Hands-on Activity Creative Engineering Design:
Model EV Design Challenge

Learning Objectives

After this activity, students should be able to:

• Understand and apply the engineering design process (EDP) to design, build, test, and iterate a model EV.
• Construct a basic EV motor circuit and explain how it works.
• Use basic CAD technology for design.
• Understand greenhouse gas emissions and carbon footprint, and how different vehicle fuels affect them.
• Explain connections between transportation and environmental justice-related issues and solutions.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

International Technology and Engineering Educators Association - Technology

Materials List

EV motor circuit provided for each team:

• DC Motor
• two AA rechargeable batteries
• AA battery pack for two batteries with on/off switch
• two alligator clips

Basic car components (team chooses component materials):

• Chassis:
  • stiff, lightweight frame material (cardboard, wood, plastic container, popsicle sticks, etc.)

OR 

• CAD modeled and 3D printed or laser cut
• Drivetrain (attached to chassis to integrate motor, axles, wheels):
  • pulley system (two pulley wheels, one on motor spindle, one on axle, connected by a rubber band)

OR

• gear system (two interlocking gears, one on motor spindle, one on axle)
• Wheels & Axles:
  • axles (metal, wood, plastic, etc. dowel rods)
  • straws (glue to bottom of chassis, thread axle through)
  • toy wheels, plastic caps, etc. to attach to axles

Suggested additional materials for class use:

• classroom battery charger and extra batteries
• basic tool kit for the classroom (rulers/tape measures, hammers, screwdrivers, wrenches, pliers, etc.)
• foam core, Styrofoam
• stiff base material (thin plywood, balsa wood, plastic or metal sheeting, etc.)
• hot glue gun and glue sticks
• duct tape, rubber cloth tape
• scissors, utility knives, hand saws
• sandpaper
• markers
• toy/model wheels, plastic bottle caps, spools
• wood, metal, plastic dowel rods
• cardboard boxes and tubes
• cans (aluminum, tin)
• plastic bottles
• straws
• Popsicle sticks, craft sticks
• rubber O-rings
• rubber bands various widths
• coat hangers, wire
• silicone or other caulking
• nails
• screws, eyebolts
• miscellaneous extra materials provided by teacher and students

Worksheets and Attachments

Pre-Req Knowledge

Students should be familiar with the EDP, and have basic knowledge of energy forms (electrical circuits, chemical and mechanical energy), and physics principles (simple machines (pulleys, axles, and wheels), complex machines (gears), and motion of objects (friction, speed)).

Introduction/Motivation

Welcome to the Creative Engineering Design Electric Vehicle Challenge! By working as an engineering design team, you will learn the basics of electric vehicle (EV) technology and make your own model EV car that will run on rechargeable battery power.

In this project, your team will plan, design, build, and test an electromechanical vehicle. You will have to apply what you know from math, physics (including simple machines, pulleys, gears, friction, energy, electrical circuits, and Ohm’s Law), and the engineering design process (EDP) to optimize the performance of your vehicle.

When your vehicle is complete, you will compete in a final showcase that judges your electric battery cars on speed and design.

You will gain first-hand experience of the EDP by going through several of its steps:

When you design your car, you will start with some ideas in your head and turn them into real-life models that work. Design is different from normal problem-solving, because:

• You don’t know what the problems are (you discover and solve problems as you go along, and everyone’s challenges will be different).
• There is never one right answer!

Designers have to deal with trade-offs. For example, when a car designer uses a larger engine for greater performance, this usually sacrifices fuel efficiency. In a sports car, performance and speed are very important. But in a city car, fuel efficiency is more important. So it is up to the designer to decide which are the most important goals. Even though there is no one right answer, some answers may be better than others for a particular application. Obviously, the best-designed car is the fastest!

Procedure

Getting Started:

The digital engineering notebook will provide student teams with information and ideas as they build their model EV cars. Each team will keep a digital engineering notebook using the slide deck to document the model EV design-build-test. Include photos, videos, and narrative descriptions at each stage.

• Power source: How the EV battery-powered motor works
• Chassis: How to build the frame of the car
• Wheels and bearings: How to make wheels that turn
• Transmission: How to transfer power from the motor to the wheels
• Body shell: How the shell affects car performance

In general, when teams design, it is good for them to keep the different parts in mind, but they should not worry about the details of each component until they are ready for them. Each build section includes four informational parts:

• Purpose
• Ideas
• Concept
• Suggested materials

The concept section will raise issues that will help teams decide how to make the right decisions and build their model EV car.

