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HINDSIGHT – MERCEDES-BENZ TYPE 80


Porsche recognised the inherent suitability of the 300-degree, DB600 series V12 engine, which was narrower at the top than the bottom, so suited a streamliner shape perfectly


Bf110 twin-engined heavy fighter and was designed from the outset to be able to fly inverted. So the crank is at the top and the cylinders project beneath it. This put the narrowest part of the engine at the top where it fitted neatly behind the profile of the driver, while the wider part with the cylinder heads and manifolds was buried out of the airstream between the chassis rails. This allowed the car to


have a low upper deck, only broken by fairings for the driver, engine and wheels. Add to this a remarkably narrow track of just 4ft 3in (1295mm), which the Allied report noted was a full 6in (150mm) narrower than the company’s 1939 grand prix car. Together with the use of just one engine, these measures significantly reduced the overall frontal area, compared to the equivalent English cars, to around 18-20sq.ft. Its drag coefficient was claimed to be just 0.18.


AERODYNAMICS To execute the all-important aerodynamics, Porsche shrewdly brought in specialist, Josef Mikcl. One danger was the combination of the front-mounted cockpit canopy and the large fairings forced by the 32in wheels, which raised the possibility of the centre of pressure being too far forward, particularly with


driven wheels. Power from the engine was transmitted via an hydraulic torque convertor to a single-speed final drive. As the drag on the car at slower speeds would be very small compared with the power of the engine, lower gears were redundant.


Using his experience with the all-conquering Auto Union grand prix cars, Porsche sat the driver up front, minimising frontal area as far as possible


the largest single mass in the car – the engine – being toward the rear. Porsche’s solution was to extend the rear wheel fairings a long way behind the rear axles, turning them into stabilising fins. This created a very long car,


of aerofoil-profiled wings at an angle of incidence of -5 degrees. This was not a first, as Fritz


von Opel’s rocket car, RAK 2, had used wings to aid stability a decade earlier. However, as it was thrust driven, traction was


“The final masterstroke… was the car’s ‘anti-spin control’”


at 26ft 8in, almost double the length of its 14ft wheelbase. Not content with reducing the demand on the car’s traction, Mikcl went one step further, incorporating his own patented devices. Either side of the car, amidships, he mounted a pair


34 www.racecar-engineering.com • January 2012


not an issue. On the Type 80, at more than 300mph, they would certainly have helped cancel lift, if not make a net contribution to the load on the driven wheels. The next step was to feed the


power through twin rear axles, doubling the contact patch of the


SKID CONTROL The final masterstroke, which shows most clearly how Porsche was thinking, was the car’s ‘anti- spin control’. Two flexible drives, like speedometer cables, were taken from the wheels, one from the front and one from the rear. They were then fed into either end of a miniature mechanical differential unit, much like a final drive. Because they turned in opposite directions, under normal circumstances their motions cancelled each other out. However, if the rear wheels broke traction and started to turn faster than the fronts, the unit’s outer cage started to turn. This motion acted on the engine’s injector unit, rolling off the power. It was a simple mechanical manifestation of a system that is now commonplace in most road and some racecars, thanks to digital management systems. However, it was ground breaking in 1935 and could have been invaluable to help accelerate a very powerful car within a limited distance on a potentially low-grip surface.


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