L&T Motorsport

Legendary F1 Cars – Brabham BT46B Fan Car

In a world where stats are easily accessible one F1 stat that is sometimes forgotten about is car win ratio. And there is one car that has the best of the lot, 100%. That car is the infamous Brabham BT46B – the fan car.

The origins of the fan car lie in the previous seasons BT45. The first Alfa V12 powered Brabham in 1977 was a wide as it was bulky due to the dimensions required to fit the flat 12 engine and the fuel needed to last a race distance. It didn’t matter how much power the engine put out the design used to incorporate it didn’t work. The design team, led by Gordon Murray, were able to make it competitive but without race wins. Mid season Murray made the choice to start designing next seasons car to allow them time to incorporate changes to improve performance with the Alfa engine.

Early development of the BT46 seen a number of Murray design signatures from an aluminium alloy monocoque to some more advanced features like early carbon brakes, something that the team had been developing for two seasons and would become the norm in years to come. The biggest change was the removal of the conventonal radiators in place of flat plate heat exchangers. The idea here was to reduce weight of the car that would bring the car in line with the field, the BT45 was around 40kg heavier compared to the others in the field due to the Alfa engine. The idea however would prove to be one of Murray’s failed designs, a rare thing for the South African, a conventional radiators were soon added again.

The car was to prove competitive on its debut in South Africa but reliability was suspect with multiple DNF’s recorded. And then the teams arrived in Anderstorp, Sweden with what looked like a dustbin lid on the rear of the car. The hidden secret was a game changer.

Over the last year Lotus had developed the 78 and then the 79,now one of the most successful cars in F1 history. What Colin Chapman and Peter Wright had discovered was ‘ground effect’, the shaping of the underside of the car to accelerate the airflow under the car with minimal effect on drag, thus pushing the car down more to the ground and giving faster corner speeds without the effect of reduced straight line speed that conventional wings caused. Lotus then changed the design of the sidepods to include venturi tunnels to further improve the effect and, with improved reliability, the 79 was the class of the field and would take Mario Andertti to the title in 1978.

Many in the paddock where unable to grasp what Lotus had done to gain such an advantage and Chapman and his team were experts and throwing curve balls to put others off the scent and were known for hiding parts like driveshafts under blankets to deceive the opposition and keep them guessing on the secret. By early 1978 however Murray had figured out what Lotus was doing. However he had a problem to gain full ground effect, the Alfa engine.

The V12 meant that with the wider car the venturi tunnels for sidepods was not possible to obtain real ground effect. Murray had therefore decided to look at other options to obtain similar levels of grip. At the beginning of the decade in 1970 a car in Can-Am in North America, while suffering reliability issues, was casing a stir. The ‘sucker car’ had two rear mounted fans that sucked the car to the ground giving more grip. It could have dominated the field if it was reliable and then the authorities banned its use. Murray started to work on a concept around this.

He started with a number of clutches that ran a large single fan at the back of the car from the engine, the faster the car went the faster the fan spun and thus sucked the car more to the ground. Murray claimed that the reason for the fan was cooling to get around the moveable aerodynamic devices rule and there was legitimacy in this with Brabham running a small cooling fan at the hot South American races early in the year. The chassis were modified BT46s with major alterations required to incorporate the fan design and the clutches to run it.

Niki Lauda was the lead driver at Brabham at the time alongside John Watson and a young Nelson Piquet as test driver. It was Lauda himself that tested the fan car in secret and found that the best benefit came from adjusting the driving style by accelerating through corners instead so it ran on rails. The downside for the driver was the massive increase in lateral g-force and, for Lauda, the over emphasis on aero over driver input, something that still rears it ugly head today.

And so back to Sweden where the two BT46B’s were rolled out. When not in use a dustbin lid was used to cover the fan but once on track it was clear what the real purpose was for. As soon as the driver hit the throttle the car squatted down on the suspension with Andretti claiming it was ‘like a great big hoover, throwing muck and stones everywhere’. Murray dismissed this claim stating that the exit speed of the fan was too low for this to happen and that if there was any stones they would exit sideways but the teams were already protesting the design.

The cars were cleared to race and qualified second and third behind Andretti. Watson would retire early doors while Lauda passed Andertti around the outside with relative ease and went on to win by over half a minute from Riccardo Patrese’s Arrows after Andretti dropped out with value issues. With the teams in uproar and Lotus already working on their own version there was a political minefield to go through. This was not just because of the cars ‘legitimacy’ but also due to the fact that Brabham’s owner at the time was one Bernie Ecclestone. Ecclestone was head of FOCA, the Constructor’s Association and with him also planning for what would be a power play at the commerical rights the possiblity of losing favour with the teams was high on his mind.

The FOCA team’s threatened to withdraw their support for Ecclestone unless the car was withdrawn and a deal was agreed to allow the car to run for three more races before it was voluntarily withdrawn. However the commission Sportive Internationale intervened and the car was banned moving forward. The win in Sweden was to the first, and last race and win for the car.

Murray had already started work for next season that was to incorporate two smaller fans, similar to the fan car from Can-Am that inspired the idea, but the closing of the loophole meant it never made design or development.

The team reverted back to the original BT46 for the rest of the season with one more win at the infamous Italian GP that saw a crash at the first start that led to the death of Lotus driver Ronnie Peterson. Murray would continue to look for the ‘unfair advantage’ in the rule book including championship winning cars BT49 and BT52 before moving to McLaren and a time that produced the most dominant car in F1 history, the Mp4/4.

The fan car was a great example of brains being used to find an advantage. Although theses days advantages are harder to come by the general concept is still there with engineers and designers alike. The Fan car still sees the occasional running as a demo car at the likes of Goodwood and other festivals but never raced in anger again. It makes you wonder where we would be if F1 was an arms race free for all, especially in the late 70s and 80s. The fan car will always be remembered as the ‘one and done’ car of F1.

Andrew Campbell
Andy81287
Photo Credit: wtf1

Andrew Campbell

F1 and motorsport fan in general, been watching for over 25 years with much knowledge across different catogaries. Also part time youtuber when time allows and father which is full time.

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