The Brabham BT46B “Fan Car”

Fundamentally, the development of the Brabham “fan car” was due to the introduction of the Lotus 79, and in a sense the latter part of the Lotus 78. Both of those cars were essentially ground-effect cars with sliding skirts. The initial concept of the Brabham BT46 was to have surface-cooling through panels on the sidepods. This was one reason, not in totality but in part, the car had a triangular shape, whereas its predecessor, the BT45, had gone away from that shape and was designed along the lines of a somewhat more conventional car. Gordon Murray, the Brabham designer, had come up with a concept that in theory was totally brilliant. I drove the car in its surface-cooling configuration; what it did was reduce the drag of a conventional radiator, with a result much like having an extra 100hp. It was phenomenal. The problem was the cooling surface was far too inadequate for the amount of heat produced by the engine, thus making the panels inefficient.

The problem left us with a somewhat radical and unconventional car that had to be conventionalized. It also meant the car we had worked on for the forthcoming season was now irrelevant. Something had to be done, and quickly. The only answer to address our cooling problems, for the interim, was to revert to the more conventional twin radiators at the front of the car like the BT44 or the BT45. The Alfa Romeo boxer engine ruled out the use of venturi sidepods and left us seeking an alternative solution. We realized that our flat-12 engine in a slab-sided chassis that was quite wide underneath wasn’t going to work when the Lotus 79 appeared at the 1978 Belgian GP at Zolder. Gordon, being a very brilliant designer and a very lateral thinker, looked at the problem. They say there’s nothing new in life, so, he looked at what Jim Hall had previously done with the Chaparral in usting a fan to create a low-pressure area underneath. It was, nonetheless, quite a revolutionary design for a Formula One car. He went to work on it and both the team and Alfa Romeo, our engine partner, produced extra parts to allow a fan to be positioned at the rear of the car with a radiator installed on top of the engine. The engine bay itself was sealed, which created a partial vacuum when the car was in motion. It’s far more technical than that, but that is essentially what we ended up with. It also allowed us to revert to the very slim front nose as used initially on the surface-cooled car. In reality it produced a gear-, or rather an engine speed-driven fan. In turn it provided us with both cooling and road-holding capacities. When driving the car, if the speed dipped the car would lift its ride height and, conversely, the more speed the closer to the ground it went.