To add to my page about Ground Effect and especially the use of it in Formula 1, it seems appropriate to also cover the only F1 car that had a twin chassis – the Lotus 88.
In the early 80s, Ground Effect had been banned by the FIA, or more specifically, moveable devices that created extra down force. This was to get rid of the skirts that helped cause a vacuum under the cars, which meant greater grip and therefore greater cornering speeds. As I described on the Ground Effect page, if this grip was lost then the resulting accident was usually much bigger!
At the time Brabham and Lotus were at the forefront of technology and both had ideas to counter the FIA ban. The rules had changed to enforce a 6mm gap between the car and road. Brabham used pneumatic suspension to lower that gap when the car was running but when stationary, the car remained a 6mm. This meant that the suspension was quite hard at speed.
Colin Chapman at Lotus had another idea. He developed a twin chassis system. The outer chassis was similar to the Brabham where the pneumatic suspension was almost rock solid and allowed the car to hug the ground. Wings were removed as the outer shell was essentially designed as one large upside down wing to maximise the Ground Effect concepts.
However, he then added in an inner chassis to protect and improve the comfort of the driver. The inner chassis had a second set of suspension components that were independent of the outer system. Nigel Mansell and the late Elio De Angeles tested the car and found it to be a very easy car to drive quickly. The tubs were made from carbon fibre, one of the first to do so and it was powered by the classic Cosworth DFV.
The other teams were outraged and complained bitterly saying
it was breaking the rules because the inner chassis was a moveable device and
therefore broke the new rules. The FIA agreed and banned it, much to Chapman’s
fury. He tried several times to overturn the decision and in the end took the
previous years car, made some mods and raced that. He then concentrated on the
next model, the elegant 91 that used some of the concepts designed into the 88,
including the use of carbon fibre.