STEM Racers – Modular 3D printed racing cars

This post will describe a fun and engaging STEM activity that kids can do in a class or at home.

We will be building a modular race car and performing a series of scientific experiments by changing different parameters (adding weight, changing tires, and more) to make the absolute fastest car!

Another advantage of this activity is that if you have a 3D printer, you probably won’t need to buy anything! We shared the 3D printed files and will explain in this post how you can use things you probably already have to build the track and cars.

Getting parts ready

You will need to following parts to build the cars:

3D printed parts

The STL files can be found here:

You will need to print two cars (two sets of parts). 

If there are several groups of kids, each group will need two cars.

We recommend printing the cars in different colors to distinguish them easily (different colored parts can also be mixed).

Print time for each set is just around 20 minutes.



To connect the 3D printed parts together you will need four(4) M3 screws with a length of 6mm.

We recommend using Allen screws because they are easier for kids to work with.



Any 1/64 scale wheels can be used for these cars.
You can buy such wheels online, but a quicker approach might be to take them off any HotWheels car or other 1/64 brand diecast cars.
We recommend using two different sets of wheels (plastic vs. rubber or small vs. big).
If you only have one set of wheels, that will be perfectly fine because other parameters can change to make the cars faster.
There are also many videos on YouTube explaining how to remove wheels from HotWheels car, here is one of them:


Assembling the car

The gallery below demonstrates the simple assembly process of the car:

Building the track

To check how fast the car is, we will need a race track.
Regular HotWheels orange track will be perfect for the task.
However, if you want to go completely DIY, YouTube can help:

Starting the cars

You will need a way to start the cars at the same time with accuracy.

We have designed a simple start gate that you can 3D print.
Download the files here:


Alternatively, you can use one of the start gates available on the market.
For example, our
PlayRobotics Smart Race Track.

Hot wheels cars at start of race track, data cable, stop light, and electrical components.

Measuring performance

Several parameters can be changed in this modular car:

1) Tires.

2) Front wheels location.

3) Rear wheels location.

4) Total weight added to the car.

5) Location of the added weight.


To build the fastest car, kids will need to perform a series of experiments by changing one parameter at a time and measuring the performance.

If using a track timer, you can easily measure how much time it took a car to complete the track. 

If you don’t have a timer, you will need to race two cars and change only one parameter between the two cars.

For example:

– Car A has added weight at the back of the car

– Car B has added weight at the front of the car

If car A wins, this means that moving weight to the back of the car will make it faster!

IMG_8352 (1)

Documenting the experiments

We have also prepared a Google Docs file for you to print. It can be used to log the experiments to find the best performing car variation scientifically.

Get the file here



Let’s race!

That’s it! time to begin racing and setting new records!