The BT46B—also known as the Fan Car—was a cunning Gordon Murray racer, designed to one-up the dominant Lotus 79 in the 1978 Formula One season.
After a year of experimenting with the idea, Colin Chapman’s squad produced in the Lotus 79 the first great racing car built on the principle of ground effects. It is the phenomenon whereby an increase in the speed of air under a car causes a drop in pressure, allowing the atmosphere above to press down, which allows the driver to take corners at vastly increased speeds. Certainly an advantage in Formula One, which tends to reward taking corners at the highest possible speed.
Gordon Murray at Brabham was probably the first rival designer to understand the genius of the Lotus 79, which propelled Mario Andretti and Ronnie Peterson to win after win, but his hands were tied. Unlike the slender Cosworth V8 engine used in the Lotus, his Brabhams were powered by pancake-shaped Alfa Romeo flat-12’s.
The powerful Alfa engine was too wide to allow him to install upside-down wings on the sides of the car in the manner of the Lotus. A devastating problem when you consider that clean, uninterrupted airflow is key for ground effects to kick in. Murray being Murray, he devised an ingenious trick. Since he couldn’t lower the pressure underneath the car by airflow, he revisited an idea first used by that great pioneer of aerodynamics, Jim Hall, on the Chaparral 2J Can–Am car in 1970: using fans to suck the air from beneath.
The twin fans on Hall’s 2J were powered by a separate engine scavenged from a snowmobile, not a viable design for Formula One because of the added weight and complexity.
What Murray did instead was install a single giant fan connected by clutches to the car’s engine, a more robust solution with the nice side effect of increased ground effects with acceleration. After sealing the engine bay to prevent atmospheric air from entering the low-pressure zone created by the fan, the car was good to go.
In what would prove to be the car’s only outing, Niki Lauda and John Watson started the 1978 Swedish Grand Prix behind Andretti’s Lotus. Lauda was immediately on Andretti’s tail after the start and passed him with a dominant move soon afterwards (watch at 01:12 in the footage below). He moved into a lead he would never relinquish, winning the race by over half a minute.
Interesting and mostly political events followed. While the car was deemed legal, it was never raced again, presumably as the fan could have been found in violation of the Formula One rule which bans movable aerodynamic devices, notwithstanding the fact that it also helped to cool the engine.
On the other hand, Brabham’s team principal at the time was none other than Bernie Ecclestone, his eyes already set on bigger sights. Running a car which skated up against the edge of regulations in such a cheeky way could have caused him unnecessary conflict with the other team owners, whose support he needed for his ulterior move to gain complete control over Formula One.
Thirty-two years later, Ecclestone is still the master of the sport—and on his way there, he accidentally made the BT46B the only Formula One racing car with a 100% winning record. As it was never raced again, Andretti regained the upper hand in the Lotus 79 and went on to win his world title.
The Fan Car shows up every once in a while at the Goodwood Festival of Speed. But if you can’t wait until July, you can also build your own as a certain Lego geek by the name of RoscoPC did.