1. CO2 CARS

2. OBJECTIVE

3. A vehicle with a smaller mass will accelerate faster!
Form Follows Function
It means the form (size, shape,weight,etc.) of any object should follow (be designed to match) its function (its intended use or purpose)
A vehicle with a smaller mass will accelerate faster!
Punctured CO2 Cartridge
AcceleratingCO2 Car
Discharging CO2 Gas

4. Aerodynamics
Aerodynamics is the study of airflow and the forces involved when an object moves through the air or when air moves past an object.
Four forces affect airflow:
* Lift
* Thrust
* Gravity
* Drag

5. LIFT DRAG THRUST GRAVITY Lift is the force that opposes gravity.
Forward force generated by CO2 cartridge
Due to friction from wheels and axles
GRAVITY
Gravity is the force due to the pull of the earth on objects.

6. Basic Aerodynamic Concepts
Skin Friction
Air is a viscous fluid that tends to stick or adhere to the surface of moving vehicles in invisible boundary layers.
Skin friction is the type of drag due to surface finish.
A vehicle with a smooth surface will have less skin friction.

7. Basic Aerodynamic Concepts
Streamline
The movement of air around a fixed or moving vehicle is called streamline.
The teardrop is the most aerodynamic and streamline shape.
A teardrop is not a practical shape for a vehicle; however your car should have a smooth surface, with rounded and tapered surfaces with no sharp corners or edges.

8. Basic Aerodynamic Concepts
Laminar Flow
When air flows around streamlined objects and remains fairly straight and even it is known as laminar flow.
Laminar flow may be improved by designing a sleek, continuous, smooth flowing, uninterrupted structural skin on a vehicle

9. This break up of the boundary layer is known as separation.
Basic Aerodynamic Concepts
Separation & Eddies
Air movement around objects that are not streamlined causes the boundary layer to break up and form swirls of airflow called eddies or vortices.
This break up of the boundary layer is known as separation.
The eddies and vortices due to separation absorb energy from a moving vehicle and reduce efficiency.

10. Friction is the resistance of movement between two touching surfaces.
Friction & CO2 Cars
Friction is the resistance of movement between two touching surfaces.
Friction between moving parts causes some of the energy to be wasted or lost.
Friction causes energy to be lost in the form of HEAT
Three main ways to reduce friction are polishing the touching surfaces, using lubricants, and using bearings.

11. Wheel & Axle Alignment
Alignment of the axles and the wheels is VERY important to the performance of a CO2 car.
If the axles are not parallel to each other, and perpendicular to the sides of an UNCUT body, the car will tend to turn to one side as it travels down the track.
Axles
Car body
Axle holes drilled through the body
Looking down at the top of the blank, the axle holes must be drilled perpendicular (at right angles) to the sides of the body

12. Ramp Test
The ramp test will determine how well your wheels and axles are aligned.
If the axles are not parallel to each other, and perpendicular to the sides of an UNCUT body, the car will tend to turn to one side as it travels down the track.

13. Vehicle Parameters Height (at rear with wheels) ……. 56 mm 75 mm
The following are the minimum and maximum specifications for your CO2 racing vehicle. ALL of the specifications MUST be met. Failure to meet all of the specifications will result in loss of points and/or disqualification from racing.
SPECIFICATIONS
Structure (one piece, solid wood body) Min. Max.
Length ………………………………… 200 mm 305 mm
Height (at rear with wheels) ……. 56 mm 75 mm
Width (at axle holes) ……………. 35 mm 42 mm
Width (including wheels) ……….. NA 80 mm
Mass (with wheels, no CO2) …… 100 gram 220 gram

14. Vehicle Parameters Chamber diameter …………… 19 mm 20 mm
The following are the minimum and maximum specifications for your CO2 racing vehicle. ALL of the specifications MUST be met. Failure to meet all of the specifications will result in loss of points and/or disqualification from racing.
SPECIFICATIONS
Propulsion (CO2 Cartridge) Min. Max.
Chamber depth …………………… 50 mm 52 mm
Chamber diameter …………… 19 mm 20 mm
Housing thickness …………….. 5 mm NA
Location (center line from body bottom) .. 31mm 35 mm

15. Vehicle Parameters Length …………………………. 42 mm 70 mm
The following are the minimum and maximum specifications for your CO2 racing vehicle. ALL of the specifications MUST be met. Failure to meet all of the specifications will result in loss of points and/or disqualification from racing.
SPECIFICATIONS
Suspension (only allowed 2 axles) Min. Max.
Diameter ………………………….. 3 mm 3 mm
Length …………………………. 42 mm 70 mm
Bearing Diameter …………… mm 4.5 mm
Hole Diameter ………………… 3.5 mm 4.5 mm
Location (from bottom of the body) …… 5 mm 10 mm
Location (from either end of body) …….. 9 mm 100 mm

16. Vehicle Parameters Diameter (Rear) …………………. 30 mm 40 mm
The following are the minimum and maximum specifications for your CO2 racing vehicle. ALL of the specifications MUST be met. Failure to meet all of the specifications will result in loss of points and/or disqualification from racing.
SPECIFICATIONS
Suspension (wheels) Min. Max.
Diameter (Front) …………………….. 32 mm 37 mm
Diameter (Rear) …………………. 30 mm 40 mm
Width (Front at greatest diameter) 2 mm 5 mm
Width (Rear at greatest diameter) 15 mm 18 mm
Wheel base ………………………. 105 mm 270 mm

