Lotus 78: F1's first true ground effect car

However, Rudd’s summary mid-season ’69 dismissal from BRM meant he was snapped up by Chapman for Group Lotus, while Peter Wright had followed him there after a spell running racing body company Specialised Mouldings’ wind tunnel. The 1969 wing car notion had been junked by BRM, but although Wright had eventually rejoined Rudd at Lotus to run its plastics research, his brilliant mind then addressed Colin’s Formula 1 wing car questions.

The first BRM concept had used stub wings sprouting either side of the central monocoque to clean up aerodynamic turbulence between front and rear wheels and perhaps find some extra download. Robin Herd followed in his 1970 March 701 design, but airflow management was not applied to close off the underwing airstream from the diffuse airflow around the car.

Wright joined Rudd and Bellamy at ‘Fawlty Towers’, as Ketteringham Hall became known, and through the autumn of ’75 this trio explored The Guv’nor’s quest to harness the car’s entire form to generate advantageous aerodynamic effect, instead of relying upon bolt-on wings at front and rear.

At that time, while every F1 designer had studied in varying depth the effect of airflow around the sides and over the top of his car, few – apart from Gordon Murray of Brabham and McLaren – had tackled proper management of airflow beneath it. Indeed, even these exceptions had tried to stop much air flowing under their cars at all.

Now the Lotus R&D group retained Charlie Prior, a first-class model and pattern maker from the Esprit team, to build quarter-scale model cars and aerodynamic devices for extensive wind tunnel testing by Wright at Imperial College, London. A wind tunnel there had a moving-belt floor which mimicked the track surface at speed beneath a car. Little such previous research had been done. Normally test models sat on a stationary surface, or were suspended in space – fine for aeronautical testing but with little relevance for land-borne vehicles.

Much attention was paid to radiator siting. Rudd recalled his Rolls-Royce aero-engine work, especially the radiator mounting of the De Havilland Mosquito – buried within ducts in the inner wings’ leading edges, with air exiting from conveniently sited ducts further back on the wing. Would similar sidepods generate download when slung either side of a single-seat racing chassis?

A model mimic section was made and tested upside down in the wind tunnel to provide negative lift. Lift/drag ratio was the vital criterion — best possible lift/least possible drag. Tony Rudd fondly remembered the message he received from Imperial College that Christmas – “The Mosquito flies”.

Mosquito-type ducted radiators and sidepod sections would be used to harness airflow beneath the pod underfloors — or underwings — to generate download. The low-pressure areas created by airflow acceleration would be protected from infilling on each side by a skirt system hung from each pod side panel down to the road surface.

Once this overall format for what would become the Lotus Type 78 had been decided, Ralph Bellamy began to draw the car while Wright delved further into its aerodynamics. Mike Cooke set up and ran a test rig, simulating racing loads on every component as it was made. Unacceptable deflection brought immediate redesign until stiffness became adequate. The rig itself was rather crude, loading parts via cables passing over pulleys to concrete-filled oil drums, but it was invaluable in building structural reliability into the new car. It served to pinpoint some of the contemporary Lotus 77’s deficiencies and helped that to competitiveness by the end of 1976, when Mario Andretti won the Japanese GP in his.

Once Bellamy had finalised his layouts, Martin Ogilvie detailed the new design’s suspensions and other ‘bits that moved’, while Bellamy completed the chassis and they then combined on body design.

The prototype Lotus 78 — known in the curious sponsor-pleasing ‘John Player Special’ series as chassis ‘JPS/15’ — was first driven at Hethel by Ketteringham’s shop foreman, Eddie Dennis. Although a new Lotus racing gearbox was under development, it was not used on this prototype car “to limit the unknowns” as Chapman put it.

“Mario Andretti enthused about the 78’s ‘boulevard ride’ ”

Nigel Bennett, the former Firestone tyre engineer who had joined the team at the end of 1974, conducted onboard instrumentation tests using borrowed Goodyear equipment while Andretti and team-mate Gunnar Nilsson test drove. By the time Chapman decided to race the new car his R&D group had accumulated 2.2 miles of test-recording tape, completed over 150 individual investigations, 54 rig tests and 400 hours of wind tunnel time at Imperial College. But did the car work?

Testing indicated that it did, although aerodynamic values realised full size were 25-30 per cent less than predicted. On 21 December 1976 the new ‘John Player Special Mark III’, alias Lotus 78 — and actually the second car ‘JPS-16’ – made its public bow at a reception in London’s Royal Garden Hotel. Andretti was there, enthusing about its “boulevard ride”; it certainly looked different.

Its centre monocoque fuselage was slim, like the preceding Type 77’s, but with broad panniers each side between front and rear wheels. The tub encompassed a fully stressed tank section behind the driver’s shoulders, while a structural scuttle panel enclosed his legs. The fuselage was light and stiff through liberal use of Cellite dural/aluminium honeycomb sandwich sheet.

