Build a Mousetrap Car For Your Science Project

A mousetrap car is powered by the energy of a wound-up mousetrap’s spring. In its most basic form, a mousetrap car consists of four wheels, a mousetrap, and a string. The string is tied to the tip of an arm that is attached to a drive axle by a string. As the string is wound around the axle, the lever arm on the mousetrap is pulled and the spring is wound, thus storing energy in the spring. When the drive wheels are released, the string is unwound from the axle which causes the mousetrap car to move.

Things You Need

To create a basic mousetrap car, you will need the following materials:

1 Victor Mousetrap
4 Wheels (old CDs or DVDs work well)
2 Tubes for axles (these should just fit inside the holes in the CDs)
Superglue
36 Inches of string
Scissors
1 Small zip tie
2 pieces of balsa wood, 2 ½ inches wide and long enough to extend 1 ½ inches past the front edge of the mousetrap
Wood glue
Clamps
Drill with drill bit large enough to cut a hole for the axles to pass through
Graphite powder
Wire cutters
Sand paper

Construct the Body

Drill holes for the axles in the balsa wood. Remove the metal catch and hook from the mousetrap and discard. Glue the pre-drilled balsa wood to the mousetrap, lining up one side with the mousetrap and having the other side extend past the mousetrap body. Sand the insides of the axle holes smooth. Clamp and allow to dry completely.

Attach the Wheels

Attach one CD to the one end of an axle tube and superglue in place, and then repeat with the second axle. Slide the axle through the holes and superglue the second CD in place only after you are sure that the axle will rotate freely. On the axle that extends past the mousetrap body, attach the zip tie to the center of the axle. Add a drop of superglue to prevent it from slipping. Trim the excess zip cord with scissors.

Power Your Car

Tie one end of the string to the center of the mousetrap lever. At the other end of the string make a loop, and then wrap that loop around your finger and pull through to make a loop with a knot. Take care not to make the loop too large. Slip the loop over the end of the zip tie on the axle and wind in the opposite direction that you want the mousetrap car to travel. Place the mousetrap car on a hard surface and let go. The mousetrap car should move forward.

Troubleshooting Techniques

Here are some ways to make your car zip past the competition:

If the wheels spin out, cut the center out of a balloon and secure it around the drive wheels.
The string should be long enough to just barely reach the axle when the mousetrap is unwound.
Use graphite powder to lubricate all moving parts.
Allow the mousetrap to load by wrapping the string around the axle. Do not hold down the mousetrap level while winding the string.

Tips for Success

If you want to have the fastest car, here’s what you need to know and to do.

Thicker axles increase speed.
Try using different sized wheels in front or in back.
Adjusting the length of the body and string alters the speed of the mousetrap car.
Kevlar string lasts longer than anything else. Monofilament string or fishing line tends to slip and tangle.
Securing the balsa wood to the mousetrap body with finishing nails adds durability to the car.

For additional resources and help check out Doc Fizzix website.

References

Doc Fizzix Mouse Trap Racers, http://www.docfizzix.com/
Image: Mousetrap cars by WillMcC under CC-BY-SA 3.0