Ben
Lv 4
Ben asked in Science & MathematicsEngineering · 8 years ago

# Car Aerodynamics - Drag Vs Down Force?

I am planning on designing/building a race car with the use of an aluminium frame and sheet metal to enter in a small contest, I am having trouble deciding how I should build the body, I read about aerodynamics and found that it is important to have a low Drag Coefficient so that there is very little air resistance but after I continued reading I found that formula one cars do the opposite there drag coefficient is the same as an average van but they have a lot of down force, so I got confused, should I be concentrating on drag or down force?

Just some extra information if needed: The race car weights very little, can be picked up with one hand. It is ran by a small electric motor and can reach speeds WELL OVER 50mph.

Update:

Thank you for the comments, so should I not worry about down force and just concentrate on the drag coefficient?

Relevance
• RossK
Lv 7
8 years ago

You can divide total drag of a well designed race car (similar to aircraft) in two types: dynamic drag and parasitic drag. In a race car, the designer tries to minimize parasitic drag, which is drag due to the frontal area of the car and attaching parts such as mirrors, wheels, and undercarriage. The whole body and undercarriage are designed to be as aerodynamic as possible, and the coefficient of parasitic drag of race cars is very small compared to typical production vehicles. The designer also minimizes the mass of car by using lightweight body and frame materials, and a lightweight, high performance engine. Decreasing mass allows the car to accelerate and decelerate quicker and consume less fuel. But in reducing mass to a minimum, the designer is also reducing traction which is the product of car weight (mass x gravity) and the dynamic coefficient of friction between tires and pavement.

The faster a car goes, the more traction it needs, so a race car designer adds a wing that acts opposite that of airplanes; it pushes the car downward with increasing force as the car travels faster, which in effect makes the car heavier without increasing the car's mass. The wing is a compromise because its dynamic drag increases total drag requiring additional power. Wings have to be very critically designed because they can make the car unstable in certain conditions.

An additional note: at 50 mph or so, you will create very little downward force with a wing of the scale of a small model car. For your design, the amount of traction you need depends on whether the car is traveling in a straight line or has to negotiate a curved track. Either way, you can increase traction by such means as providing wider wheels or using wheels with softer rubber.

• terri
Lv 4
4 years ago

Bike will win 99% of the time... To cgriffin1972 with the 2006 Suzuki GSX1300R - HOLY F*CKIN' SH1T DUDE - straping NOS to a bike that rattling fast is like attaching a bayonette to a crusemissile - it is overkill.