Williams FW08D
Patrick Head
Two very enjoyable days at the Goodwood Festival of Speed prompted me to think of our six-wheeler, the FW08D, which Jonathan Palmer drove up the hill in 1994, I believe achieving the fastest time in that year.
The thinking behind the car was entirely logical as we worked to keep up with the turbo-powered cars of Renault, Ferrari and the BMW-engined Brabhams, but had no turbo engine ourselves. We did conduct a programme with John Judd of Engine Developments and valve gear specialist Chris Walters, which resulted in our long-stroke 3-litre Cosworths being raised from about 480 to just over 540hp, which powered Keke Rosberg in his 1982 title year. But this power level was a long way shy of the turbo.
A parallel approach was to reduce the car's frontal area, dominated by two huge rear tyres on 20in-wide rims, so we settled on using four smaller fronts on the rear, hiding one behind the other to reduce drag. This in turn meant we could bring the inner face of the rear tyres a long way outboard and run flexible skirts all the way to the back of the car, between the rear wheels, which gave us huge expansion at the back and increased downforce.
We produced a 'mule' vehicle to see if it would go round corners and if we could get it balanced. We'd tried to design it so that the exact centre of the two rear axles was where our normal single axle would be ***8211; which in turn meant that the forward axle had to be angled well forward from the output.
We took it to Croix-en-Ternois in northern France, with Jacques Laffite and Palmer driving, and discovered that it had no problems in tight corners and extremely good traction, particularly in the wet. But it was at least 100 kilos overweight and we knew we'd have to build a new gearbox and design a new rear suspension layout, which would have been a major task.
We did know that it had huge potential, running near-identical times to a conventional car despite being over the weight limit.
Alan Jones had initially run the car, on the back of an FW07 chassis, at Donington at the end of 1981 ***8211; and perhaps that's why he decided to retire on the spot***8230;. Or, more likely, it was the English winters that prompted the decision! You may recall that in 1982 FW08 was a short and stubby car with a high fuel tank behind the driver, and that's because it was designed to be the front end of the six-wheeler.
Frank Dernie was developing the car in our wind tunnel and had a specification well in advance of the mule test car. He ran the figures, downforce, drag etc in our simulation programme using the Paul Ricard circuit and the car was something like 12sec faster than the conventional car. Mind you, he didn't add the 100 kilos of extra weight, he said that was my problem, so it was optimistic.
I think it would have been possible with a complete redesign to get to the weight limit but we just didn't have the resources. So you could say it was lucky for us that we never had to build a new car following the ban on six-wheelers and ground-effect aerodynamics.
FW08/1 was converted to 6 wheel form in Autumn 1982 using fixed length drive shafts as lower location members (a la Lotus 18, except 'upside down') to clean the airflow through the under-wing tunnels. It showed phenomenal straight line speed and 30% more downforce than the 4-wheeler. In fact the Williams lap simulator predicted a lap round Paul Ricard 6 seconds quicker than Arnoux's pole time of 1:34.4!
Unlike March, Williams had the engineering resources to develop the FW08D properly. The additional weight involved with the extra parts needed was not a huge handicap as their usual cars without ballast were significantly below the minimum weight limit. The same advantages of extra traction, better airflow to the rear wing, less drag over smaller rear-wheels, less lift from those wheels, and being able to use what would normally be front tyres with their continued development all applied as (at least in theory) for the 2-4-0. The hugely significant difference was that this was the era of full ground effects. There were no flat bottoms with diffusers at the rear doing the best they could to pull air from under the car. As much as possible, the whole underside of the car acted as a gigantic diffuser with skirts along the bottom outer edges of the sidepods to contain the low pressure under the floor with the main body of the chassis effectively being a huge wing.
The skirts were only allowed to run back to the rear axle so the six-wheeler enabled greater exploitation in this aspect, as well as the skirts not having to awkwardly deviate inside the conventional rear wheels with the new arrangement giving wider airflow out the back of the car. The main and acceptable disadvantages seemed to be an increase in mechanical complexity and higher friction losses in the transmission to four wheels.
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