CARS & HISTORY: TATRA T77 & T77A (1933-1938)

After completion of the two V570 prototypes in the early 1930s, the Tatra management took the opinion that any new aerodynamic car would only be an additional model. This would mean a very limited production and therefore such a car should be aimed at the top of the automobile market. The Tatra management ordered Ledwinka's design team to stop any further development of the V570 prototype and concentrate on a larger, more luxurious car. The 1933 V570 prototype was used by Tatra engineers as a study model for a new direction in automobile construction and styling. They aimed at keeping up a level with the contemporary progress in the fields of new technology, architecture and the visual arts. The new car should be established on a rear-engined air-cooled layout with an aerodynamically efficient body. These ideas were based on the studies and scientific papers of Dr Paul Jaray who designed and tested streamlined automobiles in the wind-tunnel of the German Zeppelin works in Friedrichshafen. The car required would have to be fast, silent, stable, economical and built to the most rigorous engineering standards and also reflect modern aerodynamic research. Ledwinka was very consistent in his belief that an air-cooled rear-mounted engine would bring with it several big advantages like reducing efficiency loss in the drive shaft and noise and vibration caused by the drive shaft. No drive shaft also ment a more comfortable passenger compartment as there would be no central floor tunnel and the passengers would be able to sit fairly low and well forward of the rear axle. This ment a lower centre of gravity and a more favourable inter-axle weight distribution. Mounting the engine in the rear would mean shortening the front part of the body to make a longer tail possible, which was consistent with the laws of aerodynamics.



<<< Tatra design engineers working on aerodynamic body shapes for the new T77, producing 1:1 drawings and scale models (1933)

The second V570 prototype - with a rear-mounted two-cylinder air-cooled engine and an aerodynamic body shape - was used by Tatra as a study model for the construction of the T77 (1933) >>>


The first prototype of the new aerodynamic Tatra concept was constructed in 1933, named the type T77. This prototype was severly tested by Tatra engineers. Although it was only a pre-production prototype Tatra did print a brochure for this car in 1933 with descriptions, pictures and technical specifications. The car was equipped with a rear-mounted air-cooled 90 degree V8 engine with a cylinder capacity of 2970 cc and a power output of 60 hp @ 3500 rpm. The engine transmitted its power to the driven rear wheels by means of a four-speed gearbox, bolted together with the engine and the axle drive as one big monoblock. This monoblock was enclosed by the forked welded box frame of the chassis, which also housed the gear-change rods, cables and fuel lines. The monoblock could be easily removed from the car for repairs and changing parts. High-speed road testing in Italy had proved that directional stability was improved by re-positioning of the air vents onto the engine cover.

 


<<< Tatra T77 prototype, featuring split windscreen and air louvres behind the rear side windows (1933)

The Tatra management decided to take the T77 into production on a small scale. The cars were almost totally hand-built and aimed at the top of the automobile market with their well equipped interior and leather upholstery.

<<< Original French advertisement for the Tatra T77: La Voiture Élégante (The Elegant Car) (1934)

<<< Original German advertisement for the Tatra T77: Der Wagen der Zukunft (The Car of the Future) (1934)

The world's first serially produced aerodynamic car with a rear-mounted air-cooled engine was introduced to the press on March 5th, 1934, in Prague. The T77 was a real sensation, overtaking the world's motor car industry by several decades. Shortly after its introduction in Prague the T77 was shown at the Berlin Motor Show in 1934 where it was hailed by the motoring press. The T77 was like nothing else available at that time. The body was based on an almost all-steel monocoque construction with timber infill. The wings and headlamps were integrated with the body, running boards were absent, door hinges and handles were sit into the body and the underbody was made as smooth as possible, like the body, avoiding protrusions. The large tailfin running over the rear end of the car was used to decrease the effects of side winds and increase the roadholding, but also had a large contribution to the car's excentric and futuristic image! The five passengers sat between the axles in the most comfortable position, while the luggage, battery and two spare tyres were carried in the front. The main luggage compartment was located on top of the rear suspension, between the rear passengers and the engine. The engine was placed backwards to the rear axle, which gave the 1700 kg heavy car an 'interesting' roadholding.

An interesting feature equipped on a few of the T77 models was the steering wheel in the centre of the dashboard. The front seat passengers where seated on either side of the driver and the seats placed slightly back. This unusual feature was also fitted in the Panhard Dynamic of that time. All other T77's had the steering wheel on the right hand side as they drove on the left-hand side of the road in Czechoslovakia before W.W.II, like in various other European countries.

In it's introduction year, 1934, the T77 was used for the '1000 Czechoslovakian miles' race. It finished in 4th place in the absolute classement.


TATRA T77A

In 1935 the T77 was updated and improved which resulted in the T77a. The capacity of the V8 was increased to 3.4 litres. This was achieved by enlarging the bore diameter from 75 to 80mm. This increased the output to 75hp and the maximum speed to 150kph. The front now had three headlamps of which the central unit was linked to the steering on some models, making it possible to turn this lamp with the steering. Some T77's and T77a's were also equipped with canvas Webasto roofs. The smooth body of the T77a gave a coefficient of aerodynamic drag of 0.212. An incredibly low value even for today's cars as only a few modern prototypes are able to achieve this figure.

