Gather a mousetrap, a lightweight chassis, 4 wheels, 2 axles, string, glue, tape, and a long wooden dowel or arm
Use a light, stiff base for the car body
Attach two straight axles under the chassis
Make sure the wheels spin freely without rubbing
Secure the mousetrap firmly on top of the chassis
Extend the mousetrap arm with a longer lever if needed
Tie one end of the string to the mousetrap arm
Wrap the other end of the string around the drive axle
Wind the mousetrap arm back slowly to pull the string tight
Place the car on a smooth floor
Release the mousetrap arm to drive the car forward
Keep the car as light as possible
Align the wheels and axles straight
Test and adjust the string length, axle position, and wheel alignment
Use larger rear wheels if you want more distance
Use smaller front wheels if needed for balance
Reduce friction by making sure parts do not touch unnecessarily