Brabham BT46

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.[13] 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.[14]

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.[15] At Murray's instigation, Alfa went on to produce a V12 engine for the 1979 season.[16] 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 North 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.[14]

The contemporary Tyrrell 008 designed by Maurice Philippe had been built with a small fan fitted at the rear and driven from the engine's crankshaft. Ostensibly to act as an extractor fan for the radiators, which were mounted underneath the car, the fan had the side effect of its operation providing a modicum of downforce. However, in testing, the system was found to not be particularly effective. The car overheated, partly as a result of the size of the fan which was limited by the amount of space available. The fan concept was abandoned in favour of conventionally mounted radiators. [17] Nevertheless, Cox, who was present at the tests and saw potential in the idea if properly developed, informed Murray of what Tyrrell had attempted.[18]

Cox produced the overall layout for the car, utilising the cooling properties of the fan to be able to argue that this was its primary purpose, thus satisfying the regulations. Gordon 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, anticipating problems caused by the momentum of the fan during gear changes, although in practice these were not required. 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.[19] 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 BT45Cs 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 issues that had affected the original design at the start of the year.[20]

The cars were modified BT46s—chassis numbers BT46/4 and BT46/6.[21] 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.[20]

The two modified cars were prepared for the Swedish Grand Prix at Anderstorp on 17 June 1978, for Niki Lauda and John Watson. When not in use, the fan was covered by a dustbin lid, but it soon became clear what the modified Brabham was intended to achieve: when the drivers blipped the throttle, the car could be seen to squat down on its suspension as the downforce increased. Lotus driver Mario Andretti said "It is like a bloody great vacuum cleaner. It throws muck and rubbish at you at a hell of a rate".[22] Murray says that this was untrue: "The fan couldn't spit anything out the back because the fan efflux [exit speed] was only 55 mph. Besides the radial fan would have sent any stones flying sideways".[23] The legality of the cars was soon protested, but they were allowed to race. They qualified second and third behind championship leader Andretti. In the race, Watson spun off on the 19th lap. Once the slower Didier Pironi dropped oil onto the track and with both major front-runners out of the race, the remaining Brabham was in a class of its own, seemingly unaffected by the slippery surface. Lauda passed Andretti around the outside of one of the corners, who dropped out shortly afterwards due to a broken valve, and went on to win by over half a minute from Riccardo Patrese in an Arrows.[20]

There was uproar from rival teams, who saw the "fan car" as a threat to their competitiveness. Lotus immediately started design work on a fan version of the 79. Bernie Ecclestone, owner of the Brabham team, had also been secretary of the Formula One Constructors Association (FOCA) since 1972 and became its president during 1978. According to Ecclestone's biographer Terry Lovell, the heads of the other FOCA teams, led by Colin Chapman threatened to withdraw their support for Ecclestone unless he withdrew the BT46B. Ecclestone negotiated a deal within FOCA whereby the car would have continued for another three races before Brabham would voluntarily withdraw it.[23] However, the Commission Sportive Internationale intervened to declare that henceforth fan cars would not be allowed and the car never raced again in Formula One. The car was not considered to have been illegal when it raced however, so the Swedish Grand Prix win stood. The two converted chassis were returned to standard BT46 configuration for the next race.[24]

A BT46 competed in 'B' specification once again in 1979 in the Gunnar Nilsson Trophy race at Donington Park. This was an event held to raise funds for the Gunnar Nilsson Cancer Fund. Originally intended as a non-championship Formula One race, without FIA sanction it was instead run in a time trial format, with victory going to the fastest single lap recorded. As it was not an FIA event, the car's illegality was not a factor. Nelson Piquet drove, coming fourth of the five cars competing.[25]

Murray had designed a car for the 1979 season called the BT47 that had a Chaparral 2J-type box rear end with twin variable geometry fans on the rear to maximize ground effect. The car was never built due to the FIA closing the loophole in the regulations for the 1979 season.[26]

Another variation on the theme was produced later in the season. Like the BT46B, the BT46C removed the radiators from the front wing assembly leaving a clean aerodynamic wing and moving the centre of gravity further back again. The standard radiators were replaced by units from a Volkswagen Golf[27] mounted behind the front wheels out of the airstream in a region of positive pressure.[28]

The BT46C only ran in practice for the 1978 Austrian Grand Prix. The drivers complained of reduced revs and straight-line speed. It was not used in the race and did not appear again.[28]