Rim Weight Reduction

Summary

Background Information 

The rims, originally designed for MSXI, were never properly analyzed and weighed in at 4.1kg. The rims themselves are bulky, overbuilt, and add excessive rolling resistance to the vehicle (if it ever actually rolled...). The goal is to remove weight from the rims through smart pocketing to reduce rolling resistance and wheel assembly mass. 

Requirements

FS of >3, minimum 1kg material removed. 

Loading and Boundary Conditions 

The loading conditions for the rim are based on the FEA loading document found here. The boundary conditions emulate a "worst case" scenario of loading: modeling a non-linear material (rubber tire), combined with a compressible fluid (air) all interfacing with a deformable part proved to lead to long and inconsistently convergent sims.

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The inner faces of the rim that interface with the hub are constrained by compression only supports (representing the preload in the hub). The hub insert holes are constrained by cylindrical supports to prevent rotation of the whole part. 

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A dummy "contact patch" is modeled tangent to the rim, with the rim in the worst case scenario (the contact point of the rim is positioned exactly between two spokes). The normal force due to bump loading as well as Z-dir loading is applied to the lower point of the contact patch. Split lines were added into the rim and the remaining load applied to the section part. This represents the force translated "through" the tire to the inner bead of the rim. 

Results

Conclusion & Recommendation 

Future rims should be designed with much more consideration. Modern alloy rims on production cars are significantly less beefy than the rims for MSXI. Additionally, stress concentrations upper bounded the material that could have been removed. Finally, while unrelated, the rims were designed for tubeless tires yet neglected to include a bead feature, required for sealing tubeless tires.