Build a Car!

Here’s a cute little car that’s fairly easy for young kids to build with the right parts. And, you can then motorize it with a small motor and fan!

Supplies Needed

For Car

Cardstock for template. Axles and wheels. (And a hole punch and some markers to decorate with.)

(I used the 42x19mm Eudax wheel and axles They are about $1.00 per car. The 30 x 8 mm are about half that cost, and would likely work OK, though you might need to adjust where you punch the holes for the axle. You could also use wooden wheels and dowels as we did in our other car design, or use these other ideas for wheels like bamboo skewers and plastic lids.)

If you want to motorize the car

battery holder, battery, motor, propeller

What I used = battery holder. One AA battery. One 1.5-3V motor with clips. Propeller. Cost: approximately $3.30 per car: battery holder .68, battery .50; motor $1.80, propeller .30. Note: there are LOTS of other options for battery holders and motors. I like this exact combination because the clips on the motors make it really easy for the kids to connect and disconnect from the battery. Teacher Geek has a great battery pack and motor that I like for scribble bots, but it won’t work for this project, because the motor has an adapter pin on it that’s not compatible with the propellers.

Step 1: Print the Template

Print the template double-sided (flip on long side) onto cardstock. You can use regular paper, but it’s much stronger / sturdier on cardstock. (Note: the version below has directions written on it. If you’d rather not have the directions, there’s another version here without the words.)

Step 2: Decorate the Car

Step 3 – Fold the Car

Flip the paper over so you can see the back. (i.e. you can’t see the car.) Fold in one side along the dotted line, then fold in the other side, so they meet in the middle.

Then, fold up along the bottom pair of dotted lines and crease. Unfold it. Then fold up along the second pair of lines. Crease. Unfold it. Then fold on the third set of dotted lines. Crease. Unfold. Then fold down the top segment, crease and unfold.

Now fold it so the bottom and top edge overlaps. Tuck the skinnier flap inside the wider flap. Now you’ve got a sort of trapezoid shape that is a little car that will stand up on its own.

Step 4 – Add the Wheels

Use a hole punch to punch out the center of each wheel area. Slide the axles through the holes and put the wheels on.

Step 5 – Add the Fan and Motor

Mount the fan onto the motor. Put tape on a flat side of the motor and mount it on the top of the car in the back. Put tape on the battery holder. Tape it on top on the front end of the car. Connect the motor to the battery – if you have short wires, you could go over the top. My wires were so long I was afraid they’d get tangled in the fan or wheels, so I ran them through the inside of the car up to the front.

Step 6 – Test Your Car

When you connect up the battery, the fan will start to run. Then set the car down with room to roll.

If you’re lucky, it will immediately roll across the room. If it does not move at all, it’s OK! Your fan may run clockwise or counter-clockwise depending on whether the wires are hooked to the positive side of the battery or the negative. One rotation will make your car fly across the room. When it rotates the other way the car doesn’t move. Do some experiments to figure out which wire you have to connect to which terminal to make it roll.

Have fun building and playing!

Past Car Designs

Coming up with a good car design is something I have struggled with for the past several years. In my Designing a Car post from 2016, I talk about all the challenges and all the options I considered. My criteria were it has to be something that 5 – 6 year olds can do with minimal support. The materials need to be low cost and that I can get in bulk. (40 kids making cars = 160 wheels!) Can’t take a lot of prep time. The end product needed to be fun, and not too delicate for 3 year olds to play with.

My 2016 final design (find the tutorial here) uses a corrugated plastic (or cardboard) body, wood dowels for axles, and a retractable badge to “motorize” it. You could also add CD wheels to the car, and it would travel much further. (See video in the post.) It’s a fun project, but TONS of prep time!

retractable-badge-car-stem-project-for-kids

We considered the rubber band racer from Teacher Geek. The kits are pricey, so I worked out what the cost would be if I bought the supplies in bulk from them. It was about $3.40 per car. But minimal prep time! And nice result.

20190212_225823098_iOS.jpg

In early 2021, I created another new design. Tutorial here. It uses a folded cardstock template for the body, wooden dowels and straw bits for axles, and wood wheels and/or CD’s. It’s “motorized” with a rubber band. So, it’s less prep time and less cost than the 2016 edition. But not nearly as cute as our new design!

Learn More About Wheels and Cars

We build these cars in our class on Wheels and Axles, the final class in our Simple Machines unit. The week after this, we study Cars to wrap up Engineering quarter.

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