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This project is from my upcoming book, Making Things Move.  In it, we’ll use the energy that a torsion spring can store to power a small car. Refer back to this main figure as you step through the recipe to build your own!

I built about 60 of these simple kits to show people how to make and race mousetrap powered cars at two events run by artist  Aki Sasamoto, co-director of Culture Push.  The first was a DOING workshop where I taught a small group of 10 professionals from other fields. The second was a larger scale public event with 100 people called Storm Your Brain, held at the Whitney Museum as part of the Biennial.  It's a fun project with just a few simple parts that just about anyone can make.

Step 1: Ingredients

• Mousetrap
• 1/4” diameter wooden dowel
• 2 eye screws that the dowel fits into (like McMaster #9496T27)
• 24" of monofilament (fishing line)
• 2 laser cut wheels (use template below, make yourself, or order from Ponoko.com.  I made these myself on Eyebeam's laser cutter  - one of the perks of being a resident!)
• Wooden paint stirring stick
• Ping pong ball
• Multi-tool with knife and file
• Duct tape

Step 2: Screw Eye Screws Into Mousetrap and Attach Base

Twist the eye screws into the side of the mousetrap opposite the “bait” hook. They should be as close to the edges as you can get them without splitting the wood.

Duct tape the mousetrap down to one end of the paint stirring stick. If the mousetrap arm is held down with a little staple type thing, remove it.

Step 3: Attach Axle and Wheels

Cut a 4" length of the wooden dowel by scoring it with your knife and snapping it with your fingers.  File off an rough ends or edges.

Check to make sure the wooden dowel fits through the eye screws and can spin freely.  Too loose is okay, too tight is not.  If it's too tight, use your file or some sandpaper to remove some material.

Insert the wooden dowel into one of the laser cut wheels. It should be snug. If it’s too loose, wrap the dowel in a little duct tape and try inserting it again. If it’s too big, use the file to sand down the end until it fits. 

Then feed the dowel through the two eye screws and attach the other wheel.

Step 4: Add Ping Pong Ball Caster

Duct tape the ping pong ball to the other end of the paint stick.  If you set your car down now it should balance.  The ping pong ball will skip along on just about any surface since it's so light weight and smooth.

Step 5: Wind the Axle and Go!

In order to stop the wooden dowel from sliding back and forth, wrap strips of duct tape just inside the eye screws around the dowel. The dowel should still spin freely.  These also help the fishing line to stay centered and not get tangled in the eye screws.

Cut at 2 ft length of fishing line. Tie one end around the center of the wooden dowel. Tie the other end to the center of the the mousetrap arm. Secure with duct tape if necessary. 

Now spin the axle to wind the fishing line around it.  When you get to the last few spins, help pull the mousetrap arm up and set the trap.  To set the mousetrap, bring the long hook over the U shaped arm and catch it on the “bait” hook. This takes a delicate touch sometimes - watch your fingers!!

Once you’ve set your mousetrap, you’re ready to race! Set it down on the floor and use a pencil or other long object to trip the mousetrap. The fishing line attached to the arm will pull on the line wrapped around the axle and it will start to unravel. Your car should be able to go about 10 ft with this design. Now try some variations and see if you can get the car to go faster or farther!  Feel free to leave suggestions and modifications in the comments.
<p>This really does not work that well! But it is built really well.:)</p>
<p>it didn't work... we had 2 more days to build and we did this and when we tested it... FAIL!!! so we made our own that looked like star lords ship and it works wayyy better... (you know... guardians of the galaxy)</p>
<p>its doesnt even work i made it for one of my elective classes and it got me an f on my progress report thanks</p>
<p>this is trash</p>
<p>thanks for saving my science grade! I suck at engineering and stuff like that. Thanks again!</p>
Good <br>team work. Latest technology with well deigned is appreciable in automobile <br>industry. It becomes more powerful in case o0f sports car. Still the concept of <br>Mousetrap Powered Car is interesting; it is not successful in market yet. What <br>should be the reason behind this? I like the storing energy concept. I found Valvetronic <br>Engine Technology also effective. You can follow this for your next <br>activity. <p><a href="https://www.youtube.com/watch?v=5YnHDVHT3c4&feature=youtu.be" rel="nofollow">https://www.youtube.com/watch?v=5YnHDVHT3c4&amp;feature=youtu.be</a></p>
So you all are nerds right I love it
Next we need someone to I'ble a car-powered mousetrap.
so the mousetrap is powered by the car????
how big does wheels have to be and how fat? does it matter how heavy the wheel is?
Excellent question. The CD size works well, and doesn't have to be thicker than that if you get get it on the shaft straight. Smaller wheels will spin faster but cover less ground, larger wheels will be slow starting but cover more ground. So if you're racing for speed over a short distance, small might work, if you're shooting for max distance, slightly larger wheels could work. Heavier wheels just have more inertia so will resist getting started, but once they are going will help keep your car rolling for longer. It really depends a lot on your surface too and the friction.
it wold be nice so please let me know dustynrobots
it would be nice if you could make it so it is free
Do you suppose this design could be expanded to power an actual car? I'd love to have some sort of alternate vehicle that doesn't waste fuel and hurt the environment. This would be a way cool solution! Is there a way to calculate how many mouse traps I'd need?
I've never built one, but does the dowel unroll the line, then re-roll it?
Good question. I tie the knot around the axle loose enough that when the line unravels it will just slip. However, if you tie it tight, it will unroll the line and re-roll it. The car won't have much momentum at this point anyway so it won't make too much of a difference. I first designed this kit to go about 10 feet, but you can easily get 20 out of it. Good luck!
I was thinking, if you were to push a pin through the axle, shorten your line, and make a loop in the end of it. Hook the loop over the pin and spin the axle until the slack line has been wound up. When the car is triggered, the line will unroll as per usual, and when it has fully unrolled the loop will slip off the end of the pin. Hopefully, the car will have enough momentum to move quite far, and won't have a trailing piece of line. Although I haven't tested this or anything, it's just an idea I had. Do you get what I'm describing?
I do! And I bet it would work as long as you kept the pin short enough so it didn't catch on the line as it unraveled. Good call.
what about putting a little notch in the axel and knotting the end of the line so when it unravels it will pop out of the notch? GREAT instructable!
Excellent! If you ever try it let me know how you get on!
we made one of these for a science olympiad competition and we built a balsa frame with four wheels and then wrapped half of the line on the axle put it around the cutoff tip of a ziptie and wrapped it the other way so it would go in reverse. The goal was for it to go 7-9 meters and then reverse back to the starting line.
We used to make those at school. An alternative was to use a rubber band that we would stretch around the axle, so when released, it made it spin and the car would go forward on a longer distance than mousetrap.
I think I know what you mean, but it's hard to picture. You should write up a counter-instructable!
Unfortually I don't have this car we had to build. It was going so fast that we needed to put elastic on both wheel so they did not spin.
You should put up a video of it in action.
lol ingredients... Your making me hungry!
nice
This would have been great for me a few months ago when I had to do this for a science project haha :-)

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Bio: I'm an enginerd, author, and teacher.
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