Speedy Gonzales: How to Make a Mousetrap Racecar




Introduction: Speedy Gonzales: How to Make a Mousetrap Racecar

Oh, what better a way to start off the new semester than by building a racecar? Why, building a racecar using a mousetrap, of course!

In this Instructable, I will not only show you how to build a mousetrap car, but also some tips and tricks that I learned in my own building process.

Back off, PETA. No animals (or pet rocks ;]) were harmed in the making of this Instructable.

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Step 1: Gather Thine Materials

In order to built your Mousetrap car, you will need:

1. (2) Balsa wood side rails (8" x 1/2" x 1/4") - mine came pre-drilled; but you'll have to drill holes (slightly larger than 3/16") in yours for the axle

2. (2) Brass axles (6" x 3/16" tube)

3. (1) Brass lever arm (6" x 1/8" Tube)

4. (4) CD's to use as wheels - I used those clear things that you get when you buy a pack of black disks; these work fine, too

5. (8) Rubber CD spacers

6. (4) Metal thrust washers

7. (1) Victor Mousetrap

8. (1) Zip tie to use as axle hook

9. 36" Kevlar String - if you can't find Kevlar, any type of thin string, even fishing wire, works well enough

Note: In class we were provided with these kits; you can order them rather than trying to gather all the parts individually.

You'll also want these tools:

1. A hot glue gun and hot glue or super glue

2. Needle-nose pliers

3. Wire cutter

4. Scissors

5. Protractor, optional

6. Sandpaper, optional

Step 2: Mousetrap Surgery

1. Use your wire cutters to sever the mousetrap's snapper arm at the point where the spring is pushing the snapper arm. Discard the snapper arm.

2. Use the wire cutters again to remove the mousetrap's locking bar. You'll need to save this for the next step.

3. I used my needle-nose pliers to straighten the locking bar's tip, but if you'd like you can just cut it off with the wire cutters; take care not to take off too much.

4. Slide the locking bar into either end of the brass lever (the smaller tube) and glue into place.

5. Put a dab of hot glue into the other end of the brass lever and slide it over the mousetrap's snapper arm.

Step 3: Fabricating the Chassis...

...out of balsa wood... Now we're rollin'...

1. If you want to, go ahead and sand the balsa wood side rails and the axle holes.

2. Glue the side rails to the bottom of the mousetrap, NOT the sides. Gluing the rails to the side of the mousetrap will not allow your brass axles to make it through the axles holes... Not good, assuming you want the car to go. :]

Step 4: Time to Kick Some Axle

1. Place the brass axles (the larger two tubes) through the front and rear axle holes of your car's frame.

2. Slide on a metal washer on each side of the axles. Then, slide on a rubber CD spacer.
(Actually, I guess I should say 'force on a CD spacer', because they're tricky little things. Try coaxing them into place with a little dish soap. Or, try to drive the brass axle through the CD spacer rather than the vice-versa, if that makes sense)

Heads up! Loose axles? That's good, provided they're not too loose. They do need to be able to rotate, remember? Later if you find out that your car doesn't go straight, you can always adjust - I'll show you how :]

Step 5: Wheel Installation

1. Pop a rubber CD spacer into the center of each CD wheel.

2. Pop a CD wheel onto each end of the axles. Voila! You now have motion.

It should be noted that by adjusting the wheels' camber, you can help your car to go straight, even if your axles are uneven. It's just a matter of finding that sweet spot.

Step 6: Time to Hook Up Your Ride With an Axle Hook

This is gonna be one of those steps where you just really want to thank Eric for comments on pictures...

Step 7: Adding the "Chain"...

err... string, rather.

Uh, sorry about the lack of visual aid on this one, guys...

