GreenPower F24 FrontUpright Design
2024-3-14|2024-3-15
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2024.03.15 持续更新ing…
Brief & Objective :
Brief:
In our last qualifying race at the Lotus test track the The Leys electric racing car was 10% off the qualifying distance required to attend the finals.
Objective:
The goal of this work-stream is to increase the performance of the car by reducing the weight of its key components by 10%**. *The current weight of the car is 8750g
**The general rule of thumb for automotive racing is that every 10 percent reduction in weight has a comparable 10 percent reduction in the force required to accelerate or decelerate the vehicle.
Parts list and weight analysis:
Initial CAD design and weight comparison:
Using the measured dimensions, I rebuild the part in Solidworks, and by applying both Steel and Carbon Fiber materials to the built Solidworks 3D model part. By the evaluation tools, I’ve got the mass of part made by Steel and Carbon Fiber.
It shows that by using carbon fiber as the material for the part, it reduced 444.46 grams of the mass which reduced 76% of the original mass.
Initial Stress Analysis:
Sketches of New Design Ideas:
Prototyping: Initial Prototype Printing & Testing
What Went Wrong:
The initial prototype for the redesigned front upright was not designed with a space for the brake mechanism to fit in which prevented its installation. Additionally, the position of the screw hole was not correct which resulted in the wishbone not being able to connect with the front upright prototype.
Prototyping: Second Prototype Printing & Testing
What Is Improved / Went Wrong:
The second prototype had improved with the correct spacing for installing the brake mechanism. Although the prototype was able to be connected with the wishbone and axles, the movement seemed to be restricted by the width of the prototype, the inner side of the Front Upright was hitting on the framework of the car. Furthermore, even though the top screw hole are now in the correct position, the bottom one was still wrong which by installing it, the prototype cracked.
Prototyping: Final Prototype Printing & Testing
What Is Improved:
To fix the problems occurred on the second prototype, the position of the bottom screw hole is changed and now fits perfectly onto the car.
The radius for the rounded edges are also longer than the previous prototype which prevented the edge of the front upright collide with the framework and removed the restriction of the movement from the car framework.
A Further Problem:
On the original Front Upright, the axle for the wheel was welded onto the part. However, the improved Front Upright is going to be using Carbon Fibre as its material which is not possible to weld.
Therefore, I need to find a reliable solution to bond the axle to the Front Upright.
Prototyping: Designing Inserts For The Axle
In order to hold the axle and bond it with the Front Upright, I decided to use a Carbon Fibre tube and design the inserts on both sides of the tube which could let it be bonded tightly with the part.
On the Front Upright end, the insert is designed to plug into the tube with Loctite E-120HP which is a high-viscosity, non-sag aerospace grade epoxy adhesive. For the end with the wheel, I decided to use a
Ball lock bolt with a designed inner layer to hold the wheel.
By reading the datasheet of the adhesive, I found that the Tensile Strength after cured for 7 days is 41N/mm^2, and from the data collected last year’s race, the total mass of the car is around 156 Kg which gives total weight of 1569.8=1528.8N.
Therefore, the minimum surface area the required for the
adhesive to work will be 1528.8/41 = 37.288 mm^2. The diameter of the cross-section of the tube is 16.5mm, using the surface area (see pic1) finding the min. length for the insert: h=37.288 / (16.5π)=0.719mm.
Prototyping: Flow Simulation in Solidworks
By testing both the original and improved parts under 200m/s wind flow using Solidworks Flow Simulation, I could observe (by scaled color bar and arrows) a much higher flow velocity on the improved part than the original one. The center part of the original front upright has an estimated average flow velocity of 148m/s, whereas the improved part has an estimated average flow velocity of 182m/s. The result gives that the improved part has an approximately 23% faster flow velocity than the original one.
