Formula One Trend of Design

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Aerodynamics

It seems that every time we reach the threshold of a new and fascinating development in Formula One somebody panics and brings in new rules to set development back a step or two. However, it does not take long for designers to catch up again and either make progress up the same channel or better progress up a different one.

One such point was reached in 1958/59 with the all enveloping body on Formula One cars. In 1954 Mercedes-Benz and Connaught had shown the way with aerodynamic bodywork that enclosed all four wheels and for a time this looked as if it was going to be the way to go. The variations in circuits in use, from the high-speed Avus track to the street circuit in Monte Carlo, showed up the impracticability of total enclosure for a full season, but on some circuits it was a definite bonus. When Cooper produced a totally enclosed 2 1/2-litre at Reims, that was very fast but aerodynamically unstable, officialdom clamped down on the all-enveloping bodywork for single-seaters, though oddly enough there were no restrictions on sports car bodywork.

Later the development of aerodynamics to provide down-force began, which was very different to the objects of the total enclosure bodywork. In the Mercedes-Benz, Connaught, Cooper experiments the aim was more speed on the straights by reducing the drag, though Connaught were also seeking to give the car improved aerodynamic stability at the same time. The advent of aerodynamic devices, that started off as small fins on the nose and ended up with vast aerofoils above the car, was to increase the loading on tyres and thus increase the tyre’s grip on the road-surface when cornering, braking or accelerating. By the time this had begun, tyre development had made many major strides forward, notably in the tubeless construction, which allowed wide and low profiles with square shoulders, thus putting a greater area of rubber in contact with the ground, and in rubber compounds. Meanwhile the cars themselves had become lighter and engines had become more powerful. Tyre development was way ahead of car development, whereas in the past it had always been the other way round. People will talk about the 1937 Grand Prix cars having 580 b.h.p. (not the 646 b.h.p. flash-readings quoted by the media) but they forget that the starting line weight of such cars was about 2,500 lb. whereas the modern Formula One car with 500 b.h.p. has a starting line weight of around 1,700 lb., and it has about ten times the area of rubber in contact with the road and that rubber has far greater adhesion than 1937 rubber. It is no wonder that circuit average speeds have gone up from 100 m.p.h. to 140 m.p.h. at somewhere like Silverstone. With the relative low weight the tyres are not being used to their limits, as is shown by the temperature readings, so that the advent of aerodynamics to increase the effective weight of the car, without suffering the penalty of having to accelerate and brake this increased load, was an avenue in the endless quest for speed up which everyone went with alacrity.

It was getting interesting, with movable aerofoils that “feathered” when no down-force was needed, such as in a straight line, and went on to full effect when braking and cornering. Aerofoils over both front and rear wheels were being used, and divided aerofoils to split the down-force between left and right hand wheels to counteract roll when cornering, were appearing. Some of the methods of “feathering” for the straights were intriguing, Ferrari were using the engine oil pressure, the oil pressure varying with the speed of the engine so that at peak r.p.m. the aerofoil was completely flattened. Lotus provided their driver with an extra pedal which he operated with his left foot, pushing the pedal down to flatten the aerofoil, while Cooper had a spring-loaded and balanced mechanism that relied on the wind pressure to flatten the aerofoil; the faster you went the flatter the aerofoil and as you shut off and braked the fall in speed through the air let the aerofoil rise up.

All these devices were mounted on the chassis to start with but it was soon obvious that much of the down-force being created was being used to compress the suspension springs before any effect was transmitted to the tyres, so the next move was to mount these aerofoils directly on the wheel uprights so that all the down-force was used to increase the load on the tyre. (Remember that these aerofoil “wing” sections were all being used upside-down from the way they are used on aircraft. An aerofoil section generates “lift” on an aircraft, described as positive lift. For a racing car you turn the aerofoil upside-down and create negative lift, or down-force.) Mounting the aerofoils directly on to the wheel uprights meant that the mountings received all the road shocks and vibrations and we suffered alot of breakages, with near disastrous results, due to inadequate design and inadequate testing in laboratories. It was mostly done by “suck-it-and-see” methods prevalent in the kit-car racing industry at the time. When the Brabham cars suffered aerofoil mounting breakages before the very eyes of officialdom in Spain, and Lotus suffered two horrific crashes due to breakages, a major clamp-down was imposed on the aerodynamic trends. Had there been some serious engineering manufacturers in Formula One at the time, instead of a collection of well-meaning special-builders, the restrictions might not have been so severe. All movable aerodynamic devices became illegal, sizes were restricted, as were the positions, and mountings had to be attached to the sprung part of the car.

