page_title: Tatra 77
section_title: Tatra 77a
hierarchical_section_title: Tatra 77 / Design / Tatra 77a
caption_attribution_description: Photographed at the Nationaal Oldtimer Festival Zandvoort 2009, The Netherlands. OLYMPUS DIGITAL CAMERA
context_page_description: The Czechoslovakian Tatra 77 is by many considered to be the first serial-produced, truly aerodynamically-designed automobile. It was developed by Hans Ledwinka and Paul Jaray, the Zeppelin aerodynamic engineer. Launched in 1934, the Tatra 77 is a coach-built automobile, constructed on a platform chassis with a pressed box-section steel backbone rather than Tatra's trademark tubular chassis, and is powered by a 60 horsepower rear-mounted 2.97-litre air-cooled V8 engine, in later series increased to a 75 horsepower 3.4-litre engine. It possessed advanced engineering features, such as overhead valves, hemispherical combustion chambers, a dry sump, fully independent suspension, rear swing axles and extensive use of lightweight magnesium alloy for the engine, transmission, suspension and body. The average drag coefficient of a 1:5 model of Tatra 77 was recorded as 0.2455. The later model T77a has a top speed of over 150 km/h due to its advanced aerodynamic design which delivers an exceptionally low drag coefficient of 0.212, although some sources claim that this is the coefficient of a 1:5 scale model, not of the car itself.
context_section_description: In 1935 the T77 was updated and improved, which resulted in the T77a. The capacity of the V8 was increased to 3.4 L (207 cubic inches). This was achieved by enlarging the bore diameter from 75 to 80 mm (3.0 to 3.1 inches). The new motor increased output to 75 hp (56 kW) and maximum speed to 150 km/h (93 mph). The front now had three headlamps of which the central unit was not, as has been suggested, linked to the steering on some models. The central headlight never moved with the front wheels, but had an electro-magnetic system enabling the reflector to move to illuminate the kerbs, as street illumination was poor at the time. Some T77s and T77a models were also equipped with canvas Webasto roofs. The smooth body of the T77a gave a coefficient of aerodynamic drag of 0.212.  This is an incredibly low value even for today's cars: only a few modern prototypes are able to achieve this figure.  Some sources, though, claim that this figure was based on a 1:5 scale-model test.
caption: Tatra 77a at the Circuit Park Zandvoort in the Netherlands
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