Dernburg car

The "first passenger vehicle with all-wheel drive for everyday use" ( Mercedes-Benz QUOTE) designed the Daimler-Motoren-Gesellschaft (DMG) in 1907, after the Dutch company Spyker in 1903 their two-seater race car Spyker 60 HP was the first four-wheel car with an internal combustion engine . The so-called Dernburg car even had all-wheel steering . It is named after the then State Secretary Bernhard Dernburg , who covered many kilometers with him in 1908 in the former colony of German South West Africa , today's Namibia .

The Dernburg car from 1907

Bernhard Dernburg (with helmet in hand)

The Reichskolonialamt knew at the beginning of the 20th century when ordering exactly what it from Daimler-Motoren-Gesellschaft expected: mastered without complaint A reliable vehicle that bad and long distances and was flexible with the man. The engineer Paul Daimler , son of the company's founder Gottlieb Daimler , was in charge of the design of the desired vehicle, which was finally built as a one-off in 1907 at the Berlin-Marienfelde plant. The four-wheel drive vehicle was based on a truck chassis from DMG, it had a wheelbase of four meters and a track width of 1.42 meters. The ground clearance of 32 centimeters was not unusually large for the conditions at the time, as almost all automobiles were often driven on heavily rutted roads. The “Allgemeine Automobil-Zeitung” (AAZ) commented on the Daimler construction in 1908: “All higher obstacles are removed by the stable front and rear axles, and a tough steel armor is placed around the most endangered lower part of the gearbox between the pressed frame cross members , strong enough to put the whole frame on. ”The vehicle cost 34,750 marks. It had a touring car body with two seats on the chauffeur's bench and a total of four seats in the rear. There were only doors for the rear passengers. Generous steps made it possible to climb the entry height of around one meter. A sunroof was fixed on eight posts and reached almost to the front of the vehicle so that the driver was not dazzled even when the sun was very low. A luggage rack for suitcases or spare wheels was attached to the rear of the vehicle. There was another large luggage rack on the roof, protected by a tarpaulin. Tent tarpaulins were attached to the right and left below the roof, which could be lowered and thus closed the structure in order to protect the passengers against wind, weather and sand.

Features for special use

With a length of around 4.90 meters and a height including roof of a good 2.70 meters, the car weighed around 3.6 tonnes, including all the special features expressly requested by the Colonial Office, for example a particularly heavy clutch, as well as petrol adapted to tropical conditions - and cooling water supply, spare parts and tools. The four-cylinder engine delivered an output of 35 hp (26 kW) from a displacement of around 6.8 liters at 800 rpm, which ensured a top speed of around 40 km / h on a flat asphalt stretch. But more important for the vehicle with its special field of application was the enormous climbing ability with the help of the all-wheel drive: It was 25 percent. The vehicle had permanent four-wheel drive, and the engine sent its power to the four wheels via a sophisticated mechanism. A shaft connected it to the precisely centered gearbox that had four forward gears and one reverse gear. From there, cardan shafts transmitted the rotary motion to the differentials on the front and rear axles, which they in turn split up using bevel gear combinations and sent to the wheels.

Protection of the mechanics from drifting sand

The designer Paul Daimler took special precautions to keep fine drifting sand out of the power-transmitting parts. In many joints, the grease lubrication was already pushing back the sand from the inside and preventing it from wearing out quickly. However, the front axle initially posed a challenge: The otherwise usual protection of the bevel gears in the running wheels , which followed the steering angle in a telescopic manner, could not be used because of the strong vibrations to be expected and because of the fine drifting sand. Daimler wrapped the sensitive parts in a stable, cylindrical shell. However, since this solution severely restricted the steering angle, to a maximum of 23 degrees, the vehicle also had rear-steered wheels in order to achieve an adequate turning circle. The rear wheels were also encapsulated to protect them from drifting sand. A side effect: the front and rear axles were constructed identically with almost all components including the differentials, wheels and brakes, which simplified the provision of spare parts.

Side view of the Dernburg car

The closed wheel disks made of sheet steel also served to protect the mechanics and the drum brakes against dirt - wooden and (less often) steel-spoke wheels were common at the time, but they would have left sand on the drive components. In addition, it was almost impossible with spoked wheels to free yourself on your own if you were once sunk in the sand. The sheet steel rims had pneumatic tires measuring 930 × 125, which is another special feature, because solid rubber tires were still widespread at that time . Paul Daimler presumably made this choice in order to support the work of the robust leaf springs with the heavy vehicle weight . As was not uncommon back then, only the rear tires had a profile, while the front tires had a smooth tread. The valves on the pneumatic tires were located on the inside of the rim so that they could not be damaged so quickly.

