Engineering at Home: Build a Mousetrap Car
Did you know there are simple and fun crafts you can make to share engineering at home with your kids? Building a mousetrap car is one of those simple crafts, and it's fun for all ages. Building a mousetrap car is so enjoyable that there are events all over the nation for mousetrap car races!
And here I bet you thought that mouse traps were only good for catching mice.
We know engineers like to take things apart to see how they work. They want to teach their kids the same thing. While a simple mousetrap car may not go very far or very fast, it will show you how stored potential energy becomes kinetic energy.
When you’re finished with this project, you can try building a more complex mousetrap car by changing a few things. Think about what you could do to design the car to go a longer distance and go faster. Consider the wheel-to-axle ratio, inertia, the rate of energy release, and friction. These areas might help get your creative juices flowing for future improvements to your mousetrap car.
Here are a few other things to consider when creating a mousetrap car for speed and distance.
Long Distance Mousetrap Car
Smallest fraction for mechanical advantage
Faster Mousetrap Car
Largest fraction for mechanical advantage
Good traction in rear wheels
Reduce rotational inertia
Let’s dive into the instructions now, shall we?
Safety Note: Before you begin, please note that mouse traps are dangerous. If one snaps back on your hand while you’re holding it, it could cut you, or worse, break your finger. This project requires adult permission and supervision to complete.
2 - 4” X 10” pieces of heavy cardboard: other dimensions will work, but this is an excellent place to start.
4 - DVD’s or CD’s: Recycle old ones that no one watches or listens to. You can also use new ones found at an office supply store if you cannot use old ones.
4 - 1/4L (19/32”) Beveled faucet washers: You can find these washers at most hardware or home improvement stores in the plumbing department.
2 - 3/16” Dowels that are 6” long: If you change your cardboard’s dimensions, these dowels will need to be scaled up or down accordingly.
1 - ¼ inch dowel that is 10“ long
2- drinking straws
Masking or duct tape
Zip ties: An assortment of 4” will work
Build the Body of the Mousetrap Car
Before you begin, visualize your mousetrap car. You’re going to need to create a body that’ll form the frame of your car, wheels, and an engine to power everything.
Cut a rectangular notch about 1” x 2” on one short side of each cardboard piece so that the notches overlap. The cardboard becomes the frame of your car.
Then place the two pieces of heavy cardboard on top of each other and use your masking or duct tape to tape them together, making a double-thick, heavy-duty piece of cardboard.
Make sure your notches line up.
Tip: If you’re going for distance with your mousetrap car and not speed, you’ll need to lighten the load as much as possible. You can cut holes in the frame to do this.
Prepare the Mouse Trap
Once you’ve gotten your cardboard taped together, you’ll need to attach the straws. Using your ruler, measure the short side and the two sections on either side of the cutout. You’ll need to cut your straws to match these lengths and hot glue them in place.
Be sure the straws are parallel to each other and the leading (short edge) of the cardboard, making the underside of your mousetrap car.
While your glue is drying, prepare the mousetrap. Take your trap and remove the small pieces that make up the release trigger. These are called the bait holder and wire bail.
Get 2 or 3 4” zip ties and secure the ¼” dowel to the snap arm. You can reinforce this arm with your tape or hot glue. Be sure your dowel is pointing forward, away from the notch you placed in your cardboard. Also, make sure that the dowel lines up with the notch center when it’s pulled back.
Get your string and attach a piece to the end of the ¼” dowel with another zip tie. You want your string to reach a bit longer than the hook on the rear axle. Tie a small loop at the end of your string. You want your loop to just reach the hook on the rear axle.
Prepare the Wheels
Now to prepare the wheels for your mousetrap car. Put a piece of tape over the hole in the center of the DVD or CD you are using. Turn the DVD or CD over and put a beveled faucet washer into the center, sticking it to the tape.
Then, use a generous amount of hot glue to hold it in place. Do this for all 4 of your wheels.
Add the Axles and Wheels
Once all of your hot glue has dried, you’re ready to start adding the axles and the wheels to your mousetrap car’s body.
Slide the 3/16” dowels into the straws and then press a wheel onto each end of the dowel.
If you have difficulty getting the dowels through the tape, rounding or slightly sharpening the dowel ends can help make this part a little easier.
Once you have attached all four wheels, do a test run and see if your mousetrap car rolls straight. If it doesn’t, you may need to straighten your straws.
Attach the Hook
Now that you’ve gotten your wheels on and your mousetrap car is rolling straight, it’s time to attach the hook to the rear axle.
Attach a 4” zip tie to the center of the car axle exposed by the notch in the heavy cardboard and cut it short, about ¼ inch, which will be the hook for your string. Use a dab of hot glue to hold it in place.
And now you’re done! Attach the string to the hook and wind it backward. Put your mousetrap car on the ground and let go. It should start rolling away.
Now you can take some time to get to know your mousetrap car. You'll want to roll your vehicle to test it multiple times. Watch its performance. If it's not rolling smooth or veering off to the right or left, take some time to adjust it. You'll want to get it right.
Once you understand how the mousetrap car works, you can experiment with different materials.
Tip: To make your mousetrap car more durable, use lightweight wood instead of heavy cardboard.
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A set mouse trap is full of potential energy. When released, it gets converted into kinetic or motion energy. Your mousetrap car’s design allowed that energy to be transferred to the axel to make the wheels turn.
When the mousetrap in your car snapped closed, it yanked the string forward. As the string got pulled, friction between it and the axle caused the axle to rotate, which turned the wheels and moved the car forward.
Wasn’t that fun?
Hopefully, everyone had a great time putting together their mousetrap car and learning about potential and kinetic energy. Now the mousetrap car makers can build their science fair project, share the ideas with their friends, or even better, join the mousetrap car races.
We’re not only engineers, but we’re parents, too! That’s why we created this post.
We understand what it’s like to want to teach your kid how fun engineering is. We know how great it is to be a hero and help your child win with the best science fair project or now, the mousetrap car races.
Now that your kids are excited and want to learn more engineering fundamentals, you'll want more kid-friendly ideas for projects you can do together.
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