Brabham BT19 - Chassis and Suspension

Chassis and Suspension

Tauranac built the BT19 around a mild steel spaceframe chassis similar to those used in his previous Brabham designs. The use of a spaceframe was considered a conservative design decision; by 1966, most of Brabham's competitors were using the theoretically lighter and stiffer monocoque design, introduced to Formula One by Lotus during the 1962 season. Tauranac believed that contemporary monocoques were not usefully stiffer than a well-designed spaceframe and were harder to repair and maintain. The latter was a particular concern for Brabham, which was the largest manufacturer of customer single-seater racing cars in the world at the time. The company's reputation rested in part on BRO – effectively the official 'works' team – using the same technology as its customers, for whom ease of repair was a significant consideration. One mildly novel feature was the use of oval-section, rather than round, tubing around the cockpit, where the driver sits. In a spaceframe or monocoque racing car, the cockpit is effectively a hole in the structure, weakening it considerably. For a given cross sectional area, oval tubing is stiffer in one direction than round tubing. Tauranac happened to have a supply of oval tubing and used it to stiffen the cockpit area. The car weighed around 1250 pounds (567 kg), around 150 lb (68.0 kg) over the minimum weight limit for the formula, although it was still one of the lightest cars in the 1966 field. The race starting weight of a 1966 Brabham-Repco with driver and fuel was estimated to be around 1,415 lb (642 kg), about 280 lb (127 kg) less than the more powerful rival Cooper T81-Maseratis.

The bodywork of the BT19 is glass-reinforced plastic, finished in Brabham's usual racing colours of green with gold trimming around the nose. Although the science of aerodynamics would not greatly affect Formula One racing until the 1968 season, Tauranac had been making use of the Motor Industry Research Association wind tunnel since 1963 to refine the shape of his cars. Brabham has attributed the car's "swept-down nose and the upswept rear lip of the engine cowl" to Tauranac's "attention to aerodynamic detail". During the 1967 season, the car appeared with small winglets on the nose, to further reduce lift acting at the front of the car.

Against the trend set by the Lotus 21 in 1961, the BT19's suspension, which controls the relative motion of the chassis and the wheels, is outboard all round. That is, the bulky springs and dampers are mounted in the space between the wheels and the bodywork, where they interfere with the airflow and increase unwanted aerodynamic drag. Tauranac persisted with this apparently conservative approach based on wind tunnel tests he had carried out in the early 1960s, which indicated that a more complicated inboard design, with the springs and dampers concealed under the bodywork, would provide only a 2% improvement in drag. He judged the extra time needed to set up an inboard design at the racetrack to outweigh this small improvement. At the front the suspension consists of unequal length, non-parallel double wishbones. The front uprights, the solid components upon which the wheels and brakes are mounted, were modified from the Alford & Alder units used on the British Triumph Herald saloon. The rear suspension is formed by a single top link, a reversed lower wishbone and two radius rods locating cast magnesium alloy uprights. Wheels were initially 13 inches (330 mm) in diameter, but soon upgraded to 15 in (380 mm) at the rear, and later still 15 in at the front as well. These increases enabled the use of larger, more powerful brakes. Steel disc brakes are used on all four wheels and were of 10.5 in (270 mm) diameter for the smaller wheels and 11 in (280 mm) for the larger ones. The car ran on treaded Goodyear tyres throughout its racing career.

The BT19 continued Tauranac's reputation for producing cars that handled well. Brabham has since commented that it "was beautifully balanced and I loved its readiness to drift through fast curves." Brabham referred to the car as his Old Nail; Ron Tauranac has explained this as being "because it was two years old, great to drive and had no vices."