X-ray spec

Lotus 63

4WD worked at Indianapolis, so it had to be good news for F1, right? Wrong. John Miles, GP driver and engineer, explains why to Keith Howard

To innovate is to take risks. So within the CVs of all motorsport’s most daring designers there are abject failures cheek by jowl with the successes. In Colin Chapman’s case, one of the misfires was the four-wheel-drive F1 car. He wasn’t alone in pursuing this, as it turned out, misguided path, and there is some consolation in the fact that the Lotus Type 63 of 1969 was (ignoring the anomaly of the earlier Ferguson P99) the best of the breed. But the contrast with Chapman’s next F1 creation – the 72, one of the most successful GP cars ever – could hardly have been starker.

Yet 4WD had seemed such a good idea, such a logical response to the traction problems anticipated from burgeoning 3-litre power and restrictions on the use of wings, that a handful of teams set to work on it Even Cosworth was tempted to step beyond making engines to create a prototype driven at all four corners. All of the resulting cars, albeit in varying degrees, would prove to be duffers.

Two key factors contributed to this. First, the widely foreseen traction problems simply didn’t materialise. Significant advances in tyre technology and higher amounts of aerodynamic downforce than anticipated after the banning of high-mounted wings conspired to ensure that 3-litre rear-wheel-drive GP cars did not in fact squander the available torque. Second, it quickly became apparent that 4WD imposed a particular balance on the car one ‘built in’ by the torque split that made its cornering inherently non-adjustable.

John Miles, who drove the 63 more than anyone else and offers his comments on the experience overleaf, recalls how it was the siren voice of oval racing which first attracted Chapman and others to all-wheel drive: “What sucked the Fl teams into 4WD was the fact that it worked well at Indianapolis. Take early 4WD road cars like the Quattro as an example: they are extremely stable, very forgiving, but they don’t have adjustable handling, they aren’t particularly fun to drive. Which is exactly what you want to have at Indianapolis a car that’s very stable, that takes fast corners with great confidence. If you back off in the middle of a fast corner you don’t want the car to suddenly change balance, you don’t want a nervous reaction. That stability is exactly what 4WD gives you.”

Unfortunately this isn’t what is required in an F1 context where the mix of corner speeds requires, above all, a car that is minutely adjustable by both steering and throttle.

The Institute of Mechanical Engineers published a paper by Miles in 1986 entitled ‘Four-wheel-drive Grand Prix cars’. As well as analysing the F1 4WD phenomenon, it included quotes from designers and drivers caught up in it. Two of the contributions summarise why 4WD was a flop.

Jackie Stewart: “The biggest problem was the front end understeering under power, and not being able to get rid of that either by deceleration or trailing throttle into a corner and reapplying power. You would get the car going into a ‘half-neutral position’, apply the power, and you had to be a real artist to be able to catch it at the right moment to have what would really amount to a four-wheel drift. It only happened once every six corners.” And that wasn’t enough.

Jochen Rindt, less analytically but with abundant feeling, said of the 63: “You just can’t ‘race’ the cat” That, in a single phrase, is why 4WD proved to be a cul-de-sac.

Knowing what we know now, could 4WD have been made to work?

“Perhaps,” says Miles. “I didn’t have enough experience then, nor did anybody else other than Chapman, to try to better understand what was going on. And, of course, the cars weren’t instrumented. We thought we were extremely clever, but now we realise how little we knew.”

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“Keith Duckworth used to say that the steering on the Cosworth car was unmanageable — heavy and with a lot of kickback—but obviously the Lotus was much better designed in that respect. The steering was heavy but it was not unmanageable. In very slow corners there was a lot of load through the steering if you were using full throttle, like in a front-wheel-drive car. But the steering and the front end didn’t behave abnormally in the sense of any lack of control or any massive amount of corruption, because Chapman understood these things. The steering system was a work of art, really. In order to package it around the diff and the inboard brake discs, it had to be a clever piece of articulation. It’s that kind of thing that Chapman’s lot was so good at.”

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From the centre differential the drive is taken forwards and aft to the differentials at each axle. Mechanic Bob Dance recalls that the 63 was originally fitted with ZF lsd units front and rear, but Miles recalls racing the car fitted with an open front diff, so this may have been a change during the season.

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Pushing the driver forward meant that he had to pass his legs under the front axle tube to reach the pedals: “Hill and Rindt hated the front axle tube because of the safety implications. It looked as if it would either chop your feet off or pin you in the car following an accident. I was a young blood, I didn’t even think about it. People say to me the 63 must have been a terrible thing to drive, but it wasn’t. It was actually rather nice to drive. It was very stable and we got it going well at Mosport and Oulton Park, where Rindt came second. Because I was more or less left alone to plod on with it I was quite happy. It was only when I got into the ‘proper’ F1 cars that in some senses things started to fall apart.”

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Although the additional transmission components sapped some engine power, it wasn’t something Miles recalls being an issue: “I never noticed a tremendous difference in top speed between it and other cars. Audi used to say that rolling resistance was reduced by 4WD, and they had data to prove it. When you’re driving fast in a RWD car the rear tyres are in a constant state of slip. With a 4WD car you reduce the amount of slippage. What I did notice was that the car lost more time in slow corners — where you’d expect it to do well — than fast comers. I wrote the IMechE article just before Chapman died, and I asked him where 4WD works best and why he thought it failed in Fl. He summed it up beautifully by saying that 4WD works best in situations of low driving torque — exactly the opposite of what you’d expect. In other words, it works in rallies where the traction is so low, or at very high speeds where there’s no possibility of an excess of drive over fraction.”

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The layout of the 63 is typical of the 4WD F1 cars of the period. To achieve a more even weight distribution between front and rear axles, the major masses were moved forward within the wheelbase (which could be increased to accommodate the changes). Turning the Cosworth DFV through 180 degrees allowed the modified gearbox (a Newland) to be situated behind the driver’s seat, with the drive taken out at 90 degrees to an epicyclic torque-splitting differential mounted to one side of the car.

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The 63 began the season with a front/rear torque split of 40:60, but torque was redirected more to the rear wheels as the season progressed. Asked whether the car responded to the change, Miles says: “It was responsive insofar as it just got worse! It became like a very bad rear-wheel-drive car. Everybody waited for the wet, but it was a dry season. Mario Andretti was the only one to drive the car in the wet, at Watkins Glen, and it was dreadful. By that time the torque split had been changed so that more than 80 per cent was going to the rear [what Keith Duckworth wryly termed two-and-a-half-wheel drive] so it was basically a rear-wheel drive car with only 70 per cent of the rear tyre. I drove it like that at Snetterton and the thing was just awful. As soon as you touched the throttle it spun. There was enough drive at the front axle to make the steering unresponsive, and no traction at the rear.”

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“For some reason this car almost always broke when I drove it, and for the same reasons: either the gearshift disintegrated or the fuel pump would seize. I have no idea why, although maybe it was an installation issue as a result of turning the engine around. Likewise, the oil pressure on my 72 always ran about 20psi lower than on Rindt’s; he never had any engine trouble and I blew mine up. Again, I have no idea why. I guess someone up there was messing me about!”