Brabham BT46


The Brabham BT46 was designed for the 1978 Formula One season by Gordon Murray. Born to Scottish immigrant parents, Murray was born and grew up in Durban, South Africa. Murray studied mechanical engineering at Natal Technical College. Murray moved to England in 1969, hoping to find a job at Lotus but a meeting with then Brabham designer Ron Tauranac saw him join the Australian firm. When Bernie Ecclestone took over the Brabham team, he appointed Murray Chief Designer.

It was powered by Alfa-Romeo’s sportscar-derived flat-12 engine had a capacity of 2995 cc and employed fuel injection and electronic ignition. The engine featured a cast magnesium alloy engine block with aluminum alloy crankcase and magnesium cylinder heads. There were four gear driven valves per cylinder. Initially it delivered about 520 bhp at 11,500 rpm, about 50 bhp more than the Cosworth DFV engines used by most teams, however the power came at the expense increased fuel and oil consumption and about 40 kg more weight. Brabham designed the gearbox casing, which was cast by Alfa Romeo and used Hewland gears.


The BT46 was an aluminum alloy monocoque featuring the trapezoidal cross section. The most radical feature of the car was its use of flat plate heat exchangers mounted flush to the surface of the bodywork in place of conventional water radiators. The absence of standard radiators allowed Murray to compensate somewhat for the large engine and fuel tanks. Unfortunately the heat exchangers did not provide enough cooling capacity, and had to be replaced with standard radiators in the nose of the car compromising its aerodynamic efficiency. The car also employed a very early version of the carbon brakes that would become universal in the next decade.

The BT46 debuted at the third race of the 1978 season, the South African Grand Prix on 4 March 1978, with the revised nose mounted radiators. The cars, driven by Niki Lauda and John Watson were immediately competitive, although reliability was suspect. Defending World Champion, Lauda took his first pole for Brabham but was out before midway with an engine failure. Watson was able to secure third place on the cars debut. At the Swedish Grand Prix the team introduced the famous “fan car”, the BT46B.


Having seen the Chaparral 2J “sucker car”, 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. This resulted in the faster the engine ran, the stronger the suction effect. Much to the indignation of the other teams, Niki Lauda won the first and last race for the radical car. Brabham’s lead driver, Niki Lauda, realized he had to alter his driving style primarily while cornering. He found that if he accelerated around corners, the car would “stick” to the road as if it were on rails.

Concept
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 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.

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 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 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.

Racing history and aftermath
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”. Murray says that this was untrue: “The fan couldn’t spit anything out the back because the fan e-flux [exit speed] was only 55 mph. Besides the radial fan would have sent any stones flying sideways”. 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 a back-marker dropped oil onto the track and with both major front-runners out 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.


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. 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.

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.

High Level Technical Background
The 1978 Swedish GP will remembered for just one thing. The race itself being rather uneventful, it was the winning car that created its own footnote in history by dominating the meeting, thus to great lengths contributing to its uneventfulness in the first place. Responsible for this overwhelming coup was some clever thinking by Brabham’s Gordon Murray, who was trying to eclipse Colin Chapman’s ground effect invention on the Lotus 79, the skirted car that had swept the front row since its debut at Zolder. Center of the BT46B concept was a huge fan taking ground effect to a higher level (at least engineering-wise) by pulling a vacuum from under the bottom of the car, thereby creating an enormous amount of downforce. From its skirts up the car stuck on the track like glue, allowing the reigning champion to win conclusively. Immediately after, the fan was deemed illegal, contravening the rules on moving aerodynamical devices, although the Brabham team claimed its use was primarily for cooling – which wasn’t far from the truth, actually. In typical FIA style the win was allowed to stand, however, which cost Arrows their chance of victory in its debut season.

