sexta-feira, 21 de julho de 2017

1937-1977, 40 years later or the evolution of a concept


1937-1977, 40 anos de evolução de um conceito, 40 anos depois.

Em 1937, Ferdinand Porsche e a Auto Union, pegaram no Typ C de Grande Prémio e fizeram um streamliner para bater um recorde de velocidade. O carro, avançava com um conceito que só foi compreendido por quase todos quando em 1977 apareceu o Lotus 78, que fundamentalmente associava outros dois conceitos: o de Peter Wright no 1º carro asa, o March 701, combinado com o efeito de solo apresentado no Chaparral 2J, ambos no mesmo ano de 1970.
No March 701, os tanques de combustível nos flancos tinham a forma de asa invertida, com o propósito de criar maior força descendente com a deslocação. A ideia era boa, mas teve resultado nulo. Faltavam-lhe tão simplesmente umas placas verticais que canalizassem o fluxo da deslocação do ar, por forma a produzir o efeito aerodinâmico desejado. Repare-se que até na indústria aeronáutica, apenas nos anos 80 se começou a aplicar umas pequenas caudas verticais nas extremidades da asa, "winglets", apesar de ser uma solução aerodinâmica do final do sec XIX. Porque tal ordena o fluxo de ar, diminuindo o turbilhão posterior e o esforço de arrasto, aumentando de 5 a 10% o rendimento energético, ou seja, o mesmo avião que voava 1000 Km, passa a poder voar 1100 Km com a mesma energia. Hoje em dia, essas placas verticais (difusores) são tão importantes nos carros de competição e são tantas, que tornam o aspecto de qualquer carro num peixe-dragão.
No Chaparral 2J, aplicou-se um efeito de sucção por produção mecânica, força bruta sem grandes preocupações aerodinâmicas. Graças a umas placas de policarbonato (hoje muito conhecidas em coberturas transparentes) e à Lexan que as produzia, que as deu a conhecer ao mundo (de tal forma que Lexan significa policarbonato) e que apoiou a Chaparral, encontrou-se o modo de canalizar eficazmente esse fluxo de sucção, com umas placas verticais limitadoras, aquilo a que vulgarmente se chamou de saias.
Peter Wright estava na Lotus em 1977. Juntaram-se os dois conceitos, o do carro-asa e o dos limitadores verticais com Lexan, sobre um Lotus 77 e nasceu o Lotus 78. Neste, o efeito de sucção era criado com o avanço do carro, um fluxo dinâmico provocado pelo vácuo em formação no maior volume aberto na traseira, que puxava o ar necessário a ser ocupado nesse espaço, pela única entrada possível: o estreito espaço à frente, entre o carro e o solo, limitado pelos flancos fechados. No ano seguinte, a Lotus foi mais longe, introduzindo esse conceito até ao limite posterior, com um cone "Venturi" de cada lado da caixa da velocidades, técnica que é utilizada até hoje em todos os automóveis de competição. No Auto Union de recordes de 1937, porém, toda a superfície inferior formava um único canal terminando num único cone
Alguns anos depois, as saias de Lexan foram proibidas após uma série de terríveis acidentes provocados por súbitas alterações do efeito de solo. Bastava um ressalto ou até uma rajada de vento para súbita e dramaticamente se perder o fluxo de sucção inferior e consecutivamente a aderência, atirando os carros para qualquer lado. Uma rajada de vento lateral tinha sido, aliás, a razão da morte de Bernd Rosemeyer: seguia a cerca de 430 Km/h, quando o efeito de solo se perdeu subitamente e o atirou para fora da pista.
Os cones posteriores, porém, hão-de continuar até à eternidade.
Se em 1977 se lembraram que o princípio do Venturi e do efeito de solo já tinha sido aplicado num automóvel em 1937? Duvido. Mas se o C Streamliner foi a inspiração, tal foi ocultado. Tal como foi ocultado que o B2 foi inspirado pelos Horten. Mas esta é outra "estória".



