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| CSIR
Wind Tunnel |
Broadcast
dates : 10th October 2004
14th October 2004 |
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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."
Today’s 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.
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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 car’s 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 Adlem’s 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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