It did not take long for ingenuity to overcome these restrictions and progress forwards again and then we moved into the under-car air-flow “ground effect” principles, which Jim Hall had pioneered with his Chaparral Can-Am cars. Colin Chapman developed the use of the air-flow under the car at a time when everyone else was trying to prevent the air from going under the car, as it was causing disturbance and drag. The Lotus 78 and 79 encouraged the air to flow under the car and it was then used to create a negative pressure so that the air flow over the top of the car that was creating a positive pressure on the bodywork, would be more effective. An important factor in this principle was to seal the sides of the car to the ground to prevent any of the air passing under the car from going anywhere but through the venturi shaped undersides and out the back. Ceramic-faced skirts were designed that slid along the road surface, making an effective seal, but because the car was moving up and down on its suspension these skirts had to slide up and down in slots, with spring mechanisms to keep them down in contact with the road. They also had to be able to move up and down, relative to the rest of the car, over road irregularities.

All this was in search of more down-force to increase the load on the tyres to be able to make better use of the adhesive properties of the improved rubber and improved tyre construction, and thus generate higher cornering power or better braking, while accelerative traction was an added bonus. It had nothing to do with sheer speed, in fact almost all improvements in down-force go in opposition to ultimate speed. It is average speed round any given circuit that is important, measured in time, and you can often sacrifice maximum speed for greater cornering power and show a better lap time. It is a question of compromise and balancing down-force against drag, cornering power against speed. There is a lot of loose talk about such-and-such aerodynamic device being “faster” without the qualification that “faster” means lap-time, not m.p.h. down the straight. This mis-quoting and mis-use of words was used by the uninformed with regard to sliding side-skirts. They were said to make the cars “faster” which a lot of people assumed meant m.p.h. in a straight-line, when what they did was to give the aerodynamic effects the possibility of producing better adhesion from the tyres and produce “faster average speeds” round a given circuit.

As the technique of “ground-effect” improved it was possible to reduce the devices producing down-force above the car, so that front and rear aerofoils could be reduced in size and bodywork shape was becoming much smoother. Nose-fins had almost disappeared and rear aerofoils in some cases were minimal. Sufficient down-force was being generated by the shape of the car, both above and below, and all the while average speeds round circuits were rising (Silverstone had nudged 150 m.p.h. average speed) not due to the ground-effect or skirts, but because their effect was permitting greater use to be made of the tyres and the tyre designers were still ahead. Aerodynamics and ground-effects do not keep a car on the road when cornering, it is the tyres that do this, and then only the small “contact-patch”. Aerodynamic effects provide a means of using the “contact-patch” more efficiently.

Once again officialdom moved in as there was growing concern over the continual rise in average speeds round circuits and the continual rise in the G-forces being developed in cornering and under braking. The sliding side-skirt had crept in before anyone admitted that it constituted a “movable aerodynamic device”, but as everyone was cheating it was considered legal! In the Spring of 1980 it was ruled that sliding-skirts would be banned as from January 1981 and by mid-summer 1980 Renault were testing without sliding skirts and by autumn Ferrari had designed a new car without sliding-skirts. All the British “kit-car constructors” went Bolshie over the rule and used it to fan the flames of a power-struggle going on within the management of Formula One on the International level. It was all a wasted effort and the first World Championship Grand Prix for 1981 ran to the new rules and sliding side-skirts, like total enclosure and movable aerofoils, were a thing of the past. The reasoning behind the ban was that ground-effects were providing big increases in lap speeds and sliding skirts were a key factor in the effectiveness of ground-effect. Remove the key factor and you remove the effect, and reduce lap speeds, but nothing is as simple as that.

At the moment we have returned partially to the pre-ground effect era and the cars have sprouted nose-fins or full-width front aerofoils and rear aerofoils have become larger and deeper. Just when these appendages were beginning to disappear thanks to improved techniques elsewhere, they have all returned, but it may only be temporary as new ideas formulate for regaining or maintaining down-force without suffering the penalty of increased drag.

One thing that has gone (thankfully) is the driver excuse for a mediocre performance. Last year you would hear a driver explain how he suffered from a sticking skirt and how this stopped him being at the front of the grid. Or a retirement was caused by a driving error letting the car run over a kerb and damage a skirt, and to listen to some drivers you would think a car without moving side-skirts was undrivable. This year they all seem to be getting on pretty well without sliding side skirts and some of them have lost a good excuse for being hopeless. In sheer practical terms the elimination of sliding side-skirts has reduced the cost of a Formula One car by at least £700 (each skirt cost around £350) and there is £700 worth less damage done when a driver spins off over a kerb. No doubt they have all found other ways of dissipating that much money, which is an important factor in Formula One for some teams.

In addition to re-introducing nose-fins, full width front aerofoils and larger rear aerofoils to gain more down-force there are other subtle tricks being tried, the most obvious one being the Brabham hydro-pneumatic “ride-height” adjustment, but more of that in a future article. – D.S.J.