jet cut outs. The trailing arm sees more loads than any a-arm previously, so durability was a major concern. SolidWorks Simulation was used to analyze components. Loads were determined through previous suspension failures (or lack thereof) and shock absorber spring force measurements.
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Trailing arm FEA under 1500 lb shock absorber loading showing an increased FOS of 1.35 (from .85 previously)
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Part 3 |
Part 3: Fabrication
Jigs are designed and manufactured in house to help ensure the quality and repeatability of the welded components. All components (aside from the splines in the wheel hub) are designed to be machined in house. Aluminum is used for jigging because it wicks heat away from the welded component, reducing weld pull. Tight tolerance bores have cylinders lightly pressed into them to hold the shape during welding and improve assembly.
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Trailing arm welding jig
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Part 4 |
Part 4: Final Assembly and Results
The full system is 13.5 lbs (13 %) lighter than the previous system, a full 5% reduction of the total vehicle weight. The reduction of OTS parts cut the cost by almost 30% and the stability is greatly improved at high speeds than the 2016 vehicle. Low speed maneuverability was improved through an improved toe curve.
After two full endurance races in 2017 the system experienced no mechanical failures, an improvement over the repeated failures of the dual a-arm system. |
Trailing arm welding jig
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