Siemens-Schuckert designed a number of heavy bombers early in WWI, building a run of seven R-series bombers. Intended to be used in the strategic role in long duration flights, the SSW R-series had three 150 h.p Benz Bz.III engines in the cabin driving two propellers connected to a common gear-box through a combination leather-cone and centrifugal-key clutch in SSW R.I to the SSW R.VII models(the SSW R.VIII utilized four engines). In the case of engine failure, which was extremely common at the time, the bomber could continue flying on two engines while the third was repaired by the in-flight mechanic. Two transmission shafts transferred the power from the gear-box to propeller gear-boxes mounted on the wing struts. Although there were some problems with the clutch system, the gear-box proved to be reliable when properly maintained. The SSW R.1 through the SSW R.VII designs were noted for their distinctive forked fuselage. Several of these aircraft (SSW R.V through the SSW R.VII) fought on the Eastern Front. Although interesting in concept, the cost of these and the R-types from other companies was so great that the air force eventually abandoned the concept until more practical designs arrived later in the war.
They also tried their hand at a fighter design based on the French Nieuport 11 in 1915. Like the Nieuport's Le Rhône 9C, the SSW D.I was to be powered by a rotary engine of about 100 hp. The Germans had licensed the Le Rhône just before the war and was producing it as the Oberursel UR.II which they intended to use on the D.I, but demand was so high that Siemens decided to start producing their own version as the Siemens-Halske Sh.I. The engine took so long to get to production quality that by the time it was ready in 1916 the fighter was no longer competitive.
Instead of simply dropping the work, Siemens-Halske decided to re-work the engine into a much more powerful design, resulting in the 160 hp Sh.III, perhaps one of the most advanced engine designs of the war. When placed in a modified D.I it suddenly became one of best climbing aircraft in the world, and found use in home defense units as an interceptor. Further modifications improved its handling and performance, becoming what is often considered to be the best fighter of the war, the Siemens-Schuckert D.IV. Several offshoots of the design included triplanes and monoplanes, but none saw production.
With the end of the war production of the D.IV continued, mainly for sales to Switzerland who flew them into the late 1920s. With the signing of the Treaty of Versailles the next year all aircraft production in Germany was shut down. Siemens-Schuckert immediately disappeared, but Siemens-Halske continued sales of the Sh.III and started development of smaller engines for the civilian market. By the mid-1920s their rotary engines were no longer in vogue, but "non-turning" versions of the same basic mechanicals led to a series of 7-cylinder radial engines, the Sh.10 through Sh.14A, delivering up to 150hp in the 14A. The Sh.14A became a best-seller in the trainer market, and over 15,000 of all the versions were eventually built.
Siemens-Halske no longer had any competitive engines for the larger end of the market, and to address this they negotiated a license in 1929 to produce the 9-cylinder Bristol Jupiter IV. Minor changes for the German market led to the Sh.20 and Sh.21. Following the evolution of their smaller Sh.14's, the engine was then bored out to produce the 900 hp design, the Sh.22. In 1933 new engine naming was introduced by the RLM, and this design became the Sh.322, when Siemens was given the 300-block of numbers. The Sh.322 design had reliability problems and never became popular.
The company reorganized as Bramo in 1936, and continued development of what was now their own large engine. Modifying the Sh.322 with the addition of fuel injection and a new supercharger led to the Bramo 323 Fafnir, which entered production in 1937. Although rather outdated in terms of design, by this time the engine had matured into a highly reliable powerplant, and 5,500 were produced until the lines shut down in 1944.
In design terms the 323 was basically a dead-end with little growth potential. By the start of the war it's 1,000 hp was already at the low end of the performance scale, and use was limited to transports and bombers. In order to build a 1,500 hp-class engine Bramo started development of a two-row version of the engine as the Bramo 329, mirroring similar developments at BMW who were trying to scale up their Pratt & Whitney Hornet into the two-row BMW 139. Design of both engines was well advanced in 1939 when BMW bought Bramo, and cancelled work on the 329 to concentrate on what would become the excellent BMW 801.
Realizing the two-row radial development was a risky proposition, Bramo engineers had also started developing axial-flow jet engines in 1938. They were awarded a development contract to continue work on two designs, which would later become the 109-002 and 109-003 when the RLM officially started supporting jet development. The -002 used an advanced contra-rotating compressor for added efficiency, while the -003 used a simpler compressor/stator system that remains in use in modern designs today. The -002 proved to be too complex and work on it soon ended, but the -003 showed definite promise and eventually became the BMW 003.