Praga S5T: the road-going five-tonner from the V3S

The Praga S5T (silniční pětituna, “road five-tonner”, colloquially espětka) was a medium-weight road truck built on the basis of the off-road Praga V3S, from which it took the drivetrain, a modified frame and the cab. Unlike the V3S it had two axles and rear-wheel drive, and it was produced from 1956 to 1972.

Praga S5T at a glance

Written from the Czech and German Wikipedia articles only, as there is no English page for the S5T.

History of the Praga S5T

After the Second World War Praga carried on building its pre-war RN and RND trucks, and from the late 1940s it developed a new range of two- to five-tonne trucks designated N2T to N5T, due to enter production in 1952. A reorganisation of the Czechoslovak motor industry and the start of the Cold War stopped that plan, and priority went to the off-road truck for the army, the Praga V3S. The V3S, however, was uneconomical in ordinary civilian use, so a road truck of five tonnes was developed alongside it, taking its drivetrain, modified cab and many parts from the V3S to speed up the work. A prototype with a bonnet in the V3S style appeared in 1955, pre-series vehicles in 1956 and series production in 1957.

The S5T-1 kept the T 912 engine of 72 kW (98 hp), the clutch and the main gearbox of the V3S, adding a two-speed auxiliary gearbox with electro-pneumatic selection. It had a single driven rear axle with dual tyres, and the wheel reduction hubs were partly replaced by a double reduction in the final drive; the new, simpler front axle had no drive. The frame was a flexible ladder frame of its own dimensions, the cab from the V3S gained better sound insulation but lost its opening front windows and roof hatch, and the truck received a larger bonnet and grille with an S5T badge. Production of this version ended in 1962 after 9,330 vehicles.

The S5T-2 of 1962 brought the T 912-2 engine developed by Tatra, raised to 81 kW (110 hp) by higher engine speed and new injectors, with improved lubrication, new pistons and a better air cleaner. The gearbox was made quieter and easier to shift, the frame and axles were strengthened and the tyres uprated, so that a 20 per cent overload, up to six tonnes, could be tolerated. The handbrake gained a servo, the exhaust brake an air-operated flap, and the cab four-point mounting with a telescopic driver’s seat adjustable in height and reach. The S5T-3 of 1966 had a further enlarged engine. Beside flatbeds and three-way tippers a great number of municipal, refuse, box and mobile-shop bodies were mounted, and there were long-wheelbase and long-cab versions; the S5T-TN tractor units used a Škoda 706 RT cab. Production moved to Avia Letňany in 1961 and ended in early 1972 to free capacity for the Avia A15 and A30, by which time more than 50,000 S5T trucks of all types had been built.

Design and features

• V3S underneath: the air-cooled Tatra diesel, gearbox and cab came from the off-road truck.
• Lighter and cheaper to run: two axles instead of three cut weight and fuel consumption to about 20 l/100 km.
• Endless bodies: flatbed, tipper, municipal, refuse, box and mobile shop, plus long-wheelbase and long-cab versions.
• Tractor units: the S5T-TN with a Škoda 706 RT cab.

Praga S5T versions

• S5T-1 (1956–1962): T 912 engine of 72 kW, 9,330 built.
• S5T-2 (1962–1966): T 912-2 of 81 kW, strengthened frame and axles.
• S5T-3 (1966–1972): further enlarged engine.
• S5T-TN: semi-trailer tractor on a modified chassis, later S5T-2-TN and S5T-3-TN.
• Long chassis and long cab: five-seat, three-door cab version.
• Special bodies: municipal, refuse, box and mobile-shop bodies on the standard chassis.

The S5T was derived from the Praga V3S and replaced the road-going Praga RN. More vehicles are in the Praga collection.

Video: Praga S5T cold start

Video on YouTube.

Sources

• Praga S5T, Czech Wikipedia: history, versions, bodies, production
• Praga S5T, German Wikipedia: engine, top speed, fuel consumption, production years