Rear Wheel Adapter Redesign

This project explored how I could better design the interface between our car's rear axle and it's carbon fiber monocoque in order to make it lighter and more accessible. This was a critical part that must not fail in competition as it supports the weight of the car. While this project was not as complex or as in depth as some of my others, I think that it is a good introduction to my engineering mindset.

Previous Design

The original design was composed of an iron L bracket and an aluminum 7075 part that connects to three things: aluminum inserts in the monocoque, the rear truss supporting the firewall, and the part that holds the rear wheel axle and the hydraulic brakes. I first spent some time to see how these parts all interface together to understand what could be changed and what could not.

Gathering User Data

As I was new to the team, I asked other members what could be better about the assembly, learning that this assembly was really difficult to install and adjust. I then tested their claims myself so I knew exactly what I was dealing with. It was really difficult to adjust the wheel position with the screws shown in the picture, because the moncoque blocks the way of a hex key. I also knew that a lighter part could increase performance.

These screws are ridiculously hard to loosen/tighten

Defining Objectives

With this information, I started from scratch, thinking of the main characteristics my part should have:

1. Adjustability screws that are easy to reach and turn

2. A lighter mass than the original design

3. Thorough validation through load analysis

4. Ability to be manufactured on a three axis mill

Brainstorming

With this information in mind, I created some quick sketches of potential ideas. It was especially difficult for me to understand how to accomplish the first goal as the current design interfaces with the part that holds the brakes and rear axle through screws parallel to the axis of the rear wheel. Because those parts were expensive to remanufacture, I was constrained to that same interfacing method. After four sketches, I found a solution:

The screws circled in the left image go through these holes

The redesigned part must connect here using these screws

Ask me for anything; I'll always deliver more

My Solution

I realized that I could rotate the adjustability screws and holes by 90 degrees so that they were facing upwards. This meant that the screws would be easy to reach and turn. I would simply have to make a part that had the male component of this adjustability on one end and the brake and axle on the other. Additionally, I had to create a part with the female component of the adjustability which connected to the aluminum inserts in the carbon fiber monocoque, and a third part that reached from those inserts to the firewall truss. Overall, this resulted in a 52% lighter part.

Designing the Solution

I used sketches from the assembly drawing in Solidworks to design each component, using the hole wizard feature to create screw holes. I designed each part by extruding in one direction, creating material, and then performing an extruded cut in a perpendicular direction to remove material. This helped me design for manufacturability on a 3-axis mill. I made sure to add fillets on tight corners and made sure that the radii of any curves were rather large in order to aid in manufacturability. After verifying that the parts I had designed fit in the assembly, it was time to validate their strength. For this, I used FEA analysis with Ansys.

Future Steps

For now, I am waiting on the green light to manufacture these parts on the three axis mill in our shop and have taken on several other projects.

Learnings

This was a project where I was able to use my creativity along with my technical ability in order to make this assembly lighter, and easier to service, while validating its functionality. I especially learned how important it was to spend a significant amount of time brainstorming through simple sketches or very simple CAD drawings before designing it perfectly, as it was that time that allowed me to come up with the radically different and radically improved design that I eventually ended up on.