Encourage teams to experiment as much as possible early on and not worry about making mistakes: “Mistakes” are essential to engineering! It is always the case with design that you don’t know what the problems are until you encounter them. Tell teams to get their hands dirty and have fun!

Before the Activity

• Order and collect project materials and equipment, as listed.
• Assign 2-4 students to engineering design teams.
• Make and share digital copies of the Engineering Digital Notebook for each team.
• If possible, make your own model EV.

Project Summary

Week 1: Creating a plan to build the drivetrain developing the initial design sketch.

M: Introduce model EV design project, student engineering notebook, explain collection of resources for final design expo at each stage

Tu: Brainstorm car design ideas, students start collecting and bringing in materials.

W: Students start designing individual car components and assessing component material choices.

Th: Students continue designing and selecting car component materials.

F: Students finalize car design and material choices.

Deliverable: Assignment 1: Final design of Concept Sketch

Week 2: Creating a plan to build the drivetrain. Designing and creating a car body.

M: Students get approval of final design and gather materials, start building chassis.

Tu: Students continue chassis building.

W: Students start building drivetrain using  motor, battery, battery holder, alligator clips, gears or pulleys, axles and wheels.

Th: Students complete the drivetrain and finish building chassis.

F: Students connect drivetrain to chassis (front or rear), use bearings to connect axle and wheels to chassis, align gears on motor and axle.

Deliverable: Assignment 2: Drivetrain-motor circuit, gearing, axles and wheels, bearings, and chassis integration

Week 3: Optimizing and testing performance.

M: Students complete drivetrain to chassis, start building the car body.

Tu: Students finish car body and final car details.

W: Students test car and record data.

Th: Students revise car design based on trial results.

F: Students retest cars to analyze redesign effectiveness.

Deliverables: Assignment 3: Car chassis, drivetrain, and body completed; Assignment 4: EV car trials; redesign, iterate, and re-test, if possible.

Week 4: Presenting final EV model car.

M, Tu: Students finalize presentation slides, video, or poster, of team’s car design choices

W-F: Students conduct Design Expo team presentations

Deliverable: Assignment 5: Design Expo Final Presentation (summative assessment)

During the Activity

Introduction and Motivation:

1. Read the Introduction/Motivation section to the class.
2. Divide the class into engineering teams of 2-4 students.
3. Project the activity slides, and go over the introduction to the Creative Engineering EV Design Challenge and NREL Junior Solar Sprint video, which inspired this project.
4. Go over the EDP of the activity.
5. Go over the project assignments.
6. Go over the project timeline of the activity.
7. Go over the rubric for this activity.
8. Optional: Have teams assign 1-2 students as co-leads per team role:

1. Lead Designer - This person is primarily responsible for creating the Concept Sketch and leading the overall design of the car.
2. Electrical Engineer - This person is primarily responsible for planning how the batteries, motors, resistors, and LEDs will connect, and also responsible for creating the Circuit Diagram. This is the only team member who can use the soldering iron.
3. Mechanical Engineer - This person is primarily responsible for planning how to connect the motor to the drive axle and optimizing the car’s Performance.
4. 3D Modeler / Artist - This person is primarily responsible for 3D-modeling the car body and enhancing the Aesthetics of the car.
5. Project Manager -  This person leads discussions, resolves disputes, assigns tasks, manages time, and makes executive decisions. They should have strong leadership skills. They should also have one of the 4 roles listed above.

9. Go over the Model EV Design-Build Constraints.
10. Go over the Model EV Materials & Equipment.
11. Describe expectations and the digital engineering notebook for teams to use throughout the project:

1. The digital engineering notebook provides teams with information and ideas as each team builds their model EV car.
2. Each student will keep a digital engineering notebook using these slides to document the model EV design-build-test.
3. Students should include photos, videos, and narrative descriptions at each stage.
4. Remind students: When you design, it is good to keep the different parts in mind, but don’t worry about the details of each component until you are ready for them. Each build section is composed of four informational parts: purpose, ideas, concept, and suggested materials.
5. Let students know that the concept section will raise issues that will help students decide how to make the right decisions and build the team’s model EV car.
6. Remind students: Experiment as much as possible early on and don’t worry about making mistakes. It is always the case with design that you don’t know what the problems are until you encounter them.

Assignment 1 – Concept Sketch: Plan and design model EV:

1. Tell the students: Engineers start with concept to build out their ideas to solve problems or find solutions when designing products and processes. This important step saves time and money as the engineering design process is followed to make ideas become reality.
2. Have students get into their teams and brainstorm ideas for their vehicle.
3. Have students consider the following questions:

Chassis & Body: What object(s) will the team use for the chassis and body of their car? Consider size, weight, material, and aerodynamic qualities.

