3D Print Your Own Engine

In this multi-day lesson 6th-12th grade students will learn about internal combustion engines and will create their own working 3D-printed air-powered 4-cylinder internal combustion engines.

Objectives:

Students will:

• learn how an engine works
• use Tinkercad to design and print several engine pieces
• learn about combustion
• learn about the history of the internal combustion engine
• see how engines are manufactured today
• assemble a working 3D-printed, air-powered engine
• see examples of what engines are able to do
• use building bricks to design something that their engines can power

This lesson is adapted from a week-long camp that my husband and I designed and led this past summer. The camp, designed for 6th-12th graders, introduced students to 3D printing while they learned about internal combustion engines. We used an engine design developed by Eli Smith, one of my husband's former university students. As part of the camp, students used CAD software to re-create the different parts of the engine, printed them out on 3D printers, assembled their engines and designed Lego projects that could be powered by their engines. At the end of the week, each student was able to take his or her engine home.

Materials and Resources Needed:

• 3D printer(s)
• Filament (PLA)
• Computers (ideally one per student)
• One completely printed and assembled engine (as a sample for students to see)
• Pre-printed engine parts (See Step 1: Preparation for a list of the parts needed.)
• Hardware (1 set per student) (complete kits available here or you may piece the kit together)
• Classroom Projector (optional for showing explanatory YouTube videos)
• Balloons (for optional experiment on Day 2)
• Hydrogen Gas (for optional experiment on Day 2)
• Candle attached to the end of a stick (i.e. yard stick) (for optional experiment on Day 2)
• Classroom set of precision screwdrivers (for assembly on Day 4)
• Classroom set of small files (for assembly on Day 4)
• Several sets of pliers (for assembly on Day 4)
• Super glue (for assembly on Day 4)
• Air compressor (for testing and running the engines on Day 4 and Day 5)
• Building bricks, including axles (for Day 5)

Timeline

This lesson has been written as a 5-day project. However, depending on the experience level of your students and the length of your class periods, you may need to modify that time frame. In particular, Day 4 may require 2-3 days.

Modifications

If your budget and/or timeframe do not allow, you can also modify the lesson so that you do not need one engine per student. You could allow all of the students to participate in the design process but only print out one engine for the class. Or you could have students work together in teams of 3 or 4 to design the pieces and only print out one engine per team.

Step 1: Preparation

Students will design and print 6 of the engine pieces. See pictures above. (Optional: You could have students design more pieces if your students are more advanced or if you have more class time.)

You should print the other engine pieces ahead of time so that they will be ready for Assembly Day (Day 4). The .stl files for all engine pieces are available below. You will need the following pieces for each student:

• Engine Block
• Cylinder Head
• Main Camp (2)
• Engine Stand
• Crank Gear (2)
• Crank Middle
• Crank Throw (2)
• Flywheel Hub (2)
• Cam Middle (3)
• Cam End
• Cam Driver
• Header (Optional: The header is for aesthetic purposes only.)

Tips for printing:

• Be sure to allow enough time for printing these parts. You will likely want to start a few weeks ahead of time (especially if you only have one 3D printer).
• Most of these pieces are small so that you will be able to fit the pieces for multiple students on one plate.
• You can allow students to choose their colors. However, if you want to keep things simple, print them all in one or two colors (maybe silver and black), and then consider allowing students to choose the colors for the parts they design.

If you haven't used Tinkercad before, go to www.tinkercad.com and create an account. Once you have created your account, click on the option to Create a Class. Follow the steps to set up a class. Be sure to note your Class Code and your students' usernames, so that you can give that information to your students when they are ready to begin designing.

Step 2: What Is an Internal Combustion Engine?

Part 1: Explanation

Engage students and evaluate their background knowledge by asking questions, such as:

• What makes your car go?
• What makes an engine work?
• What happens to the gas when it gets to the engine?
• How does the engine actually make the tires move?
• Why are traditional cars considered bad for our environment?
• What causes these emissions?

There is no need to tell students the answers to these questions now. You just want students to think and hopefully debate and discuss with one another. Assure students that you will discover the answers as part of this lesson.

Show students the following YouTube video describing how an internal combustion engine works:

You can illustrate the same principles using a different video, a PowerPoint slide or a drawing on the whiteboard, if you prefer.

