Building a CO2 Race Car

What even is a CO₂ dragster?

CO₂ dragsters are miniature racing cars which are propelled by a carbon dioxide cartridge.

Required Materials: (Wheels can be 3d printed from the tinkercad file)

-30x7x5 cm block of wood

-two axles

-two straw bearings

-four wheels

-four washers

-two screw eyes

-CO₂ Cartridge

-Paint

Required Tools:
-Drill Press

-Scroll Saw

-Hacksaw

-Sandpaper

-File

Step 1: Design Your Car

Rough Sketch:

The best way to start is with concept sketches, also known as thumbnail sketches. These are small, quick sketches used by designers to quickly communicate ideas. They should not be detailed or even carefully done. You should experiment with different ideas and be as creative.

Detailed Sketch:

Next, on a clean sheet of paper, sketch your favorite design from the thumbnail sketches on a larger scale with more detail. Draw the top and side views. Show the location of hidden details (such as the cartridge hole) by using dashed lines. When make this sketch check the specifications in the image attached to make sure that you stay between the minimum and maximum values for the design. You may find it necessary to change your design.

Step 2: Make a 1:1 Scale Drawing

You must make a working drawing which is a precise, 1:1 scale drawing that describes your car and its features. Working drawings should have top and side views. A copy of the working drawing serves as a template for rough-cutting your car blank. Have a look of the tinkercad file as a reference for making a scale drawing.

Cut out the top and side (profile) views from a copy of your working drawing. Then, carefully trace the outline of the views onto the wood blank as shown in the image.

Step 3: Cutting and Rough Shaping the Car

DRILLING AXLE HOLES

Transfer the axle hole locations onto the blank by using a sharp pointed tool such as an awl to puncture through the template and into the wood blank.

Lay the car blank on its side and drill 3mm axle pilot holes. The holes should be drilled perpendicular to the car’s longitudinal axis in order for the car to roll freely and straight down the track. A drill press is highly recommended because it makes drilling perpendicular holes a cinch.

ROUGH SHAPING THE CAR BODY
1. Use a bandsaw to roughly shape the block:

Turn the block on its side and cut out the profile view first.

Fit the waste pieces and working piece back together and secure them by wrapping two bands of masking tape around the assembly.

Set the blank assembly upright and cut out the top view.

Remove the masking tape and discard all the waste pieces.

Step 4: Fine Tuning the Shape of Your Car

Smooth the corners of your car body. Use wood files, or rough sandpaper (80 grit) to smooth the car to its basic rounded shape.

Now at this point, your car has assumed its basic shape. Now you’re at the stage that separates the really fine cars from the mediocre cars. Extra time and effort spent during the fine shaping, or pre-painting, stage have a huge payoff in the kerbside appeal of the final product.
Use sandpaper to remove unwanted bumps and irregularities from the body. Use progressively finer grit paper as you go. For example, you might start with 80-grit paper (very coarse, removes a lot of material) and progress to 220-grit (medium coarse) then finally 500-grit(fine paper for smoothing surfaces).

Check your car for symmetry, and sand the body as needed. Also, exposing your car to bright light can help reveal imperfections that need attention

Step 5: Painting Your Car

Painting:

It is recommended to use spray paint to paint your car but you can also paint your car with aclyrric paint and a brush if you are unable to find spray paint. Be sure to tape off areas of the car you don't want to paint. As in the fine shaping stage, extra patience and effort put into the finishing stage can have big benefits. Be aware that using several coats of paint can add weight to your car and slow it down.

Step 6: Final Assembly

Final Assembly:

Mounting Wheels and Hardware don’t overlook the importance of this stage. A huge factor in race performance is how smoothly the car rolls down the track. Some meticulously shaped cars have failed to finish races because of improperly installed hardware!

1. Gather your hardware: two axles, two straw bearings, four wheels, four washers, and two screw eyes. Depending on the configuration of the car body, different hardware might be required. Cut the axles so they are 1cm longer than the width of your car.

2. Check your specification image in step 4 for rules about installing wheels, axles, washers, and spacers.

3. Carefully mount the wheels and axles as dictated by your design. Be careful not to damage the fragile car body during installation.

4. Insert the CO2 cartridge into the hole in the back of car.

5. Screw eyes are optional but can be used to run a string or wire through them to make sure the car goes in a straight path on a CO2 car track.

6. Roll test the car on a smooth, horizontal surface. The car should roll freely, and the wheels should spin without restriction. Make adjustments if necessary.

Now your car is ready to race!

Note that a CO2 car launcher or safe method of puncturing the CO2 cartridge is required to launch the car.