Classroom Activity: Make a Motorized Cardboard Dinosaur

Today they will build an electric dinosaur that moves its arms using the power transferred from its wheels. Also, the body and wheels will be built using recycled cardboard and other reused materials! Students will learn about electrical circuits, mechanics and Eco-design. If well this guide shows how to make a basic dinosaur, students are encouraged to use their creativity and test alternative designs.

This lesson is based on “Yoshi the Trashosaurus”, a DIY dinosaur toy created with plastic trash. This version uses easier-to-get materials and it's classroom friendly, being that it doesn't require a rotary tool, a soldering iron or a heat gun.

Some definitions:

Eco-design: design of products with special consideration for the environmental impacts of the product during its whole lifecycle.

Upcycling (or Creative Reuse): is the process of transforming waste materials, useless, or unwanted products into new materials or products of better quality and environmental value.

Gearbox (or Reduction Box): a device that uses gears to convert the speed of a rotating motor into torque.

Switch: electrical component that can interrupt an electrical circuit, interrupting the current or diverting it.

Supplies

• 1 Pointy tool for making holes on plastic (small screwdriver, pointy scissors, soldering iron, etc.)
• 1 Roll of black double side tape
• 1 hot glue gun per 2 students
• 2 hot glue sticks per 2 students
• 1 Needle-nose pliers per every 2 students.
• 1 Plastic gearbox or Reduction box (with motor); like this.
• 1 AA Battery holder for 2 batteries, with switch.
• 2 AA Batteries
• 2 paper clips
• 2 plastic caps, more or less of 5 cm diameter (like the ones of 5 lt bottles water bottles)
• 1 Plastic hard straw for balloons (gearbox’s shaft must fit inside it)
• 1 Pencil
• 1 ruler
• 1 pair of scissors
• 1 Craft stick
• 1 Bamboo stick for kebab (thick)
• 4 brass fasteners
• 2 Small metal washers
• 2 Googly eyes
• 2 sheets of cardboard, more or less A4 size, maximum 3 mm of thickness (rigid, but easy to cut with scissors)
• 2 Dinosaur printed templates (Appendix)
• Color pencils for decoration

Step 1: Before the Lesson

1. Take the plastic caps and open a hole in the center. The hole must be big enough for the plastic hard straw for balloons to be inserted in a tight way. You can use pointy scissors, a screwdriver, or a power drill. Be very careful with your fingers. Also you can use a soldering iron, but there are risks of toxic fumes and burns, so you need to be extra careful, use respiratory protection and do this activity in a ventilated area. Also, make a smaller hole, more or less 1 cm away from the center of the caps.

2. Print the Dinosaur Templates – Right Side and Left Side (Appendix), one set of copies per student.

3. Make bags with the materials to distribute later to each kid.

4. Make a prototype of this robot, so you can show it to the students.

Step 2: Electromechanical Components

Take the craft stick, the battery holder and the gearbox. Stick a strip of mounting tape in the side of the battery holder opposed to the switch, and another strip of mounting tape to the gearbox. Then stick the battery holder, the craft stick and the gearbox together, in the way depicted by the photos.

Connect the wires of the battery holder to the poles of the motor. Insert the batteries, and check the rotating direction of the gearbox shaft. Consider that the battery holder will be the back of the dinosaur and the gearbox, the front; so the shaft must be spinning in a direction that allows the dinosaur to go forward. If it doesn’t, change the polarity of the cables.

Carefully cut 2 cm from the top end of the craft stick.

Step 3: Carboard Body

Stick each printed template on the cardboard sheets, using glue stick.

Carefully cut the cardboard following the pattern of the templates. Open a hole in the points marked with a white circle, using the point of the scissors. The holes must be big enough to allow the plastic straw to pass through.

Step 4: Wheels

Take the plastic straw and cut one segment of 8 cm and two segments of 3 cm each one.

Insert the 3 cm segments into the center hole of the plastic caps. Add some hot glue to fix them together. Caps will be the wheels, straws will be axles.

Step 5: Clips

Prepare the needle-nose pliers, the clips, the washers and the brass fasteners. Straighten the clips and using the pliers, make a small loop on each end.

Insert the brass fastener in one of the loops of the wire. Then, insert it inside the metal washer. Then, insert the fastener in the smaller hole of the wheel. Open the brass fastener’s legs so it gets locked on the wheel. Repeat the same procedure with the other fastener, wheel, washer and clip.

Step 6: Assembling the Body

Insert the 8 cm straw through the holes near the head of both templates. Then take the template piece marked as “head” and glue it to the head part of the body’s template.

Insert the gearbox/battery holder set from step 4. Check that the gearbox is facing front, the battery holder is facing back and the gearbox shafts are aligned with the inferior templates holes.

Take the wheels and fit the axle of each one to each shaft of the gear box.

Take the template marked as “jaw” and stick it with hot glue in the jaw of the dinosaur.

Step 7: Arms

Grab the kebab stick, the arms and two little squares made from cardboard. Insert the kebab stick through the small square, and then insert it in the hole located in the “shoulder” of the arm. Pass the kebab stick through the 8 cm straw. At the other side of the dinosaur, place the arm and the other cardboard square. Cut the remaining part of the kebab stick, leaving a little end of 5 mm on each side. Add a little of hot glue to fix the cardboard square to the kebab stick, being careful of not limiting the movement of the arms.

Step 8: Connecting the Arms to the Wheels

Now take the other two brass fasteners. Insert a fastener in the available loop of each clip. Then insert the fastener into the available hole of each arm. When this operation is done, open the “legs” of the fasteners to lock them on the arms.

Bring the cardboard template marked as “Tail”, and glue it to the tail.

Congratulations! Your “Trashosaurus Rex” is ready! Customize it with googly eyes, markers and color papers.