A total of 255 cars have been built of the type T77 and it's successor the T77a between 1933 and 1938, including the prototypes. There were plans of the Austrian Stoewer firm to manufacture the T77 under license. After thorough test with the car they were very optimistic but were unfortunately stopped by their financial situation.

Ledwinka was not entirely satisfied with the T77's handling, caused by it's rather heavy rear. He started work on a successor to the T77, which was to be less heavy and with an improved weight distribution. Tatra did just that and in 1936 they introduced the now famous Tatra T87.

The Tatra T77 was the particular favourite of Tatra design engineer Erich Überlacker, who owned and used a T77 himself since 1934. Other famous owners of T77s were Mr. Milos Havel, the proprietor of the film studios in Prague who bought a T77 in 1935, German car designer Mr. Edmund Rumpler, who designed the aerodynamic Rumpler Tropfen-Wagen in 1921, Mr. Edvard Benes, the 1930s minister of Foreign Affairs of Czechoslovakia and later president of Czechoslovakia, who both owned a T77A.


<<< The elegant front view of the T77A, featuring streamlined curves, a three-piece windscreen and three headlights of which the middle one could be turned to the kerb-side (1936)

PRODUCTION FIGURES T77 & T77A

YEAR NUMBER
1934 60
1935 35
Total T77 95
1936 82
1937 60
1938 12
Total T77A 154
TOTAL NUMBER 249

<<< The elegant rear view of the T77A, featuring streamlined curves, a large tailfin and air louvres for the engine cooling (1936) Only a total number of 249 cars were build of the T77 (95) and T77A (154) together. Of these cars only a few remain today. In 2000 an extremely rare completely original and unrestored T77A was dicovered in Russia. The 1938 car was complete with original chassis (chassis number 35719) and bodywork, original leather interior and dashboard instruments and original engine (engine number 201742) >>>>>>

TECHNICAL SPECIFICATIONS


Shortly before the T77A was introduced, the T77 was equipped with a new three-headlight front (1936) >>>




TYPE OF CAR TATRA T77 TATRA T77A
Year of production 1933-1936 1936-1938
Number of cars sold 101 154
Type of engine 90º V8 petrol engine 90º V8 petrol engine
Engine cooling air-cooled air-cooled
Location of engine rear rear
Bore x stroke 75 x 84 mm 80 x 84 mm
Cylinder capacity 2973 cm³ 3380 cm³
Compression ratio 5,3:1 6:1
Maximal revolutions 3500 rpm 3500 rpm
Maximum output 44,1 kW (60HP) 51,4 kW (70 HP)
Valve gear OHC OHC
Valves: IO/EO - 8º after TDC
Valve clearance 0,15 mm 0,2 mm 0,15 mm 0,2 mm
Carburettor dual Zenith 36 DIB dual Zenith 36 DIB
Ignition battery ignition Bosch 12V battery ignition Bosch 12V
Firing order 1, 2, 7, 8, 6, 3, 5, 4 1, 2, 7, 8, 6, 3, 5, 4
Type of clutch Komet Mecano dry one-plate clutch Komet Mecano dry one-plate clutch
Gearbox mechanical 4-speed mechanical 4-speed
Number of gears 4 + Reverse 4 + Reverse
Synchronised gears 3, 4 3, 4
Gear ratio 1st 1:4,14 1:4,14
Gear ratio 2nd  1:2,7 1:2,7
Gear ratio 3rd 1:1,58 1:1,58 <<< Original CzechoSlovakian advertising brochure for the T77A (1936)
Gear ratio 4th 1:1 1:1
Gear ratio reverse - -
Final drive differential 1:3,75 1:3,75
Front axle swinging parrallelogram swinging parrallelogram A couple of T77s featured as futuristic decor in the British science fiction film The Transatlantic Tunnel, in which a daring effort is made to dig a tunnel from England to America (note T77 in film poster!) (1935) >>>
Rear axle swinging axles Tatra swinging axles Tatra
Front suspension 2 transversal leafs 2 transversal leafs
Rear suspension transversal leaf transversal leaf
Rim size: F/R 16"/16" 18"/18"
Tire size: F/R 16x45" (45x18") 45x18"
Petrol consumption 14 - 16l/100km 14 - 16l/100km
Petrol tank volume 75 l (80 l) 80 l (90 l)
Oil consumption 0,3 l/100 km 0,2 - 0,3 l/100 km
Oil tank volume - -
Brakes hydraulic drum brakes all round hydraulic drum brakes all round
Weight of car 1700 kg 1800 kg
Maximum load rating - -
Front track 1300 mm 1300 mm
Rear track 1300 mm 1300 mm
Wheelbase 3150 mm (3250 mm) 3150 mm (3250 mm)
Overall width 1650 mm 1660 mm
Overall length 5000 - 5200 mm 5300 - 5400 mm
Overall heigth 1420 - 1500 mm 1600 mm
Road clearance 220 mm (240 mm) 220 mm
Turning circle diameter 13,8 m 14 m
Maximum speed 150 km/h 150 km/h
Maximum climbing ability - -
Number of seats 4 - 6 5 - 6
Body type limousine limousine

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