This project involves the design, fabrication, and testing of prototype transport systems. The transport systems must carry a raw egg on the forward edge of the system, travel five feet towards a solid wall, and stop within one foot of the wall. Students teams must design and integrate several interacting components, such as a propulsion device, brakes, and an egg cradle into a total design. You can expect to see some eggs crash into the wall, creating lots of excitement.
Students learn about designing systems in which interactions between several components must be considered. This inspires teams to generate and evaluate several ideas, choose the best combination of component parts, and split up the fabrication work.
Safely transporting hazardous and/or fragile materials is common in our modern world. Many types of engineers are involved with this type of activity. Mechanical and civil engineers design most of the systems that move these materials. The primary design goal of such systems is to carry a given cargo to its destination. Often, the starting point, path taken, or destination bring dangerous cargoes close to environmentally sensitive or populated areas where the consequences of an accident are serious and many times life threatening.
This project requires about five hours to present the project; allow students to design, construct and refine prototypes; test the final designs; and wrap things up. We suggest that you give the students about four hours for the design and fabrication. The students will also need about 16ft2 of area per team for fabrication. A large, smooth, flat surface in front of any solid wall will work for testing.
A ruler and yardstick will be necessary to make the staring line and measure the final distances that the eggs are from the wall. The system can be made and powered using any of the following materials but no others (let the students bring to class any items from this list that you wish to use):
string
aluminum and tin cans (opened or unopened)
spaghetti
cardboard (including corrugated)
cardboard rolls (such as paper towel and toilet paper)
paper
glue
paper clips
rubber bands
tape (Scotch type)
balloons
plastic straws
plastic soda bottles and milk jugs
wire coat hangers
aluminum foil
Also, provide some simple hand tools such as pliers, sheet metal cutters, scissors, a hammer, etc. so students can take advantage of all the available materials.
This project works well with teams of three to five students.
The first step in preparing for this project is to try it yourself. Read the Student Project Description and limit yourself to the listed materials. This will give you insight to the different ways the materials can be used. A week or so before you plan to start the project, ask the students to begin collecting the items on the materials list. Be sure each team will have enough raw materials to work with.
We recommend the following approach:
Divide the class into teams made up of three to five students per team. Have each team arrange themselves such that they are sitting together.
Distribute the student documents to each student.
Present this project to the class following the suggestions in the handbook (15-25 minutes).
Provide the students with about 60 minutes to discuss the principles, read the materials, and generate design ideas.
Give the students the working materials. At what point you distributing the eggs is really up to you. Since each team's design must support an egg, they will need to design and build an egg holder. We suggest that you have each team request an egg only when they are ready for it. You can emphasize that the egg is "rotten" and will smell terribly if they break it. You can also assess "penalty points" if a team breaks their egg prior to testing.
Give the teams 90 to 120 minutes to design, sketch, fabricate, and perform preliminary test on their transportation designs.
Formally test each transport system. Each test of a design should take about two minutes from preparing the design to running and recording results. We suggest that you might want to jot down notes about each design as each team comes up to test for later discussion.
Discuss the results of testing (about 5 minutes per design).
Review the project, discussing differences in designs, and pointing out innovative or interesting design solutions even if they were not outstanding performers.
Testing can be extremely exciting as each design transports a "rotten" egg to its destiny. Your class will probably enjoy watching each other's designs during testing; however, we emphasize that it is important to keep the testing procedure flowing smoothly. You will need to be organized for this stage of the project.
We suggest that you make up a chart on which to record each team's performance data and your notes about each design. You should have a "clean up crew" of two or three students standby with paper towels in case an egg breaks during testing. You might also want a student to act as a timing official and one that measures distances from the wall.
A test run commences when the timing official says "GO" (and starts the timer) and finishes when the design stops moving (the timer is stopped). The distance from the wall when the device stops moving is then measured and both the travel time and distance from the wall are recorded. A design's test run will deemed a failure if the egg is broken. A broken egg is one in which at least a visible crack is observable. If time allows, you can have this team replace their egg and go again.
Depending on the number of designs the class creates, we have found that the students enjoy making several runs with their designs. A team's total score would then be the average of all their formal test runs.
This project emphasizes teamwork and cooperative mechanical subsystems. Students will need to work well in teams in order to be successful and have a positive experience. This factor might influence how you make up teams; however, you will need to emphasize teamwork and keep teams whose members begin to diverge from common goals from doing so.
The main engineering principle involved is to harness some form of stored energy that will cause each design to travel towards the wall. Most students will opt for storing energy in a rubber band that they wind around an axle. There are other methods, but this one is the most obvious.
What students who take this approach do not immediately realize is that they might need some form of driving gear that increases the efficiency of the windings. Another consideration is the length of the rubber band. If the rubber band is too short, the momentum of the vehicle will cause the elastic to wind back around the axle and then unwind in reverse, causing the vehicle to move away from the wall. Proper testing by the students prior to formal testing will quickly show the students these problems.
This project illustrates to students that engineering designs often require cooperating subsystems, and in order to effectively build these subsystems, engineering teams must work well together toward common goals. This is the same principle as any other form of teamwork. Although we are not trying to emphasize competition, you should recognize those design that performed well. You might want to announce the final scores for each team; you should expect that they are ranked relatively closely, so that unless a team utterly failed, all teams performed well.
You should summarize what each team did by recognizing what types of subsystems were employed for different tasks and how successful they were. You should positively recognize even those designs that did not work well since most might have done so if more time were allowed. You should give special positive feedback to those teams who did not follow the norm and were especially creative, even if they were not so successful.
Working with tools that cut is always a concern. If students use cans or any metallic item, cutting metal tends to require more leverage that what most students are familiar with. This results in students using tin snips or sheet metal cutters in awkward ways. You need to remind those students to be careful and make sure that any slip will not cause them to hurt themselves or any other person.
This project was developed by John Garcelon.