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F24 Front Upright Redesign William Wang
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 workstream 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.
AISI 1015 Steel, Cold Drawn Thornel VCB-20 Carbon Cloth
Initial Stress Analysis:
Material & Manufacturing (Research) : 3D Printing Carbon Fibre Materials
Material & Manufacturing (Research) : 3D Printing Carbon Fibre Materials
Property Comparison: Steel & PET Carbon Fibre
Material & Manufacturing (Research): Forged Carbon Fibre & Compression Moulding
Design Molds & Construction
Apply Release Wax
Load Molds With Fibre And Resin
Clamp the molds …
Sketches
Prototyping: Initial Prototype 3D Modelling
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 3D Modelling
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.
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. of the movement from the car framework.
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
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 156*9.8=1528.8N. Therefore, the minimum surface area the required for the
section of the tube is 16.5mm, using the surface area (see pic1) finding the min. length for the insert: h=37.288 / (16.5*π)=0.719mm.
adhesive to work will be 1528.8/41 = 37.288 mm^2. The diameter of the cross-
Prototyping: Flow Simulation in Solidworks
Original Improved
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.
Prototyping: Flow Simulation in Solidworks
Original Improved
Manufacturing: Prepreg
- - - - - - Creating Templates Cutting the prepreg Molding Laminating Oven Cure Demold Part
Prepregs
- Conventional dry reinforcement like carbon fiber. - Pre-impregnated with a resin that already has the hardener in.
- Only need to laminate the prepreg material itself
into the mold.
Steps:
Manufacturing: Mold made in Solidworks
Manufacturing: Shopping List
https://www.easycomposites.co.uk/eb700-high-temperature-epoxy-tooling-board?authuser=1
- THICKNESS 100 mm
EB700 High Temperature Epoxy Tooling Board £116.35
- SHEET SIZE 250 * 250 mm
Loctite EA E-120HP (237128) Toughened Non-Sag 120-Min Set Epoxy £49.49
- 50ml/1.7oz Cartridge
https://uk.vicedeal.com/products/loctite-loctite-e-120hp-epoxy-2-1-ab-resin-adhesive-high-strength-bonding-meta
l-glass-ceramic-glue-50ml?variant=UHJvZHVjdFZhcmlhbnQ6MTQ3Mjc4NjY4&gad_source=1&gclid=CjwKCAiAz
c2tBhA6EiwArv-i6fGVYKR9yTZikY6bVEbdZjpkgptUIRsAMmBp5Hbh2jhMwAqTqW_9eBoCq5MQAvD_BwE
https://www.easycomposites.co.uk/xc110-416g-22-twill-6k-prepreg-carbon-fibre
- 0.24sqm Sample Pack
XC110 416g 2x2 Twill 6k Prepreg Carbon Fibre £23.00
Name | Link | Size/Quantities | % Weight Saved On Part & On the Car | Cost |
EB700 High
Temperature Epoxy Tooling Board | https://www.easyco mposites.co.uk/eb70 0-high-temperature-epoxy-tooling-board ?authuser=1 | Shared with Monte | N/A | £ 96.57 |
Loctite EA E-120HP (237128)
Toughened
Non-Sag 120-Min
Set Epoxy | ㅤ | 50ml/1.7oz Cartridge | N/A | £49.49 |
XC110 416g 2x2 Twill 6k Prepreg Carbon Fibre | ㅤ | 0.24sqm Sample Pack *2 | 77.16% / 1.5% | £23.00 *2 |
Total | ㅤ | ㅤ | 77.16% / 1.5% | £192.06 |
Manufacturing: Mold Cutting
I made my mold on Solidworks and exported it as a .stl file,
then imported into the QuickCAM Pro to make the
command file for CNC production. Then set up the machine
using 3D printed holders and calibrate using the xyz values
of the starting point. Afterall, start the machine and cut the
molding board.
Manufacturing: Prepreg processing
I had to cut the made molding
board in half to make sure it gets When oven cure is done, simply out easily after oven cured the hammer out the pre-cut mold and prepregs. Also making templates locates the screw holes required, for prepregs and cut the
after drilling the screw holes, the prepregs into desired shape prepreg carbon fibre part is done which wraps the mold around in
layers.
After laying and wrapping the mold with
prepreg carbon fibre, the mold is then put into
a vacuum bag and into the oven to follow the 4
stages suggested on the technical sheet of
prepreg for oven cure.
Final Assembly & Race
- Author:QiyueW
- URL:qiyuetech.net/article/1bead529-8cc7-4ce2-98c6-ad92aef8a230
- Copyright:All articles in this blog, except for special statements, adopt BY-NC-SA agreement. Please indicate the source!