Steering Mechanism for Shell Ecomarathon EV

BLUF - I wrote a calculator for steering mechanisms, designed the front wheels assembly, and fabricated the physical components.

Building the world’s most fuel efficient car requires optimizing every component, including the steering system. A car’s steering system involves wheel mounts and a linkage mechanism to transform the rotation of the steering wheel to the pivoting of the wheels. Wheels pivot based on the linkage geometry that dictate whether a no-slip condition will be met. Known as the Ackerman steering condition, a paper that presented three equations to closely simulate the profile provided the basis for designing and optimizing a car’s steering mechanism.

Methods

In order to design and build a steering mechanism, several software and hardware tools were leveraged:

MATLAB
By representing the three equations in the paper related the inner and outer wheel angles with vehicle dimensions, and rack width, travel, and position in a script, a developed method solved for the linkage lengths much more efficiently than by hand.

Solidworks
After vehicle dimensions were decided, which informed the steering mechanism design, all parts were modeled in Solidworks, providing a visual representation and a pipeline for generating part drawings. The designs were then validated in the finite element analysis (FEA) software to ensure robustness and optimized for stiffness to weight ratio using topology optimization.

Machining
Raw materials were sourced from McMaster and Midwest Steel Supply and waterjet components were outsourced to SendCutSend. To form linkages, aluminum shafts were machined in house on a lathe, with external threads cut and rod ends attached to create the linkages for the steering system.

Results

The mechanism achieved the following outcomes:

Turning radius of 4.6 m, under the 6 m competition specifications
Achieve near Ackerman steering conditions within 8% of error at turning angles greater than 15° and maintain no slip conditions throughout
Gross mass of 9.68 kg

Conclusion

Leveraging computational tools led to quick iterations early in the design phase.. Using modern workflows for part design and generation amply powered the optimization of creating geometries that power a functional and lightweight steering system. The project highlights the process by which theory can be translated into reality. Future work would involve combining separate waterjet components into a single complex structure manufacturable by metal powder bed fusion.