How to build a mouse trap car

Your basic mouse trap car is quite easy to build. Experiment with your first model, then go on to further customization.

A mouse trap car uses it's own force to propel itself. Here's how: a string connected to the jaw is attached to the car's rear drive axel, and wound around it. When the trap is sprung, it forces the string to unwind, propelling the car forward. The trap's jaw is it's "motor".

Mouse trap cars are popular for two reasons: they are rather customizable, and they are often used in competitions, where builders modify their cars to obtain maximum distance and/or speed.

Below are instructions for building a basic mouse trap car.


1 mouse or rat trap, any size

4 wheels

thick string

2 axles: plastic tubing, wooden dowels, or lightweight metal tubing ( brass, copper, aluminum, etc.)

two lengths of wood (scraps, plywood, etc.)


tape measure

a pair of pliers

two-part epoxy

a drill

a small hand saw (jeweler's saw)

a jeweler's file

a vice

1) Cut your axles down to a size that spans your mouse trap and wheels, with a bit of extra room to spare (enough to prevent friction between the car and the wheels).

2) Remove the wire catch and bait holder from the mouse trap with a pair of pliers. Keep the wire catch.

3) Mark a spot that is 3/4 of the way down the length of one axle. Using a small saw (such as a jeweler's saw) and a vice, cut a notch half way through the axle. The wire catch needs to fit into this slot.

4) Cut the wire catch so one end of it protrudes from the axel. The protruding wire should be long enough to hold the pull cord, and short enough to let go of the pull chord when the car is propelled. Make the end of the wire catch smooth by cleaning it up with a jeweler's file. This will prevent the pull cord from getting stuck on the wire.

5) Cut two lengths of wood so they are equal to, or longer than the length of your mouse trap. These two lengths of wood will create side rails, connecting the axles and wheels to the car. Choose an appropriate drill bit, and drill two holes in each length. Connect these two lengths of wood to the mouse trap with epoxy.

6) The axle with the notch cut into it is the rear drive axle. The back of your car is the end where the trap arm lies when it is set. Slide the rear axel through the back of the car. Now, glue the wire catch into place with two-part epoxy.

7) Use epoxy to attach your wheels to the rear axle. Before the glue dries, spin each wheel while holding the car parallel to the ground. Doing this allows the force of gravity to straighten your wheels. Repeat this with the front axel and wheels.

8) Take the length of string, and tie it to the center of the mouse trap's jaw. Tie a small loop in the string where it meets the wire catch in the rear axel, and cut off the excess.

And there you have your basic mouse trap car! To get it going, pull the trap's arm up a bit. Attach the pull cord to the wire catch, and wind the string around the rear drive axel by turing the rear wheels in reverse.

© High Speed Ventures 2011