After the video, show students a complete 3D printed engine. Show them how it works. Point out the parts that were described in the video (the cylinders, the pistons, the crank shaft, the cam shaft, the connecting rods, etc.)

Part 2: 3D Design Time

Explain to students that today they will create the spacer and the piston. Show them where those parts are located on the sample engine and discuss the function of those parts.

Have students go to www.tinkercad.com and log in. You will need to give them your Class Code and let them know their usernames.

Then have students open a second browser window. In the second window they will watch a tutorial that will walk them through the design process. Give students the following link:

Crank Spacer & Piston

Show students how to re-size and position their two windows, so that they can see both simultaneously. Explain to students that they should:

1. Watch one step in the video tutorial.
2. Pause the video.
3. Complete the step in Tinkercad.
4. Play the video again to see the next step.
5. Repeat until they have completed the tutorial.

(Without this explanation many students will try to watch the tutorial and complete the action in Tinkercad at the same time and will generally get behind and lose track of what they should be doing.)

Students will likely all finish at very different times, so be sure to have some options ready for those who finish early. Some things these early finishers can do:

1. Encourage them to help out their classmates who are still working.
2. Allow students to design other pieces of the engine. Advanced students can learn to re-create the engine pieces by examining the pre-printed pieces and using calipers to determine the sizes and placements.
3. Show the early finishers how to go from the saved .stl file to the final 3D printed piece. Demonstrate the slicer software and how to set everything up on the 3D printer.

Step 3: What Is Combustion?

Part 1: Demonstration

Introduction

Show students the following video to review what they learned in the previous step and to prepare them for today's demonstration.

Ask students about the process of combustion, replaying the video in slow motion, if necessary:

• When the valve opens, what fills the combustion chamber? (a mixture of air and gas)
• When the piston comes up, what happens to the air and gas mixture? (It is compressed.)
• What happens when a spark is applied to that compressed mixture of air and gas? (an explosion, pushing the piston down again)
• What happens when the second valve opens and the piston comes up? (The spent emissions from the explosion are released.)

Experiment

The following experiment is an impressive demonstration of combustion, one that students are unlikely to forget. It does involve explosions, so be sure to follow usual safety precautions. Wear safety goggles and ear protection. Perform the experiment under a hood in a chemistry lab (or somewhere else with a clear blast shield). Be sure to warn others who will be in the vicinity (i.e. nearby classrooms) that there will be loud explosions. Use 9"-12" balloons and do not inflate them fully.

Note: If you are unable to perform the experiment, you may show students videos of others performing it. It won't be quite as effective, but it will still prove the point.

Materials

• Balloons
• Candle attached to a long stick (such as a meter stick)
• Hydrogen Gas

Procedure

• Encourage students to use their phones (if they have them, or give one reliable student your phone) to video the experiment. It is especially fun and useful if they use the slow motion feature.
• Blow up one balloon as you usually would. Hold it under the hood. Touch the lighted candle to the balloon. It will pop and make the noise that students are accustomed to.
• Blow up the next balloon using only hydrogen gas. Tell students to put their fingers in their ears. Then hold the balloon under the hood and touch the candle to it. There will be a much louder bang and a flame. Explain to students that hydrogen mixes with the oxygen in the air, forming an explosive mixture.
• Fill up the balloon about 2/3 of the way with hydrogen gas and then finish blowing it up with air. Again, warn students to cover their ears. Place the balloon under the hood and touch the candle to it. This will produce an even louder bang and a larger flame. Explain to students that it is the mixture of the hydrogen and oxygen that is so explosive. In the second trial it took time for the hydrogen to mix with the oxygen in the air after the flame was applied, so the explosion was not as violent. In the third trial the hydrogen and oxygen were pre-mixed before the flame was applied, making the reaction faster and more extreme.

Wrap-up

Remind students how this experiment applies to internal combustion engines. In an internal combustion engine, gas and air combine in the combustion chamber. Then a spark is applied by the spark plug producing the explosions that ultimately power the engine. Also, show them the sample 3D printed engine and explain that it is air-powered only. Since there is no gas, there is no explosion, and it will therefore be safe to take home!

Part 2: 3D Design Time

Explain to students that today they will create the lifter and the cam gear for their engines. Show them where those are on the model engine and explain what they do.

Follow the same procedure as you did for Design Time in Step 1, except give students this link to the tutorial for creating the lifter and the cam gear.

