Design of Lightweight Electric Vehicles

This article introduces the paper 'Design of Lightweight Electric Vehicles' submitted to the University of Waikato

1. Overview:

Title: Design of Lightweight Electric Vehicles
Author: Travis de Fluiter
Publication Year: March 2008
Publishing Journal/Academic Society: University of Waikato (Thesis)
Keywords: lightweight electric vehicles, Ultracommuter, titanium aluminide, automotive industry, electric vehicle design

2. Research Background:

Background of the Research Topic:

The research addresses the increasing importance of lightweight electric vehicles due to the rising cost of petrol and the environmental impact of emissions from petrol-powered vehicles. The design and manufacture of lightweight electric vehicles are presented as a solution to ongoing transportation issues.

Status of Existing Research:

Existing research and literature on electric vehicles are reviewed, focusing on the history of electric vehicles, their design, and development. The literature review covers various vehicle options including hybrid vehicles, hydrogen fuel cell vehicles, bio-fuels, and battery electric vehicles, with a detailed historical overview of electric vehicle development phases from the 1880s to the 21st century. The review also touches upon lightweight vehicle design, light weight alloys in the automotive industry, and fundamental vehicle mechanics.

Necessity of the Research:

The research is necessitated by the finite nature of crude oil resources and the urgency to reduce CO2 emissions from transportation. New Zealand's reliance on personal transportation and the global trend towards stricter emission regulations and fuel efficiency standards highlight the need for alternative vehicle technologies, particularly electric vehicles. The research aims to explore the potential of lightweight design and advanced materials to enhance the viability of electric vehicles.

3. Research Purpose and Research Questions:

Research Purpose:

The primary purpose of this research is to design and build a working prototype of a lightweight electric vehicle, named the Ultracommuter, as a solution to transportation challenges. A secondary purpose is to investigate the potential use of gamma titanium aluminide components in battery electric vehicles.

Key Research:

The key research encompasses:

Designing and manufacturing a lightweight electric vehicle prototype.
Integrating various vehicle components and systems in a cohesive design.
Utilizing advanced materials and manufacturing techniques for weight reduction and efficiency.
Testing the performance and driving characteristics of the Ultracommuter.
Exploring the potential application of gamma titanium aluminide in automotive components, specifically for electric vehicles.

Research Hypotheses:

While not explicitly stated as hypotheses, the research operates under the premise that:

An integrated design approach is crucial for successful electric vehicle development.
Lightweight design is essential for improving the efficiency and reducing emissions of electric vehicles.
Virtual engineering techniques can significantly aid in the design and optimization of electric vehicles.
Titanium aluminide components can offer performance benefits in specific electric vehicle applications due to their lightweight and material properties.

4. Research Methodology

Research Design:

The research employs a design and development approach, centered around the creation of a functional electric vehicle prototype. This involves conceptual design, detailed engineering design using Computer Aided Engineering (CAE) tools, material selection, manufacturing, and testing.

Data Collection Method:

Data collection methods are implied through the research process, including:

Literature Review: Gathering existing knowledge on electric vehicles, lightweight design, and materials.
Engineering Design and Simulation: Utilizing SolidWorks and FloWorks for CAD modeling, FEA, and CFD analysis.
Prototype Testing: Performance testing of the Ultracommuter chassis and vehicle, including driving performance evaluation during the World Solar Challenge.
Material Property Analysis: Reviewing existing data on titanium aluminide and other materials.

Analysis Method:

Analysis methods include:

Engineering Analysis: Applying fundamental vehicle mechanics and physics principles to design and performance calculations.
Finite Element Analysis (FEA): Using SolidWorks for structural analysis of components like suspension mounts and brake callipers.
Computational Fluid Dynamics (CFD): Employing FloWorks for aerodynamic analysis and optimization.
Performance Evaluation: Assessing the Ultracommuter's performance against design specifications and through real-world testing.
Cost Analysis: Estimating manufacturing costs for different production volumes.

