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English   Alternative drive systems in Buses of Daimler AG – Part I
23.12.2008 von admin

Wheel hub motors for hybrid and trolley operation

At the same time, Ferdinand Porsche, then employed at Hof-Wagen- and Automobilfabrik Jacob Lohner in Vienna, invented the wheel hub motor. When the young engineer went to Austro-Daimler in 1905, DMG seized upon the patent and produced the electric motors, which were fitted into the front wheels, in large numbers so that the system soon simply was called “Mercedes Electrique” or “Elektro-Daimler”.

At Austro-Daimler, Porsche also sought to bring his invention together with the core competence of the gasoline engine manufacturer by replacing the heavy lead storage batteries of the electric vehicle by a gasoline engine and generator which produced the electricity for the wheel hub motors: the hybrid drive, called Daimler-Mixte, was born. The bigger range compared with the storage battery, but above all the vehicles’ problem-free, permanent readiness for use, made the Mixte drive system an attractive solution for fire departments which until then had turned out to the scene of a fire at worst with horse and cart and bicycles, at best with electric and steam-powered automobiles. The big professional fire departments in Berlin and Hamburg soon put Mixte vehicles into service. Of course, the twin drive was a little more expensive for the customer than pure electric or gasoline drive.

Rapid start: In 1908, the Berlin fire brigade opted for the Mercedes Electrique with electric drive and purchased a fleet consisting of four vehicles. The wheel hub motors in the front wheels are clearly visible.

O 6000 and O 10000: Trolleybuses of the 1930s

Trolleybus operation was discontinued during the First World War, and after the war there were no funds for new investment at first. Daimler-Benz first presented a trolleybus again in 1936 at the International Automobile and Motorcycle Show (IAMA) in Berlin. Since 1930 trolleybuses had begun to see service again in Germany, but the concept really owed its renewed breakthrough to the policy of the National Socialists, who wanted to make themselves independent of imported oil.

The 9.375 meter long 32-seater, developed jointly by Daimler-Benz and Brown, Boveri & Cie. (BBC), appeared astonishingly up-to-date: It was a square-faced, all-steel, cab-over-engine vehicle built on a low-frame chassis with a floor level of 70 centimeters above the ground and with wide, double folding doors at the front and in the middle. The engine output was 73.5 horsepower; the top speed was 40 km/h. But what made it special was that the contact-wire bus, as it was called then, needed no gearshift.

“We’ve trodden completely new paths with the electric controls. Starting from the realization that the driver of such a vehicle must direct all his attention to the road, the REGULATION of the motor has been AUTOMATED, i.e., the usual gradual flooring of, or repeated stepping on, the accelerator was eliminated. In this new design the ACCELERATOR ONLY HAS TO BE STEPPED ON ONCE to start off and accelerate; the further shifting of the drum of the drum starter from step to step is performed automatically by a rotary magnet. The rate of progress depends on the supply of power from the motor: the speed adapts to the topographic conditions and is slower on gradients than in the flat. This avoids excessive OVERLOADING of the motor.”

In 1937 the company then launched a complete series of trolleybuses starting with the O 4000 for 39 passengers. However, of the four models, which now came in rounder shapes, only two were ever produced, the O 6000 and the O 10 000. All in all, though, no more than 26 units were produced, as an internal investigation found in 1952. Actually, another 264 orders were received through 1942, but a decision by the Nazi rulers to take trolleybus production out of the war program brought the further completion of these orders to a halt on March 12, 1943.

Mercedes-Benz trolley bus for 33 people with 70 hp electric motor, 1930-1931.

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