Where first prototype ‘JPS/15’ had housed a 4-inch longer rear tub section, all subsequent 78s were built along ‘JPS/16’ lines, with a shorter tub and an engine oil tank integral with the bell-housing between engine and gearbox. Their wheelbase was 107 inches against the prototype’s 110-inch.

But the new Lotus’s magic lay within its side panniers, housing wing fuel tanks towards the rear, around the car’s centre of gravity, with the water radiators ahead of them in their buried ‘Mosquito’ mounts, exhausting expended air upward through pannier-top vents. The ramp surface guiding this air up through the top vents was actually the upper face of the wing fuel tank. Beneath each pannier, the tank undersides curved upward to their trailing edges, terminating in line with the engine mounts to present to the airstream an inverted wing section.

Having generated an area of low pressure beneath these underwing sections, capable literally of sucking the car down onto the road surface, measures then had to be taken to prevent air infilling this depression from either side – the crucial step missed in the BRM wing car and March 701. Now Wright recommended that the ‘tips’ of these very long-chord, short-span pannier wings be closed off by Cellite endplates which extended virtually from front to rear wheel each side. Extending beneath the Cellite side plate was a bristle brush curtain, to prevent outside airflow flooding in to the low-pressure area.

The problem was to find an air-impervious material which could survive high-speed rubbing contact with the road surface. The brush was just a reasonable initial expedient but solid hingeing, then sliding skirts would follow. Conventional wings and fins provided trim and balance, but there was more…

Mounting the side radiators just behind the front suspension increased forward weight bias, enhanced by the nose-mounted oil cooler and far-forward driving position, due to the three fuel cells abreast behind the seat. They concentrated fuel load around the car’s centre of gravity, achieving Chapman’s requirement for “minimum change in handling and response as the fuel load lightens”. Experience with the highly adjustable Type 77 had decided Colin “…that only three things mattered: how long it is, how wide it is, and where the weight is! We’d tried seven different rear suspension geometries and the drivers were hard pressed to notice a difference. But when we increased the front track by an inch they raved”.

So the 78’s front track was extended close to the regulation maximum, so it could stick out a paw as its driver turned in, when the longer lever arm would give extra ‘bite’. Lotus 78 front-end grip was the greatest the drivers had ever known. That in turn allowed use of near zero-slip differentials to limit wheelspin. In a design with less front-end bite such a diff would merely have induced uncontrollable understeer. This move came partly at Mario Andretti’s request. He also prompted addition of a USAC-style driver-adjustable rear anti-roll bar, plus a preferential fuel drainage system whereby the driver could choose the order and degree in which his three available fuel cells drained down, further tuning car balance as its fuel load diminished.

Mario simply had the experience and innate sensitivity to trim his car into optimum balance on the fuel changeover tap and anti-roll bar adjuster. He would work unceasingly to set-up his Lotus 78s to an unprecedented pitch. Mario tweaks adopted from USAC left-turn-only track racing included ‘stagger’ — the use of unequal-circumference tyres to give the car a directional bias under power and braking — and ‘cross-weighting’ — diagonal stiffness in the car adjusted on its spring platforms to achieve optimum traction in any circuit’s most critical corners. He and Team Lotus painstakingly matched tyre sets.

“Through 1977 Andretti led more race laps than any other driver”

In the team’s Lotus 78s through 1977, Mario then led more world championship race laps than any other driver. He won four Grands Prix – at Long Beach, Jarama, Dijon and Monza – and his team-mate Gunnar Nilsson a fifth, at Zolder. But a string of five engine failures and three other mechanical breakages kept Andretti, Team Lotus and the world championship titles apart. Still the sweetest victory for the Italian-born American driver came at Monza where his 78 proved simply uncatchable.

While the improved Lotus 79 ground-effects car was introduced for 1978, the team retained 78s ‘JPS/16’ and ‘JPS/17’ – Mario winning in Buenos Aires and new team-mate Ronnie Peterson at Kyalami, before the 79s became available. They won in Belgium, Spain, France, Germany, Austria and Holland before Mario clinched his World Championship title in the Italian GP – and Ronnie Peterson was killed after being barged into a trackside barrier in the spare Lotus 78 – ‘JPS/17’ – which was destroyed. And that, for me, was one of the saddest days of my enthusiast life…

But overall the drivers of the Lotus 78s loved its secure feel in corners, the confidence that they could blind round their opposition often on an outside line with some adhesion to spare. Above all, the 78 excelled on turn-in bite into corners and traction out of them. The wing-car aerodynamics worked and Team Lotus’s place on top of the Formula 1 pile had been reconfirmed.

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