Skip to main content

Wheels

Overview & Design Intent

The rover uses a non-pneumatic, cellular wheel design. The goal of this was to provide compliant deflection, passive damping, and terrain conformity without the risk of punctures or pressure loss. While technically these wheels would not be feasable on the martian surface due to temperature fluctuations and radiation, these wheels will be fine since the competition takes place on earth.

The deep dive into the engineering, geometry, and finite element method (FEM) optimization lives in the companion report: "Design and Development of a Rover Drivetrain". Check that document if you need to understand the structural load calculations or deformation simulations.


Requirements

  • Primary Role: Provide ground traction, terrain conformity, and passive shock absorption for the drivetrain.
  • Target Load: 12.5kg per wheel
  • Outer Diameter / Width: The diameter of 200mm was chosen due to the torque requirements in the worst case scenario being to high. The width was chosen to be 140mm because the original motor and gearbox combination that was supposed to be used with these wheels was that length.

Material Choices

  • Outer Tire (TPU 95A): TPU 95A was chosen as it was flexible enough so that it woud not get damaged with hard impacts but also not too flexible like TPU90A which would have required more material for similar rigidity. This would have made the wheel heavier, increased its printing time, and increased its cost.
  • Inner Hub: Currently the hubs consits of 3 differnet materials, PA6-CF20, Fiberon PETG rCF-08 and Polymax Polycarbonate. The first 2 were printed from PETG rCF-08 as that was the strongest filament on hand at that time. These were done at 100% infill, however this caused a problem known as the "blob of death". This is when the print nozzle slighlty collides with already printed lines, causing a buildup of matieral which if not stopped can cause the material to buildup all the way into the printhead wiring and if not carefully removed can cuase damage to the wiring which is a big annoyance to fix. So for the following hubs an infill of 80% was decided as that was the infill where no blob was seen.

    The next 2 were printed from polycarbonate as the general idea was that these were stronger than the PETG rCF. While this is true,true in general, the specific verion of ploycarbonate (Polymax) from polymaker is generally weaker than other polycarbonates (Polylite) and even the PETG rCF. While it seems to have held up to this point, extensive stress tests have not been conducted in order to see their feasibility.

    The     final 2 where made from PA6-CF20. It is one of the strongest filaments offered by polymaker. It is very rigid and the best filament for this purpose as the entire rover's weight rests on the mounting points that connect the hubs to the plate that connects to the motor. In the future this should be used mainly for the hubs if the same design is kept, however other materials could suffice such as CoPA, Polylite PC, or others depending on the weight of the rover.


Manufacturing & Assembly Guide


1. 3D Printing Settings

  • TPU 95A Tire Settings: asdsa
  • PA6-CF20 Hub Settings: asdsad

2. Component Interfaces

  • Tire-to-Hub Interface: adsad
  • Hub-to-Gearbox Interface: asdsad

3. Maintenance & Lessons Learned

  • Wear Indicators: asdsad
  • Spares & Replacements: asdasdas






Back to top