The engine cooling was specially designed for the tropical climate: a larger cooling surface, an enlarged cooling jacket around the cylinders and a total of more cooling water - a total of 140 liters were in circulation. In addition to the radiator on the front of the vehicle, another radiator was mounted on the bulkhead, which encompassed it in a horseshoe shape and in this way stretched its honeycombs into the airstream. Both coolers were connected to one another via two laterally arranged water tanks. The heated water had to pass through all pipes and tanks before it flowed around the cylinders again.

Testing under realistic conditions

Extensive testing of the colonial car over 1677 kilometers took place in Germany at the end of March / beginning of April 1908. The route led from Berlin-Marienfelde to Stuttgart-Untertürkheim and back. Untertürkheim was reached in the morning of the fourth day, again four days later the vehicle was back in Marienfelde. However, it also covered stretches off the beaten track to test the all-wheel drive. "A turn [curve] in a deep fall field with an incline of five to ten percent was carried out flawlessly," said an internal report from the colonial office. “In the vicinity of Wittenberg, a sand pit was driven into, in which the car sank abundantly into the sand up to the axles, but from which it could easily be freed again on gradients of 20 and 21 percent.” In the Thuringian Forest “one was about Climb 150 meters high on stony, winding, narrow roads with gradients of up to 20 percent without difficulty. Even the steering, which is cumbersome due to the four-wheel drive, has proven itself ”. The acceptance protocol from the colonial office was positive.

In May 1908 the vehicle was shipped to Swakopmund in Africa on the steamer “Kedive”. In June it was available to the State Secretary of the Reich Colonial Office, Bernhard Dernburg, in German South West Africa. Many years later the all-wheel-drive vehicle was given the nickname "Dernburg car" because of its journeys. At the same time, the tours were generally used to test the automobile as a means of transport in the colony. For this purpose, at least at times, other rear-wheel drive vehicles from Benz and Daimler accompanied the four-wheel drive vehicle, namely a seven-seater, largely armored passenger car from Benz and three trucks from Daimler.

All-wheel-drive vehicles from Daimler-Motoren-Gesellschaft (DMG) in action

In a contemporary travel report it said about a stage of the Dernburg trip: “The 600 kilometer route from Keetmanshoop via Berseba to Gibeon and then from Maltahöhe, Rehoboth to Windhoek was covered in four days without an accident. That saves an enormous amount of time, because an experienced rider on horseback needs twelve days for the same distance [...]. "The civil servant was even able to use a mobile means of communication:" When [the car] was carrying State Secretary Dernburg, it ran another one Field telephone that could be connected to the telegraph line anywhere on the way. "

In the service of the national police

After this trip, the vehicle was available to the state police in German Southwest Africa as a permanent means of transportation. There was a precise logbook, for example around 10,000 kilometers had been covered by the beginning of 1910 .

Daimler-Motoren-Gesellschaft had sent the chauffeur and mechanic in personal union to Africa in an all-wheel drive vehicle - a very common practice at the time. And because the car belonged to the state police, the chauffeur Paul Ritter was quickly appointed a police officer. He stayed in the country after Dernburg's departure and looked after the vehicle, returning to Marienfelde again and again to get spare parts and skills for servicing and repairing the car.

The construction of the vehicle was precisely tailored to its intended use. Every detail has been thought through with driving in rough terrain. However, the journeys did not always go smoothly. Because the high weight of the vehicle, largely due to the special requirements of the colonial office for the vehicle properties, put a lot of stress on the pneumatic tires, so that they only had a comparatively short service life under the strain on rough roads - 36 tires and 27 tubes were during this time of the aforementioned 10,000 kilometers until the beginning of 1910. Attempts with solid rubber tires were negative, as too great a force then acted on the rims and destroyed them.

The Dernburg car from 1907

The all-wheel drive, on the other hand, proved itself particularly on deep sandy stretches, where the vehicle made better progress than the rear-wheel drive trucks that were also available. Nevertheless, after a detailed inspection, a lieutenant colonel of the state police spoke out in favor of converting the vehicle to pure rear-wheel drive: the all-wheel drive with its numerous components was time-consuming to maintain and repair. This conversion was apparently also carried out, but precise details are not available. No record is known of the vehicle's use during World War I in South West Africa . After that and with the end of the German colonial era, the trail of the "Dernburg car" got lost - its whereabouts are unknown. Paul Ritter, however, the chauffeur and mechanic, returned to Marienfelde in 1919 and found work again at Daimler-Motoren-Gesellschaft.

The reconstruction of the "Dernburg car"

In 2006 , DaimlerChrysler decided to recreate the “Dernburg car” as a detailed model in order to celebrate the company's “100 years of all-wheel-drive passenger car” anniversary. The model was supposed to be as close to the original from 1907 as possible - but that was a big challenge. Because technical drawings did not exist, and the company's own specialists only had six contemporary photos available, the quality of which is more or less good. In addition, just five dimensions were known: the center distance, the track width, the smallest ground clearance, the tire diameter and the tire width.