There’s no doubt you can’t explain the Brabham fan car without explaining the reasons for it. The reasons for it were caused by Ground Effect and Team Lotus, and you can’t really explain the importance of Ground Effect without going over its history…

Putting it simply as possible, Ground Effect is the art of creating a low pressure area underneath the car so that the atmospheric pressure pushes the car to the ground, which is the reverse of what happens with an aircraft wing. The way this is achieved is by utilising the Bernoulli Effect – if a moving fluid or gas is accelerated, its pressure falls correspondingly. This was achieved by creating a upside-down wing profile underneath the side panniers of the racing car. A fixed amount of air flows into the front of the side-pods of each car, where the side-pods are closest to the ground. As you go further back beneath the side-pods, the underside of them rises. The air entering the side-pod accelerates to fill this increased area, generating a lower pressure. The outside air then pushes the car towards the ground.

The origins of Ground Effect in racing go back to 1961, when Jim Hall was experimenting with a front-engined Chapparal-Chevrolet V8 sportscar. Jim Hall, in conjunction with the aerodynamicists of Chevrolet, built a car whose entire body shape was that of an inverted aerofoil, with both the nose and the tail upswept to form half-venturi tunnels at either end of the car, the idea being to speed up the airflow beneath the car. The problem was that the front venturi caused the car to lift, the weight of the engine being the only thing stopping the car from flipping. A massive air-dam was then fitted to counteract this, but it generated so much downforce that the wheels started to grind their way through the top of the bodywork. The concept was not fully understood, and the idea was left to languish.

However, in the 1968-’69 off-season, an anonymous fan sent Jim Hall a sketch of a car with a fan on the back of it, the fan being used to extract the air from underneath the car. Hall again worked in conjunction with Chevrolet and its parent company General Motors, who developed the idea of having a skirt around the side of the car to stop the outside air rushing in from the side of the car to break the low pressure created by the fan. The result was the Chapparal 2J sucker-car which was raced in the 1970 Can-Am series. The car worked so well that it was promptly banned – an omen of what was to come.

The concept bubbled under the surface for a number of years, Robin Herd designing wings into the side-pods of the March 701, and Gordon Murray playing with airdams and splitters with the Brabham BT44. The concept finally saw its re-emergence with Peter Wright’s brilliant Lotus 78 and Lotus 79.

The evolution of Ground Effect on the Lotus 78 came about by accident. Peter Wright was at Imperial College, London, testing out the idea of putting water radiators in the leading edge of the side-pods. In a bid to try and improve on the unsuccessful Lotus 77, Wright was using a wind tunnel with a rolling road, a novelty at the time. However, the instrumentation began to show some unrepeatable results. Closer examination showed that the side-pods on the model were sagging, and as they got closer to the floor of the wind tunnel, the downforce increased.

Wright then proceeded to cut up bits of cardboard, extending the side-pods right down to the ground – the downforce level doubled. This accidental discovery showed the importance of maintaining an air-tight seal along the bottom of a car with profiled side-pods, and resulted in the successful Lotus 78 of 1977. The prototype, known as JPS/15 or 78/1, was first driven by Eddie Dennis, the shop foreman, at Hethel, but subsequent development work was done by Gunnar Nilsson. This car was later sold to Hector Rebaque, while Team Lotus raced JPS/16 and JPS/17 (78/2 and 78/3). Andretti, in 78/3 (here in the car’s debut race in Argentina), won four races for Lotus, but had many reliability problems through the year. As the advantage of the car wasn’t clear cut, most of the other teams hadn’t cottoned on to the technical advantage. Colin Chapman himself publicly attributed his team’s success to the special differential and its preferential tank-draining system – anything in fact but Ground Effect, in order to hide the discovery.

The “problem” with the Lotus 78 was that the centre of pressure was too far forward in the car, which resulted in the drivers having to run with lots of rear wing in order to prevent too much oversteer, with a corresponding lack in straight-line speed. This was rectified in the Lotus 79.

Apart from construction differences (sheet aluminium being used rather than aluminium honeycomb, as Ralph Bellamy, the main advocate of the material, had left for Copersucar), the major difference was in the treatment of the rear suspension, everything being moved in order to reduce the amount of drag in the air exiting the side-pod. This resulted in the aerodynamic load being generated over the whole car length, rather than mostly at the front, and gained the Lotus 79 25% more downforce than the Lotus 78. The prototype, JPS/19 (or 79/1), was rolled out at Paul Ricard in December 1977.