Research Subjects and Scope:

The primary research subject is the Ultracommuter, a prototype lightweight electric vehicle designed and built as part of this research. The scope encompasses the design, manufacturing, and testing of this vehicle, along with an investigation into the potential application of titanium aluminide in electric vehicles. The research is focused on personal transportation and the automotive industry context, particularly concerning electric vehicle technology and lightweighting strategies.

5. Main Research Results:

Key Research Results:

Ultracommuter Prototype Development: Successful design and construction of a functional lightweight electric vehicle prototype, the Ultracommuter, capable of participating in the World Solar Challenge.
Lightweight Design and Material Selection: Effective use of aluminium honeycomb for the chassis and fibreglass for the body shell, achieving significant weight reduction.
Aerodynamic Optimization: Implementation of aerodynamic features like rounded front end, windscreen design, fastback rear end, full underbody, and wheel spats, resulting in a low drag coefficient (Cd of 0.24-0.25 estimated).
Electric Drive System Integration: Successful integration of in-wheel motors and Tritium Wavesculptor controllers, demonstrating high efficiency.
Battery System Performance: Utilization of Thundersky Li-ion batteries, showing good energy storage and thermal performance during testing.
Titanium Aluminide Potential: Identification of potential applications for titanium aluminide components in electric vehicles, particularly in brake systems and motor components, due to their lightweight and high strength properties.

Data Interpretation:

Testing of the Ultracommuter demonstrated driving capabilities comparable to internal combustion engine vehicles in terms of handling and acceleration, although ride comfort and high-speed stability required further refinement.
Aerodynamic analysis and efficiency figures suggested that the Ultracommuter achieved a low drag profile, contributing to energy efficiency.
Battery testing indicated satisfactory performance of the Thundersky Li-ion batteries, although battery management and reliability were identified as areas for improvement.
FEA analysis of a brake calliper design indicated the potential weight saving and increased safety factor achievable with titanium aluminide compared to aluminium.

Figure Name List:

Figure 4.1 Ultracommuter Chassis design
Figure 4.2 Chassis pieces laid out in SolidWorks model, and water jet cut aluminium honeycomb
Figure 4.3 Aluminium honeycomb chassis under construction
Figure 4.4 Roll cage design
Figure 4.5 Chassis testing by Dr Mike Duke and Jing Zhao
Figure 4.6 Interior models of the Ultracommuter
Figure 4.7 Ultracommuter Interior
Figure 4.8 Ultracommuter front profile
Figure 4.9 Windscreen bubble
Figure 4.10 Large curved A-pillar and windscreen transitions
Figure 4.11 The rear end of the Ultracommuter, a classic fastback design
Figure 4.12 FloWorks analysis
Figure 4.13 Ultracommuter surface area
Figure 4.14 Prototype hemp composite body shell
Figure 4.15 a) AlphaCam creating a cutting program b) An engineer simulates a virtual mill of the Ultracommuter body shell.
Figure 4.16 a) The 5-axis CNC creates a rough cut b) the finishing cut
Figure 4.17 Plug after molds have been lifted with mocked shut lines on it
Figure 4.18 Ultracommuter mold, blue gelcoat coated by fibreglass layers
Figure 4.19 a) Ultracommuter body fresh from the mold b) Aluminium strengthening bars laminated in
Figure 4.20 Ultracommuter Split lines
Figure 4.21 Ultracommuter bodyshell fitted to vehicle
Figure 4.22 The Ultracommuter body shell completed in red
Figure 4.23 Ultracommuter front suspension.
Figure 4.24 Rear suspension design.
Figure 4.25 Torque application of wheel motor vs conventional driveshaft
Figure 4.26 Ackerman steering geometry of the Ultracommuter
Figure 4.27 Pivot points of Ultracommuter steering
Figure 4.28 Ultracommuter wheel and tyre
Figure 4.29 High power system schematic
Figure 4.30 Electronics layout
Figure 4.31 Ultracommuter motor
Figure 4.32 Tritium Wavesculptor efficiency plot (www.tritium.com.au)
Figure 4.33 Zinc Air Issue source: www.electric-fuel.com
Figure 4.34 Battery testing rig
Figure 4.35 Cell discharge curves for Thundersky cells.
Figure 4.36 Ultracommuter battery pack
Figure 4.37 Ultracommuter Charging on WSC
Figure 4.38 Ultracommuter battery monitoring – Labview and DAQ card
Figure 4.39 Ultracommuter range verse velocity graph
Figure 4.40 Ultracommuter LPE lighting
Figure 5.1 Ultracommuter driving on WSC 2007
Figure 6.1 γ-TiAl structure (Leyens & Peters, 2006)
Figure 6.2 Comparions of lightweight materials (Leyens & Peters, 2006)
Figure 6.3 The 1956 Titanium Firebird II with a body made completely from titanium source:http://www.diseno-art.com/images/firebird_II_rear.jpg
Figure 6.4 Ultracommuter Brake calliper FEA comparison
Figure 7.1 Ultracommuter on a lotus chassis (courtesy of HybridAuto)

