CO2 Dragster Competition 2009 Chantel Verner Professor: Dale Brown AQ – Design and Technology Part 2 May ~ 2009 CO2 Dragster Competition 2009 Problem Statement: To research, design, engineer and report a CO2 powered dragster to race down a 65-foot track in the least possible time as outlined below. Design Criteria: 1. The dragster must have a mass of 50 grams or more. 2. The completed dragster must have a minimum/maximum length of 10”. 3. The completed dragster must have a maximum body width at front and rear wheels of 1 ¾”. 4. The dragster must have a cartridge hole depth of 2”. 5. The dragster must have a cartridge hole diameter of ¾”. 6. The height of the cartridge hole from bottom to centerline of the hole must be 1 ¼”. 7. The dragster must have a minimum of 1/8”of wood around the entire cartridge hole. 8. The dragster must have two screw eyes, one toward the front and one toward the back of the centerline, on the bottom of the dragster. 9. The dragster must be made of solid wood of sufficient strength to withstand racing. 10. Bearings, bushings, and lubricants may be used in the construction. 11. The dragster must have at least three wheels with a maximum diameter of 2 inches. 12. Wheels must be made of plastic. 13. The dragster must have two axles. 14. Axles must go through the body of the dragster. External axle tubes are not permitted. 15. In the opinion of the judge(s), any dragster deemed unsafe will be disqualified. Competition: 1. Dragsters will run two at a time. 2. Dragster will run on a fishing line down a 20-meter track. 3. Race will begin when firing mechanism is fired. Both dragsters will start simultaneously. 4. Race will end when the dragster passes at the finish line. 5. Winner will be determined through single elimination. Research: 20 Fast Facts 1. The less wheel or road surface friction, the faster the car will travel. 2. The wheels do not propel the car, the CO2 cartridge does. 3. The more the car disrupts the air flow around it, the more drag is developed, the slower the car. 4. The less turbulence created, the faster the car. 5. The smoother the car’s surface, the less aerodynamic drag. 6. Wheels create friction which slows the car. 7. The lighter the wood, the faster the car will travel. 8. Shell cars, with the wheels on the inside of the frame reduce drag. 9. The drag force produced by the axle will slow or stop the car. 10. Aluminium wheels will be lighter then steel wheels. 11. Balsa wood is easy to work with and it is light weight. 12. A set of two hooks linked to a string at the bottom of the car prevent the vehicle from losing control during launch. 13. As the airflow moves from the front of the car to the rear it becomes turbulent and causes unstable forces on an object. 14. The front end needs to be thin and it has to get thicker and thicker as you go to the rear to reduce drag. 15. Deflectors located between the front wheels eliminate a source of turbulent air. 16. Axles that have bushels that fit on the inside of the car help to reduce the friction of the axles by 50%. 17. Laminar flow is the fluid (air) is moving in smooth layers around the object. 18. Air flow becomes turbulent moving from the front to the rear of the car when forced around obstructions such as mirrors, helmets, and wheels. 19. Skin friction will likely form a large portion of the aerodynamic drag. 20. If you can keep the body up and away from the ground it will have less interference and friction. 21. The weight of the car is more important and aerodynamics is secondary. Solution Chart and Rational: Criteria Design 1 Design 2 Time to - 3 hours - 2 hour construct function - fairly solid frame - solid frame - speed - speed materials - wood block - wood block - plastic straw - plastic straw - 4 wheels - 4 wheels - 2 axels - 2 axels - Acrylic paint - cost - $0.30 (paint) - N/A aesthetics - excellent - good - fin to add design interest - aerodynamic skill - need to measure accurately - will need to measure accurately - need more than basic shop - need basic shop experience experience to cut around fin weight - most amount of weight due to fin - little amount of weight - still under 100g - under 90g aerodynamics - less turbulence created by design - lightweight frame - less surface drag because of - as little wood left as possible paint - smaller, thinner frame may break during racing Rational: The first car design won because it looked more like a traditional dragster. Although both cars would have relatively the same shape and weight, I decided to add the fin for aesthetic reasons. The paint was added due to aesthetics, but also to have less surface drag as there may be limited time for fine sanding. List of Materials: - One piece of spruce 2 x 4 ( 10” x 2.75” x 1.5” ) - 4 pitsco plastic wheels - Two 1/8” diameter steel axle rods - Four brass axle bushings - Two metal eyelet screws - One C02 cartridge per race - Red and white pin-striping - Silver high gloss rim paint Chart of Results: Name Weight of dragster Overall standings Mike 72 grams 1st place Dave 92 grams 2nd place Chantel 101 grams 3rd place Myles 103 grams 4th place Rod 107 grams 5th place Conclusion: The designs that were most successful were those that had a combination of lightweight materials and little to no friction. Although most of us had relatively similar designs, the ones that had less material, were the ones that were the most successful. My car was the 3rd lightest, hence coming in 3rd place. The winning car was the lightest, which is what Dale predicted the whole time. If I were to do this project again, I would spend more time analyzing the thumbnail sketch designs so I could try and find the lightest way to create one. It would have been much easier to know more about the car’s potential performance before construction.