Picture of Lego Mousetrap Car
Do you need to make a Mousetrap car for science class? Do you have some Lego's around the house that aren't being used? Do you have 10 minutes of free time?

Well this simple design will leave you with a quick accelerating, compact mousetrap car that will beat the competition. With this design I ended up getting 1st place in acceleration, and 6th in distance.

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Step 1: Parts You Need

Picture of Parts You Need
Parts you will need:

Duct Tape
Fishing string
(x4) Small Lego Technic tires
(x2) Skinny gray spacers
(x2) Fat gray spacers
(x2) 1x16 bricks with holes in them (the yellow ones in the picture)
(x2) 1x6 plates
(x2) 1x8 plates
(x1) 2x6 plate
(x2) 1x4 plates
(x4) 4x6 plates
(x1) 10 long axle (about how many brick dots long it is)
(x1) 8 long axle
(x1) Red K'nex piece
(x1) Mouse Trap (duh...)

Step 2: Layout the Base Pieces

Picture of Layout the Base Pieces
Simple Enough...

Step 3: Add Front Support

Picture of Add Front Support
Attach two 4x6 base plates onto the top and bottom of what will be the front.

Step 4: Attach More Support!

Picture of Attach More Support!
Add the two 1x8 base plates into the top of the vehicle.

Step 5: More Support...

Picture of More Support...
Flip the car over and add the two 1x6 base plates as well as the 2x6 base plate.

Step 6: More Pieces to Add

Picture of More Pieces to Add
Flip it back over and add the two 1x4 base plates to the top rear end of the car.

Step 7: Final Support... Finally!

Picture of Final Support... Finally!
Flip the car over and add the final two 4x6 base plates onto the bottom of the vehicle.

Step 8: Add the Axles

Picture of Add the Axles
Place the 8 long axle in the front of the car, and the 10 long axle in the rear.

Step 9: Add Spacers

Picture of Add Spacers
Put the two larger spacers on the rear axle, and the two smaller on the front. Make sure to leave some space so that the axles can rotate easily.

Step 10: Wheels!

Picture of Wheels!
Add the wheels!

Step 11: Prepare the Mousetrap

Picture of Prepare the Mousetrap
For this step you need to attach the red K'nex on to part of the mouse trap (duct tape works well). Then you need to tie your fishing string on the tip of the red K'nex. Place the mouse trap on the vehicle and line it up with the front and sides.

Step 12: Attach the Trap

Picture of Attach the Trap
Get a piece of duct tape and cut if in half, length wise. Attach the trap on the back over the V logo, and wrap it to the bottom. Then lift up the red K'nex part and release mechanism and attach a piece there and secure it underneath.

Step 13: FIN!

Picture of FIN!
Now you need to wind it up, which some people find difficult. First you need to pull the string tight, but don't pull the trap up, just make the string taught. You should have around 3 inches of excess string behind the rear axle. Start wrapping it around the axle. Once you have around a half an inch or so left slide what you have done together. You then need to push the excess string under the taught portion, so that when you wrap it up more it will run over it and hold it there. Once you get that to work, wrap up the car from the wheels so that the string remains taught. Horrah! This wrapping technique allows for the release of the string after the mouse trap has expended its energy.

Oh, and make sure to wrap it the right way, or your car will go backwards...

Step 14: In Conlcusion!

With my testing, it didn't go straight. It used too... So I have no idea what went wrong. Well on the bumpy tile, and running over the measuring tape it ended up going 10 ft in 1.25 seconds. Pretty good!

yea10 days ago

this sucks m8

yea10 days ago

this sucks so bad eh

yea10 days ago

this sucks

yea10 days ago

this sucks

Z.Backas4 years ago
Thanks for your design! I won first place in distance and speed with it in my class! I added a longer arm for distance, and bigger wheels in the back too.
yea Z.Backas17 days ago

uh how do u make the car go???
ive made the car but dont know how to make it actually drive...


thenks for da design! @_@ ;]

Adidas13983 months ago
How Long does the string have to be?
Col-Singleton4 months ago

Do you need to use fishing line? I really need to know.

Vynash6 years ago
HAHAHA Awesome! 5*s!
jackieg1 Vynash8 months ago

This is awesome and i love it

LivyT10 months ago

Can you tell me what's wrong? I have 1x14 hole bricks and the mousetrap is a little too big and it goes a little bit over the place where you wind the string is that ok?

asdfghjkl810 months ago

i cant wind it up!

that could realy haelp my mouse problem

jonesy10ftw5 years ago
 what kind of wheels did you use, bc all my lego wheels fall off the axis?
LegoBrickMaster7 (author)  jonesy10ftw5 years ago
The wheels are fairly standard Technic wheels.

Here's a link to a set that uses the same kind of wheels and axles. (The website is used for piece inventory.)

Also, if you don't have the right wheels, you could always pick up a cheap Technic set that has the right ones.
i need fishing rod and knex!!!!!!!!!!!!!!!!1
um.....do you have to use a fishing rod and i think it is better if there is a video of how to build it.
REDefiant5 years ago


Nez19935 years ago
we have not made this yet, but i guess it looks cool enough to give it a try.
bloggingman6 years ago
that's a really easy way to make a mouse trap car... plus using a lego will help reduce weight... which is good for long distance cars and fast cars....
whats with the weird thing ehn you click on mouse trap car
ouuhh this looks sexy
senario 1586 years ago