Otto Martin Maschinenbau S
1 model in this series
Otto Martin Maschinenbau S 11 (1949-1950): single-cylinder diesel tractor with evaporative cooling, 8.1 kW output and a top speed of 15 km/h from the S series
The S 11 was built in the first post-war years of 1949 and 1950 as a small farm tractor of the S series and, like many models from these early post-war years, belongs to the group of simple single-cylinder diesels aimed at smaller agricultural holdings.
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The single-cylinder diesel engine displaces 1,099 cm³ and delivers 8.1 kW, equivalent to 11 horsepower. Cooling is evaporative, relying on the boiling-off of water rather than a pressurised circuit with a pump. With a weight of 1,270 kg, a wheelbase of 1,630 mm and a top speed of 15 km/h, the S 11 was a typical small tractor for fieldwork on smaller plots.
Evaporative cooling was a common solution for small German diesel tractors in the 1940s and early 1950s, doing without a radiator, pump and thermostat: the coolant heats up during operation and partly boils off, so it must be topped up regularly. This design lowered production costs but required close monitoring of the water level.
When buying a used S 11, the condition of the evaporative cooling system is decisive: if the original coolant tank is missing or leaking, the engine overheats quickly. The single-cylinder injection pump should also be checked, since spare parts for this little-known maker are only available to a limited extent. Anyone restoring one should expect to have worn parts remade individually rather than ordered from stock.
Sources: SpecCodex-Register: Kennwerte des Modells S 11
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Tractor in 3D section
Turn the model, look inside and click an assembly — each one is explained.
