|FORMULA ONE RACING|
Braking is one of the biggest strengths of a Formula One car. The
brake disks of Formula 1 cars are made of a composite material
reinforced with carbon fibre. The coefficient of friction between the
pads and the discs can be as much as 0.6 when the brakes are up to
temperature. Steel brake disks would exhibit a higher wear rate at
these high temperatures. Furthermore they are heavier.
The temperature of an F1-brake disk varies between 400 and 1000 degrees Celsius. You can often see the brake discs glowing during a race. If the racing driver hits the brakes full on before the brake disks have reached a temperature of approximately 400 degrees, the disks could explode under the thermal stresses created. These stresses are the result of large temperature gradients leading to expansion which causes large stress gradients.
As the heat created in the modern Formula One brake disk is so high, there is a constant demand to find more and more cooling. In 2001, Ferrari conceived an original way of dealing with the heat problem in brakes. The brake-duct, conducting the slipstream wind along the brake disks, is equipped with a kind of turbo. This is a rotor mounted on the wheel shaft, providing additional suction to get even more air into the brake-duct. Thanks to the rotor, the brake-duct can be made smaller, benefiting the aerodynamics. The other F1 teams have now copied the idea.
In F1 the maximum dimensions of the brake disks are laid down in regulations. They must not be more than 28 mm thick, and the diameter cannot be larger than 278 mm. For fast circuits, the 28 mm thickness is insufficient. During qualification, relatively thin and hence light brake disks are used because the cars only need to complete 12 laps. For the race itself the cars are fitted with the thickest possible discs. It means the incurred heat can be better distributed over the brake disk material. During the race a sensor continuously measures the thickness of the brake disks. The measurements will help the driver to know when he has to go easy on the brakes to make it across the finishing line, or whether the disks need to be replaced in a pit stop. A set of disks and pads costs as much as a compact car. For every Grand Prix race each team reckons on using twenty sets of brake disks and pads per car.