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.

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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.)



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    17 Discussions


    Answer 22 days ago

    You haven't really read the instructable did you ;-)
    A piece of string is wound around an axle and the spring lever pulls on that string


    1 year ago

    That would be really great to use in a science class!

    1 reply

    Reply 7 months ago

    your right that is what we are doing in science class


    1 year ago

    What do you think about using discarded CD or DVDs for the wheels? It may be a bit more work to add a hub to take the axles, but less expensive for those who have a few otherwise useless disks.

    1 reply

    Reply 7 months ago

    that is what i am using for this design


    7 months ago

    this is a good mousetrap car design for my project. how far does it go and hwo do i make it go?


    1 year ago

    Those wheels looked like the hubs from 3-1/2 inch floppies, which I am always looking to recycle on something. Never throw anything good away, I always say.


    1 year ago

    Never thought of using a mousetrap as a source of energy. Incredible !!


    1 year ago

    I worry about the filament breaking at launch. Might want to use a stick/poker.

    1 reply

    Reply 1 year ago

    I agree, if your string breaks it could end up with a broken finger and some blood. You could add on a popsicle tab going to the side so to keep fingers out of harms way.


    1 year ago

    id be afraid the spring would break and then break my finger


    1 year ago

    Mouse mobile

    So not only can you catch mice now, the car will automatically drive them back to you. I positively love this idea. LOL

    Alex in NZ

    1 year ago

    I love this. What a great use of a mousetrap!

    If you split the driven axle in two (would need a central brace to support and various other bits) then you could also add steering to the car (trap a length of line without winding it around one of the axles, and that side will sit idle while the other side will be driven on the outside of the turn.

    This youtube video (not great quality) gives a better explanation of how different windings can be used to induce changes in vehicle behaviour. There was a great article an American Scientist about eight years ago, but I can't find a reference.