Wheels for Roving on Extraterrestrial Landscapes

8/2023 - 5/2024

Wheel Design Requirements:

Compatible with current rover chassis & drivetrain
Reduced weight
Use a mounting system simlar to conventional vehicles
Airless

After researching other wheel designs for the NASA Human Exploration Rover Challenge, my team chose a center-disc based design. This was to ensure a easier fabrication process and simplify the modeling process. For materials, we chose oak lumber for the disc, carbon fiber for the rim, and re-used rubber floor mats for tread. Using the cheaper materials, although not ideal, has allowed us to stay within our budget.

FEA Testing

Analysis done on SolidWorks Simulation.

This simulation, due to the fact that both carbon fiber and plywood can have varying properties, is used to visually establish potential weak areas. This is used a reference during fabrication and physical testing, so we can reinforce and keep an eye on potential damage in those areas.

Tread was not simulated statically, and although we could have used dynamic simulation, we have chosen to calculate the stresses by looking at the shear on the bolts that will hold the center disc to the rim and tread. The bolts will be reinforced with glue to help stabilize the tread, and will be physically tested once fabricated.

Carbon Fiber Process

The rims are comprised of a carbon fiber "sandwich", layers of carbon fiber with structural foam in the middle. We are using a vacuum bagging process, so the rim is topped with breather fabric and film, and sealed with a vacuum bag. This method ensures the carbon fiber is not over saturated with epoxy.

Pictured are the test sample we created to prove our method (below), as well as the rim in its vacuum bagging (left). Since we are using the same dimensions as the old wheels, we are using one as the mold.

Wheel Assembly & Mounting

Commonly, spokes are used to provide central support to wheels. However, due to the complexity of said design, it was simplified to a solid central disc. The disc was made with 1” thick solid oak lumber, joined using dowels and glue. They were cut to size using a circle cutting jig and bandsaw. The rims and discs were joined using epoxy adhesives. The tread was made from rubber industrial mats, and glued down using contact cement. The entire assembly was attached to the axle with bolts, similar to everyday vehicles. This configuration will make it easier to remove and replace the wheels.

Conclusion

The fully constructed wheels have been fully tested, proving our methods and designs are viable. The design was tested up to 300 lbs, far exceeding the necessary weight requirements. This weight was also applied with the wheels at an angle, with no cracking of the carbon fiber. In addition, the new wheels weighted 40% less then the previous iteration. At the competition, they performed well under the full weight of the vehicle and the drivers, and due to their exceptional performance, they will continue to be used for the next NASA Rover vehicle.

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