Figure 5.1 Ultracommuter driving on WSC 2007

6. Conclusion:

Summary of Main Results:

The research successfully demonstrated the design and construction of a lightweight electric vehicle prototype, the Ultracommuter, showcasing the potential of integrated design, advanced materials, and virtual engineering in achieving energy efficiency. The vehicle participated in the World Solar Challenge, validating its functionality and performance in challenging conditions. The study also highlighted the potential of titanium aluminide for specific automotive applications, particularly in reducing un-sprung mass in electric vehicles.

Academic Significance of the Research:

This research contributes to the body of knowledge on lightweight electric vehicle design by providing a practical example of integrated design methodologies and the application of advanced materials. It underscores the importance of considering vehicle mechanics, aerodynamics, and material science in the development of efficient electric vehicles. The detailed documentation of the Ultracommuter project serves as a valuable case study for future research and development in this field.

Practical Implications:

The research demonstrates the feasibility of building a functional and relatively high-performance lightweight electric vehicle using available technologies and manufacturing techniques. The findings have practical implications for the automotive industry, suggesting pathways for developing more efficient and sustainable electric vehicles. The exploration of titanium aluminide applications offers insights into potential material solutions for enhancing vehicle performance and reducing weight.

Limitations of the Research

The research acknowledges limitations primarily related to cost and experience constraints during the Ultracommuter project. Specifically, the reliability of the electronics system was identified as an area needing improvement. Handling and ride comfort also require further refinement. The study also notes that the high cost of titanium aluminide currently limits its widespread application, and further research is needed to optimize manufacturing and reduce costs.

7. Future Follow-up Research:

Directions for Follow-up Research
Future research directions include:
- Battery Technology Advancement: Continued research into battery technology to achieve higher energy densities, improved battery management systems, and enhanced reliability.
- Integrated Design Optimization: Further optimization of integrated vehicle design, focusing on body shell integration with the chassis and improved component integration for weight reduction and structural efficiency.
- Aerodynamic Refinement: Detailed aerodynamic optimization, particularly in areas like wheel spats, split lines, wheel arches, and cabin airflow, to further minimize energy consumption.
- Titanium Aluminide Material Research: Focused research on manufacturing and production methods for cast and PM titanium aluminide parts, as well as comprehensive testing of material wear and thermal properties for automotive applications.
- Suspension and Handling Improvement: Further development and refinement of the suspension system to enhance ride comfort and high-speed stability.
Areas Requiring Further Exploration
- Long-term reliability and durability testing of electric vehicle components and systems.
- Cost-effective manufacturing methods for lightweight electric vehicles and advanced materials.
- Comprehensive life cycle assessment of electric vehicles, considering material production, vehicle operation, and end-of-life disposal.
- Exploration of regenerative braking systems to potentially replace mechanical braking systems and further reduce un-sprung mass.

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9. Copyright:

This material is "Travis de Fluiter"'s paper: Based on "Design of Lightweight Electric Vehicles".
Paper Source: http://waikato.researchgateway.ac.nz/handle/10289/219

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Tags: Applications; ,CAD; ,CFD; ,Computational fluid dynamics (CFD); ,Efficiency; ,Electric vehicles; ,Microstructure; ,Review