Drivetrain: How will the team transfer energy from the electric motor to the drive axles? Potential options include:

• Option A: Use pulleys and rubber bands to connect the motor to a drive axle.
• Option B: Use gears to connect the motor to the drive axle.

Wheels/Axles: What type and size of wheels and axles will the team use?

Optimizing Performance: How will the team optimize their car to perform well in all Triathlon events?

1. Increasing wheel traction to minimize slippage.
2. Reducing weight.
3. Reducing axle friction.
4. Increasing aerodynamics.
5. Selecting the optimum gear/pulley ratio for maximum torque and minimum slippage.
6. Optimizing the drivetrain to ensure the rubber bands, gears, or fan blade consistently transfer the maximum amount of energy from the motor to the wheels.
7. Optimizing alignment so the car drives straight.
8. Wiring the motor, battery and battery holder, alligator clips

Aesthetics / Decoration: Stickers, paint, markers, logos, and LEDs will be available to decorate the car.

Assignment 2 - Drivetrain: Motor circuit, gearing, chassis, bearings, axles and wheels integration completion:

1. Your team’s next task will be to design and build a drivetrain to power your model EV.
2. Have students get into their teams and brainstorm ideas for their vehicle.
3. Have students consider the following questions:

Motor Circuit: Build and test your motor circuit using the required materials provided.

Gearing: Build your gear choice using selected materials. How will the team transfer energy from the electric motor to the drive axles?

• Option A: Use pulleys and rubber bands to connect the motor to a drive axle.
• Option B: Use gears to connect the motor to the drive axle.

Wheels/Axles: Select an axle and wheel combination. What type and size of wheels and axles will the team use?

Bearings: How will the team attach the wheels and axles to the chassis? How will the motor, gears, and axle and wheels integrate?

1. Increasing wheel traction to minimize slippage.
2. Reducing weight.
3. Reducing axle friction.
4. Increasing aerodynamics.
5. Selecting the optimum gear/pulley ratio for maximum torque and minimum slippage.
6. Optimizing the drivetrain to ensure the rubber bands, gears, or fan blade consistently transfer the maximum amount of energy from the motor to the wheels.
7. Optimizing alignment so the car drives straight.
8. Wiring the motor, battery and battery holder, alligator clips

Chassis: This is the foundation of the car. Will the drivetrain be front-wheel drive or rear-wheel drive?

Assignment 3 - Car Body: Model car body, including aerodynamics and aesthetics, completion:

1. Your team’s next task will be to design and build the body of your model EV.
2. Have students get into their teams and brainstorm ideas for their vehicle.
3. Have students consider the following questions:

Car body: What object(s) will the team use for the body of their car? Consider size, weight, material, and aerodynamic qualities.

Aerodynamics: How will you design and build the body of your model EV to have the least air resistance?

Aesthetics / Decoration: Stickers, paint, markers, logos, and LEDs will be available to decorate the car.

Optional: Car & Track Connection: How will you design and attach the eye hook to the under chassis to attach the track guideline?

Assignment 4 - Model EV Test: Conduct time trials over a set distance and record the time in seconds. Calculate speed by dividing distance traveled by time to complete the distance. If extra time is available, iterate on car design and re-test:

1. Three Car Trials: Create a data table with distance, time, and speed columns (speed=distance/time). Record model EV cars results.
2. Re-design Ideas: How will the team propose to re-design your model EV to make it faster? To make it lighter? To make it sturdier?, etc.
3. Re-test Results: How did your re-designed EV model car perform? Run three more trials (data table with distance, time, calculate speed) Record your model EV cars results.

Assignment 5 - Design Expo: Final presentation of model EV design, function, and reflections:

1. As teams, have students create a final Design Expo product of their choice:

• Slides
• Video
• Poster
• Other presentation ideas with teacher approval

2. Teams will present their final product and model EV car during the final Design Expo presentation in class:

1. Demonstrate/explain your model EV design.
2. What components did you use to build your model EV?
3. How does your model EV motor circuit work? What is the motor power source (type/number of batteries)?
4. How did your team work together on the model EV project? Did you have team roles or a leader?
5. What successes did your team have in designing your model EV? What are you most proud of?
6. What challenges did your team face in designing your model EV? How did you overcome them?
7. If you had additional time and/or materials what future changes would you make to your model EV? Why?
8. What aspects of the Environmental Justice StoryMaps resonated most with your team in relation to EVs (air quality, health, community and environmental impacts, transportation connections)?

