by Adrian-Liviu Dorofte

Fire protection under the three-pointed star: The history of Mercedes-Benz fire-fighting vehicles and their predecessors - PART I


Stuttgart, Germany, Jan 01, 2007

The beginnings from 1888 - 1905

Rapid help

Fire brigades have a reputation for providing rapid help in all kinds of emergency. This reputation is not least attributable to the engines and chassis of commercial vehicle manufacturers. The diverse and often extreme challenges encountered in fire fighting, rescue operations and disaster aid place the highest demands not only on those companies which specialize on fire engine superstructures – the right chassis also has to be available for every purpose. Market leader Mercedes-Benz offers a range of matching chassis, which, in its diversity, is second to none. Above all, high speeds call for powerful engines. More often than not, the engine compartments of fire-fighting vehicles contained the most powerful engines that were available at any given point in time.

Things were still quite different one hundred years ago. Steam-powered fire engines – mammoth syringes, you might say – rattled along to a scene of fire on horse-drawn carriages at speeds of three to three-and-a-half kilometers per hour. While the machinery built up steam pressure, water hoses dispensed their wet charge under carbonic acid pressure. Only bicycles reached the scene of fire more quickly than horse-drawn carriages: up to six firefighters worked the pedals of tricycles and quadricycles, to arrive on the scene completely exhausted. Gottlieb Daimler and Karl Benz were among the first to look for new solutions in this field. The undisputed advantages of their vehicles finally convinced even the greatest skeptics.

The world's first fire-fighting pump driven by a gasoline engine

Stuttgart 1888: Two years after the successful trials with the first automobiles designed by Gottlieb Daimler and Karl Benz, Daimler was able to present a gasoline engine for the fire brigades. On July 29, 1888 he obtained a patent for an engine-powered fire-fighting pump which was, however, still drawn by horses. A single-cylinder 1 hp engine operating at 180 rpm was connected by means of a reduction gear to a piston pump made by the renowned fire pump manufacturer Heinrich Kurtz from Stuttgart. In the same year, Daimler exhibited such a motorized fire-fighting unit – already equipped with a two-cylinder 4 hp unit – at the 13th German fire brigades' convention in Hanover.

A third model with 6 hp engine attracted worldwide attention in 1892. This fire engine was displayed in St. Petersburg, Leipzig, Munich, Florence and Milan and in the following year at the World Exposition in Chicago. The pump, with a capacity of 300 liters per minute delivered at a pressure of three bar, was for the first time used in a major fire in 1892. For five hours, it sucked water from a depth of five meters and pumped it through a 150 meter long pressure hose 20 meters high into the roof structure of a factory producing bed feathers in Cannstatt near Stuttgart. In 1896, the pump was sold at a price of 5,610 Goldmarks to Erfurt where it did valuable service for 25 years. Today, it is displayed in the Mercedes-Benz Museum.

Gottlieb Daimler realized the major advantage of his fire pump with gasoline engine drive: its instant readiness for operation. By contrast, steam-powered pumps took almost a quarter of an hour before the required pressure was built up. There was, however, room for improvement where the matching of engine and pump was concerned. The low-speed piston pump customary at the time was ideal for the steam engine – but not for the high-speed combustion engine.

New propulsion systems: steam engine and electric motor

The gasoline engine had already been invented but the fire brigades continued to use horse-drawn carriages exclusively in the early 20th century. Initially, it was not even speed that was the focus of motorization plans but the high expense associated with keeping horses. A single horse cost as much as 1,500 Marks, and its upkeep incurred more than 1,000 Marks annually. Horses had to be curried, fed and exercised, they produced quite a lot of manure and were even prone to illness. It was therefore not surprising for fire brigades to consider the possibilities of using the new motor vehicle technology for themselves.

Initially they were far from opting for the gasoline engine, however. The first motorized fire engine fleet in Germany, put into operation by Hanover's fire brigade in 1902, consisted of two vehicles with electric motors and a steam-powered pump whose steam engine also drove the vehicle. Steam engine and electric motor dominated the field until 1906 and remained the two most important propulsion systems until around 1910. The biggest disadvantage of the steam engine, quite apart from its price and weight, was the fact that the boiler had to be heated first or kept under a constant pressure. Electric drive also posed a weight problem because of the onboard batteries. A less serious disadvantage at the time was the limited range, given the fire brigades' radius of action at the time.

Ferdinand Porsche's wheel hub motors improved the situation considerably. The 21-year-old design engineer had joined the Viennese company Jacob Lohner & Co., a court vehicle and automobile manufacturer. He came up with the ingenious idea of minimizing the power transmission travel by installing two electric motors directly in the front wheels – a feat for which he received a gold medal at the Paris World Exhibition the following year. Daimler-Motoren-Gesellschaft in Berlin-Marienfelde soon recognized the advantages of the Lohner-Porsche system and from 1906 produced wheel hub motors in large numbers. The manufacturer's vehicles became known as "Mercedes Electrique" or "Electro Daimler".

The commissioner of the Berlin fire brigades, Maximilian Reichel, who had already put the first German motorized fire engines in operation in Hanover, was enthusiastic. In 1906, he had compared a steam-powered vehicle with a vehicle with Lohner-Porsche wheel-hub motors – with the result that he was convinced of the advantages of electrical propulsion. In 1908, he therefore ordered the first combination of four electrically powered vehicles from Daimler, composed of gas extinguisher, steam extinguisher, implement carrier and turntable ladder. Each powered by two 7.5 hp wheel-hub motors, the four vehicles reached top speeds of 36 kilometers per hour. The battery, weighing 900 kilograms, fitted under the driver's seat and supplied by Akkumulatoren-Fabrik Berlin-Hagen, provided for a radius of 50 kilometers.

Premiere of the hybrid mixte drive of Ferdinand Porsche

Porsche had changed to Austro-Daimler in 1905 after having worked for quite some time towards combining the advantages of his wheel-hub motor with the key competence of the leading gasoline engine manufacturer. He replaced the excessively unwieldy battery by a gasoline engine which provided the required electricity for the wheel-hub motors via a dynamo, thereby reducing the weight and enlarging the radius of action significantly. The example set by the Berlin fire brigade was soon followed by the professional fire brigade in Hamburg – the latter ordered twelve Daimler mixte vehicles some of which remained in operation right into the thirties.

The undisputed advantage of the electric motors over steam engines was that they didn't have to be preheated over a lengthy period of time and were therefore operational at all times. The gasoline engine contributed to enlarging the vehicles' radius of action and made it possible to dispense with the bulky and heavy batteries. On the other hand, the question arose why an electric motor was required in the first place if the gasoline engine was capable of driving the vehicle.

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