Cal Poly Racing: Baja SAE

As a Composites Subsystem Lead for Cal Poly Racing, I worked with my co-lead to design and manufacture composite components for our 2024 vehicle to compete in Baja SAE. A few of my specific responsibilities in this position are detailed in my resume. Below, I describe some of the molds and 3D layups I've created. These molds have been used to create the eCVT case and cover, propshaft guarding, and front skid plate. I have also collaborated with fellow team members on a variety of wet layups and resin infusions for our body panels, hood pieces, and skid plates. Additionally, I've worked on impact and abrasion testing on dozens of composite samples to analyze material properties for optimal layup selections.

eCVT Case and Cover Molds

The guarding for the vehicle's 2023 and 2024 eCVT is made out of composite materials such as carbon fiber and foam core. The first of its kind, this case and cover have been designed to be lightweight, durable, and heat resistant. To achieve tight tolerances and integration with the eCVT itself, the molds needed to be manufactured with CAD-specific geometries.

The first picture is my first iteration of the 2023 eCVT case mold. I 3D printed this portion of the case mold in six sections, using built-in dovetails to securely locate and align them for gluing.

In the second picture, I also 3D printed the 2023 eCVT cover mold. Having had difficulty removing the layup from the first mold, this second iteration was designed to be disassembled during de-molding. I used locking sections to screw together the six main components of this mold, which were then taken out piece by piece during demolding. The part also had a greater draft angle. To maintain the accuracy of the threads and featured geometry, I printed over 35 components in optimal print orientation.

The third picture features the 2024 eCVT cover mold: a culmination of the previous year's lessons learned. A negative mold was used to demold the part more easily. The bottom of each segment's joining face is also chamfered, allowing easier access for wedges during demolding. Instead of using dovetail features to fasten throughout the part's height, they were designed into the bottom only.

Looking Forward

I am also developing the designs of future molds for increasingly complex geometries for the 2025 Baja car. Tests are being performed to improve mold surface quality and demolding procedures with industry-level molding practices. I am also developing a process for 3D-printed air-tight mold designs. These molds will replace CNC-machined foam molds with less cost and manual labor, thus aiding in quicker prototyping and manufacturing timelines.

PLA

CAD design and rendering on Fusion 360
3D printed on Prusa i3 MK3S+
Lightly sanded through 180 grit wet sandpaper

Dimensions for eCVT case mold: 21" x 7" x 5"January 2023
Dimensions for eCVT cover mold: 21" x 7" x 4"March 2023
Dimensions for eCVT cover mold: 14.5" x 8" x 4.5"February 2024

PLA, High-density machinable foam

CAD design and rendering on Fusion 360
3D printed on Prusa i3 MK3S+
Lightly sanded through 180 grit wet sandpaper

Dimensions: 28" x 3" x 1.75"
February 2023

Propshaft Guard Molds

The guarding for the vehicle's propshaft has been made out of carbon fiber for the past few years. It's intended to protect the driver and any other bystanders against any "hazardous release of energy" (HROE). Additionally, this part lies beneath the seat and is protected by the skid plates.

The top and bottom components of the propshaft guard were 3D printed and attached to blocks of high-density machinable foam for their respective layups. After 3D printing and joining them together, the molds were sanded and taped over to improve surface quality and aid the de-molding process.

Front Skid Plate Mold

The vehicle's front section of the skid plate helps protect the chassis, driver, and internal components from debris and other obstacles. This part is made from a resin infusion of composite materials such as aramid, fiberglass, and foam core.

The mold for our front skid plate is typically machined on a CNC router, however, due to machine complications, this year's was made by hand. I manually cut the profile of the mold from high-density machinable foam. It consists of 9 layers of varying thickness to achieve an optimal width for the resin infusion.

High-density machinable foam, Bondo body filler

Table saw, band saw, and orbital sander
Power-sanded and hand-sanded through 220 grit sandpaper
Gaps and dips filled with Bondo body filler

Dimensions: 22" x 14" x 6.5"
January 2023

Carbon fiber, Foam core

Wet layup with a high-temp resin system
Multiple layers of carbon fiber and foam core
24-hour cure under vacuum and low-temp oven
34-hour post-cure in an oven w/ gradually ramping temperatures to increase thermal resistance

March 2023

eCVT Case & Cover Layups

The case (left) was created as a wet layup using a second iteration of the case mold, made out of high-density machinable foam (right). The cover (top) was made as a wet layup using my 3D-printed mold, as described above.

Both molds were designed for improved de-molding. With the complex shapes for these layups, we'd had difficulties in the past removing the layups from the molds without damaging the part and the mold itself.

For the case mold, pieces of the mold could be separated. For the cover mold, pieces could be removed and disassembled. Both parts were iterative processes that forced the team to answer well-known problems in professional mold design. By the end of the 2023 Baja season, we were equipped to answer those problems while designing the next year's car.

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