History: Forgotten ingenuity: the twin-chassis Lotus 88

By: Bas Naafs

‘’Colin Chapman, 54, a designer of racing cars, dies in England’’, The New York Times of 17 December, 1982. Not really an exciting header, is it? It might as well have said that Joe, a fisherman, died aged 85 somewhere in Far Far Away. Of course Joe’s life is not worth less than Chapman’s, but it feels like a repressed bit of information, a scream into the deep and dark, knowing that there actually is a  lot more to say than ‘’a designer of racing cars’’. We don’t really need to sum up everything Chapman did for Formula One. After all,  his name is intrinsically connected with the sport up until today. A sport driven by innovation. Chapmans life is one with highs and lows, controversy and success –most of the time happening simultaneously. From his rich past involving innovation, three developments can be ascribed to him: the monocoque, ground effect and active aerodynamics. Today we will take a moment to have a look at the latter: active aerodynamics. This was an phenomenon that was connected with the rise of ground effect cars. It was done by making  a car aerodynamically as inactive as possible. Sounds a bit weird, but bear with me, it’s true. In the end, the 1981 Lotus 88 was to be Chapman’s last feat in his career as a Formula One engineer. It featured not one but two chassis’. It  proved to be so difficult to pass through regulations that Chapman lost his faith in Formula One racing as being driven by innovation. After producing a more conventional Lotus 91 for the 1982 season, he passed away.

Ground effect

The 1978 Lotus 79 is one the most legendary race cars. It mastered the art of ground effect so well, it dominated the 1978 season. Still being a Lotus, it didn’t won every race due to retirements. So statistically it wasn’t as dominant as the 1988 McLaren Honda MP4/4, but it still managed to win both the drivers’ as the constructors championship with relative ease. The idea behind ground effect is surprisingly simple, you just have to come up with it, as with everything. Air moving underneath the car was previously unused, not creating any aerodynamic effect. Chapman figured out that creating a tunnel underneath the car would compress the airflow, creating a low-pressure zone which would suck the car down onto the tarmac. This is called the Venturi-effect. You compress air into a bottleneck which makes the air speed up through the tunnel. To get this effect working, the air running through the tunnels had to be closed off from the high-pressure zones outside the car; enter the rubber ‘skirts’ round the sides of the car. By 1979, most of the competitors picked up the idea and the Lotus 80 wasn’t as competitive anymore. Chapman knew how to create more and more ground effect –resulting in the aforementioned T80, but the insane amount of ground effect created a few problems. The aluminium material wasn’t strong enough for the extreme forces, as were the drivers, who were already thinking of G-suits. Also, the car started bouncing, or porpoising, at high speeds when irregularities in track surface distorted the low-pressure zone. For the drivers, this was terrifying and it would frequently result in high speed accidents or cars missing their corners.  The answer to the bouncing was to set-up the car a lot stiffer. This however, meant that the drivers had to walk the track after every race to pick up their shattered vertebra’s, teeth and bits of tongue. Needless to say, this didn’t work. Chapman was aware of that. They built a more conservative T81 for the 1980 season, taking a step back to reproach the ground effect concept with a fresh mind. At the end of the 1980 season though, the secret operations chamber in the Lotus factory started buzzing.

