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As part of the Longhorn Racing Combustion team, I was a Vehicle Chassis Engineer for the 2022-2023 Formula SAE competition season. Formula SAE is a collegiate engineering competition involving designing, manufacturing, and testing a formula-style race car. On my team, I helped with development and testing of the vehicle's steel tube chassis and with the design and manufacture of other projects, such as the vehicle pushbar and a plasma torch gantry mount
2022-2023 LHR Combustion Vehicle
Projects/Contributions
Vehicle Chassis/Frame
Frame CAD
The frame consists of both the steel tube spaceframe as well as the necessary components for integrating other systems. As part of the team, I helped manage the full frame CAD in Solidworks, designing and adding necessary mounting tabs for other subsystem components while cooperating with other system members to ensure proper placement and compliance with Formula SAE design guidelines.
Additionally, as seen in images (2) and (3), I assisted with investigating and modeling different methods of mechanical attachment for the frame's main roll hoop bracing. Shown in the full frame assembly image (green bar in the rear), the chosen method was the double-lug joint attachment. Although both methods were removable and allowed for easier vehicle maintenance than a solid welded brace, the double-lug joint proved more convenient and easier to use during physical testing while also being 3 lbs lighter in comparison.
(4) Total Deformation FEA Analysis of Frame in Solidworks
FEA Analysis of Frame
The primary metric our team used in designing our chassis was torsional stiffness, the resistance to twisting under a torque along its longitudinal (front-to-back) axis. This metric was chosen because of its critical impact on driving stability, driver feedback, and suspension behavior.
I assisted in the development and investigation of simulation setups that would allow my team to quantify our frame's torsional stiffness. Initially, I began development in Ansys Static Structural, but our team later switched to Solidworks Simulation for faster and easier analysis of each new frame iteration. As shown in the included image (4), Torsional Stiffness was measured through a total deformation FEA simulation of the frame. With the control arms included and the suspension modeled as a steel beam, torquing forces were applied to the front uprights (parts connecting lower and upper control arms) while the rear uprights were fixed. The suspension dampers/springs were included and modeled as steel beams to simulate loading more realistically while focusing the simulation on the frame stiffness and not the suspension. Torsional Stiffness was then calculated by measuring the displacement of each front upright in the y-axis and calculating angular displacement using the distance to roll axis.
Performing frame simulations in Solidworks allowed for more rapid design iterations and analysis than using an external simulation software. The included image (4) shows one such example in which our analysis setup allowed us to iteratively improve our frame design. The addition of an extra Side Impact Structure (SIS) member in the chassis design seemed to nearly double the chassis stiffness while adding less than 4 lbs.
Physical Testing/Validation of Frame
To further test torsional stiffness of our chassis and validate our FEA analysis in Solidworks Simulation, I helped in conducting physical testing of chassis stiffness using a corner scale method recommended by a Formula SAE Competition Judge.
Prior to testing, I helped machine steel, "dummy" suspensions dampers and installed them in place of the actual suspension shocks (Shown in images (8) and (9)). This ensured that the suspension stayed rigid, allowing us to test the frame more effectively and consistently with our FEA analysis.
As shown in images (5) and (6) the testing involved placing the vehicle on 4 corner scales, placing 10 sheets of ~1mm shims between the front wheels and scales, and recording the scale readings. We then removed 1 sheet from the Front Right wheel and added it to the Front Left wheel, creating a slight twist in the chassis. The weights of each corner were then recorded. This process was repeated until the Rear Left scale measured zero or very close to it. The Torsion angle was calculated through the total height of shims added/removed and the front track width. The Front and Rear torque were calculated based on the normal force variation (scale readings) and respective track widths. Combining the difference between the two torques with the torsion angle, we can calculate torsional stiffness.
Although we only had time to test this method on the previous year chassis, we were able to compare physical testing with FEA analysis results of the same chassis. Because the results were relatively similar, this allowed us to validate that our FEA methodology was reasonably accurate. Additionally, performing this physical testing method saved our team hundreds of dollars in material and proved to be a much cheaper alternative to manufacturing a whole rig capable of fixing the rear frame and loading torques on the front.
Vehicle Push bar
I also helped with the design, simulation, and manufacturing of the vehicle push bar, a required device for transporting the vehicle around the competition site.
(10) Push bar CAD Front View
(11) Push bar CAD Side View
Push Bar Design
Unlike the Frame, the push bar design was largely unregulated and did not have many rule restraints. Thus, without any specific rule restraints, we opted to design the push bar solely on what it needed to do, and then add bracing/structural support as needed by FEA Analysis. Prior to design, we talked with members who would likely have to operate the push bar during competition and gathered data on good features and design considerations, such as ability to both push and pull the vehicle, ability to roll on its own wheels for easier transport, and ease of operation.
