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CSIR Wind Tunnel

Broadcast dates : 10th October  2004
14th October 2004

When a leading F1 race-car engineer was asked recently what the three most important areas of car performance were, he replied: "Aerodynamics, aerodynamics and aerodynamics."

Todayís top F1 race teams spend countless hours in wind tunnels refining the bodywork of their cars, before testing the results on the track.

Yet the aerodynamic revolution in motor racing is relatively new.

As recently as the 1950s top teams were only interested in making their cars as slippery as possible.

There was no thought given to what today is known as down-force, or the ability of aerodynamic shapes to push the car to the road.

The Le Mans winning Jaguars of the 1950s were capable of 260 km/h, and the only aero aid to stability was a tail fin.

More intensive wind tunnel testing the following decade exposed some major fallacies amongst sports cars.
For instance it was shown that the sleek E Type Jaguar had, in fact, more wind resistance than the boxy Alfa Romeo Giulietta.

Careful attention to detail saw this 1960s Alfa with a small four-cylinder engine able to run a very high top speed, thanks to what is known as a low drag co-efficient.

The CSIR Defence Aeronautics Programme in Pretoria has the only large-scale sub-sonic wind tunnel in South Africa.

Recently the up-and-coming Wesbank V8 racer Mackie Adlem conducted intensive wind tunnel tests on his Mustang, in the hope of shaving seconds off his lap times.

Adlem is one of many racing drivers that have used the facility in the past to gain a greater understanding of the aerodynamic variables on a racing machine.

Peter Skinner is manager of the sub-sonic wind tunnel at the CSIR Defence Aeronautics Programme.

One of the challenges with a racing car like the Mustang is to get sufficient air into the engine bay without creating lift.

Hence the large extraction ducts on the bonnet. But these cause their own aero problems, such as turbulence.

To achieve a visible flow pattern, a jet of linseed oil is directed over the surface of the car when the wind tunnel is being activated.

Although racing cars are designed for maximum efficiency, the presence of large wings such as those found on the Mustang create lots of drag, which slows them down on the straights.

The idea is to find the right balance of drag and downforce, and this is measured by placing the carís wheels on load-measuring platforms on the CSIR test rig.

A supercar such as the Lamborghini Murcielago is in fact much more aerodynamic than the racing Mustang.

It has a narrower frontal area and a smoother shape at the rear.

It achieves its top speed of over 300 km/h with 367 kiloWatts, whereas the 5,7 litre Ford V8 in Adlemís car has 425 kiloWatts to reach a similar top speed.

In fact when the Lamborghini is traveling at over 100 km/h, a wing is raised at the rear, but this was not possible to test during our visit to CSIR, as it would have required special rigging to raise the car up to simulate 100 km/h with the car in gear and the wheels revolving.

At his first outing with the new aero tweaks incorporated on the Sabat Mustang, Mackie Adlem could feel an immediate difference.

He reported a massive increase in front downforce on the car, thanks to some detail work on the wheel arches to clean up the air flow, and on the nose of the car.

The increased frontal downforce enabled Mackie to turn the Mustang in much more crisply, and he was able to run in the lead pack at Phakisa Raceway in Welkom.

The next step will be a new rear wing for the car, which is also the result of the CSIR wind tunnel tests, and Mackie hopes to have this ready in time for the next race meeting in East London this month.

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