Bumpy Interlagos tough on cars

Visitors to the city of Sao Paulo don't see knee pads being worn in public very often. But for Formula One drivers, knee protectors are as much a part of the Brazilian Grand Prix as the infamous heat, dust and fanatical spectators. Drivers need...

Visitors to the city of Sao Paulo don't see knee pads being worn in public very often. But for Formula One drivers, knee protectors are as much a part of the Brazilian Grand Prix as the infamous heat, dust and fanatical spectators. Drivers need the padding for the bumpy Interlagos circuit to prevent their knees from slamming against the walls of the cockpit. And Interlagos is tough on cars as well as drivers. F1 engineers face a difficult balancing act trying keep the cars from grounding on the tarmac at bumps and undulations on the track surface, while also keeping them as low as possible to the ground.

Track engineers work hard to provide an ideal racing surface -- ie a smooth surface with as much grip as possible. Nevertheless, racing cars at Interlagos come into contact with the asphalt several times, especially on the straights. To keep this problem to a minimum, the FIA ordered that the track be resurfaced last year and the work cost almost ten million Euros. But even circuit designers are powerless to dictate the weather, and the heat and rain of Brazil's tropical climate ensure that irregularities form again in the track surface.

The uneven surface makes braking into corners especially difficult, and in extreme cases, strong vibrations can cause damage to the cars. The exhaust pipe and the rear wing are especially at risk. Softer settings on the springs and dampers can compensate for this. Dampers on Formula One cars feature an essential combination of lightweight construction and high stability.

Tube frames and pistons are made of high-strength aluminum, the piston rods of steel, and the mounting parts of titanium. The four shock absorbers on a Formula One car weigh only one kilogram in total, but they do a superb job of stabilising the 600kg vehicle. Moreover, they partially absorb wheel and axle vibrations, and also ensure better grip and thus permit higher cornering speeds.

Tyres are every bit as important for the stability of the car. In addition to their traction function, they take on a fair portion of the damping duties for the suspension, which is kept extremely stiff to improve the car's driving dynamics and keep the distance between the track and the undercarriage as constant as possible.

Formula One cars have a large tyre diameter in relation to their modest 13-inch hubs, and this also helps transfer traction to the track surface. Finding an optimum relationship between tyre stiffness and suspension plays a decisive role on uneven track surfaces such as Interlagos.

Springless damping only works if tyres are extremely tough. When cars go over an uneven surface, the walls of the tyres are pressed together under several hundred kilos of weight. Tyre bodies cannot be too soft, or protrusions on track would impact against the hub.

This challenge for Formula One track engineers is also a problem for road traffic. Heat 'warping' and the weight of heavy trucks can also create bumps, whose presence is sometimes highlighted on road signs. Besides reducing your speed, keeping your vehicle in good condition is an important safety consideration when driving on uneven road surfaces.

In the words of Dr. Hartmuth Wolff, a safety expert at the Allianz Center for Technology (AZT): "Shock absorbers are especially important when road conditions are poor. They have to ensure that the wheels follow the uneven surface without losing contact with it. Inadequate dampers can cause the wheels to 'jump,' which interrupts the transfer of power to the road. If a steering correction is made at that precise moment, or if the car is going through a bend at the time, control over the vehicle can quickly be lost."

-allianz-

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Series Formula 1