Brabham BT46B
Lotus had introduced the concept of ground effect to the Formula One world championship in 1977 with their fast, but not always reliable, Type 78. Peter Wright and Colin Chapman had discovered that by carefully shaping the underside of the car, they could accelerate the air passing under the car, thereby reducing the air pressure under the car relative to that over it and pushing the tyres down harder onto the track. The increased downforce gave more grip and thus higher cornering speeds. Ground effect had the great advantage of being a low drag solution, unlike conventional wings, meaning that the increased cornering ability was not compromised by a decrease in straight line speed. In 1978 Lotus ironed out the reliability problems and further developed the concept from relatively simple sidepods with a wing profile into full venturi tunnels under the car. As soon as they appeared at Zolder, the black and gold Type 79s of Mario Andretti and Ronnie Peterson outpaced the opposition by a comfortable margin.
It had not been clear to other designers just what Wright and Chapman had done with the Type 78, but by early 1978, Gordon Murray had grasped how the Lotus design was achieving its remarkable levels of grip. He also realised that the Alfa Romeo flat-12 engine used by Brabham that season was too wide to permit the venturi tunnels needed for really significant ground effect. At Murray's instigation, Alfa went on to produce a V12 engine for the 1979 season. Ferrari, however, persisted with the flat-12 design and therefore lacked full ground effect until their disastrous 1980 season. In the meantime, Murray's idea was to use another way of reducing the pressure underneath the car. In 1970 the Chaparral 2J "sucker car" had proved significantly faster than its opposition in the American Can-Am sportscar series. The 2J had two fans at the rear of the car driven by a dedicated two-stroke engine to draw large amounts of air from under the chassis, reducing pressure and creating downforce. It had suffered from reliability problems with the second engine before being banned by the sporting authorities.
Murray designed a version driven by a complex series of clutches running from the engine to a large single fan at the back of the car. Therefore the faster the engine ran, the stronger the suction effect. Like the Lotus, it had sliding "skirts" that sealed the gap between the sides of the cars and the ground. These prevented excessive air from being sucked into the low pressure area under the car and dissipating the ground effect. There was a rule banning "moveable aerodynamic devices", but the fan also drew air through a horizontally mounted radiator over the engine. Using a fan to assist cooling was legal—Brabham had used a small electric fan to this effect on the BT45Bs at the South American races at the start of the year—and Brabham claimed that this was the primary effect of the new device. These claims were lent some legitimacy by the cooling system design issues that had affected the original design at the start of the year.
The cars were modified BT46s—chassis numbers BT46/4 and BT46/6. Modifications to implement the fan concept were quite extensive—involving sealing the engine bay as well as adding the clutch system and the fan. They were designed and tested in some secrecy. Brabham's lead driver, Niki Lauda, realised he had to adjust his driving style, mostly for cornering. He found that if he accelerated around corners, the car would "stick" to the road as if it were on rails. This had the side effect of exposing the driver to very high lateral acceleration, which would become a major problem in the ground effect era. In his autobiography, Lauda described the car as being unpleasant to drive due to the lateral loads and reliance on aerodynamics over driver skill. He realised early on that the rate of ground effect development meant that in the future, every driver would be exposed to such G-loading while behind the wheel of such a car, and the physical effort needed to drive the cars would leave the drivers exhausted by the end of the races.
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