Engine development at Daimler-Benz

Aircraft engines

Daimler-Benz AG can also look back on a long tradition in aircraft engine design. As early as 1888, Wölfert's airship was powered by a 1.5 kW (2 hp) Daimler internal combustion engine. The first engine developed specifically for an aircraft was delivered by Daimler-Motoren-Gesellschaft in 1900. The Benz works in Mannheim did not begin aircraft engine design until 1908, but by the outbreak of the First World War, they had caught up with the competition.

After the end of the war, the German aviation industry initially came to a near-complete standstill, as a general ban on the manufacture and import of aircraft equipment existed until May 5, 1922. After that, production for the civil aviation sector was permitted again— under strict controls and conditions.

The real upswing in aircraft engine development, however, only began after the Nazis seized power. The Reich Air Ministry (RLM) promoted aircraft engine production as part of its job creation and rearmament program. Daimler-Benz AG, which aimed for large-scale, serial production with the 'F4' introduced in 1931, was also involved. The Berlin-Marienfelde plant was to repair aircraft engines, produce engine parts, and build copies of the BMW VI aircraft engine under license. Daimler-Benz was also encouraged to look for a suitable location for the construction of an engine factory.

The 'F4', an engine with 12 overhead V-shaped cylinders, was the starting point for the 600 series aircraft engines (DB 600, DB 601, DB 603, DB 605) and their numerous variants developed in the 1930s and 1940s. The first further development of this engine, the water-cooled 12-cylinder DB 600 carburetor engine, was produced from 1936 onwards. Continuous work continued on its technical improvements, which particularly benefited subsequent models.

For example, problems with the carburetor led to the development of the 3-jet carburetor, which was first used in the DB 600 G and H models in 1937. From 1938 onwards, production of the DB 600 was discontinued in favor of the DB 601.

The mechanics of the DB 600 formed the basis for the DB 601, a 12-cylinder fuel-injected engine. The focus of development for this engine was on increasing takeoff power and achieving 1,000 hp at 4,000 m altitude, which was achieved through fuel injection. By May 1937, development work on the DB 601 A and B was almost complete, and production began in 1938. The DB 601 series was expanded to include the DB 601 C and D, high-altitude engines with two superchargers arranged in series, the DB 601 E, and the DB 6065.

In September 1936, initial preparations for the development of the DB 603 fuel-injected engine were made in the design office. At the same time, work was also underway on an aerobatic X-engine. The DB 604 with 24 cylinders was also designed as an X-engine, and work on its design began in 1937. Its complete production was scheduled for 1939. By this time, however, the RLM's interest in this engine had already waned, as other engine models were available for installation in single-seat aircraft.

While the Air Ministry shelved the DB 604 and even prohibited further development of the DB 603 until 1940, it also promoted two further developments of the DB 601 E, the DB 608 and especially the DB 605 E. 9 The DB 605 and ultimately the DB 603 were of essential importance for the war effort.

As early as the end of 1936, Daimler-Benz AG had offered the RLM the DB 603, an enlarged DB 601. Despite the official prohibition by the Ministry, the engine was further developed in Untertürkheim. Finally, in 1940, the engine, whose blower and entire unit were interchangeable without special readjustment, was completed with the greatest urgency, so that it could finally go into series production in 1942.

At this time, the DB 605, with a smaller total displacement than the DB 601 E, was already in production. Its innovative spark plug arrangement improved fuel consumption. It also featured plain bearings instead of roller bearings for the connecting rods for the first time. However, the DB 605, the most produced aircraft engine during the war years, experienced lubrication problems for a long time. Piston seizure and connecting rod breakage were also recorded, leading to numerous accidents. These incidents certainly contributed to the DB 603 ultimately being preferred. The RLM therefore ordered the priority development of the DB 603 E, F, G, and K. The DB 632 was given equal priority. In a "major feat," this engine model was to be developed, designed, and built in the shortest possible time.

A particular focus of aircraft engine development from 1939 to 1943 was the high-altitude engine with an exhaust gas turbocharger to increase engine power. Test engines with exhaust turbochargers were the DB 623 and DB 625, which reached their full pressure altitude at approximately 9,000 and 9,500 meters, respectively. Both engine types were tested in a Ju 52, and the DB 625 was also tested in an Me 10911.

As early as 1936, Daimler-Benz AG was working on the development of exhaust turbocharging. For this purpose, the company engaged Brown, Boveri & Cie., which collaborated on the design and was to produce initial prototypes.

Difficulties led to a further contract being awarded to Rheinmetall-Borsig, which was to design two exhaust turbocharger types, one with air cooling and one with water vapor cooling. Furthermore, close contact was maintained with the DVL (German Air Force) during this development.

In 1943, Daimler-Benz AG completely stopped developing exhaust turbochargers, and in April/May 1945, it also stopped designing aircraft engines.

Marine engines

Another, albeit less extensive, branch of production was marine engine production, for which Dr. Kissel had been particularly committed since 1928. Daimler-Benz AG primarily manufactured speedboat engines (S-boat engines), but Daimler-Benz marine engines were also installed in submarines.

The DB 602, an airship engine with the type designation LOF 6, was used as a boat engine under the designation MB 502 or BOF 6. Daimler-Benz AG first delivered this 16-cylinder diesel engine with a maximum output of 1320 hp as an S-boat engine in 1935/36. Production preparations for the improved MB 502, the MB 501, a 20-cylinder diesel engine with a maximum output of 2000–2500 hp, were completed in 1936. However, various tests and measurements were still being conducted on this engine model. In the same year, the development department also worked on the BOF 9 (MB 500), a 950–1000 hp diesel engine.

In 1938, the Navy received the first MB 501 S boat engines. That same year, the first 12-cylinder MB 500 diesel engines with an output of approximately 1000 hp were also delivered. In contrast, the MB 507, a diesel engine with vertical cylinders developed from the DB 603 and DB 607, only existed as a prototype for engine break-in.

Equipped with a mechanically driven supercharger, the MB 501 was offered as the MB 511. Further development of the MB 511 into the more powerful MB 518 began in the early 1940s. The first test runs of the engine, designed for a maximum output of 3,000 hp, were conducted in October 1942. The Navy had planned to field this engine in the fall of 1944, but delivery difficulties and testing deficiencies thwarted these plans. In March 1945, MB 518 production had to be completely halted.

Airship engines

Count Zeppelin's airships, built up until 1909, were already powered by Daimler engines. In that year, Karl Maybach took over engine development at the newly founded Luftfahrzeug-Motorenbau GmbH, which operated its own engine design department.

It wasn't until the 1930s that Daimler-Benz airship engines were used again. For the Hindenburg (LZ 129) airship, built from 1932 to 1936, Daimler-Benz AG developed the DB 602 (= LOF 6). This 16-cylinder diesel engine, with a maximum output of 1,320 hp, proved its worth in continuous operation.

DB 602 engines converted to Kogasin fuel were also used for the Graf Zeppelin II (LZ 130) airship. A further reduction in specific fuel consumption was achieved through additional improvements to the burners.

In November 1938, the development department at the Untertürkheim plant began designing a new, lighter airship engine. This 16-cylinder engine was to have an even smaller displacement and better fuel consumption. This project was likely discontinued shortly thereafter, as the airship era ended with the scrapping of the LZ 127 and LZ 130 airships in 1940.