   

Vocabulary/Definitions

axle: A bar connected to the center of a circular object such as a wheel or gear that allows or causes it to turn.

battery: A device that produces electrical energy from chemical energy.

chassis: A supporting frame or structure, such as for an automobile.

circuit: A closed (connected) systems of wires and parts through which electricity can flow.

drivetrain: A system including all the parts linking the engine or motor of a vehicle to the wheels.

gear: A complex machine consisting of a circular object with teeth of such form, size, and spacing that they mesh with teeth in another gear to transmit or receive force and motion.

motor: A device that changes a form of energy (in this case, electrical energy) into mechanical energy to produce motion.

pulley: A simple machine that uses a wheel with a groove in it and a rope that fits into the groove.

Assessment

Pre-Activity Assessment

Show the Engineering Design Process graphic to the class. Have students do a think-pair-share to describe what the engineering design process is and overview of how they would use it if they were creating or improving a product or process.

Activity Embedded (Formative) Assessment

Students complete the following activities:

1. Complete one or more 1-day engineering design challenges to introduce the engineering design process.
2. Apply the engineering design process in crash test and mousetrap design challenges.
3. Use Tinkercad 3D Design to learn basic CAD skills and design an EV concept car.
4. Use Tinkercad Circuits simulator to learn basic circuits skills.
5. Build an EV motor circuit with basic electrical components.
6. Complete the Environmental Justice (EJ) StoryMap collection check for understanding documents to build understanding EJ concepts.

Post-Activity (Summative) Assessment

Student teams create and give a presentation to demonstrate learning and knowledge in applying the engineering design process to design, build, test, and iterate a model EV to answer the following summative questions?

• Demonstrate/explain your model EV design.
• What components did you use to build your model EV?
• How does your model EV motor circuit work?
• What is the motor power source (type/number of batteries)?
• How did your team work together on the model EV project? Did you have team roles or a leader?
• What successes did your team have in designing your model EV? What are you most proud of?
• What challenges did your team face in designing your model EV? How did you overcome them?
• If you had additional time and/or materials what future changes would you make to your model EV? Why?
• What aspects of the Environmental Justice StoryMaps resonated most with your team in relation to EVs (air quality, health, environmental impacts, transportation connections)?

Safety Issues

Provide students with safety glasses when they are building EV motor circuits, and if they are using hand tools. Have students ground themselves by touching something metal to discharge static electricity before working on any circuits. Keep liquids (water bottles, etc.) away from all electrical circuits. Use only brushed DC hobby motors (with two leads) and 1-2 AA or one 9V battery as the power source for the model EV motors.

Troubleshooting Tips

There are myriad of elements too numerous to list in this project that teachers can search the internet for advice or guidance in designing, building, and testing model EVs. The following NREL Junior Solar Sprint reference resources were referenced in this project to support the designing, building, testing, and iterating on an alternative energy model vehicles:

Junior Solar Sprint Classroom Investigations

Junior Solar Sprint Teacher and Mentor Guide

Junior Solar Sprint Student Guide

So...You Want to Build a Solar Model Car

Inside Tips on Parts and Construction

Junior Solar Sprint Host Guide

Activity Scaling

For lower grades or beginner-level students: Use the same motor components and kit materials for all teams’ model EV designs to limit variability and failure points, etc. Model each step of the design-build-test-iterate process for teams. Ask teams that have mastered an element to near-peer teach other teams that are struggling or have questions.

For higher grades or advance-level students: Use the different motor components (e.g., different number of batteries, 9V batteries, different DC motor sizes, incorporate breadboard and microcontrollers for additional light circuits, breaking, etc.), allow CAD and 3D printing of chassis and drive train gears/pulleys, offer open-ended selection of materials for teams to create a wide-range of EV model designs, etc. Mentor student teams, as needed, instead of giving direct instruction. Ask teams that have mastered an element to near-peer teach other teams that are struggling or have questions.

Other Related Information

The following NREL Junior Solar Sprint reference resources were adapted for this project:

Junior Solar Sprint Classroom Investigations

Junior Solar Sprint Teacher and Mentor Guide

Junior Solar Sprint Student Guide

Inside Tips on Parts and Construction

Copyright

Contributors

Supporting Program

Acknowledgements

This curriculum was developed under National Science Foundation grant numbers 1941524 and 1941701. Any opinions, findings, and conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.