Rapp Motorenwerke
 Rapp emblem featured in a 1916 advertisement | |
| Company type | GmbH |
|---|---|
| Industry | Manufacturing |
| Founded | October 27, 1913 |
| Founder | Karl Rapp |
| Defunct | 1922 |
| Fate | Integrated into present-day BMW |
| Successors | Brake production: Süddeutsche Bremsen-AG Engine production: Bayerische Motoren Werke AG |
| Headquarters | , |
| Products | Aircraft engines |
Rapp Motorenwerke GmbH was a Munich-based German manufacturer specializing in aircraft engines. Established in 1913, the company was renamed Bayerische Motoren Werke GmbH (BMW) in 1917.[1] In 1922, following the transfer of its engine manufacturing division and the BMW brand to Bayerische Flugzeugwerke (previously known as Otto Flugmaschinenfabrik), the original company became known as Süddeutsche Bremsen-AG. Bayerische Flugzeugwerke subsequently adopted the name Bayerische Motoren Werke AG, which later developed into the well-known automotive corporation BMW AG.[2][3]
Early engines
On 27 October 1913, Karl Rapp and Julius Auspitzer founded Rapp Motorenwerke GmbH with an initial capital of RM 200,000. The enterprise was situated in Milbertshofen, occupying the location formerly used by the Munich branch of Flugwerk Deutschland GmbH, a company where Karl Rapp had previously held a senior position before its dissolution in mid-1913.[4] Julius Auspitzer served as the sole shareholder, while Karl Rapp was responsible for managing daily operations. The company’s primary objective was to manufacture and market "engines of all kinds, especially internal combustion engines for aircraft and motor vehicles."
By acquiring Flugwerk Deutschland, Rapp Motorenwerke also inherited the four-cylinder engines developed by Karl Rapp at that firm. These were promptly offered to the Prussian military under the designation Rapp 100 hp.[4][5] Although some aircraft utilized this 100 hp four-cylinder engine, it failed to gain significant favor with German military officials, who increasingly preferred six-cylinder engines due to their superior smoothness.
Besides the four-cylinder model, development began on a 125 hp inline six-cylinder engine with a weight of approximately 215 kg (474 lb)[6] and a displacement near 14.8 L (901 cu in)Template:Fix/category[citation needed] for entry into the second Kaiserpreis (Kaiser's Trophy) competition for aircraft engines. However, this project was not completed before the deadline.[5]
Building upon the Rapp 100 hp design, further progress resulted in the 150 hp Rapp Rp III inline-six engine by early 1914. During World War I, this engine's power output was increased to roughly 174 hp[5] (with an actual rating of 162 hp at 1,400 rpm)Template:Fix/category[citation needed], though it achieved limited acceptance among German military customers.[5] Additional developments included a Rapp 200 hp V-8 and a Rapp 300 hp V-12 engine sharing identical cylinder dimensions, as well as a smaller-displacement 125/145 hp Rapp Rp II V-8.
All these powerplants were derived from the foundational Rapp 100 hp four-cylinder model and featured overhead camshafts operated via forged steel liners screwed onto cast steel cylinder heads. The cylinders were arranged in pairs throughout. A distinctive characteristic of Rapp aero engines—setting them apart from contemporaries such as (Mercedes, Benz, and Basse und Selve)—was the vertical timing shaft driving the overhead camshaft positioned between the two rear cylinder pairs rather than at the extreme rear end.
Wartime production
At the onset of the First World War, the company emerged as a significant Bavarian contributor to the war effort and garnered some recognition, although none of its engine designs or innovations achieved substantial success. Due to the inability of established manufacturers such as Argus, Daimler, and Benz to satisfy the demand for aircraft engines, German military authorities began placing orders with Rapp Motorenwerke. With this influx of capital, the firm expanded swiftly, employing 370 workers by late September 1915.
Nevertheless, the initial Rapp engine deliveries were rejected by the Prussian Army Administration as inadequate, leading them to cease further procurement. Despite this setback, limited orders continued from both the Bavarian Army administration and the German Navy. Additionally, the Austro-Hungarian Army and Navy, facing shortages in aircraft engine production, commenced purchasing Rapp Rp II and Rapp Rp III engines. These powerplants suffered from multiple issues such as irregular operation and vibrations, frequent bearing breakdowns, and carburetion difficulties—problems attributed in Austro-Hungarian reports to flawed engine design.
In response to a commission from the Prussian Army Administration, Karl Rapp enhanced the output of his Rapp Rp III engine to 175 hp. However, this reinforcement increased both engine weight and vibrations. After failing acceptance testing in January 1916, German authorities placed no additional orders, leaving only the Austro-Hungarian Navy as a customer.
Later that year, Rapp introduced a completely redesigned six-cylinder engine featuring four valves per cylinder operated by an innovative system of pushrods and rocker arms driven by a single camshaft located within the engine block. Some sources identify this as the Rapp IIIa; however, other authors use this designation for the 175 hp overhead camshaft variant of the Rapp Rp III engine. The engine’s displacement and four-valve configuration suggest it may have belonged to a higher power category—possibly the otherwise undocumented 250 hp Rapp Rp IV six-cylinder model. Little information exists about this engine, but it evidently failed to achieve commercial viability or improve the company's standing—the Rapp name had deteriorated in reputation to such an extent that military departments ceased purchasing engines from the firm.
