Back in the early days of racing it was all about power. No one cared that your car had the handling ability of a falling brick, as long as it was fast. This
way of thinking led to cars which just couldn't take the added weight and power of their massively overpowered engines and it didn't take long for teams to realize that
circuit racing wasn't all about straight lines. The importance of handling became known and today is one of the most developed areas of car tuning. There are four
aspects
of race car design which directly affect the handling of the vehicle.
- Balance - By achieving 50/50 (front/rear) weight distribution you ensure that neither end of the car carries more inertia than the other whilst cornering.
- Tyres - The more grip you have on the track surface, the faster you can take a corner without ending up in the sand.
- Suspension - There are many complex parts to a modern suspension system so I won't go into details, but keeping the tyres on the ground is a good idea.
- Aerodynamics - Less drag = more speed and less lift = more grip. Speed and grip are both desirable for obvious reasons.
I will be focusing here on the aerodynamic features of modern racing cars because of the above areas it is the most recent and has yielded some of the largest
improvements in performance over the last 30 years. Aerodynamic configuration can also be used to offset problems with the other three areas (to a degree). As far as open
wheeled aerodynamics go there are 3 main sections of the car which are under constant development - the Front wing, the Chassis and the Rear wing.
Wings:
The first aerodynamic devices began appearing on Formula 1 cars in 1968. These took the form of wings on the front and rear of the car. The wings
operate in exactly the same way as those found on an aircraft, except that they're turned upside down to provide downforce instead of lift. The inverted aerofoil shape
ensures that the air going under the wing travels faster than that travelling over it. In accordance with the Bernoulli Principle this creates higher pressure
above the wing than below, so the wing (which is rigidly attached to the chassis) gets 'pushed' into the ground. The harder it gets pushed, the more friction there is between
the tyres and the track and the force required to break traction increases, resulting in higher cornering speed.
The main factors affecting how
efficient a wing is are:
- The Aspect Ratio: This is the length to width ratio of the wing. The larger the Aspect ratio, the more efficient the wing. Most classes have maximum wing dimensions
as part of the formula to prevent extreme aspect ratios which may not be acceptable (eg 10m long and taking up the whole track).
- The Angle of attack (AOA): This is the angle at which the wing surface meets the incoming air. The greater the AOA the more downforce (and drag) will be
produced.
As the oncoming air travels towards the back of the car it becomes more turbulent, decreasing the effectiveness of the rear wing (which is at the extreme rear of the car).
Due to the decreased effectiveness of the wing due to this turbulence, rear wings are generally configured for higher downforce than their leading counterparts.
Many types of race cars make use of aerodynamic wings these days including most open wheel racing categories (F1, Champ car, F3000 etc) and almost all
production based classes (Touring cars, Stock cars). In the latter case, as only limited modification is generally permitted add on bodykits are used. These usually
include a front spoiler, Side skirts, rear diffuser and a wing.
The main problem with these extra appendages is that they sit out in the airflow (as they must to be effective) and therefore create extra drag. Of course, they aren't the
only parts of the car to do this - Wheels, suspension arms, driver's helmet - all these things affect the airflow over the car creating turbulence, which is undesirable. To get
around this many classes have small vertical winglets on the ends of the front wing. These are designed to shape the airflow around the car - usually to divert the air
around the front wheels and into the radiator ducts. This can reduce as much as 60% of the drag produced by the chassis and wheels/suspension while adding much needed cooling for the engine.
Ground effects:
With the restrictions placed on wing construction and size in classes such as IRL and Formula 1 designers have looked to other ways of creating downforce. The first
ground effects cars appeared in the late 70s (The very first was a Lotus F1 car in 1977). The cars had specially shaped underbody sections that incorporated a pair of
tunnels or grooves running the length of the car. These were shaped to produce lower pressure under the car than above it, once again holding the car to the track. This
allowed the cars to run 'less wing' - a lower AOA which in turn produced less drag. Current F1 regulations limit the cars to a flat underbody and Indy Racing
league cars are limited by the required shape of their underbody grooves. Other devices such as skirts are banned in most top classes as well, further reducing the
effectiveness of this technique. Despite the limitations this remains an important part of modern race car development.
Development:
Aerodynamic improvement is an ongoing cycle for many racing teams. At the top levels the aerodynamic package is constantly being revised and tailored to each specific
track. So important has this area become that a single Formula 1 team may spend 100 days a year wind tunnel testing with a team of experts in an attempt to gain a small advantage over their opposition. Current cars can create over 2 tons of downforce at 200mph with some GTP cars going much higher (required due to their added weight). Interestingly this means that they could concievably drive upside down (ie on the ceiling) if they already had the speed up. At least one example is known to produce over nine tons of negative lift! The spin off technology from these machines has spilled over into high end road cars such as the Porsche GT2 and Ferrari 360 Modena. It seems that aerodynamic development is in for the long haul, and what is currently possible may be just the tip of the proverbial iceberg.
Transitional Man says BTW, Wings and aero devices first appeared on Can Am cars in the US thanks to Jim Hall who inovated them and the low pressure downforce Chapparal 2J sucker car