Tatra T77A Limousine
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Car producer : |
Tatra |
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Model: |
T77A Limousine |
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Year: |
1935-1938 |
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Type: |
Sedan |
The Czechoslovakian Tatra 77 (T77) 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 (45 kW) rear-mounted 2.97-litre air-cooled V8 engine, in later series increased to a 75 horsepower (56 kW) 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 (93 mph) 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.
The T77/77A cars were quite probably the last production use of the "walking-beam" valve train principle, their dry-sump air/oil-cooled V8 engines having overhead valves in hemispherical heads, but no pushrods. Instead the valves are opened by enormous drilled rockers operated by a single high camshaft between the two cylinder banks, and pivoted inboard of their centres to extend the lift applied by the cams. The principle had been used much earlier in the Deusenberg 16-valve straight-4 low-twin-cam racing engine, later adopted by Rochester for use in passenger cars, but Tatra's use of a single camshaft to open the valves of a V8, rather than two low shafts on a straight engine, must be unique. A consequence is that the mechanical layout is much less obvious to the observer, with the big box-shaped engine giving few immediate clues to its V configuration, unlike its T87 successor. Belt-driven squirrel fans in cast alloy ducting draw air forward, up and around the four shrouded pairs of finned iron cylinders, and a large hinged alloy cover maintains a warm environment for the carburettor in winter.
Hans Ledwinka was the chief designer responsible for the development of the new car, while Erich Übelacker was responsible for the body. Development was very secretive until the last moments of the official presentation on March 5, 1934 at Tatra's offices in Prague. The car was demonstrated on the road from Prague to Karlovy Vary, where it easily reached 145 kilometres per hour (90 mph), and amazed journalists with its great handling and comfortable ride at speeds of about 100 kilometres per hour (60 mph). That same year the T77 was presented at the Paris motor show, where it became the centre of attention due not only to its atypical design but also to its performance. There were even demonstration rides after doubt was cast on the ability of the car to reach 140 kilometres per hour (87 mph) with a mere 45 kilowatts (60 hp) of engine power: normally at that time twice the power was required for a car to reach such a speed.
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.
The Tatra 77 was a hand-built car with a leather interior. Some cars had a glass partition between the front and rear seats. A sliding roof was available.
An unusual feature on a few of the T77 models was a central position for the steering wheel in the dashboard. The front-seat passengers were seated on either side of the driver and the seats placed slightly rearwards as in the modern-day McLaren F1. All other T77's had the steering wheel on the right-hand side as Czechoslovakia (like a number of other European countries) drove on the left before the Second World War.