As seen in images (10) and (11), we settled on a design featuring two wheels, two hooks that can push and pull on the vehicle's rear jacking bar, and a slight angle that positions the main bar parallel to the ground when in use, allowing the vehicle to be pushed easier.
Push Bar FEA Analysis
Images (12) and (13) show FEA simulations of an earlier and later iteration of the vehicle push bar. The simulation was performed by fixing the hooks/points of attachment onto the vehicle, and loading two ends on each side of the handle to simulate two operators pushing the device on either side with both hands. This loading was based on an estimated force required to push/roll the vehicle forward.
Through these simulations, we were able to effectively iterate and improve the push bar design, increasing its simulated Minimum Factor of Safety (FOS) to a value of about 2.8.
Push Bar Manufacturing
Prior to welding the device, I helped prepare the steel tubes. Starting out as long, 1-inch tubes of mild steel, the separate tubes were cut to length and hand mitered in-house using common machine shop equipment, such as bandsaws, bench grinders, and belt sanders.
I then joined the Steel tubes together with Tig Welding. Aluminum jigs and magnetic holders were also used whenever necessary, as shown in image (15) to ensure the physical device stayed consistent with the CAD.
The practically complete push bar can be seen in the images (17) and (18).
Overall, this new push bar design proved to be much easier to use than the previous push bar, as its horizontal configuration when hooked to the vehicle required less effort to push forward. It also had the new ability to pull the vehicle, which was not present in the year before.
(19) Push bar at Competition (Bent)
Lessons Learned
Despite the push bar's successful improvement from past years and its performance under its intended use, it suffered some unexpected deformation. Because my team's main priority was with the vehicle frame, the push bar did not start development until very late into our season timeline. Consequently, I was required to begin manufacturing the push bar with less time for design and simulation.
The effects of rushed simulation did not become as apparent, however, until it came to competition day, where the push bar suffered some permanent bending, as shown in image (19). This was due to a vertical downward loading likely in an effort to lift the rear of the vehicle. This could have been easily prevented with some simple design modifications, such as extending the bracing of the main tube closer to the handle to decrease the bending moment caused by vertical forces (on the handle).
Although it was unfortunate, this taught me the importance of not only spending more time with simulation and analysis setup, but also in accounting for operation and loading conditions that may be unintended, in order to design a more robust product.
Aluminum Plasma Torch Mount
After receiving a bare gantry kit for in-house plasma cutting of steel, aluminum, and other metallic materials, we needed a way to securely and effectively mount a plasma torch onto the CNC gantry. I contributed heavily in the development of this mount from design to manufacturing.
(20) Isometric View of Mount CAD in Solidworks
(21) Side View of Mount CAD in Solidworks
Plasma Torch Mount Design
Before beginning design, we met with engineers in the manufacturing team to better understand and list the requirements and constraints for this mount. The requirements were simple: 1) be compatible with the Gantry mounting baseplate, and 2) allow for slight degree of rotation (pitch and roll) to make minor leveling adjustments. From these requirements, I designed a mount in Solidworks that met both requirements and added adjustability for other size plasma torches and tools.
The mount consists of three main components.
1) A main base plate that attaches to gantry and has a cylindrical slot for the rest of the amount to be secured into.
2) A cylindrical connecting rod that is inserted into the main base plate and allows for the final piece to be secured. Because this rod is cylindrical and has a slightly smaller diameter than the baseplate cylinder, it is allowed to rotate (roll). After it has been leveled to the correct amount of roll, the rod can be secured and constrained using set screws inserted on the top and bottom of the base plate cylinder (shown in image 20).
3) An adjustable clamp. This two piece clamp can be adjusted to tighten onto varying diameter tools by simple adjustment of the connecting bolts/nuts. The clamp is secured by a single bolt onto the cylindrical connecting rod and has the ability to hinge/pitch up and down, meeting the requirements.
Plasma Torch Mount Manufacturing
After completing the design and verifying it with manufacturing members, I prepared a large block of aluminum suitable for the mount and generated CNC toolpaths in Solidworks using an HSMWorks CAM plugin. This is shown in Images (22) and (23). After simulating the machine operations in the CAM software, I then operated a 3-Axis CNC Mill to machine the cylindrical baseplate component, as shown in image (23). After completing the CNC operations, the mount components were cleaned and refined using manual mills and sanders.
The fully manufactured and assembled mount can be seen in image (25). Having our own gantry and plasma torch with proper mounting allowed the team to cut out steel tabs and mounting hardware in-house, greatly speeding up manufacturing times and saving the team potentially hundreds of dollars.
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