Mouse Trap Car




About: Mostly a programmer and random computer guy, but like to mess with hardware and other real life objects sometimes.

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

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

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

Step 3: 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

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

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

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

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

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

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

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

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

Step 12: Wind Up

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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529 Discussions

little bell

Question 6 months ago

What is the second law of Newton´s motion in this project?


Question 1 year ago

how do make the mouse trap not slam on your fingers while you are working

1 answer

7 months ago

A lot of typos but otherwise, very good instructions. 9/10


10 months ago

this is very confusing please be more clear instructions are very difficut to understand


Question 1 year ago on Introduction

Can you use a smaller mouse trap than the one you used?


Question 1 year ago

can you use tape instead?


Answer 1 year ago

I think I used them to clam around pen next to the eyelets so that the axels don't move side to side (relative to the mousetrap) and eventually make the wheels/balloon mounts bump into the mouse trap and come apart. I'm sure something else would work (washer, appropriately sized nut, etc), tabs from soda cans was the available shapeable piece of metal I grabbed at the time.


Question 1 year ago on Step 3

Have you tested the mousetrap car without balloons around the wheels and if you have does the balloon help the car to go farther?

1 answer

Answer 1 year ago

Yes. The way it's geared here, the rear wheels will spin out and it'll go almost nowhere. If the floor has much better grip, it might work ok without them. It might also work if it was geared differently, such as having a narrower read axle, so that it doesn't deliver as much torque to the rear wheels and starts out more gently.


Question 1 year ago on Step 10

what does it mean by when you said to

Pull the string through the eyelets so that it's between them (or slide through the gap if you had to widen them).


3 years ago

About how far does this go? My sience rubric requires it to go at least 12 ft..

1 reply

2 years ago

Que chevere carro va de cabeza a mi proyecto de fisica.

bob and fredDrago335

Reply 2 years ago

yess same us!!!

have to make one that goes the furthest...