Seeing the light

So, what was the biggest issue when trying to maintain the Venturi-effect? Yes, keeping the skirt on the track. If high-pressure air reaches the tunnel, the effect is lost. So the car had to be pinned to the track as rigid as possible. But what happens when you set up the car as stiff as that? Indeed, the drivers’ back won’t last long. Lotus tried, but Andretti couldn’t manage and understandably so. In the end, this wasn’t going to work and so Lotus went back to the drawing board. Lotus engineer Peter Wright took a few notes with him and went to an aeronautical research facility where data on car characteristics were collected. Not long before, Wright got an idea when visualising the use of ground effect on their road cars, for example the Esprit-Turbo. His idea proved to be a glimpse of absolute brilliance as it would excite Chapman in such a way that  the secret room at the Hethel factory was once again taken in use. What was it that Wright came up with while visualizing ground effect for road going cars? The idea was to bring the best of both worlds into one car. The mechanics of the car, including the driver were to be reasonably sprung while the aerodynamic shell of the car were to be kept as rigid as possible. Wright came up with the concept of a twin-chassis. The internal chassis were to be sprung while an external chassis were to be placed on the lower beams of the suspension, practically terminating any springiness. Although the FISA regulations demanded every aerodynamic part of the car to be sprung, it didn’t put any maximum on the rigidity. So you could practically give the car 99.99% stiffness, and it would still be legal, or so Wright and Chapman thought. Because of the rules, Wright wasn’t able to attach the external chassis directly to the hub, so he fixed them onto the lower beams. The result was a car with which the aerodynamic components were pretty much fixed, giving Lotus a huge aerodynamic efficiency, while the ‘organs’ –or: the monocoque- of the car were still sprung. Funny enough, it was Wright’s colleague at the aeronautical institute who advised Wright to pursue active suspension as an answer to the bouncing at high speeds. Wright put aside the advice, marking is as ‘plan B’.

Troubles

By no means did the creation of the T88 caused zero issues. The biggest issue of all was the fact that the two chassis’ had to work independently from each other. This provided issues for the radiator, the airbox, the exhaust and the roll-cage. Pretty much everything that required the two chassis’ to work with each other. A different part of the car that proved to be problematic was the aluminium monocoque. The ever growing cornering speeds caused proved materials to be stressed beyond their limits. Lotus became aware of this while testing the twin-chassis in a concept car. Wright, as a composite expert, started work on a composite and honeycomb structure for the monocoque. For this they used Carbon Fibre Reinforced Polymer. Even though McLaren’s 1981 bid, the MP4/1, was awarded first place in using a CFRP monocoque, Lotus was working on it as well. They even built it indoors, while McLaren took their plans to Hercules Aerospace (USA). The rigidity of the material was tested by building a 50 feet high tower from which a concrete block was thrown down. Wright found out that enforcing the CFRP with Kevlar made the monocoque strong enough to withstand the stress involved in high cornering speeds. Another problem that occurred was the sudden decision of FISA’s Jean Paul Balestre to ban the skirts and set a minimum ride height. It didn’t took Wright long to realise that the only way for the scrutineers to check the ride height was during scrutinizing before and after the race. A simple hydro-pneumatic cylinder to lower the car during the race and raising it afterwards was already being developed.

How did the T88 fare?

Not well. Not well at all actually. Well, the car was working quite well actually. During a test at Paul Ricard, Alfa Romeo sent out their championship contender, the 179/C after the T88 to calibrate its speed. The Lotus appeared to be a second quicker. This immediately resulted in a lobby, consisting of ten constructors, to get the T88 banned. The tone was set before the season even started, and when it did –at the Grand Prix of Long Beach California- the car was black flagged during the first practice session even though it past scrutineering. Chapman was furious and appealed. The Automobile Competition Committee US (ACCUS) gave Chapman the benefit of the doubt. The FISA however claimed that their statement was only valid on American soil. Even though the Lotus was declared legal after scrutineering, the FISA continued to wave the black flag whenever the T88 hit the track in following Grands Prix. Champan took the case to court. An independent technical expert from the Krakow university backed the twin-chassis concept, declaring it to be fully legal. The FISA, however, declared it illegal anyway. The aerodynamic part of the car was un-sprung, and therefore illegal. Chapman tried his luck one more time at the British Grand Prix with a slightly adjusted version, the T88B, passed through scrutineering, but upon the arrival of FISA officials the car was once again declared illegal. Again Chapman appealed it in front of the RAC, who reversed FISA’s decision, but the car was once again declared illegal in the following FISA hearing. The T88, in the end, never raced. Chapman saw Gordon Murray’s Brabham BT49C win the championship. A car that used hydro-pneumatic suspension. Chapman was gutted, and extremely disappointed in the FISA’s ideology. We will never know how fast the T88 would have been. However, it was pure genius.