Lifter and Cam Gear

Step 4: How Was the Internal Combustion Engine Invented?

Part 1: Explanation

Ask students questions about the history of the internal combustion engine to test their knowledge and to stimulate their interest.

• When was the first car invented? (Make it a competition to see whose guess is the closest.)
• How is the modern car better than a car 20 years ago? 50 years ago? 100 years ago?
• What were some of the challenges that early engine and vehicle inventors faced? What problems did they have to solve?

Show students the following video (25 minutes) and then re-visit the questions you posed.

Part 2: 3D Design Time

Explain to students that today they will create the flywheel for their engines. Show them where the flywheel is on the model engine and explain what it does.

Follow the same procedure as you did for Design Time in Step 1, except give students this link to the tutorial for creating the flywheel.

Step 5: How Is an Engine Made?

Part 1: Explanation

This is a great time to invite a guest speaker. Most cities and towns have some type of manufacturing plant related to engines or cars. Find out what is available near you, and see if someone from the facility would be willing to come to your class to talk about the work that they do, or you could consider taking a field trip. We live in Jackson, Tennessee, home of the Toyota Bodine Aluminum facility, which manufactures engine blocks for Toyota. The plant sent a representative, who showed the students a short PowerPoint and video with information about the facility and a brief description of the manufacturing process they use. The students were then able to ask questions and really see how what they are learning is useful in the "real world."

If you cannot find a guest speaker or arrange a field trip, show students a video from a manufacturing facility (preferably something local). Here is the video from Toyota Bodine Aluminum:

Part 2: Assembly

It is time to put everything together. Consider inviting volunteers (i.e. parents, other teachers, older students) to your classroom to help with the assembly process, especially if you are using this lesson with younger or less technically-inclined students. Anyone who can use a screwdriver will make a great volunteer. There are multiple bolts to attach, and younger students may begin to complain that their fingers are tired.

When you are ready to begin assembly,

• Set up a gluing/cutting station (with super glue and wire cutters) and a testing station (with an air compressor).
• Give each student a small box with their pieces in it. (We used old filament boxes.) Emphasize to them the importance of keeping everything together. If they drop anything, pick it up immediately.
• Give each student a small screwdriver, a small file and the directions for assembly.
• The directions for assembly are available using this Instructable or with the .pdf document below.
• Allow students to assemble at their own pace, assisting those who need it. Encourage students to help each other, too.
• Let students know that for Steps 3 and 16 they should go to the gluing/cutting station and that when they think their engine is ready (Step 19), they should go to the testing station.

Step 6: What Can Engines Do?

Part 1: Explanation

Have students hold their assembled engines as they watch the following video. Point out that this describes a diesel engine, not a gasoline-powered one. See if they can figure out what is different. Also, encourage them to point to the parts of the engine as they are described in the video.

At the conclusion of the video, ask students the following questions:

1. What is different between a diesel engine and a gas-powered one? (There is no spark.)
2. According to the video, what type of motion does the engine generate? (Rotary motion)
3. What does that mean? (The engine spins things.)
4. On a car how do we see this in action? (The engine causes the wheels to spin.)
5. Can you think of things besides cars that can be driven by an engine? Encourage students to think of things that spin. (Carousels, ferris wheels, windmills, helicopter blades, ship propeller, etc.)

Part 2: Design Time

Students will now design their own "machines" made of building brick toys that can be driven by their engines.

We have 3 boys and an overabundance of Legos, so we brought in our own Legos for this project. If your supplies are more limited, encourage students to bring their own pieces from home. Let them know that they will especially need axles and gears. Of course, you can also purchase Lego sets. The Simple Machines Set or the Lego Classic Bricks and Gears Set are good choices.

Encourage students to brainstorm ideas for what they could create with their building bricks that their engines could power. Show them where the axle attachment point is on their flywheel. Many students will likely want to build cars, but remind them that the car will be tethered to the engine and the air compressor. They can build a car, but they will only be able to watch the wheels spin. Encourage them to think of other things that spin (Question #5 above). If they need further inspiration, you can show them this video:

As students build, help them test their ideas with the air compressor.

Step 7: Show Off!

Once your students have completed this lesson on internal combustion engines, give them the chance to show off what they have learned. Have an open house and invite their parents or other teachers and students at school. Give them the chance to explain how their engines work and how the engines power the machines they created.