The model makers reconstructed the "Dernburg car" on a scale of 1: 4 from this sparse material. The approximately 1.25 meter long result is very close to the original. A solid knowledge of how cars were built at the beginning of the 20th century also helped the model makers. In addition, with the help of photos and other historical material, they put themselves in the position of time and its technical possibilities. The work was like a demanding, three-dimensional puzzle game. First of all, it was a matter of completing the basic dimensions in order to at least approximately determine all dimensions. At the same time, technical details related to the basic construction were worked out, such as the position of the gearbox housing and the length of the leaf springs. A lot of energy was put into the reconstruction of the all-wheel drive, because the finished model was supposed to show this as detailed as possible. The specialists initially assumed that the center of the wheel was at the same height as the shaft that led from the differential to the wheel. Exact details of the construction were not known, and in the photos the rims covered the appropriate places. But when determining the other dimensions on the axles, there was always a difference in height that they could not explain at first - until the realization matured: The construction of all-wheel drive and all-wheel steering requires a bevel gear combination on each wheel, and that required exactly the size of the puzzling difference. With this, the model had also been recognized by the logic of the sophisticated design by Paul Daimler.

Little by little, all the individual parts of the Dernburg car were rebuilt on a small scale: for example the chassis, the leaf springs, the all-wheel drive, the body, the crank for starting the engine, the interior and the convertible top. Maple wood was mainly used as the building material for the model because it is easy to work with, but is still comparatively hard. The side members of the chassis are made of plastic that has been reinforced with aluminum.

Sometimes the methods of the experts were almost detective-like: they took the position of the sun from the original photos with the help of the shadows that could be seen and simulated it on the model with the help of a flashlight.

Pieces were repeatedly changed because they didn't fit into the puzzle as expected. It became clear to the specialists: Daimler itself might have worked similarly from time to time, because after all, the “Dernburg car” was a one-off, so that the production of the original was probably not completely straightforward - because in practice something was not so worked as the designer had intended.

The paintwork corresponds to the historical specification of the vehicle to be used for the police - it is a medium gray. The seats are covered with leather that has been specially scraped to a thickness of three tenths of a millimeter for the model scale so that it can nestle perfectly against the seats. The fabric blinds could really fall into the window openings to close the structure. Only the rear tires have tread, the front ones are smooth - like the big original. Only the model does not have an engine. The model made its first major appearance at the North American International Auto Show (NAIAS) in Detroit in January 2007 .

Technical data of the all-wheel drive passenger car of the Daimler-Motoren-Gesellschaft from 1907

engine
Daimler engine	Type E4 with cylinders cast together in pairs, 2 side camshafts
Number of cylinders / arrangement	4 / R, 2 valves per cylinder, valves on the side in a T-arrangement
Displacement	6786 cc
Bore × stroke	120 × 150 mm
rated capacity	35/26 hp / kW at 800 rpm
ignition	Magnet-electric detonator
Mixture preparation	Daimler piston carburetor, centrifugal regulator
cooling	Front radiator with fan, additionally a horseshoe-shaped radiator attached to the bulkhead, connection of the two radiators via two laterally attached water tanks, engine cooling jacket around the cylinder increased to 28 liters, total amount of cooling water in circulation: 140 liters
Power transmission
drive	Permanent all-wheel drive, bevel gear drive, torque distribution 50:50 (v / h)
coupling	Aluminum cone coupling
transmission	Four-speed manual transmission, one reverse gear
Protective measures	All power-transmitting parts were protected against drifting sand, the motor was completely encased, and the gearbox was provided with a stable lower part of the housing
landing gear
chassis	Straight, pressed steel frame
Front axle	Rigid axle, leaf springs
Rear axle	Rigid axle, leaf springs
Braking system	Water-cooled external shoe brakes can be operated at the front using a pedal , the rear external band brake can be operated using a hand lever
steering	Screw all-wheel steering
rims	Closed sheet metal rims made of nickel steel
tires	930 × 125
mass and weight
wheelbase	4000 mm
Front / rear track	1420 mm
Ground clearance	320 mm
Overall length	Around 4900 mm
Overall width	Around 2000 mm
Total height	Around 2700 mm
Mass ready to drive	3600 kg
Driving performance and fuel consumption
Top speed	40 km / h
Climbing ability	25%
Fuel consumption	Around 25/100 km
price
New price 1907	34,750 marks
number of pieces	1

literature

S. Schepp: Under the Southern Cross - In the footsteps of the Ksl. State Police of German South West Africa. Frankfurt am Main 2010, ISBN 978-3-86676-103-2 , pp. 278 f.