When Gordon Murray Automotive unveiled its gobsmacking GMA T.50 overnight, featuring an innovative aero device, also known as a fan, sticking out the back of the otherwise reasonably conventional looking supercar, it wasn’t the first car to come from the pen of the legendary Gordon Murray to feature the innovation. It wasn’t even the first car to feature an aero fan.
To trace the – short – history of the ‘fan car, we have to go back to 1970, and American racer/engineer Jim Hall.
Hall was an innovator and revolutionary in race car design. Back in 1966, it was Hall who conceived of attaching wings to his car to improve downforce. The Chaparral 2E is the grand-daddy of aero, its huge, high wing adding downforce where there had previously been none, or very little.
When Formula 1 followed suit in 1968 and starting attaching wings to F1 cars, Lotus founder Colin Chapman was credited with starting the aero revolution. In a 2017 interview with Road & Track, Hall recalled his reaction to being told that Chapman was credited with conceiving wings on race cars.
“I saw it written somewhere, “Isn’t it wonderful what Colin Chapman invented, that wing he put on the car in 1968?’ I said, ‘It took them until 1968?’”
But if Hall’s legacy is as the grandfather of automotive aerodynamics, it's perhaps the Texan’s Chaparral 2J, the first fan car, affectionately known as the ‘sucker car’ that remains the most radical example of his 'outside-the-box' thinking.
It looked unlike anything seen before, a slab-sided, straight-edged behemoth with enclosed rear wheels and not a wing or air duct in sight. Instead, its party trick lay out the back where two fans extruded from the rear of the car. It looked less like a race car, more like some sort of sci-fi creation.
Powering the Chaparral 2J was a conventional big block Chevy motor, ZL1 for those who like to know such things, 427ci (7.0-litre) with 484kW at 7000rpm. That provided the conventional motivation for the Can-Am racer that weighed a smidge over 800kg thanks to its fibreglass body.
To help keep the 2J stuck to the road, however, was an auxiliary engine mounted behind the rear wheels. Normally found in snowmobiles, the Rockwell JLO 247cc two-stroke, two-cylinder motor pumped out a meagre 33kW that powered the twin fans out back. Those fans came straight out of a military tank, an M109 Howitzer specifically, and, when spinning at 6000rpm, could expel more than 27,000 litres of air per minute.
That air was drawn from underneath the car and exhausted out through the fans – along with, it was said, the usual dust and debris found on a race track. The drivers who found themselves behind the Chaparral 2J often complained about getting sprayed by the detritus. Hall, in his trademark laconic Texan humour, would respond, “Well, why don’t you pass me then?”
Of course, all that sucked-up and expelled air wasn’t enough on its own to create significant downforce improvements. To do that, Hall needed to create a vacuum under the car. He achieved this by inventing skirts that were fitted around the base of the car. The skirts, manufactured out of the then new polycarbonate plastic, moved up and down with suspension travel to ensure near-perfect alignment with the road surface and thus creating a sealed vacuum chamber, literally sucking the car to the ground.
The result was a car that could corner faster and harder than ever before, thanks to the 1000kg of downforce the 2J generated.
But was it any good? Well, it was certainly quick, (Vic Elford qualified the car at Laguna Seca, posting a sub-one-minute lap, remarkable even now) although the technology proved unreliable over the course of the only season it was deemed legal, 1970, with auxiliary engine failures and complications from all the dust and debris sucked up by those imposing fans.
By the end of the year, the Sports Car Club of America had banned the Chaparral 2J, although its legacy lasted well into the 1980s, with Formula 1 adopting movable skirts in 1977 (again, years after Hall had pioneered the concept) to create the ground effects era.
It was in this era that Gordon Murray, then chief designer at the Brabham F1 team, came up with a workaround solution to creating a ground effects car.
When Lotus and Colin Chapman introduced ground effects to Formula 1 in 1977, the rest of the grid was left slightly bemused and then scrambling when the black-and-gold Lotuses of Mario Andretti and Ronnie Peterson began to crush the opposition in 1978, with unthinkable cornering speeds.
In simple terms, Chapman and Lotus designer Peter Wright attached sliding skirts to the body of the Lotus that, along with a specifically shaped undertray of the car, created a Venturi effect, essentially sucking the car to the ground.
Murray watched what Lotus was doing with great interest, and by 1978 had worked out how the British team was creating its ground effects. However, the flat-12 Alfa Romeo engine bolted into the back of the Brabham BT46 was too bulky to allow for significant Venturi effect, its dimensions blocking the efficient flow of air needed under the car.
Murray came up with a different solution. Working in tandem with Brabham’s David Cox, the pair designed the BT46B with a large fan out back, much like Jim Hall’s Chaparral 2J.
That fan, which drew its power from the engine itself, literally sucked the air from underneath the car and, working in tandem with the movable side skirts, created the necessary ground effects. And to circumvent the F1 rule book of the day, which banned movable aerodynamic devices, Murray successfully argued the fan’s primary function was as a cooling devices.
Murray recalled the pivotal moment in his book One Formula – 50 Years of Car Design.
“I read the regulations again and Article 3.7 on aerodynamic devices said, ‘Anything that’s primary function is to have an aerodynamic influence on the car must always remain stationary and be fixed relative to the sprung mass of the car’.
“I spoke to a lawyer friend, and said, ‘What does primary function mean?’ and he said, ‘Well, how many functions are there?’ I said, ‘Two’.
“So he said, ‘The primary function is the one that has more than half the influence.’
“So if we could get [side] skirts to seal like the Lotus ones and have a cooling fan that uses more than 50 per cent of its flow to cool the car and the rest to suck the car down…”
Murray proved the fan provided 55 per cent cooling to the car, and 45 per cent downforce, making it legal.
Was it any good, though? In short, yes. Brabham rolled the car out at the 1978 Swedish Grand Prix, partway through a season already being dominated by Lotus.
Brabham’s Niki Lauda won the race by over half-a-minute, despite, as he later recalled in his autobiography To Hell and Back, “trying not to show how dominant the car really was”.
It didn’t work, the Brabham BT46B promptly banned, with a record of one grand prix start for one win, statistically the most successful car in Formula 1 history.
Still, it remains as an ingenious solution to a vexing problem, one that left rivals curious and bewildered. Rival engineers and designers flocked to the rear of the car in the Anderstorp paddock to try and work out the Brabham ‘fan car’. Wary of all the attention, the Brabham team used the only thing to hand to cover the innovative feature – a garbage bin lid.
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