DIY App-Controlled RC Race Car made from Milk Bottle and Yoghurt Pots

How to make your own radio controlled car from household waste

Make a fun, speedy little car that you can control with your smartphone using the contents of your recycling bin and the reusable parts from a Smartibot kit. This is a great craft project to do at home and, for people in the UK, will feel like a classic Blue Peter 'Make'.

Engineering-wise, instead of using both motors to drive one wheel each (like on the Smartibot) this project uses one motor to drive both back wheels and one motor to steer the front wheels (just like a regular radio controlled car).

What you need:

- Smartibot board + 2 motors + battery box + 3 wheel mounts + nuts and bolts + square screwdriver

- Two yoghurt pots

- A 2 pint / 1 litre milk bottle

- Two milk bottle lids

- Two bamboo skewers

- PVA glue

- Glue gun and glue sticks

- Scissors

- Cardboard

- The race car template printed on A4 or US letter size paper

Here's one with the orange and purple Crafty Robot livery and...

Here's a blank one for you to decorate yourself

Make the cardboard car chassis

We start off by making the chassis. Get the templates that you printed and roughly cut out the chassis piece.

Use the PVA glue and stick it onto the cardboard. 

PRO tip: use a small piece of cardboard to evenly spread the glue. This way, you won’t end up with bulky spots of glue.

Wait a couple of minutes for the glue to dry a little and use the scissors to cut the chassis piece out of the cardboard. 

When you’ve done that, use the screwdriver and poke holes through the small circles. Then fold the piece along the dotted lines to create a long column.

Take one Smartibot motor and place it inside the wider end of the chassis. The wires should be on the inside, the shaft (the white rotating piece on either side of the motor) should be sticking out on either side, and the holes in the chassis should be aligned with the holes on the motor. Use the two longer bolts and push them through both sides of the chassis and the holes in the motor. Use the screwdriver to tighten the bolts. Take the motor wires and poke them through the little hole that is in the middle of the chassis.

Take the second motor, and place it inside the narrower end of the chassis, with the shaft vertical. Again, the wires should be on the inside, and the holes in the chassis should be aligned to the holes on the motor. Attach the motor with nuts and bolts and poke the wires out through the same hole.

Build the front axle

When you’ve finished the chassis, you can cut the axle from the template and glue it onto the cardboard.

After the glue has dried, cut it out and poke holes on both sides of the axle.

Then, get one white disc and place it in the middle of the axle piece. Use the same screwdriver to poke through the two holes on the disc. Then, use a skewer to poke through the tiny hole in the centre of the disc.

Fold the piece along the dotted lines and use the glue gun to glue the edges together. Then, attach the white disc using two nuts and short bolts.

Milk bottle top wheels

For the wheels, we are using the two milk bottle lids and a skewer. Use a skewer to poke holes through the centre of the lids, and attach one lid onto one end of the skewer. Use the glue gun to glue it in place.

When it has all dried up, stick the skewer through the axle piece. Make sure to leave around 1cm between the wheel and the axle. Take the second lid and attach it to the other end of the skewer. Keep the wheel 1cm away from the axle, and cut the remaining bit of the skewer off with your scissors. Use the glue gun to glue it in place.

Attach the axle and chassis

Attach axle to the narrower end of the chassis, by placing the shaft of the motor onto the white disc of the axle piece. Use a pointy bolt and screw it in the centre of the axle.

Yoghurt pot wheels

It’s time to get the yoghurt pots wheel-ready. Get two white discs and place them in the centre of the two yoghurt pots, and use the skewer to poke three holes through the discs. Then, screw the discs onto the pots using the small bolts and nuts, and tighten it with the screwdriver.

After you’ve done that, place the yoghurt pots on either side of the second motor and screw it onto the shaft with a pointy bolt. 

You should now have something that looks like this:

Cut the out the car body

To make space for the driver (AKA the Smartibot circuit board), draw a square on the other side of the milk bottle big enough to hold the board and cut it out with the scissors.

Attach the circuit board

To keep the circuit board in place, we are going to cut the square from the template, stick it on the cardboard and cut it out.

With the screwdriver, poke two holes through the small circles on both sides. Place the circuit board on it and attach it with some nuts and bolts.

Wire up the motors

It’s time to wire the board up. Use the flat screwdriver to unscrew the upper two chambers on each side of the circuit board, and take the black and red wire from the chassis (the one attached to the two yoghurt pots) and push the red wire in the upper chamber on the left side of the circuit board (when it's facing you and where it says 'M1'), and the black wire in the chamber underneath it. 

Then, take the black and red wire of the motor from the axle and do the same on the right side of the board, M2.

Position the car body 

Now that the wiring is done, we are going to put the body on the rest of the race car. Place the battery box inside the body and apply a layer of glue on the bottom of the body. Place the circuit board inside square you made earlier and tilt the body so that it sits right on top of the chassis. 

The final touches

To make the car look like a real race car, we are going to attach front and rear wings and nose livery. Stick them onto the cardboard and cut them out with the scissors. 

Make the rear wing by placing the rectangular piece of cardboard upside down and glue the sides of the two purple squares onto it. When it has dried up, apply glue to the edges and place the wing onto the rear of the race car. 

For the two front wings, apply glue onto the curved edge and place it on each side of the front.

Lastly, stick the front piece with some glue and you have finished your race car!

Design your own app control pad

Because we have positioned our motors in a different way to how we use them on the Smartibots in the kit (using one for the steering, rather than both of them to drive different wheels), we need to make a new control pad with the Smartibot app. Follow the steps at this point in the video below and start driving your race car!