The Lotus 79
The casual observer could be forgiven for thinking that the Lotus 79 is little more than an updated Lotus 78, but he would be very wrong, for not only is this year’s Lotus Formula One car a completely new design, it is working on different principles to last year’s model. Agreed, the principles stem from knowledge gained with the Lotus 78, but they are a development from, rather than an extension of, what went before, Last year it became clear that Colin Chapman and his engineers at Hethel were seeking to make use of the air-flow under the car, at a time when most designers were attempting to prevent any air passing under their cars. By using the air-flow under the car to create a down-force the car was being pulled down onto the ground, thus loading the tyres more and getting more grip in the corners. This effect was also being used on the straight to keep the tyres loaded and at a closer working temperature for maximum grip in the corners from the moment of entry, rather than having to start cornering and wait for the rubber temperature to rise to the optimum during cornering. This attribute of the Lotus 78 was very noticeable on long corners that keep on going round, like the one at the top end of the Zolder circuit, and the high-speed semi-circle at Anderstorp. The cost of this increased cornering power was a diminution of maximum speed, due to tyre loading and drag of the air-flow under the car, so that the Lotus 78 was not at its best on circuits with lots of high-speed straight-line running. The side-pods on the Lotus 78, which extended outwards almost to the full width of the car, contained water radiators and under these was formed an upside-down aerofoil section, about on a level with the cockpit. The air passing under the car and flowing across this “wing” section created a down-force, and side-skirts which rubbed on the ground made sure the air flowed parallel with the axis of the car. After passing “under” this wing-section the air had to find its own way out of the back of the car, through the tangle of exhaust pipes, spring unit, suspension members, drive-shaft and rear wheel upright on each side. Petrol in the Lotus 78 was carried in side tanks and a third tank behind the driver, with a change-over valve controlled by cable from a push-pull control on the left of the instrument panel. While racing the Lotus 78 Andretti would operate this change-over valve to ensure that the level of fuel dropped the same amount on each side, rather than letting one tank empty first and then switching to the other one. This way he kept the side-to-side balance of the car the way he wanted it, which was all part of his method of driving as if the car was on rails, rather than letting the tail slide out in a spectacular, but time-wasting over-steer slide. This ability to drive smoothly with all four tyres sharing the cornering loads, meant that he could also make the most of a low-percentage limited- slip differential, almost to the point of having a solid axle in effect.
The aerodynamic theories and studies that have been going on at Hethel for a number of years now, were beginning to pay off, but not as effectively as expected. In the design of the Lotus 79 a step further forward has been made, following the aerodynamic studies. It was clear that air passing under the car could be made to work effectively, not forgetting the air passing over the car, of course, which was already working well within the CSI limits on nose-fins and rear aerofoils, but it was thought better use could be made of the shape under the car. In place of air flowing across an upside-down wing section, it was decided to go to a more basic conception of making the under-side of the car form a venturi with the ground, as air passing through a venturi drops in pressure as it expands. A drop in the pressure exerts a negative force on the walls of the venturi, and as the ground cannot rise up, the car has to be pulled down, thus giving the much desired increase in load on the tyres. A venturi is not effective if it is cluttered up inside, so the object of the Lotus 79 was to clear the path of the air on each side of the monocoque. This was done by eliminating the side petrol tanks, and putting all the petrol in a single tank behind the driver, raising the exhaust pipes up from the cylinder heads and over the top, mounting the rear suspension unit well inboard, alongside the brake discs, reducing the sizes of suspension members to a minimum and slimming down the fabricated rear hub carriers so that they were virtually inside the rear tyre width. The single fuel tank holding 34 gallons and one pint in the case of 79/2, meant the driver had to sit farther forward, and to balance out the weight distribution the oil radiator was moved from the nose to the left side of the car, while all the water cooling was in the right side of the car.
The fibre-glass side-pods that run the full length between the wheels have the venturi shape under them, from the radiators rearwards, so that the under-car aerodynamics effect is taking place farther back than on the Lotus 78. These side- pods are completely detachable, and when removed show a very slim riveted aluminium monocoque of remarkable simplicity and strength, and its underside is so clean and smooth that it is almost breath-taking when seen from below. The fibreglass side-pods extend outwards to the inner face of the rear tyres, and have side- skirts that can float up and down with the outer double skin of the pod. These skirts drop by their own weight and stay in contact with the ground as the car rises and falls on its suspension. There are limit stops to prevent them falling out if the car becomes airborne. The moveable skirt, or side wall, is made from a honeycomb material of great strength and light weight, and the rubbing surface in contact with the ground is a hard plastic material.
