One of my sons friends stayed over yesterday and mentioned in passing he'd been assigned to make a mouse trap car for school. I thought about how I had lots of fun making those way back and decided to make one out of scraps off my desk and document it. It's far from the best one ever and unlikely to win any awards, but it does work.
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Step 1: Supplies

Picture of Supplies
I used the following:

A mouse trap
4 eye hooks
6 balloons
2 bic pens (the smooth kind)
2 tops from pop cans (for the serious perhaps washers, or otherwise any other bendable metal)
some string (not pictured)
4 CDs/DVDs (expendable ones). Here 3 CDRs and a blank transparent thing from the top of a spindle. I hear DVDs are a bit lighter, but I'm not optimizing that hard.

Step 2: Strip the pens

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Pull the front and back out of the pens, making them hollow plastic cylinders.

Step 3: Cut and apply two balloons

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Cut the top and bottom off on two of the balloons. Stretch them over two of the CDs, which will later be the back wheels. This will help traction a great deal as CDs are otherwise pretty slippery.

Step 4: Check eye hooks

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Assure yourself that the eye hooks fit over the pens. They need to be loose enough to rotate easily, but not so loose that they rattle too much. If not, bend them slightly so that they do. Mine were a bit small and needed to be bent out a bit.

Step 5: Make a hole

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Make a hole roughly in the center of one of the pens. I did this simply by screwing one of the eye hooks in and ten removing it. It needs to be large enough to take the string.

Step 6: Thread the pen

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Push the string into the pen and get it out one of the sides. I pushed it in and blew on one end, then jammed then ink part I'd removed earlier in, cussed at it a bit and then did it some more. Eventually, when the string is through the pen, tie something to the other end. This one is with a small piece of a toothpick. A simple knot would probably do in most cases, but my thread was a bit thin. Pull it back through and make sure the knot/object stops against the other side of the hole.

Step 7: Put eye holes in trap

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Screw the four eyelets into the mouse trap along the short sides. Try to get them to be roughly the same depth so that the axle that will later go through them is somewhat straight. Also, take care to not crack the trap too much. More ambitious builders may want to pre-drill holes, but I went for broke and indeed it cracked a bit, but not so much that it didn't work.

Step 8: Brace

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Insert the front axle (i.e. then pen without the hole/string) pushing it through both pop tabs (or whatever you've managed to get). Pinch them to the pen so that they won't move too much and keep the pen from moving sideways. Bend them away from the eyelets enough so that they can spin freely against it and give them some leeway from it (not snugly pressed against it). Make sure it can rotate ok.

Step 9: Front wheels

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Wrap a balloon around the pen you just put in, trying to fold it so that it's somewhat wedge-like toward the edge of the pen. Gently rotate one of the CDs without balloons on them onto it in the same direction you wrapped the balloon, wedging it on the pen. Attempt to get it to point fairly straight and not wobbly in relation to the trap. Repeat for the other end of the pen.

Step 10: Rear axle

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Push the pen with the string into the back eyelets. Pull the string through the eyelets so that it's between them (or slide through the gap if you had to widen them). Tie the string to the tip of the flap that will move as the trap springs. Those more ambitious might want to brace it with something between the spring and the back to make sure it doesn't snag or fray, but I didn't bother, which does mean the string gets tangled or frays every so often.

Step 11: Back wheels

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Attach the back wheels in the same way the front were done.

Step 12: Wind up

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Gently turn the back wheels backwards (if your unsure of the direction, put it on a surface and pull it backwards). When it starts to catch, lift the flap slightly and keep turning until the trap is starting to load. Keep going until it's pulled all the way back, then hitch it as one normally would setting a mouse trap (see instructions on package I guess).

Take a bit of care, because if the string snaps the trap will indeed close (quickly) and anything you have in the way will get hit. It's not exactly deadly, but not pleasant either - these things do pack enough power to make you go "Ouch".

Step 13: GO!!

Tap the trigger and watch it go. Readjust the wheels (which are a bit flimsy with the low-rent balloon support) to get them straighter and retry. It's not very crash resistant, not very pretty, but very easy to make and can, if you're me, be built entirely out of things you can reach from your work chair (yes, that included having an old pack of mouse traps on my shelf).
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Nice. I made one of these in my Engineering class a few months back. My team did pretty... bad. We got stuck with two know-it-all sophomores, a girl who was afraid of tools, another girl who just wanted to get her math homework done that she didn't do the night before, and me... the shy, quiet girl who had ideas but couldn't voice them. D: (Haha, I'm not trying to make my team look bad, by the way. We all became friends because of that project. xD)
Oh, also... This is what we ended up with. (The first image is my design. We tried to follow it but somehow ended up with... the second image. >.<)
mousetrap car CAD.jpgMousetrap Car.jpg
T0BY1 month ago

Elegantly simple!

notazu1 month ago

I understand the instructions, but since I don't know the idea background, can you tell me what do you use it for?

