How does this F1 car have a 100% win rate?

In most cases you can argue that the success of a race car is down to one of two things:
1) Drivers skill

2) Engineering

Every so often, a car comes along with such unrivalled success that you cannot deny that its engineering gives it such a strong advantage. The Brabham BT46B is one such car. It exploits an aerodynamic principle that was accidentally discovered by, rival team, Lotus F1.

Discovering Ground Effect

Lotus F1 was doing a routine wind tunnel test on the Type 78 car when they stumbled upon an anomaly. During the testing, the increased temperature in the wind tunnel loosened the adhesive around the aerofoil side pods causing them to sink toward the ground. To prop the side pods up, the engineers used cards along the edge of the side pods touching the floor (side skirts) which lead to the downforce to dramatically increase. What the Lotus team had accidentally achieved was Ground Effect. This would subsequently spark the “The ground effect era” of F1.

What is Ground effect?

In short, as air passes through a constriction [RED] (the underneath of the aerofoil sidepods) it must speed up – creating a low-pressure area [GREEN] under the car that allows for greater downforce. The role of the side skirts [ORANGE] was to prevent the low-pressure air beneath the car from escaping out the side with the high-pressure airflow [BLUE]. This is based on Bernoulli’s principle and the Venturi effect.

Mario Andretti and the groundbreaking Lotus 78, 1977 Monaco Grand Prix

When using ground effect in racing, Lotus was outpacing the other cars by a substantial amount in straights and corners. The exceptional downforce gave the Type 78 car such grip that when cornering it was described to be “painted to the road”. This advantage wouldn’t go unnoticed by the Brabham team…

Enter the “Fan car”

Brabham found themselves in a tricky situation when they wanted to apply ground effect to their F1 car. They were limited by the Alfa Romeo wide flat twelve engine shape which, although provided for a low centre of gravity, meant that there was no space for the necessary aerofoil to produce the ground effect. Fortunately, designer Gordan Murray had a trick up his sleeve. His idea was to position a large fan to the back of the car that was powered by the engine. The fan would suck the air out from underneath the car to create the holy grail of low air pressure areas. So, Lotus and Brabham had their ground effect cars – should be evenly matched, right? Not quite. Lotus’ ground effect system only effective when the car was travelling high speeds. The Brabham BT46c, however, always had the advantage of useful ground effect.

You might be thinking: Aren’t movable aerodynamic devices banned? Well, Murray had designed the fan to draw air through the radiator and claimed that it was its main purpose. Since cooling the engine using a fan was perfectly legal – the FISA regulatory board allowed it. It was believable thanks to Alfa Romeo engines having a reputation for overheating.

Niki Lauda was at the wheel of the Brabham BT46c during testing and complained that the car was exhausting to drive as it required him to accelerate in the corners to maintain the fan speed. This would subject his body to unusually high lateral g-forces and would wear him out at the end of the race. Despite this, the team push forward with the car to race at the Swedish Grand Prix. Knowing the backlash the fan would receive from the other teams, Brabham covered it a cutting edge cloaking device: a dustbin lid.

This car would go on to win every single race that it entered in the 1978 championship and was allowed to continue racing even though the other teams were complaining that the fan was throwing debris at the cars behind. (This was untrue as the fan speeds were never fast enough to achieve this).

Bernie Ecclestone, the team boss, withdrew the car from the championship as it compromised his position as president of the Formula One Constructors Association – handing the win over to Lotus. But at least this car can boast that it was the only F1 car to have a 100% success rate.

By Jamil Jafri

Editor at The Mechanists