The effect of the huge increase in downforce had not been anticipated, and the car fatigued extremely quickly. A second version, much strengthened (JPS/20, or 79/2), was entered in the BRDC International Trophy at Silverstone on 19 March, the first three Grand Prix having been entered with Lotus 78s. The race was flooded out, but Andretti soon took his car into the lead before aquaplaning off at Abbey, damaging the car extensively. It may have been an inauspicious start, but the concept had been proved, and once the Getrag gearbox was swapped for a Hewland, there was no stopping it. Once Peterson had set stunning times practising at Anderstorp, the car was taken to Zolder for the Belgian GP, its first World Championship race. It (JPS/20) was originally meant to be Andretti’s spare car, but the team engineer Nigel Bennett reckoned it could be made into a race car. Andretti talked to Chapman, and both put $500 into a kitty to be split between the mechanics if the 79 survived the race distance without a failure. Andretti qualified on pole by over a second, and led from start to finish… At the next Grand Prix in Jarama, Andretti and Peterson qualified 1st and 2nd, and finished 1st and 2nd, taking fastest lap along the way. The rest of the field was left standing. However, Brabham designer Gordon Murray had an idea.

At the beginning of the season, the interim BT45C, with a full-width nose section, according to Niki Lauda was suffering from acute oversteer. For years Murray had been experimenting with skirts on the underside of the BT44, but he hadn’t realised that the full-width nose was creating a ground-effect downforce at the front of the car. Then he saw the Lotus 79 at Monaco (it was taken as a spare car, but not raced), and it clicked into place. He then knew how Colin Chapman achieved his speed.

The problem for him was that the Brabham used a flat-12 Alfa Romeo engine, and the heads of the engine projected into the area where the venturi tunnels would ideally be located. However, he spotted a loophole in the regulations – an extractor fan, as used on the Chapparal 2J, could be used to reduce air pressure as long as its primary function was not aerodynamic as defined in the rules. He was going to claim that the primary function of the fan was to draw air through the car to cool the engine, rather than accelerating the air to gain downforce. The fact that this beneficial effect occurred was purely coincidental… This approach was declared legal by the racing authorities.

The technical problems involved were quite huge. The whole engine bay was sealed, so that air couldn’t be drawn through the engine and break the low pressure area beneath the car. Flexible skirts were developed which extended to the road surface, as well as extending back and around the suspension arms. A thermodynamics expert, David Cox, was even employed to work out the number of fan blades, pitch and optimum rotation speed.

The fan was driven from the gearbox via a series of shafts and clutches, the clutches being used to prevent the fan from over-driving the gearbox on gear changes. The material the fans were made from proved to be problematic. While testing at Brands Hatch, the original plastic blades disintegrated, followed quickly by glass-fibre versions. Magnesium versions were then cast, but these were only available in the week preceding the Swedish GP at Anderstorp.

The system worked brilliantly. During first practice the front skirt started to wear away, but once a skid was placed on the bottom of the skirt, no further problems were encountered. The fan was so effective, that the car could be seen to suddenly squat downwards when the throttle was blipped in the pits. Its illegality was soon protested, but it was allowed to race, Lauda and Watson (here seen with Gordon Murray) qualifying 2nd and 3rd behind the Lotus 79 of Andretti. Andretti eventually dropped out due to valve spring caps breaking under load, causing a valve to break, allowing Lauda into the lead. Once a back-marker dropped oil onto the track, the Brabham was in a race of its own, seemingly unaffected by the slippery surface. Lauda went on to win by 34.6 seconds.

Rumour had it that Colin Chapman had sketched desigs for a twin-fan Lotus 79 on his flight back home, but although the Brabham car was declared legal, Bernie Ecclestone (team manager/owner of Brabham) decided that it was better to sacrifice the short term advantage of the fan car than to compromise the Formula One Constructors Association (FOCA), of which he was president. This proved to be a wise move in the event of the FOCA/FISA wars of 1980 and ’81.