Lotus 78

Colin Chapman's designs were always intriguing, frequently innovative and occasionally hopeless. But the Lotus 78 was a true stroke of genius which evolved into the legendary 79

I have chosen the Lotus 78, 'Rips 15-16, of 1977, which was a bit after my time in Formula One my last Brabham being the lobster-claw' BT34 of 1971. The Lotus, as they so often did, heralded a new era ground effect, which in one form or other has been with us ever since. The car evolved from a 27-page concept document of August 1975; Chapman realised they were falling behind while the 77 was being designed, and he simply sat down to create a new idea.

He presented this to Tony Rudd, newly appointed to be in charge of R&D. He was joined by Ralph Bellamy, ex-Brabham and McLaren, and Peter Wright, of BRM and Specialised Mouldings.

Wright had been researching a wing-carat BRM, but they had not yet developed the important part, the side-skirt which stops air sucking in underneath. Then when he was at Specialised Mouldings, he suggested to Robin Herd that they put a stub wing on the side of the March 701. Of course it had no side-fence, so it didn't really do anything; it was an OK car, but it didn't crack the problem.

True ground effect follows the Bernoulli theorem which says that air passing through a venturi accelerates and the pressure decreases. That wasn't appreciated in these early experiments; they were merely putting a wing on the side of the car. Then they found they had made hara venturi, with the ground as the other half, and had to stop the air coming in from the side as best they could. On the 78 they used a brush, which was a start; it gradually developed into a proper siding skirt on the 79. Only afterwards did they realise that this followed the Bernoulli theorem. I don' t think they were aware that was what they were doing at the beginning.

Lotus produced a full ground-effect model and tested it at Imperial College on a moving-floor windtunnel, the first time I think that this had been done. Tony Rudd suggested putting the radiators in the side-pods, an idea originating from the WWII De Havilland Mosquito, which took air in from a duct on the leading edge of the wing and exhausted it through further ducts rearward in the wing section. The chassis was drawn up by Ralph Bellamy, and was constructed with honeycomb sheet which made it a light, stiff structure despite being very narrow, to maximise the wing effect Honeycomb sheet came from the aero industry where it was used for cabin floors and the like.

It had been used in racing cars before that the Cosworth 4WD car used the odd panel of honeycomb material and Robin Herd had used balsa-cored panels previously but this was one of the first complete tubs sides, bulkheads, and a torsionally very stiff box containing fuel behind the driver. There was also a fuel tank in each side wing; the later 79 had all its fuel in the box behind the driver. Chapman got a concession from the FIA to exceed the 80-litre single-tank maximum for that

Another first on the later 78 variant, the JPS 16, was carrying the engine oil in the bell-housing. That was facilitated by using a co-axial clutch throw-out slave cylinder, an idea which Bellamy first experienced at Brabham. It fits inside a sleeve through the centre of the oil tank. I first did it on a Hewland DG300 gearbox about 1968-69 when Ralph was working for me. I dropped it the next year because they brought out the DG400 and I was in too much of a hurry to carry it on. But Ralph picked it up. The big advantage is that it allows the packaging to be smaller. If the oil tank is in front of the engine it adds 3-4in to the length, and by then they'd banned having it on the gearbox, behind the rear axle. It had to be within a certain distance of the centreline, but it wouldn't fit in the side-wings, so the bell-housing idea was a good one. Nowadays it's back in front of the engine in a scallop in the tub, which is easy to do with a composite monocoque; with flat panels it was harder.

Not everything was new on the 78: the rear end was almost the same as the 77, but with a widerbased bottom wishbone; also the track was brought up to the legal maximum to allow for the widest sidepod and thus the maximum ground effect. The front springs were inboard of course, for best airflow under the sidepods. It also had twin calipers, something Bait did on the Theodore; that puts heat into both sides of the disc so that it heats more uniformly very important when we had iron discs. Chapman's rivals didn't really wake up to what his Lotus 78 was doing for the sim ple reason that it wasn't too efficient aerodynamically; the brush side-skirts didn't do a particularly good job; they needed the sliding skirts of the 79. Also, Lotus had good drivers at the time; Mario Andretti and Gunnar Nilsson in the first year, then Andretti and Ronnie Peterson, so it was the drivers who got the credit. From the 79 on everyone was scrambling for ground effect.

The first one I did was the F2 Raft for Toleman in 1979; we used a disastrous sliding skirt made of plastic sheet which would suck under and jam and make the handling inconsistent; it was only when the team introduced a honeycomb skirt with ceramic on the bottom edge that it worked.

Chapman had a reason for wanting publicity for his innovation, because of the road cars, whereas other teams didn't really want to draw attention to what they'd done they just wanted the advantage without it being obvious where it came from. Of course, the trouble with being inventive is that others can do the Mk2 version without having wasted time on the Mk1. And that's exactly what Williams did, building a better Lotus 79 in 1979 with their FW07.

Ron Tauranac was talking to Gordon Cruickshank