Gather materials: mousetrap, lightweight chassis, 4 wheels, 2 axles, straw or tube bushings, string, strong glue or tape, wooden dowel, hook or eye screw, and tools
Build a lightweight chassis from wood, foam board, or plastic
Mark and cut axle positions so the wheels align straight
Attach straw or tube bushings under the chassis for the axles
Insert the axles through the bushings
Mount the wheels securely on the axle ends
Attach the mousetrap firmly to the chassis
Install a lever arm on the mousetrap bar using a wooden dowel or similar rod
Add a hook or eye screw to the end of the lever arm
Tie one end of the string to the mousetrap bar or hook
Wrap the string around the drive axle
Set the mousetrap by pulling back the lever arm carefully
Position the vehicle on a flat, smooth surface
Release the mousetrap to test movement
Adjust wheel alignment, axle friction, and string length as needed
Reduce weight and improve balance for better performance
Increase lever arm length for more distance
Shorten lever arm length for more speed
Use larger rear wheels or drive axle for greater travel distance
Test repeatedly and refine the design for best results