How to Build Mouse Trap Race Cars

School projects often include building various experiments and toys, and one popular physics experiment includes building a car propelled by a mouse trap. These cars can include a variety of materials, and students are often encouraged to plan and build their own designs. One simple way of building a mouse trap car is to construct a frame from cardboard, and this construction uses many household objects.

Things You'll Need

• Cardboard
• Ruler
• Scissors
• Utility knife
• Super glue
• 3 Popsicle sticks
• 2 Metal paper clips
• Needle-nosed pliers
• Snap mouse trap
• Wire clothes hanger
• Drinking straw
• 4 plastic juice caps
• Thin metal wire
• String or thread

Instructions

1. Measure a rectangular piece of cardboard 5 inches tall and three inches wide. Cut out this rectangle from your larger piece of cardboard with scissors or a utility knife.

2. Glue Popsicle sticks vertically onto the cardboard, with one stick sitting on each of the 5-inch sides. Center the sticks on the 5-inch side if they are not 5 full inches long. These pieces will serve as supports to give your mouse trap car more strength. Allow the glue to dry before continuing.

3. Cut your third Popsicle stick in half. Glue one half horizontally between the two sticks already in place, at the top of the two sticks. Glue the second half between the two sticks, leaving about 2 inches between the stick and the bottom of the cardboard. Allow the glue to dry before continuing.

4. Measure ½ inch from each side of the cardboard frame, marking the measurements on the bottom side of the frame. Measure about ½ inch upward toward the bottom horizontal Popsicle stick. Cut out this small piece of cardboard from the frame.

5. Bend both of your paperclips open, pulling each end outward so that the final shape is a zigzag that is even on both sides. Use a set of needle-nosed pliers to cut out the “S” shape in the center of each clip, leaving you with four separate end pieces. Trim any excess off of the ends, so that the two points of each piece are equal in length.

6. Insert the paper clips point-down through the side of the frame that has the Popsicle sticks. These clips will serve as the wheel holders for your car. Set two in back and two in front, one of each on each side of the frame. For the back wheels, center the paperclips on each side of the small rectangle you cut out in step 4. For the front wheels, insert the clips on either end of the horizontal Popsicle stick.

7. Remove the paper clips, leaving behind two holes in the cardboard where each was inserted. Grasp the center of each paper clip with the needle-nosed pliers and press the points against your work surface, bending them upward. When you are done, the points of each clip will run perpendicular to the loops at the top.

8. Insert the points into the holes again. When you get to the bent part, turn the clip so that the horizontal pieces protrude horizontally into the cardboard. These points will hold the paper clips secure. Bending them will ensure that there are no protrusions from the bottom of your frame.

9. Cut open a wire clothes hanger. Use the needle-nosed pliers to snip the hanger off where the straight edge goes into the hook at one side. Thread the straight end through one set of wheel holders on the bottom of the frame, creating an axle. Allow the wire to extend 1 inch beyond the frame and snip the wire off. Repeat with the other two wheel holders, using a different area of the wire hanger. You will be left with two individual axle pieces.

10. Thread the front axle piece through a drinking straw. Cut the drinking straw so that it covers the entire axle except 1 inch on each end. Cut the remaining pieces of straw so that they cover the distance between the real wheel holders and 1 inch from each end of the rear axle. The center of the rear axle should be exposed. The straw will reduce any wobble from the axle, making the car more stable.

11. Measure to the exact center point of the top of each juice cap. Use the rear axle to pierce through that center point. The top of cap should face outward. Add a drop of super glue to the hole and thread the axle, the piece of drinking straw, the frame, the other piece of straw and finally the second juice cap to complete the rear wheel assembly.

12. Repeat step 11 to form the from axle.

13. Cut the long, bottom arm of your coat hanger from any remaining pieces. Use the needle-nosed pliers to form a small loop in one end of the hanger; this will hold the string that will later launch your mouse trap car.

14. Line up the unlooped end of the coat hanger arm with the snap bar of the mousetrap, so that the end is about ½ inch from the center spring. Wrap thin metal wire around the arm and the snap bar to hold the two together; you can also use duct tape if necessary for greater strength.

15. Lay your car frame in front of you, top side up with the rear closest to you. Glue the mouse trap to the car. The snap-plate end of the trap should line up with the front-right corner of the frame, so that the hanger arm extends over the front of the car. Allow the glue to dry before continuing.

16. Tie one end of a piece of string to the loop in the hanger arm. Wrap the other end of the string around the bare area of the rear axle, until it pulls the hanger arm backward, essentially setting the trap. When you let go of the string, the snap plate will fall, turning the string and the rear axle, propelling the car.

Tips & Warnings

• Add a drop of super glue to each paper clip base to secure it more thoroughly in the cardboard.

• You can make a variety of modifications to your trap, including removing nonessential plastic pieces and reinforcing the springs for better support and longevity.

References

• You Tube: How to Build a Mouse Trap Car Part 1
• You Tube: How to Build a Mouse Trap Car Part 2
• You Tube: How to Build a Mouse Trap Car Part 3
• You Tube: How to Build a Mouse Trap Car Part 4
• You Tube: How to Build a Mouse Trap Car Part 5

Resources

• PBS Scientific American Frontiers: Building a Better Mousetrap Car