1. Mr. Sexton Engineering Technology
CO2 Dragster Cars
Mr. Sexton
Engineering Technology

2. Purpose of CO2 Activity Understand how a CO2 car works
Design your CO2 car
Build your CO2 car
Race your CO2 car

3. Overview • Intro to Racing CO2 cars • Engineering Principles
• Student examples
• Designing your CO2 Car
• Manufacturing your CO2 Car

4. Intro to Racing CO2 cars 2 Cars are set up
Cars ride on guide wire from start of track to end of track
Co2 cartridge is punctured –propelling car forward
Two cars race
Cars go through end gate
light goes for fastest car
Race time is recorded for each car

5. What do you use for the track?
Many times when people are new to CO2 racing, they hear about cars running on a "track" and think that a track specially made for CO2 cars is needed to race them.
We will race our cars on the floor. You can easily build a simple and inexpensive race track. Not as good, but a lot cheaper

6. CO2 Racetrack The only track required is 50# test fishing line.
Fishing line is used as a guide line that the eye-hooks on the bottom of the cars attach to.
The fishing line runs between the start gate and the finish gate
We will likely run our races using only fishing line along the concrete floor of my lab. The smoother the surface, the faster the times will be.

7. length of the track
The length of the track is also important. You need to have at least 60 feet without any obstructions. Any shorter distance than this, and the cars will destroy themselves upon finishing a race.
The optimum track length is 66 feet (20 Meters), which is in scale with real dragstrip lengths of a quarter mile.

8. How fast are these things?
Up to 60 mph (100 kmh)

9. Engineering Principles
The following Engineering Principles
Relate to how and why a CO2 car works
Newton’s Laws of Motion
Mass
Drag
Friction

10. Newton’s 2nd Law of Motion
greater force = greater action.
Acceleration is dependent upon the mass and force of the car.
F = ma
F = force
m = mass
a = acceleration
For a fast car, you need:
Big force
Light car (mass)

11. Mass The Balancing Act:
– Advantages: Cars with less mass go much faster.
– Disadvantages: Cars with less mass are less stable and less durable.
Does takes more or less force to push 40g than it does to push 130g?

12. Mass F = m* a Assuming force is the same F = 40 *1 F = 130 * 1
F would be larger with the F/40. (A piece of cake divided by 40 parts or 130 parts, which gives you a bigger piece of cake?)
Therefore, the smaller mass requires less force.

13. Acceleration Acceleration is produced by the CO2 gas cylinder.
The CO2 canister produces thrust when you puncture it – propelling the CO2 car forward
It works similar to sticking a pin in a balloon - The balloon is propelled around the room by the thrust created by the escaping gas.

14. Forces of Resistance
Drag (from air resistance) (FW)
Friction

15. Drag Take a piece of wood, slap wheels on it,
shoot it down a track at 60 MPH and the air
rushing over the body and wheels will try to
slow it down.
Scientifically this is called drag: the resistance of wind moving over an object.

16. Minimizing DRAG The Balancing Act: – Advantages:
Aerodynamically shaped cars have less
drag so they go faster.
– Disadvantages:
Aerodynamically "clean" cars are more
difficult to build, but worth the effort

17. Friction Friction is a product of gravity
• On a CO2 car, Friction occurs primarily in three places:
Between the wheels & the ground.
Between the axles & the car body.
Between the eye-hook & the fishing line.

18. Minimizing Friction Make sure the axle & tires freely rotate.
Make sure the wheels are not rubbing on the car body.
Be sure to install your eye-hooks properly. Poorly aligned eye-hooks are often the cause of a slow car.

19. What's the best design for a CO2 car?
Your Car must meet the size and dimensional requirements of TSA.
The best design is the one that wins. There is no "one design" that is best.
Generally, the two best indicators of a good car are clean aerodynamics and high craftsmanship. Often, really good designs that are built poorly will loose to so-so designs built well.

20. Designing your CO2 car
Step 1: Obtain the proper paper from me

21. Designing Your CO2 Car Step 2
Brainstorming (think about what you want your car to look like)
Sketch 6 different possible design ideas
Create drawing on the lined paper
Remember, 1 square = 2 mm

22. Designing Your CO2 Car Step 3 Complete technical drawing for CO2 car
You must have a high quality, accurate drawing
Drawing must be 1:1scale (actual size)
Identify the axles
Check your car against the TSA specifications

23. Designing Your CO2 Car Step 5 Step 6 Step 4
Get instructor to look over your drawing.
You must get instructor sign off before beginning to manufacture the car that you designed
Step 5
Locate a piece of copy paper
Trace your design onto the copy paper. Use the light table to do this.
Step 6
Cut-out the tracing that you made
Obtain a blank piece of balsa from me

24. Overview of the CO2 Car Manufacturing Process
- Sample CO2 car being made
- Step by step overview

25. Manufacturing Your CO2 Car
Step 7 – Transfer your design to the Balsa blank
Tape the cut-out onto the blank.
Trace the outline onto the car. Use a Sharpie.
Mark the axles.

26. Manufacturing Your CO2 Car
Step 8 - drill the holes for the axles (using the drill press).
Make sure the axle holes are in the right spot and are straight
The holes should be perpendicular to the center line of the car and parallel with the bottom surface of the car.
* Take care to make sure these holes line up evenly and are drilled accurately. Crooked holes mean a slow car! Use a drill press and take your time! *

27. Manufacturing Your CO2 Car
Step 9 - Using the Bandsaw, cut out your shape.
When using the band saw to cut curves, you must use relief cuts (or you will break the band).
Follow the shape that is on the template that is traced on your CO2 car.
Follow all safety precautions.
Clean your mess

28. Manufacturing Your CO2 Car
Step 10 – Shaping and Sanding
Use a rasp or wood file to remove band saw blade markings and to round corners and edges.
Also to begin the smoothing process.
Hand Sand your CO2 car until you have removed the file marks with 100 grit sand paper.
Hand sand with fine sand paper (>150 grit) to remove all scratches.
Always clean your mess.

29. Manufacturing your CO2 car
Step 11 – Finishing
Finish cars with the acrylic latex paint we have
Every brush must be cleaned out.
Loss of daily points if not done so

30. WCHS Policy We will paint the car in class.
We will not assemble with wheels, screw eyes, etc.. Until right before the race.

31. CO2 Designs
This car was created by John Vice, Mr. Sexton’s student teacher.

32. CO2 Designs

33. CO2 Designs

34. CO2 Designs

35. CO2 Designs

36. CO2 Designs

37. CO2 Designs

38. CO2 Designs

39. CO2 Designs

40. CO2 Designs

41. CO2 Designs

42. CO2 Designs

43. CO2 Designs

44. CO2 Designs

45. CO2 Designs

46. CO2 Designs

47. CO2 Designs

48. CO2 Designs

49. CO2 Designs

50. CO2 Designs

51. Manufacturing your CO2 car
Step 12 – Assembly before the race
Assemble all the parts of the CO2 car
Wheels
Axels
Body
Eyelets
CO2 cartridge

52. CO2 Cars
If you need more info on the Design and Manufacturing Process check out: