Picture of Mouse Trap car
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

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

Step 3: Cut and apply two balloons

Picture of Cut and apply two balloons
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

Picture of Check eye hooks
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

Picture of Make a hole
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.
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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
dansmy bro2224 months ago

hard i didnt use ballons

bergiemoore2 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

Sweg2DAMEX4 months ago


Sweg2DAMEX4 months ago


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?
Vikshay1 year 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... []
I think you should also put soda can tabs on the axle with the string.
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
6969691 year ago
I love Matthew Root!!! <3
6969691 year ago
yeah root!!!
yoyo325 years ago
Are you talking about taking all the stuff inside the pen, only using the outside shell?
LarrySDonald (author)  yoyo325 years ago
It looks like a pregnancy test just saying
YES! you genius !!! :)
Lol im in love with gettin prego
Just Kidding ^^^
CONDOM!!!! just sayin...
pregnancy test lol
busyramp1 year ago
make a video tutorial on this and email it to me
I can make a better car! THIS IS TERRIBLE
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
Martymotos2 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.
mturn862 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.
smann52 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.
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