A Non-Rigorous History Lesson on Ground Effect Aerodynamics
For the loss in aerodynamics above the car, with the 2022 Formula 1 Technical regulations came the rebirth of ground effect for downforce generation, in almost 40 years.
One team who has nailed this new technical revolution is Red Bull, in specific Adrian Newey — who’s thesis at The University of Southampton was based on ground effect, and unlike msot F1 engineers has had practical experience with ground effect back in the 1980s, at Leyton House.
So how did ground effect get developed, and who were the prime movers?
Ground effect isn’t anything new, nor is it uncommon. Before 2022, it was common within endurance racing cars. Watching a swan taking off from a lake — it applies ground effect aerodynamics as it flies close to the surface of the water, gaining speed before flying into the sky — its ground effect increases lift and reduces drag, enabling it to accelerate to a suitable take-off speed. Race cars apply ground effect in the opposite way, exploiting newtons third law — where as a curved surface approaches the ground, the speed of airflow between the surface and the ground reduces the pressure, creating downforce.
In 1949, Milne-Thompson calculated the theoretical effect of the ground on aerodynamic characteristics of a sphere. He concluded that the lift coefficient became negative as ground clearance is reduced, reading CL(max) = -0.375 when the sphere touched the ground.
Chaparral — too innovative for their time.
Chaparral Cars, a racing team from the US, was the first major player in trying new things and looking outside off the engine. In 1962, Jim Hall experienced lift on his Chaparral 1 sports car.
After this, Chevrolet R&D took up investigating the problem, with Bill Mitchell from GM. Mitchell suggested an inverted air-foil shape. i.e. rear wing. When driving the Chaparral 2, the front wheels lifted above the ground, until a ‘bib spoiler’ was fitted. Chapparal went on furhter to develop downforce cars with huge wings, which consequently sent huge shockwaves in the racing world, with engineers noticing the inherent enourmous performance gains in cornering, traction and braking — giving the tyres more load, without increasing the mass of the car. Genius.
This same phenomena was forseen by engineers attempting land speed records. John Stollery, involed with the Bluebird land speed record car, released a seminal paper titled, “Forces on bodies in the prescense of the ground” (Stollery, Burns 1969) — highlighting characteristics of a skirtless, ground effect, venturi car.
BRM P142 — Development In Secrecy.
By now in Formula 1, most teams had their own adaptations of rear wings on cars. Technical chief of BRM at the time, Tony Rudd was concerned with the safety of rear and front wings on cars, epitomized by a multitude of wing failures. Newly graduated engineer from Cambridge, Peter Wright shared thoughts with the idea of generating downforce without using mounted wings. Peter cracked on, and developed a car body shaped as an inverted air-foil, adapting wings in the bodywork itself. Secret wind tunnel tests at Imperial College were conducted, confirming promising results. After this, a secret workshop was set up, in preparation for the Italian Grand Prix. However, before anyu further development could be made, BRM conducted one of its “palace revolutions”, and Tony and Peter left. All work on ground effect was halted. Later, Peter was to become managing director of Lotus Engineering and both were involved with the legendary Lotus 78 and 79.
Team Lotus — Breakthrough
With venturi cars, there was one missing piece to culminate everything together — skirts. The introduction of ground effect skirts was first seem on the Lotus 78.
The Lotus 78 was as a consequence of the now obsolete Lotus 72, due to the new Goodyear tyres suiting the McLaren. Colin Chapman employed Tony and Peter to work closely with chief designer Ralph Bellamy to design a new championship winning car. Problems of the Lotus 72 was its understeer. Colin’s main aim was to make a solution to increase the pitch-sensitivity of the car, where more downforce would be generated on the front tyres under braking, improving turn-in.
By late 1975, the overall first configuration of the Lotus 78 was defined — slim nose, front wings, airfoil sidepods to house fuel and water radiators, similar to the Havilland Mosquito aircraft. Peter had previously developed sidepods housing fuel with the March 701.
After more testing in the wind tunnel, Peter spotted something wrong and was unable to obtain consistent balance readings. It became clear very quickly that under load, the sidepods housing fuel and radiators were starting to sag. The sagging of the sidepods incidated that the sidepods were generating downforce. Peter tested the sidepods with wire supprots to stop them from sagging, and reported no downforce readings.
Then, the team experimented with card skirts to seal the gap between the sidepods and the ground. TOTAL DOWNFORCE DOUBLED! The team couldn’t believe it.
To conform with the technical regulations, the T78 was fitted with brush skirts, when first built and shown to the press. In 1976, brush skirts were shown to be inefficient at sealing the floor, to polypropene skirts were tried, with little success as they sucked inward and became distorted.
Lotus — Skirt development
A new entry was in Formula 1, skirt development. To prevent excessive wear of the skirts. they has tbe sucked up by the ground efffect from the car, but not too much. The skirts could be manually activated, with steel shim springs loading them down. PFTE rubbing strips were fitted to the lower edge of the skirts to limit their wear. Later, Peter whilst investigating with ceramics experts realised than tipping the skirts with ceramic increased its durability and allowed, in fact allowed the skirts to be spring loaded harder to the ground. From this point onwards, the Lotus 78 was the car to beat.
After only a few laps, Gunnar Nilsson was 1.5s per lap faster, and said “I go quicker than I ever go before, and I look over the side of the car and there is a meter of track left!” (Wright, 2001)
In the future it looks like ground effect is very much here to stay, given its advantages for closer following of cars. The vision of a racing spectacle that F1 is following certainly seems to aim closing the grid up and creating more competiton, rather than a pure engineering contest. With ground effect, even though it has inherent issues in porpoising, it is in my opinion a great foundational base to encourage new fans and market Formula 1 in the dawn of a new era.
