The products of the Czechoslovak motor vehicle industry have always enjoyed an excellent international reputation. Advanced construction, solid workmanship and economy are still the outstanding features of these vehicles today.
In the years around 1920, the professional world took notice when the Tatra-Werke brought their unforgettable 1.1 litre Tatra small car onto the market (Fig. 1). This car, developed by Hans Ledwinka, introduced a wealth of ground-breaking innovations, the basic principles of which are still used in Tatra today. It was equipped with an air-cooled 1.1 litre two-cylinder four-stroke boxer engine of 12 hp and reached a speed of 70 km / h. Even then, the chassis had a central tubular frame and swing axles, and for the first time in vehicle construction, the engine was located above the front axle so that the space between the axles was available as a passenger compartment.
Since that time, the Tatra cars have had a special position in the world’s automotive engineering, which was reinforced by the iconic V-8 rear-engined car.
The latest creation of the state-owned Tatra works is the Tatraplan (Fig. 2 and 3), which has already proven itself a thousand times over the world. Although its trial period has long been concluded, this car is being further developed and continuously improved on a strictly scientific basis.
In terms of construction, the Tatraplan follows the development principals of the Tatra eight-cylinder car, with great emphasis on weight reduction, the best possible weight distribution on both axles, as large an interior space as possible, attractive external shape and the greatest possible economy.
An air-cooled, counter-rotating four-cylinder boxer engine of flat design serves as the drive source (Fig. 4). In the two-part light metal crankcase, the well-balanced crankshaft is mounted in four sets of plain bearings. The connecting rods also run in plain bearings on the crank pin; the fully floating piston pins are mounted in bronze bushings in the connecting rod eyes. The light metal pistons are provided with three rings each. The cylinder bore is 85 mm, the stroke 86 mm, resulting in a total displacement of 1950 cm3. The maximum engine output is given as 52 HP at 4000 rpm, the continuous output with 48 HP at 3500 rpm. The compression ratio is 1: 6, the mean working pressure at n = 4000 rpm 6 kg/cm2.
The hemispherical shape of the combustion chamber is achieved by inclining the hanging valves. The valves are controlled by the camshaft mounted in the crankcase under the crankshaft via tappets, push rods and rocker arms. The mean piston speed of the short-stroke engine reaches 10 m/s at 3500 rpm. The weight with oil filling is 145 kg, which results in the remarkably low engine power-to-weight ratio of 2.8 kg/HP with a litre output of 26.5 HP/1.
The engine has an amazing power reserve and elasticity, runs very smoothly and is characterized by high stability and an above-average service life. The cylinders as well as the light metal cylinder heads are provided with large cooling fins and are cooled in a tried and tested manner by fans. The large air fan with axially profiled blades sits on the alternator shaft, which is driven by V-belts from the crankshaft.
The gear oil pump is driven by the rear end of the camshaft and is easily accessible without dismantling the engine. To clean the oil, there is a fine-meshed pump screen and a gap filter connected to the clutch pedal. The filter is arranged in the main oil flow and embedded in the heavily ribbed lower part of the crankcase. In the front of the car there is an oil cooler that is sufficiently dimensioned for even the toughest operating conditions.
A safety valve for the oil cooler is located next to the reduction valve that regulates the oil pressure at the rear left end of the crankcase. The green oil control lamp on the dashboard is switched off by a membrane switch as soon as the oil circuit is interrupted.
Two Solex 32 UBIP downdraft carburetors with progressive starting device and acceleration pump achieve a high degree of cylinder filling, good acceleration and a clean transition via very short suction lines. Large wet filters with suction noise reduction are used as air filters.
The voltage-regulating alternator feeds the 12 V ignition system via a 75 Ah battery. The battery is easily accessible under the front hood. The distributor is driven by screw gears from the rear end of the crankshaft and is easily accessible, just like the ignition coil. The ignition sequence is 1-4-3-2, the first cylinder being the one on the right-hand side in the direction of travel. A heat value of 17 5 (electrode gap 0.4) is prescribed for the spark plugs.