17. Vehicle Parameters Screw eye (distance apart) …….. 155 mm 270 mm
The following are the minimum and maximum specifications for your CO2 racing vehicle. ALL of the specifications MUST be met. Failure to meet all of the specifications will result in loss of points and/or disqualification from racing.
SPECIFICATIONS
Guidance / Control Min. Max.
Screw eye diameter ………………… 3 mm 5 mm
Screw eye (distance apart) …… mm 270 mm

18. Building your CO2 Car
The race car drivers at Indianapolis, the mechanics at Daytona, the automobile designers in Detroit, and the automobile engineers in Germany all had to start somewhere. They started small. Then as they learned and progressed they moved on to bigger and better things.
The car you will build is like a miniature rocket powered dragster. It really goes. As you build your dragster, DO NOT cut corners. It will have a better chance of looking good and going fast if you design and build it step by step as suggested.

19. Building your CO2 Car Step 1. Thumbnail Drawings
Your thumbnail drawings do not have to be a masterpiece. Keep them simple and small. You must have 8 different ideas. Don’t be afraid to experiment with some crazy designs.

20. Building your CO2 Car Step 2. Top & Side View Sketches
Look over your thumbnails and choose the three best designs. Try to have three totally different designs. Draw a top and side view of each idea. Be sure to remember the specifications you were given earlier.
Top View
Copy of Thumbnail
Side View

21. Building your CO2 Car Step 3. Final Drawing
Choose the best of your three top & side view sketches and complete a final drawing. Final drawings are made to exact size and will serve as a blueprint for your final dragster. Be sure to locate the axle holes and allow enough room for the engine housing.

22. Building your CO2 Car Step 4. Making Templates
After you have completed your Final Drawing and it has been approved by Mr. Conway, it will be photocopied. You should now have a duplicate copy of your Final Drawing. Cut out your templates. Be sure to follow your templates exactly. One minor mistake can ruin the whole body design or cause your dragster to not meet specifications

23. Building your CO2 Car Step 5. Layout
Tape the side view template to the wood blank. Be sure to follow your templates exactly. One minor mistake can ruin the whole body design or cause your dragster to not meet specifications. Trace around the template with a pen (make sure you mark the axle holes) and then remove the template. Tape the top view template to the top of the block. Trace around the template with a pen and then remove the template.

24. Building your CO2 Car Step 6. Drilling the Axle Holes
Axle holes should be drilled first. Before drilling, check the specifications to make sure your axle positions are within limitations. You will use the drill press with a 5/32” bit to drill your holes. Make sure the wood blank is laying completely flat on the table.

25. Building your CO2 Car Step 7a. Cutting out the Blank
Begin by laying the block flat on the band saw table and cutting out the side view. Make sure you DO NOT lose any of the pieces you have cut! After you have finished cutting the side view, you need to take the pieces you’ve cut and tape them back together (you should now have a triangular wood block again).

26. Building your CO2 Car Step 7b. Cutting out the Blank
The reason you tape the wood back together is so you will know where to cut on the top view. You will now change the position of the block and cut the top view to shape. Remove the remaining tape. You should have a rough version of your dragster.

27. Building your CO2 Car Step 8. Shaping the Body
Shape the body using an electric sander, wood rasp or a wood file. Start with a lower number sand paper and then move to higher numbers to finish. (80, 120, & 180)

28. Building your CO2 Car Step 9. Preliminary Assembly
Cut and install bearings (straws or brass tubing). Insert the axles, install the washers, and attach the wheels. Be sure that the wheels are securely attached and that the axles spin freely. Next you will install the screw eyes. Using an awl, make a small hole that will mark their position (make sure to double check specifications). Use pliers to mount the screw eyes. Make sure the eyes are in a straight line, do not interfere with the axles, and have plenty of ground clearance.

29. Building your CO2 Car Step 10a. Painting
Start by removing the screw eyes, wheels, washers, axles, and bearings. Sand the body smooth with 220 sand paper. Remove all bumps, nicks, or imperfections (everything will show up worse AFTER the car has been painted). Wipe off all dust. Place your car on a paint stand. Shake the paint for about a minute and then test in on a sheet of paper. Paint ONLY in the paint booth.

30. Building your CO2 Car Step 10b. Painting
Paint ONLY in the paint booth. The dragster should have at least two coats of paint on it. Completely cover the car with one light coat of paint and build it up slowly. This will prevent the paint from having runs in it. After the first coat is dry, check for any rough spots in the paint. These can be taken off by using VERY fine sandpaper. Just sand the small area that has the flaw. Now you are ready to spray the body a second time.

31. Building your CO2 Car Step 11. Final Assembly
Re-insert the axle bearings. Spray a SMALL amount of powder graphite into the bearings. Insert the axles. Attach the washers and wheels to the axles. Spin the wheel assembly to “work in” the graphite. Install the screw eyes. Congratulation you have now finished your CO2 dragster.