BAJA (2018-2020)
I was the suspension lead for Olin's BAJA team in 2020. BAJA is an off-road vehicle design project team that competes with other institutions around the world. Through BAJA I have advanced a lot of important skills and gained new ones. I learned proper Solid Works practices when working on large group projects and became better at FEA. I also practiced my ability to problem solve with others to design around interference. Additionally, we make most of the parts in our machine shop, so I got to practice designing parts that can be manufactured using the machines we have. I also got to practice using the mill and lathe on both parts I designed and parts I had never seen before given the drawing.
Front Suspension Design
I worked to design the car's front suspension geometry. This part of the car calls for the design of the following components:
- Upper and Lower A-arms
- Shock mounting
- Steering Tie Rod
- Attachment Tabs
- Adjustments to the knuckle
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The process of this design begins with SolidWorks sketches where I change lengths and positions of a-arms/ steering tie-rod on the chassis and knuckle to optimize for the factors below:
- Gaining negative wheel camber with body roll
- No scrub radius
- Greatest steer angle range
- A calculated amount of trail
- A calculated min, max and resting ground clearance
- Minimal body roll
- Motion ratio (Ground clearance : Change in shock compression) as close to 1
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I also used brought my Dynamics class to BAJA, by writing a MATLAB script that would estimate the oscillations of the body roll with the spring damper setup that is the shock suspension design we have. I made some approximations, but it gets the idea across. The script takes the velocity and radius of the turn the car is going around and calculates the amount of body roll based on suspension geometry and shock coefficients.
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I use weldments in SolidWorks to create the a-arms and tie-rods. I also design attachments to the chassis that will prevent major damage during a crash and failure points that make fixing on the fly easy. Interference checking is the final process as there are a lot of moving components in the suspension area.
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I wrote up the process in this document for future BAJA members' reference:
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Light weighting gears
Our gearboxes weight is significantly lower than it was last year and one reason for this is light weighting the gears. I worked on light-weighting the 2nd (shown on the left) and 4th (shown on the right) gears such that the gears can be as light as possible while still being above a certain factor of safety. The second and fourth gears are the only two gears large enough for it to be worth our design and fabrication time light weighting. To do this, I used Solid Works to optimize the topology and run design simulations to find the most advantageous dimensions. Solid Works ran through different sizes for the removed material and number of holes that would satisfy the factor of safety requirement and minimize mass. For the fourth gear, we tried conducting analysis before any light weighting to see where the straining points were. Where there was high strain, we left more material. We used Fusion 360 to do this. Once I received a general shape we performed the same analysis where Solid Works adjusted the size of holes with optimization.
2nd gear
4th gear analysis in Fusion 360
4th gear
Brake Caliper
I also designed the rear brake caliper. When speccing a brake caliper, we were not given all of the necessary dimensions. This resulted in there being interferences between the brake caliper and other parts of the car. After a lot of days of ideating, the next step was to redesign half of the brake caliper. We were using a floating brake caliper, so only one side of the caliper has pistons. I redesigned the half of the caliper that did not have the pistons, as that side would be the easier side to design and fabricate. This would require flipping the caliper such that the side without pistons would be closest to the mount. I also designed a mount for this brake caliper half for the slider pins to go through. Slider pins also had to be redesigned such that it would fit with the new designed parts. A diagram of the assembly is shown below. I also designed the brake caliper mount and brake caliper half to be manufactured on a manually mill such that I would be able to mill it myself without having to use a CNC mill.
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