The engine, clutch, gearbox and differential with the rear axle are combined to form a drive set and mounted in silent blocks in the rear of the car (Fig. 5). The engine power is transferred to the four-speed gearbox through a single-disc dry clutch. With 3.55-2.26-1.44-0.96, reverse gear 4.73, the gear reductions are very favorably matched to the engine power and vehicle weight, so that you do not have to shift as often. This also applies to city trips, where the car is primarily driven in 3rd gear. The 2nd, 3rd and 4th gear are synchronized. The shift lever is on the steering column (Fig. 6). The steering wheel shift is so easy and is executed so perfectly in its mode of action that the desire for an automatic gearbox with its greater manufacturing effort does not arise.
The differential is equipped with a Gleason toothed ring gear. The rear axle reduction is normally 4.09. In addition, the car can also be supplied with a mountain reduction ratio of 4.4. The rear axle is designed as a pendulum axle and is cushioned by torsion bars in conjunction with telescopic dampers that are transverse to the vehicle's longitudinal axis. The combination of all engine parts not only resulted in a very favorable spatial design, but repair work is also made much easier because the entire drive train with drive wheels can be easily removed as a unit after loosening a few screws (Fig. 7).
The rack-and-pinion-steered front wheels are suspended from two semi-elliptical transverse springs without axles (Fig. 8), with telescopic shock absorbers also being provided. The rim size is E 4.00 X 16 and the tires 6.00-16. The oil pressure brake system has a total braking area of 1000 cm 2, which should correspond to the speed of the car. The lever of the mechanical handbrake acting on the rear wheels can be found on the left under the dashboard, so that the front footwell is free for both sides to get in and out.
The 56 litre fuel tank (of which 11 litre is in reserve), as well as the oil tank for the central lubrication system are located under the front hood, where the spare wheels are also housed.
The self-supporting all-steel pontoon body is welded to a central beam (Fig. 9) and forms a solid, closed body. The outer shape is largely streamlined. The floor of the car is also completely covered, the handles and hinges of the four doors, headlights, etc. are embedded and the rear wheels are covered with removable side panels. The body looks extremely sleek and elegant thanks to its simple, purposeful design, without excessive use of chrome (Fig. 2 and 3).
The interior, which can comfortably accommodate five people, is tastefully and solidly furnished. Mention should be made of the constructive solution of the interior heating. The air heated at the exhaust pipe is directed into the space formed by the double floor and can flow into the interior of the car from here, regulated by sliding locks. An air duct, which is located under the front hood and ends in two slots under the windshield, enables draft-free ventilation even when the windows are closed. The view is good on all sides; The two-part rear window is advantageous.
The car has luggage compartments totaling around 0.28 m3, which are located behind the rear seat back and under the front hood. The weight of the ready-to-drive car is 1200 kg, its power to weight ratio is 23 kg/hp. The speed is based on this favorable value, as is the high acceleration and mountaineering ability.
The Tatraplan can safely be extended up to its maximum speed, which is 130 km / h, because it has remarkably good road holding. Thanks to the good insulation of the engine compartment, neither noise, heat or fumes are transferred from the engine to the passenger compartment, even when driving at high speed. The driving range in the individual gearings is:
First gear - 34 kph
Second gear – 55kph
Third gear – 85kph
Fourth gear - 130kph
The streamlined shape, which greatly reduces air resistance, makes a significant contribution to achieving the consumption value of 111/100 km, which is favorable even at high speeds.
In summary, it can be stated that the Tatraplan is a fast, efficient and economical utility vehicle and confirms the truth of the slogan with which the Tatra-Werke overwrite their advertising brochures: "Tatraplan, the car of tomorrow is here today!"
KA 689
Original in German - https://tatrat600.blogspot.com/2020/11/kraftfahrzeug-1952-issue-5-tatraplan.html
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