Introduction: Mousetrap Car

This instructable will help you build a self-propulsion mousetrap car. The car uses physics and engineering concepts such as pulleys, levers, and springs to convert potential energy to kinetic energy which moves the car along.

Step 1: Supplies You'll Need


  • (1) Mousetrap
  • (1) 6" x 1.5" x 0.5" Board (Body)
  • (2) 18" x 0.5" x 0.5" Stick (Legs)
  • (4) 2.75" Diameter mason jar lids (Wheels)
  • (2) 10-24 x 3.5" All threaded rods (Axles)
  • (8) 10-24 Nuts
  • (4) 1.25" Finish nails
  • (4) 0.5" Finish nails
  • (1) 12" Wire coat hanger
  • 24" Fishing line
  • Hammer
  • (2) 3/8" or 10 mm Wrenches
  • Electrical Tape

Note: Each leg has previously drilled holes located 1" from each end using 13/64" drill bit. (see photo)

Each wheel has previously drilled center holes using 13/64" drill bit. (see photo)

One axle has previously drilled hole. (see photo)

Step 2: Label Front and Back of Mousetrap Car

  1. Label FRONT on one end of leg.
  2. Label BACK on opposite end of same leg.
  3. Repeat steps 1-2 on remaining leg. (Note: These will be will used for orientation during assembly.)

Step 3: Nail Legs to Body

  1. Measure and mark 2 inches from FRONT leg end.
  2. Align body with 2 inch mark on leg. (see photo)
  3. Nail leg onto body using two nails.
  4. Repeat steps 1-3 for remaining leg.

Note: Alignment is crucial for a straight axle. Before nailing the second leg, make sure leg axle holes are lined up by sliding the axle through the leg holes. This will ensure you have a straight axle.

Step 4: Nail Mousetrap to Body

  1. Orient mousetrap hammer and catch end towards FRONT of mousetrap car. (see photo)
  2. Center mousetrap on top of body. (Note: There will be some mousetrap overhang onto legs.)
  3. Nail mousetrap to body using 0.5" nails. (see photo)

Step 5: Wheels and Axles

  1. Screw one nut onto axle with hole. (see photo)
  2. Slide one wheel onto axle after nut. (see photo)
  3. Screw second nut onto axle after wheel.
  4. Tighten nuts using wrenches. (Note: Make sure nuts are snug and secure around wheel, otherwise you will have a wobbly, non-funtioning wheel. )
  5. Slide open end of axle through both BACK leg holes. (see photo) (Note: The axle with the hole must go through the BACK legs!)
  6. Repeat steps 1-4 on other end of axle. (Note: This will be for the second wheel on the same axle.)
  7. Repeat steps 1-6 for FRONT of legs using remaining axle. (Note: This axle WILL NOT have a hole.)

Note: Once assembled, there should be a small gap between the nuts and the legs. This will enable your wheels to move freely.

Step 6: Wire Arm

  1. Wind tape around wire arm straight end to mousetrap hammer. (see photo) (Note: Be sure the wire arm and hammer are tight and secure to ensure stability)
  2. Tie one end of fishing line to wire arm hook.

Step 7: Final Set-up

  1. Push mousetrap hammer towards BACK end axle. (see photo)
  2. Set the mousetrap. (Place holding bar under catch.)
  3. Orient mousetrap car BACK end towards you.
  4. Thread small amount of fishing line through hole in BACK end axle. (see photo)
  5. Key Step! Wind wheels towards you, top to bottom, until fishing line is completely wound. (see video)

Step 8: Ready, Set, Go!

  1. Place mousetrap car on flat, long surface.
  2. Tap the catch. (see video.)
  3. Mousetrap car will begin to move itself. (Note: Due to friction, you may need to give the mousetrap car an initial nudge.)