SENSORS OVERLOAD
A lot of cars were fitted with sensors in free practice at the Brazilian Grand Prix, this in order to gather reliable and valuable data that will be used as reference points when teams carry out measurements on their 2017-spec machines during next year's pre-season testing in Barcelona.
The title-winning Mercedes W07 was equipped with aero rakes comprising some 50 probes to measure different pressures in the area located between the rear wheel and wing. A plastic tube connects each probe to the transducer, the profiled black box attached to the rear wing end-plate.
Williams, for its part, applied chequerboard stickers on some areas of the front wing and mounted a camera aimed at these parts in order to assess front wing deflection under the aerodynamic load. One could also spot an intriguing black sphere on the nose of the FW38 and Red Bull RB12. These are 360˚ cameras that are manufactured by 360fly and can shoot videos in 4K. FOM actually mandated the installation of these devices, which are not telemetry tools like thermal cameras are.
THE TRUSTED PITOT TUBE
Among the speed sensors that are regularly used on cars, the Pitot tube features at the front of the chassis. The under-the-skin picture above, which was snapped at the Brazilian Grand Prix, gives us some good insight on the installation.
The Pitot sensor involves Bernoulli’s principle whereby airflow velocity is determined by measuring pressures. It is made up of two tubes, one for the static pressure, the second one for the overall pressure, which increases with speed.
A pressure gauge measures the pressure differential between the two tubes (dynamic pressure), which is then used to determine airflow velocity around the sensor. With the car moving the air as it goes forward, the sensor is not as accurate as the sort of high-mounted devices often seen in winter testing. The pressures are then collected in a transducer via a series of thin and transparent plastic tubes.
Combined with other speed measuring devices (including one fitted on the wheels), the Pitot sensor indicates whether the car is experiencing headwind (the Pitot speed is then higher) or tailwind (the Pitot speed is lower).
In Brazil, Ferrari engineers installed a second Pitot sensor, inside the air intake, in order to calculate more precisely air speed in that particular area.