1. Tie one end of the string into a loop knot.

2. Put the loop around the ring of the locking bar.

3. For the next few parts, you'll have to guesstimate. With the brass lever in the resting position and the loop still in the locking bar ring, pull the other end of the string down to where the axle hook is. The idea is to make a loop on this end of the string, too, to put around the axle hook. You don't want there to be too much slack in the line and you don't want your loop to be too big. This takes some fumbling with; just don't cut anything until you're satisfied.

Step 8: Start Her Up

Yes. After hours of toil, you now have in your own possession a mousetrap racecar. What are you waiting for? Start her up!

1. Make sure you've got your string attached to both the locking bar and the axle hook.

2. Pull the brass lever arm all the way back.

3. Wind up the string around the back axle.

4. Let go.

5. Sometimes I like to make Vroom vroom noises right about now.

Sorry I don't have any shots or video of my car in motion. Here's the finished product, though.

Step 9: Aftermarket Modifications

Now the whole point of Engineering class, as my instructor explained, was to find ways to make things better. The purpose of our making these cars was to tweak it and win a race that we had at the end of class.

She also mentioned something about re-purposing things...

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    32 Discussions


    2 years ago

    ahh this is cool I luv it ^^


    8 years ago on Step 7

    Could you add an illustration for this one please.


    10 years ago on Step 7

    hey i dont get how the zip tie serves as a axle hook.
    I was wondering if you could explain in more detail?


    10 years ago on Introduction

    Loos good, I've made a few in the past, but my favorite would have to be the one i'm currently building in my 10th grade engineering class, since the majority of the parts are being designed in Autodesk, then are being made on the 3-D printer our school had donated last year, ill post pics once it is completed...


    11 years ago on Introduction

    what are the size of your cd spacers??? is it the same with the axle or smaller???


    11 years ago on Step 9

    Thank you for this instructable. It's thorough, helpful and gives every single step by step needed to help you through. The illistrations help immensily.


    Reply 11 years ago on Step 1



    12 years ago on Introduction

    Yours doesn't looks too bad, I had to make mine about 6 years ago back in high school. I have a few suggestions, depending on how much modification you are allowed and/or time you have. Mine went across a full-size gym lengthwise about 3 1/2 times (probably about 300 feet or so)... the trick isn't length, but to make the trap spring very slowly. I made mine out of very light metal strips that I tack-welded together. I made it into a triangle shape with the point end being in the front. I also used a mini-cd for the front wheel with no rubber band at all (less resistance), and placed it in the middle of the triangle construction. The mini-cd made it sit lower in the front, helping it as well. The back wheels were 4 large cds that I had super-glued rubber bands around for traction, all based on one axle. I cut the mousetrap bar so it wasn't a square shape, instead just a straight bar, and took a piece of copper that was about 4 feet long and tack-welded it to that. On the end I made an eye-hook to tie fishing wire to. I found it had enough leverage when it pulled that it wanted to pull the spring out of the wood on the mouse-trap, so I also tack-welded metal bars on the bottom of the mouse-trap so that the small metal staples holding it in couldn't pull through the wood. The metal-on-metal for the axles helps it spin faster (especially with a bit of graphite!). When it came to wrapping it around the axle, I took a thread spool and covered the inside with a rubbery caulk. This caused the axle to spin slower (so you could get more distance out of the wind, instead of speed, an important aspect) and the rubbery surface made sure the fishing line didn't slip much within the spool. My total design was about 4 1/2 feet long and took me about 20 hours of hit-and-miss construction, but it was definitely a winner for length. I would post pictures, but I didn't bring it with me when I moved to college and to be honest I'm not sure if it hasn't been destroyed by now. Anyways, just a few ideas!


    Reply 11 years ago on Introduction

    sweet need to do this for school now, this will definitely help!


    11 years ago on Introduction

    i gotta do this for a project and we're allowed to copy people's designs... so do you mind if i use yours? oh, and how far did yours go?


    11 years ago on Introduction

    hey try to add a video.. i want to see this thing in action..


    Reply 11 years ago on Introduction

    Sorry. The assignment was months ago - the car is gone and done now.