In 1937, Ferdinand Porsche and Auto Union made a streamliner for speed record based on the Typ C Grand Prix car. That car had an aerodynamic concept that was only understood 40 years later, when in 1977 Lotus made the Type 78 Formula 1 car. However, the Lotus 78 joined basically two other concepts: the Peter Wright's wing car March 701 combined with the ground effect shown in Chaparral 2J, both on the same year, 1970.
The March 701, the 1st wing car, had its wing profiled fuel tanks on both sides, with the purpose of creating aerodynamic downforce. It was a good idea but the results were weak. It simply needed a vertical panel on both sides to create an inflowing duct. It is an aerodynamic solution as older as the aviation but even in aviation, only since the 80's, the "winglets" or small tails, started to be applied at the end of the wings. Because it redirects the aerodynamic fluxes and it reduces the post vortexes and the drag forces. And it increases the energy efficiency from 5 to 10%. Which means that a plane that used to fly 1000Km could fly 1100km with the same energy if having winglets.
Nowadays, those panels, tails and diffusers are so important and so many on racing cars, that Formulas and sport-prototypes look like strange lionfishes.
The Chaparral 2J had a ground suction system mechanically produced. Brutal force without great aerodynamic attention. Due to polycarbonate sheets and due to Lexan that made them and sponsored Chaparral, a very reliable way to guide that suction flux was produced, limiting it with vertical Lexan panels. Lexan was spread in the world in such a way that Lexan means polycarbonate. Polycarbonate sheets are nowadays well known in clear roofings. Side skirts would be the name adopted later in Formula One for those panels or barriers.
In 1977 Peter Wright was working for Lotus. Lotus joined the two concepts, the Peter Wright's wing car and the vertical side barriers on a Lotus Type 77 and the Lotus 78 was born. The ground suction effect was created by the forward ongoing of the car. The bigger empty volume on the back needing to be filled with air created a vacuum and a dynamic flux. As that volume was closed on its sides, that suction came through the only space available, the narrow space ahead between the car and the ground, increasing its downforce as faster as the car was running. The year next, Lotus went even further with this concept, applying it to the back limits of the new Lotus Type 79 with a Venturi cone on each side of the gearbox. This aerodynamic technique still is in use 'til today on every racing car. However, the 1937 Auto Union record car, had the whole under surface created for a single Venturi cone.
Some years later the side skirts were banned. Some terrible accidents were caused by sudden misses of the ground effect. A bounce or a gust of side wind could dramatically provoke the loss of all the downforce dependent of that ground effect and consequently all the adhesion, throwing the cars anywhere out of control. Besides, a gust of side wind was the reason of Bernd Rosemeyer's death on 1938 January 28th when he was running around 430km/h (267mph) suddenly losing ground effect and thrown out of the track.
However, the rear diffusers (Venturi cones on the back) will remain 'til the eternity.
I doubt if someone in 1977 remembered that the principle of the Venturi and ground effect had already been applied in a car in 1937. But if the Streamliner Typ C was the inspiration, it was hidden. As it was hidden that the B2 airplane was inspired by the Horten. But this is another story.

3 comentários:

asperezas disse...

As many could notice, the Brabham BT46B was not mentioned because it is irrelevant for this this article around the original ideas about the development of a concept. The BT46B brought nothing new, it was nothing else than the F1 version of the Chaparral 2J and ground effect was used in F1 more than 18 months earlier, introduced in Lotus 78 by the end of 1976. Chaparral 2J was outlawed after its only CanAm season of 1970 and the BT46B "fan car" was banned after its only race and victory at Sweden 1978, both considered of having moving aerodynamic devices, the fans.

asperezas disse...

Como muitos poderão ter reparado, o Brabham BT46B "fan car" não foi mencionado. Porque é irrelevante para este artigo em torno das ideias originais para o desenvolvimento de um conceito. O BT46B nada trouxe de novo, não era mais do a versão F1 do Chaparral 2J. Quanto ao Efeito de Solo na F1, ele foi introduzido mais de 18 meses antes no Lotus 78, em finais de 1976.
O Chaparral 2J foi proibido após a sua única época na CanAm 1970 e o BT46B "fan car" foi banido após a sua única corrida e vitória na Suécia em 1978, ambos porque as hélices foram consideradas dispositivos aerodinâmicos móveis.

asperezas disse...

And now, this:
https://www.grandprix247.com/2022/02/05/andretti-never-understood-why-formula-1-went-to-wider-cars-and-wings/
" ... Andretti recalled: “The idea came from my experience with the March 701 from 1970. Its sidepods looked like wings. During a test at Kyalami, we removed them to reduce drag. Suddenly the car became light in front.
“This showed us that the sidepods were obviously producing downforce. We had to run a lot more wings upfront to compensate, but that thwarted our plan because we wanted to save drag.
At the end of the 1976 season, we met at the Lotus factory in Hethel to discuss next year’s car. The engineers [including Colin Chapman] wanted to know what I would like. I told them that as a driver you would like to have downforce without paying a price for it.
They laughed and said: Yes, everyone wants that. Then I told them the story of March’s sidepods. They obviously produced downforce without increasing the frontal area of ​​the car. We then discussed it."
And the rest is history it could be said. From there the iconic ground-effects Lotus; Andretti continued: “We then optimized the diffuser and the ground clearance for this principle. The two channels in the sidepods have been consistently freed to get a clean flow through the whole car." ... "

SO! Peter Wright, who invented those "sidepods" for the March Team and working at Lotus when he developed the ground effect theory is not the father of those ideas, Mario Andretti is!

Duh!

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