Brabham BT46

The BT46's predecessor, the Brabham BT45, was overweight and bulky, initially weighing 625 kg and as wide as the regulations permitted, due to the difficulties of packaging the large Alfa Romeo flat-12 engine and its fuel load. Murray began design work on the BT46 in mid-1977. The Alfa Romeo 2995 cc flat-12 produced approximately 520 bhp at 12,000 rpm and 324 lb-ft (439 N·m) of torque — around 50 bhp more than the Cosworth DFV used by most rivals — but at the cost of greater size, higher fuel and oil consumption, and approximately 40 kg of additional weight. The BT46 used a 6-speed gearbox with a Brabham-designed casing cast by Alfa Romeo and fitted with Hewland gears.

The BT46 chassis was an aluminium alloy monocoque. It featured inbuilt pneumatic jacks fed from an external compressed-air supply for tyre changes during practice, and an early form of carbon composite brakes that Brabham had been developing since 1976, combining carbon composite pads with a steel disc faced with carbon composite pucks. The most radical feature of the original car was flat plate heat exchangers mounted flush to the bodywork surface in place of conventional radiators. Consultant engineer David Cox calculated that this gave only around 30% of the required cooling surface area. He contacted Brabham and, after examination, concluded the concept could not work. The heat exchangers were replaced by nose-mounted radiators before the car's race debut at the South African Grand Prix on 4 March 1978.

In 1977, Lotus had introduced ground effect to Formula One with the Type 78, using shaped underbody sidepods to accelerate airflow beneath the car, reducing underbody pressure and generating downforce without the drag penalty of conventional wings. By 1978, Lotus had developed this into full venturi tunnels on the Type 79, driven by Mario Andretti and Ronnie Peterson, which outpaced the competition immediately at Zolder. Murray understood by early 1978 how the Lotus design achieved its grip levels but recognised that the wide Alfa Romeo flat-12 blocked the Venturi tunnels needed for effective ground effect. At Murray's instigation, Alfa Romeo subsequently developed a V12 for the 1979 season. In the meantime, Murray turned to an alternative approach.

The Chaparral 2J, raced in the North American Can-Am series in 1970, had used two fans driven by a dedicated two-stroke engine to draw air from under the chassis and create downforce. Although significantly faster than its rivals, it suffered reliability issues and was eventually banned. Murray was also informed by consultant David Cox that Tyrrell had experimented with a fan on the Tyrrell 008, designed by Maurice Philippe, to extract air from underneath-mounted radiators. In testing it proved insufficiently effective and overheated; the concept was abandoned. Cox saw potential in a properly developed version and told Murray.

Cox produced the overall layout for the BT46B. The fan's claimed primary purpose was cooling — Brabham had previously used a small electric fan for cooling on the BT45Cs at South American races — which was intended to satisfy the regulations. Murray designed the fan drive through a complex series of clutches running from the engine; the faster the engine ran, the stronger the suction effect. A horizontally mounted radiator over the engine was placed in the fan's airflow. Like the Lotus ground effect cars, the BT46B used sliding skirts to seal the gap between the car's sides and the ground, preventing outside air from entering the low-pressure area underneath and dissipating the effect. The two prepared cars used existing BT46 chassis — numbers BT46/4 and BT46/6 — and were modified and tested in secrecy.

Niki Lauda found he had to adjust his driving style for the BT46B. Accelerating in corners caused the car to grip the road as if on rails, but exposed the driver to very high lateral acceleration. In his autobiography, Lauda described the car as unpleasant to drive due to the lateral loads and its reliance on aerodynamics over driver skill. He recognised early that as ground effect developed, all drivers would face such g-loading and the physical demands would be exhausting.

The two BT46B cars were prepared for the Swedish Grand Prix at Anderstorp on 17 June 1978, for Lauda and John Watson. The fan's effect was visible when drivers blipped the throttle — the car could be seen to squat down on its suspension. Mario Andretti of Lotus described it as "like a bloody great vacuum cleaner" that threw muck and rubbish. Murray disputed this, arguing the fan's exit speed of only 55 mph meant it could not spit debris backwards. The car's legality was protested but the cars were allowed to race. They qualified second and third behind championship leader Andretti.

In the race, Watson spun off on lap 19. Didier Pironi dropped oil onto the track and the other front-runners retired, leaving Lauda in a class of his own on the slippery surface. Lauda passed Andretti around the outside of a corner; Andretti dropped out shortly afterwards with a broken valve. Lauda won by over half a minute from Riccardo Patrese in an Arrows.

The result provoked uproar from rival teams. Lotus immediately began design work on a fan version of the Type 79. Ecclestone, who had been secretary of the Formula One Constructors Association (FOCA) since 1972 and became its president during 1978, was concerned that the controversy could collapse FOCA, which he was working to consolidate. According to Ecclestone's biographer Terry Lovell, FOCA team heads led by Colin Chapman threatened to withdraw their support for Ecclestone unless he withdrew the BT46B. Murray said in 2008 that Ecclestone was "working on getting his foothold in the Formula One Constructors' Association and launching himself towards what he's doing now" — referring to Ecclestone's position as chief executive of the Formula One Group, which he held from 1987 until 2017. Ecclestone negotiated a deal within FOCA for the car to continue for another three races before voluntary withdrawal, but the Commission Sportive Internationale intervened and ruled fan cars would not be permitted going forward. The two converted chassis were returned to standard BT46 configuration. The Swedish Grand Prix result was not overturned.

The Brabham team completed the 1978 season with standard BT46s. Lauda won the Italian Grand Prix in the standard car, though only after Mario Andretti and Gilles Villeneuve were penalised a minute for jumping the second race start — the first start had been halted following Ronnie Peterson's fatal accident. A BT46C variant, replacing front radiators with Volkswagen Golf units mounted behind the front wheels, ran only in practice for the 1978 Austrian Grand Prix before being abandoned due to reduced revs and straight-line speed. The BT46 made its final World Championship appearance at the first round of the 1979 season, driven by Nelson Piquet, who retired on the first lap after a multi-car collision.

A BT46B appeared once more in 1979 at the Gunnar Nilsson Trophy race at Donington Park, run as a time trial to raise funds for the Gunnar Nilsson Cancer Fund. Without FIA sanction, the car's legality was not a factor. Piquet drove, finishing fourth of five competitors. Murray subsequently designed the BT47, incorporating Chaparral 2J-type twin variable geometry fans, but it was never built as the FIA closed the regulatory loophole for 1979.

This article is based solely on the supplied corpus. No external sources were consulted; claims that could not be substantiated against the corpus were omitted under the drop-the-claim rule.