The Lotus 88 F1 car seems to be the only example of a vehicle running a twin chassis setup although in my research I have come across others who have spoken about building a new car with it, however I haven’t seen anything that suggests that one is in existence or about to be launched.
In the early 1980s, Ground Effect had been banned by the FIA (the Federation that runs non US motorsport). More specifically, moveable devices that created extra down force became illegal in F1. The rule change was to get rid of the skirts that helped cause a vacuum under the cars, which meant greater grip and therefore greater cornering speeds and thus faster lap times. If this grip was lost then the resulting accident was usually much bigger due to the higher velocities and g-forces that were created.
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 at the desired ride height for scrutineering. This meant that the suspension was quite hard at speed which would have been physically demanding for the driver.
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. The removal of the external wings removed drag at low speed as well, so the outer chassis and bodywork provided two important functions to increase speed.
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. It was a car inside a car! All the outer chassis did was to push the car down with the inner chassis delivering the power. Nigel Mansell and the late Elio De Angelis tested the car and found it to be a very easy car to drive quickly retaining the improved cornering from the earlier Ground Effect cars. The tubs were made from carbon fibre, one of the first to do so and it was powered by the classic Cosworth DFV.
The team made it to the first championship race for the 1981 season and took part in the first practice day – the car had completed scrutineering so had passed the test that mapped the car to the new rules. 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 year’s 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 – remember this was 35 years ago!
What irked Chapman the most was that the complaint was really based on the fact that every other team would have to design their own version to compete and that would have been very expensive. At a later race Brabham brought a design that also circumnavigated the rules and were successful with it, yet it could also have been argued that it broke the rules – and Chapman certainly felt that if the Brabham was OK, so was his Lotus.
In updating this post – it was originally written in 2008 for my podcast – I have found that the discussions on the Lotus 88 and the whole concept of using twin chassis components is still alive and kicking with several forums talking about trying to factor in a twin chassis system into an existing design. One is from Origin Sports Cars in northern California who have purchased a design originally from Noble in the UK. I can’t quite figure out how their cars, the HVR and HVRx, are using (or going to use) a twin chassis so I feel a road trip coming on. I’ll be in San Francisco in September, so I’ll head out and get the scoop.
Like many technological ideas, the twin chassis is really only of use at high speed and for cornering quickly and that is something that is difficult to do in many road driving conditions. For track use it would be great – perhaps an electronic system mapped into the “Race” button on high end cars.