Not forgetting the air above the car, the bodywork envelops the entire engine, and extends back over the gearbox and under the rear aerofoil, with the two exhaust tail-pipes emerging through a slot in the middle above the gearbox. At the front the chisel-nose is very slim, with wide canard fins, and the suspension units are actually inside the driver’s foot-well, covered by aluminium bulges. They are operated by fabricated rocker-arms and are joined by a tiny anti-roll bar, which is adjustable for strength within the cockpit. The lower wishbones at the front are exceedingly slim and tubular, and the braided brake pipes are inside them, emerging at the outer ends to feed into the twin calipers without being in the airstream. At the rear the top of the hub carrier, or upright, operates a box- section rocker arm, the inner end of which operates on the inboard spring unit, and an adjustable strut at the rear of the carrier locates and provides means of altering rear wheel angles. At the base of the upright a very slim tubular wishbone is pivoted at its apex and the inner pivots of this wishbone are almost on the centreline of the car, under the gearbox. Above the gearbox is an anti-roll bar, adjustable for stiffness like the front one by a cockpit control.
Whereas the Lotus 78 could come under the category of a “wing car” as popularised by Tony Southgate when he was designing the Shadow DN9 and the Arrows FA1, the Lotus 79 is more a “ground-effects” car, a principle started many years ago by Jim Hall on his Chaparral Can-Am car, except that the Lotus does not extract air from under the car with sucker fans, but uses the air. Some people in Formula One are saying that without a “wing-car” they will be left behind. What they have over-looked is that they are talking of 1977. The Lotus 79 is another step further ahead of that concept.
The prototype car 79/1 was on test at Paul Ricard during the winter, and used the Lotus- Getrag gearbox, which is a further Lotus development story in itself. This first car was never raced, but provided the knowledge for improving the detail work on the second car, 79/2. This appeared at Silverstone for the International Trophy meeting and was severely bent when Andretti went off the road at Abbey Curve and hit the stationary Shadow DN9 of Regazzoni, which had been abandoned. A major design fault in the Lotus-Getrag gearbox came to light about this time, so while 79/2 was being rebuilt the whole rear end was re-designed to take a Hewland gearbox, until the Lotus gearbox was ready. In effect, the car that eventually appeared at Monaco was the third design version of the Lotus 79. It ran in its first Grand Prix in Belgium, and won with ease. Another car was built in time for the Spanish GP and this won on its first appearance, while 79/2 finished second. The prototype car 79/1 is being used for gearbox development work at the Lotus test-track at Hethel.
Designing and building a car like the Lotus 79 is one thing, making it work is another matter altogether. With a sensitive driver like Andretti the finer points of the Lotus 79 can be used to the maximum, not necessarily to make it any faster than the one driven by the inspiration and innate skill of Peterson, but to make the driver’s task easier. Andretti is able to juggle with all the variables of tyre compounds, tyre sizes, tyre constructions, anti-roll bar settings, spring-rates, aerofoil loadings front and rear, suspension settings, wheel loadings, camber angles and so on, to get the car to handle and “feel” exactly as he wants it for any part of any circuit and, with a bit of luck, all round a circuit. When he has achieved this, providing there is time during practice, it means that his fastest lap is not a lucky fluke, but one that he can repeat to order for as long as you like. On the other hand, Peterson, who does not have this “feel” for adjusting a car to such fine limits but has enormous natural fast-driving talent, will lap as fast as Andretti, but not necessarily to order, nor indefinitely. For a given result that Peterson may find hard work, Andretti would find it easy.
In the cockpit of the Lotus 79, on the left, are two controls, one is a short lever like a small gear-lever, that slides along a tube with notches for location. It pulls and pushes a cable that controls the hardness or softness of the rear antiroll bar. Just in front of it is a round knob that moves in and out, turning to lock in any position, and this controls the stiffness of the front antiroll bar. Varying the stiffness of roll on the suspension affects the handling of the car, trimming it rather like an aircraft. Clearly these two controls on the Lotus 79 are not for decoration, so I asked Andretti if he would give me a short run-down on how he used them, while driving the car. His answer was simple and honest, “No, I won’t”. We looked at each other for a moment in complete silence, and then in all seriousness he added: “That’s information I don’t even give my team-mate.” You have to respect a driver like that.
Later, in conversation, I posed the same question to Peterson and he was much more explicit, admitting that he didn’t really mess about with them very much. He said that as the car had been tailored for Andretti he found them difficult to operate, due to his longer arms, and the only way he could slide the knob of the rear one was by using his right hand across his thighs. That afternoon on the straight at Jarama he had reached across and moved the knob ready for the right-hander at the end, only to find he could not bring his arm back. He had trapped his glove in the ratchet mechanism! After that he left them alone. You don’t need the mechanical skill and sympathy of an Andretti to go fast if you have a natural animal-instinct for high-speed driving, but if you have this sympathy you can go fast with less effort. Moss, Clark and Stewart drove in this realism by instinct, not by application as Andretti does. - D.S.J.