Guthix Priest made it!2 months ago

My fiancee had to do this for her final. this is what we ended up with. it only has to go a linear foot to pass. we tested it, and she should pass with no problem


i am making this in since class can you send it to me at @exoticdragon on twitter oh and follow me to

braviscows JakeS73 months ago
i don't think its his fault that you have learning disabilities, look at some pictures! the string goes where my thumb is⬇⬇

nice bro

migued5 months ago

OK, i'm really new to this, and I really need help trying to make this.....

lindagraham366 months ago

i got to do this for my school ,can i us your idea?

What size eye hooks did you use?
wilsonc168 months ago

what do you use the soda can tops for?

Julie7898 months ago
How long do I make the string?
bergiemoore3 years ago
I really appreciate that A. you used common, easy to get materials and 2. your photos were in focus (big thank-you) and were an aid to the instructions you wrote. Thanks for the great visual tutorial. We'll be making these this summer at my Daring and Dangerous camp :)
Would you be willing to explain step 10? The step where he installs the back pen? please? Thank you(:
To install the back pen, you will have predrilled (or poked (whatever) a hole and sent a thread through it. Tie a good knot in the thread to keep it from coming back out of the hole you just sent it through. Now put the pen through the two eye holes so it sits perpendicular to the wood trap in the two eye holes.
This is your back axle. After putting it into place I used a bit of hot glue in two single bars to keep the axle from slipping back out of the eye holes. The original creator used bottle top tabs. Mine were too big and hit the wood, not allowing it to spin freely so I decided to abandon the bottle tabs and use a line of hot glue.. After I got the back axle in place, I tied the string to the flip bar- the thing that will snap back in place once you let go it (the thing that originally was used to hold the little mouse down to the wood).
To make your car run after you add the wheels, hold the snap bar back and roll the back axle up so the thread is wound around the back axle. When you let the mousetrap bar go, it will fling forward and pull the back axle incredibly fast. I discovered that undoing one side of the bar so that it was actually straight on one side made it FAR less scary to use :) Check out a couple of the other mousetrap cars to see their strings attached to long poles. That is the mousetrap bar opened on one side and bent straight. So it goes from a staple shape to an "L" shape. It works just as well, but seems less likely to nip the user.
Good luck.
Thanks(: But the part that still confuses me is, what do we do with the string that comes out the other side (not the middle) of the cylinder ?
You drill a little hole. You put the string through the hole so it comes out one of the ends of the pen. You tie a big ol' know in it, or tie it to a bead or something that will keep it from coming back out of the hole. Now, you pull the string again so all the string is out of the center of the pen, but it is stuck in the pen and can't come out. Once the axle is in place, and the wheels are attached. Take the string that's dangling out and tie it to the center of the mousetrap bar. The string should be coming out of the center of the axle and attached to the center of the flip bar. The flip bar is what will pull the string and make the mousetrap car move forward when it spins the back axles, causing the wheels to move, causing the car to move :)
Hope this helps. Let me know if you're still unclear. I will try to explain a different way.
That makes everything SOO much clearer(: Thank you so much!

i know

What can you do when the string gets stuck and makes it stop sooner than you would like it to? In school were making mousetrap cars and mine has to go 20 meters.. Helpp?
Vikshay2 years ago
I am not sure that it goes far because i have to do a project and mine is going to be kind of the same but with a longer and lighter lever. What is mean by lever, the thing that hurts the mouse... [http://prntscr.com/ztnfc]
vedisdragon2 years ago
I think you should also put soda can tabs on the axle with the string.
vedisdragon2 years ago
I figured it out!
You stick the hollow pen thing through the eyelets. Then, on each side, you slide the pop can tabs onto the pen. They shouldnt move around on the pen. Basically, they're there so that the axle wont slide out of the eyelets sideways. They're like blockers or something.
This is a pretty good idea
6969692 years ago
I love Matthew Root!!! <3
6969692 years ago
yeah root!!!
this is good
thats is sickas men :)
pretty cool

just a quick q- is the pop caps for making sure the mouse trap doesnt slide? is there another option? could i use a washer or something on the sides to stop it from moving sideways? thanks
Martymotos3 years ago
Is it posible to have a Video Tutorial because i am trying to follow these steps but they are quite hard for me and my 13 year old son. Help would be appreciated.
mturn863 years ago
How far did it travel? i have a science prject and it needs to go at least 10m
The longer your string the longer it can travel before the string stops it.
If you have(had) a certain length requirement you could get it fairly accurate as to how far it travels and then stops. I had a project back in 8th grade where we had to make a car out of trash type materials, start it on the outside of a circle, let it go and it had to roll to the middle of the circle. Every inch was a couple points off the total score for the project. I made one of these mouse trap cars and got 100% on the project.
Because of how the string wraps around the axle, you wouldn't need more than probably 1m of string (might be wrong) to go the 10m distance, but that's all trial and error getting the right amount of string.
smann53 years ago
I just put the string in the hole in the middle of the pen, then used an unrolled paper clip to pull it through.
ultbandgeek3 years ago
can someone please explain step 10?
Once you've wound up the back wheel, the string loses is slack and will not spin once the trap is set, what do I do?
When you set off the trap, how do you get the string to not stop the axel from spinning?
breanna0983 years ago
WHY IS IT GOING IN A CIRCLE!!!!!!!!!!!!!!!!!!!!!!!
i made one of these in woodshop, but mine was all wood except for the mousetrap
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