1934 Tatra T77

Nesseldorfer Waggonfabrik, of Koprivnice, Czechoslovakia, was founded in 1897 and re-named in 1927 after the prominent mountain range on the Slovak-Poland border. Austrian-born designer Hans Ledwinka, who was with Tatra's predecessor company, engineered a torsionally rigid backbone chassis with swing-axle suspension and a front-mounted, twin-cylinder air-cooled engine for the Tatra T11, introduced in 1923. The Tatra T12 that followed continued to employ these mechanical components, while the T17 of 1926 added fully independent suspension and a water-cooled six. Through the 1930s, a series of models that used air-cooled four-cylinder power and aerodynamic design principles became paramount. Assisted by the Czech engineer Erich Übelacker, Ledwinka investigated the aerodynamic principles of Paul Jaray, who had designed airships for Luftschiffbau Zeppelin. The Tatra T77, introduced in 1934, was the result of these studies and has been called the world's first serially produced, aerodynamically designed automobile.

The Tatra T77

The Tatra 77 (T77) was a six-seat luxury automobile powered by a rear-mounted, three-liter air-cooled V8 engine and was capable of 87 mph. Its logical successor, the T87, was introduced in 1936 and improved upon the T77 with a drag coefficient of 0.36, better fuel economy, a top speed of 150 km/h, and improved handling.

Production of the Tatra T77 lasted from 1934 to 1935 and the T77a from 1935 to 1938, with total production being 249 units. Of those, 106 examples were the T77, including the pre-production chassis. These hand-built automobiles had a leather interior, with a few receiving a glass partition between the front and rear seats. A sliding canvas Webasto roof was available.

Although most famous on the modern-day McLaren F1, the Tatra T77 used a central position for the steering wheel in the dashboard. The driver was seated in the center, slightly ahead of the passenger seats on either side.

Mechanical Specification

Shedding the company's traditional tubular chassis, the Tatra 77 used a platform chassis with a pressed box-section steel backbone. The front of the car was a rectangular cross-section that was rounded to the floor. It had a 124-inch wheelbase, an overall length of 196.9 inches (as long as 204.7 inches), a width of 65 inches, and stood 55.9 inches tall (as tall as 59.1 inches). The suspension was fully independent with twin transverse leaf springs and rear swing axles. Four-wheel hydraulic drum brakes provided the stopping power.

The 2.97-liter air-cooled V8 engine was mounted in the back, directly above the driven axle. This placement allowed for a small frontal area with a lower hood line. This allowed for a flat floor and eliminated the need for a floor tunnel with a drive shaft and exhaust pipes, reducing the overall weight of the vehicle even further. The engine had overhead valves, dry sump lubrication, and hemispherical combustion chambers (overhead valves in hemispherical heads but no pushrods). The valves opened via drilled rockers operated by a single high camshaft between the two cylinder banks' heads. As they pivoted inboard of their centers, it extended the lift applied by the cams. This engine was one of the last production unit to use this 'walking-beam' valvetrain principle. Initially, it developed 60 horsepower, later increasing to 75 horsepower.

Air was directed to the engine via rectangular ventilation inlets behind the side windows. Belt-driven squirrel fans drew air forward, up and around the finned iron cylinders. Vents in the rear bodywork allowed hot air to exit.

Much of the suspension, engine, and body was formed from lightweight magnesium alloy. The crankcase and gearbox were formed from Elektron, a magnesium alloy. The four-speed manual transmission was placed ahead of the engine and rear axle. The battery, spare wheels, and oiler cooler were positioned in the front of the car. With most of the mechanical components (and weight) in the rear, the T77 suffered from handling issues. Ledwinka would work to resolve this problem, which he did with the Tatra 87 that was introduced in 1936.

Aerodynmaic Design

The curvaceous body had a low drag coefficient of 0.2455, while the T77a reduced that further to 0.212. Tatra designers preferred a shape that minimized air drag, with the design crafted through the use of a wind tunnel (a 1:5 scale model of the T77 was tested in a wind tunnel in period). With a more efficient shape, a less powerful engine was needed to reach the speeds and match the performance of more traditional 'square' designs with larger and more powerful engines.

The front bumper covered the rounded fenders, the lower portion of the lights was embedded into the bonnet, and the door handles were embedded into the door panels. Only the door hinges protruded slightly. Fender skirts covered the rear wheels.

The first prototype had a split windscreen, while most of the other prototypes had a single-piece windowscreen. At least one prototype experimented with reducing drag principles through its three-piece windscreen. The large centerpiece of glass was flanked on either side by two smaller pieces which were angled rearward and integrated into the sides of the body. This was the most common configuration for the production T77s.

In the back was a continuously sloping form devoid of a rear window, limiting rear visibility. Only slits in the sheet metal allowed for limited rearward viewing. The rear fin went beyond mere decoration, as it was intended to increase lateral stability under high speeds. Later Tatra T77 examples had a widened rear portion of the body, with the rear fenders and door hinges now embedded into the bodywork. Transverse inlets now funneled air to the engine compartment.

The streamlined Tatra T77 and T77a were futuristic, bold, and revolutionary. It had a low-to-the-ground appearance with a shape that favored a reduction in drag, maximum efficiency, and high-speed performance.

The Tatra T77a

The Tatra T77a was introduced in 1935 and was equipped with a larger, 3.4-liter (207 cubic-inch) V8 engine which had its bore increased from 75 to 80 mm. Producing 75 horsepower, the top speed increased from 145 km/h to 150 km/h. Styling updates were minimal, with the most visual change being the addition of a third headlight. This central headlight did not move with the front wheels, but it did use an electromagnetic system enabling the reflector to move to illuminate the curb.

The Tatra T77 would inspire future design, most prominently being the German People's car (the Volkswagen Beetle), but unlike the 'bug,' it was a luxurious, hand-built automobile built in limited quantities.

by Daniel Vaughan | Apr 2023