During this period, Franz Josef Popp recognized that Rapp Motorenwerke's facilities were well-suited for engine manufacturing due to their skilled workforce and equipment availability. Popp vigorously advocated for licensed production of the 12-cylinder Austro-Daimler aircraft engine. He successfully persuaded both the Bavarian Army Administration and the Imperial Naval Office of the Imperial Austro-Hungarian Army Administration to place orders for Rapp engines produced under Austro-Daimler license. Acting on behalf of the Austrian war ministry, Popp was assigned to oversee order management in Munich.
Popp also played a key role in recruiting Max Friz, an aircraft engine designer at Daimler, to join Munich’s efforts in development and expansion. Following Friz’s arrival in 1916, original Rapp designs were refined to create a "high altitude" aero engine aimed at providing the Imperial Army with strategic air superiority. The year 1917 marked a breakthrough when Friz and his engineering team developed what became known as the type III.
BMW Type III
On 20 May 1917, Rapp Motorenwerke filed the design documentation for a new engine, designated as "type III". The design, created by Friz and inspired by Karl Rapp's initial concept, featured an inline six-cylinder configuration that ensured excellent balance and minimal vibrations. Although the engine performed well, the true innovation occurred in 1917 when Friz introduced a straightforward throttle butterfly valve into the "high-altitude carburettor," allowing the engine to maintain full power at elevated altitudes. This advancement gave the engine—later known as the "type IIIa"—a distinct advantage in aerial combat. In 1919, Franz-Zeno Diemer, a pioneering test pilot for the firm, set a new altitude record of 32,000 ft (9,760 m) flying a DFW F 37/III two-seater (often called the C-IV) equipped with a BMW Type IV engine. Later that year, in September, Diemer established another altitude record for a passenger aircraft carrying eight people to 6,750 meters aboard a Junkers F 13 powered by the BMW IIIa engine.
Change of name
The Prussian Army Administration’s decision to place an order for 600 units of the advanced high-altitude aero engine (codenamed "BBE") triggered a reorganization of the company’s legal structure. Friz’s aero engine rapidly transformed Rapp Motorenwerke into a crucial participant in the war effort. From mid-1917 onwards, what might have otherwise faded into obscurity gained significant attention from military and government agencies alike. Substantial subsidies were granted, and Munich-based production orders were well-funded.
Max Friz’s rising prominence with his engine design made it apparent to senior management that Karl Rapp’s earlier designs had hindered the company’s progress. With Friz now recognized as an outstanding chief designer, reliance on Rapp diminished. Consequently, on 25 July 1917, Karl Rapp’s contract was terminated by the company’s partners.
This separation had been anticipated for some time. With Rapp’s departure confirmed, a critical decision followed: since the company bore his name, it required rebranding. Thus, on 21 July 1917, Rapp Motorenwerke GmbH was renamed Bayerische Motoren Werke GmbH—marking the first usage of this name and the acronym "BMW".
Rapp’s exit allowed for comprehensive restructuring; Max Friz assumed leadership of development as chief designer while Franz Josef Popp was appointed managing director. Aero engines remained the firm’s sole focus until war’s end. The BBE engine project achieved notable success under its new designation, BMW IIIa.
In 1922, following the transfer of BMW branding and engine manufacturing assets to Bayerische Flugzeugwerke—which had previously been known as Otto Flugmaschinenfabrik—the company adopted the name Süddeutsche Bremsen-AG. Subsequently, Bayerische Flugzeugwerke was renamed Bayerische Motoren Werke AG and evolved into today’s renowned automobile manufacturer known as BMW.
See also
References
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Bibliography
- Pierer, Christian (2011). Die Bayerischen Motoren Werke bis 1933: Eine Unternehmensgründung in Krieg, Inflation und Weltwirtschaftskrise (in Deutsch). Oldenbourg Verlag. ISBN 9783486704440.
- Pletschacher, Peter (1992). Die Königlich Bayerischen Fliegertruppen 1912-1919 (in Deutsch) (2 ed.). Planegg: Aviatic Verlag. ISBN 3-925505-20-2.
- Angle, Glenn Dale (1921). Airplane Engine Encyclopedia: An Alphabetically Arranged Compilation Of All Available Data On The World's Airplane Engines. Otterbein Press. pp. 402-404. OL 23525261M.
- "Rapp IIIa". BMW Group archives. BMW Group. Retrieved 25 December 2020., see also FF-3380-6, FF-3380-7, FF-3380-8, FF-3380-9
- Grosz, P M (2000). Rumpler C.I. Albatros Productions. ISBN 1-902207-21-1.
- Huth, Fritz (1920). Motoren für Flugzeuge und Luftschiffe. Bibliothek für Luftschiffahrt und Flugtechnik, Bd. 14 (in Deutsch) (3rd ed.). Berlin: R. C. Schmidt & co. OCLC 2116726.
External links
- BMW Group archives Archived 2022-03-17 at the Wayback Machine