CO2 Dragster Design http://www.science-of-speed.com/science.asp

Research and Development Objectives Research in CO2 auto design involves the study of a few sciences related to the motion of your dragster. Aerodynamics- the study of how solid objects displace fluid air and other gases; Physics- the study of matter in motion; Tribology- the study of friction;

Research and Development Objectives Development of CO2 auto design requires- Understanding the problem or purpose- trying to achieve the fastest speed and/or best appearance; Knowing your limitations- being aware of safety regulations, materials allowed, specifications, tolerances and functionality; Making intelligent decisions- taking what you learn and using it to your best advantage; Testing your solution- comparing results with your classmates to see what works better;

Terms to Know- Aerodynamics Fluid Mass Aerodynamics Drag Lift Rear Suction Down Force Frontal Area Aerodynamics in race cars Circle Track magazine Aerodynamics in race cars Hot Rod Magazine

Research- Aerodynamics Air- Is a type of fluid such as water that can be directed or displaced; Has mass and is measured in terms of pressure; Applies direct and frictional forces to objects in motion;

Research- Aerodynamics You should be aware of four aerodynamic principles- Drag Lift/Down Force Drag Coefficient Frontal Area http://www.hotrod.com/techarticles/body/hdrp_0609_aero_tricks_tips/

Research- Aerodynamics Drag is a combination of two forces that will work against the acceleration of your CO2 car. Frontal Pressure occurs when tiny molecules of air hit the front of your car and is forced away to make room for other molecules to hit it. Rear Suction occurs when an empty pocket of air is created in the back of your car resulting in a vacuum cleaner effect that tries to pull your car backward.

Drag Aerodynamic force that resists the motion of an object moving through a fluid (air and water are both fluids). Try this next time you are in a car… put your hand out a window and rotate it. You will notice much more force (drag) when the palm of your hand is open and vertical then when it is open and horizontal The amount of drag that your hand creates depends on a few factors, such as the size of your hand, the speed of the car and the density of the air. If you were to slow down, you would notice that the drag on your hand would decrease.

Suction Notice that liquid is pushed up a straw when the balanced air pressure is removed. The same effect happens to objects in motion. The air traveling around the object can create a pocket of less air pressure causing suction to occur

Air Flow Rear Suction

Research- Aerodynamics Lift is similar to rear suction in that a thin empty pocket occurs as air passes over a flat surface causing the car to lift. Down Force is due to high pressure in curved surfaces that causes the car to be pushed down.

The Bernouli Effect: If a fluid (gas or liquid) flows around an object at different speeds, the slower moving fluid will exert more pressure than the faster moving fluid on the object.  

Drag = Thrust & Weight = Lift the plane will fly STRAIGHT & LEVEL   In an airplane, when: Drag = Thrust & Weight = Lift the plane will fly STRAIGHT & LEVEL  

Cars create thrust using engines Cars create thrust using engines. Your dragster will use a CO2 Cartridge   If drag increases and/or thrust decreases the car will slow down  

In a race car (Indy or F1 style) the car is designed like an upside-down airplane wing which creates downforce rather than lift. This keeps the car on the ground and prevents lift-off. With cars, the principles of design are the same – which is to have the 4 aspects equal each other thus maximizing its aerodynamic efficiency.

The air moving under the car moves faster than that above it, creating downforce or negative lift on the car. Airfoils or wings are also used in the front and rear of the car in an effort to generate more downforce. Downforce is necessary in maintaining high speeds through the corners and forces the car to the track. An Indy ground effect race car can reach speeds in excess of 230 mph using downforce. In addition the shape of the underbody (an inverted wing) creates an area of low pressure between the bottom of the car and the racing surface. This sucks the car to road which results in higher cornering speeds.

Because of the amount of downforce a race car creates, (in theory) if a race car is traveling at high enough speeds (+200kph) it could travel along a wall or even upside down on a road without falling!

Air Flow Lift Down Force

Air Friction and Lift When a ball rotates in motion, it causes the air around it to flow with the rotation, often changing the direction with lift and down force. The dimples in a golf ball are also used for reducing air friction with the surface. But…read this -->Golf Ball Dimples & Drag

Research- Aerodynamics Drag Coefficient is a way of expressing how slippery a car is. Here is a tip to increase your speed and lower your drag coefficient- (the more ways you can eliminate drag, turbulence, rear suction, lift and down force, the faster your car will go)

Research- Aerodynamics Frontal Area is the total of all surfaces in the front of your vehicle which cause drag. Area = Length x Width

Review With one hand, which can be thrown further, a football . . . or a soccer ball?

Review Tips- Aerodynamics Avoid flat upright surfaces in the front of your car to reduce turbulence. Avoid flat upright surfaces in the back of your car to reduce rear suction. Shield as much air at the bottom of your car to maintain traction. Keep the surface area exposed to oncoming air to a minimum.

Terms to Know- Physics Force Acceleration

Force = Mass x Acceleration Research- Physics Force = Mass x Acceleration Heavier objects require more effort to move at the same speed; It is easier to push a CO2 car out of the ditch than to push an actual car out of the ditch. Everyone’s force on the CO2 car will be the same. The less mass, the greater the acceleration

Research Physics Heavy Mountain Bike Durable For Rough Terrain Requires more Energy Light Racing Bike Fast For Long Distance Requires less Energy

Research- Physics How does the angle of your CO2 cartridge affect the efficiency of your car?

Review Tips- Physics Avoid unnecessary extensions and ornaments that add weight to your car. The lighter you design your car, the more power will be used out of your CO2 cartridge. Make sure that your drill holes are straight and accurate to reduce extra forces acting on your car.

Research- Tribology Tribology is the study of friction between solid surfaces. Friction is a force that resists movement. Friction is found between moving parts and surfaces. Without friction, objects would never come to rest. Where will you find friction forces acting on your car?

Research- Tribology How many wheels should you have and why?

Research- Triboloby Does the paint job affect your car: Why or why not?

Research Physics Heavy Mountain Bike Wider Ground Contact More Surface Friction Light Racing Bike Narrower Ground Contact Less Surface Friction

Review Tips- Tribology Painting your car will reduce aerodynamic friction. Axel design is important to reducing friction. Lubrication of the axels can reduce friction. Less ground contact wheels have with the ground, the less friction will be present.

Review Tips- Aerodynamics Avoid flat upright surfaces in the front of your car to reduce turbulence. Avoid flat upright surfaces in the back of your car to reduce rear suction. Shield as much air at the bottom of your car to maintain traction. Keep the surface area exposed to oncoming air to a minimum.

Review Tips- Physics Avoid unnecessary extensions and ornaments that add weight to your car. The lighter you design your car, the more power will be used out of your CO2 cartridge. Make sure that your drill holes are straight and accurate to reduce extra forces acting on your car.

Review Tips- Tribology Painting your car will reduce aerodynamic friction. Axel design is important to reducing friction. Lubrication of the axels can reduce friction. Less ground contact wheels have with the ground, the less friction will be present.