Rapp Motorenwerke


Rapp Motorenwerke GmbH was an aircraft engine manufacturer in Germany. It was in operations at the turn of the 20th Century and underwent numerous mergers and changes before becoming BMW.

Early engines

and Julius Auspitzer founded Karl Rapp Motorenwerke GmbH with a capital stock of RM 200,000 on 29 April 1913 on the site of Flugwerke Deutschland GmbH. General Consul Auspitzer was the company's sole shareholder, with the operational side of the company managed by Karl Rapp. The idea was for the new company to build and sell "engines of all types, in particular internal combustion engines for aircraft and motor vehicles", in addition to building an engine for the second Kaiserpreis rally, but it was not ready in time.
Before World War I, Rapp produced both in-line 6-cylinder and V8 cylinder water-cooled aeroengines. The in-line 6-cylinder produced 125 hp @ 215 kg ; with a 901 cu in displacement. Soon, the company made the Rapp II, which increased the power output to 150 hp @ 260 kg. Shortly thereafter, early into World War I, the Rapp III 175 hp 295 kg six-cylinder aeroengine was manufactured. The V8 they developed was 1201 cu in, producing 200 hp @ 300 kg.
All of Rapp's designs were overhead cam, with forged steel liners screwed to cast steel heads. The aeroengines produced by Rapp were easily distinguished from the other aeroengines, because the vertical shaft that drove the overhead camshaft came up between cylinders #4 and #5, instead of at the rear. Additionally, all the cylinders were in pairs.
When World War I broke out, German military authorities placed orders with Rapp Motorenwerke. With the influx of capital, the company expanded rapidly and employed 370 workers by 1915. In response to a commission from the German military authorities, Karl Rapp increased the output of his Rapp III engine from 150 to 175 horsepower. However, the strengthening which this called for made the engine extremely heavy, and the engines developed severe vibrations; so much so, that it achieved no commercial success. Even a revised version with four valves per cylinder, the Rapp IIIa, was unable to rectify this situation: the name Rapp had suffered to such an extent that the military departments no longer purchased engines from his company.

Wartime production

At the beginning of the First World War, the company was one of the key Bavarian companies for the war effort, and appeared to have gained a certain reputation, despite the fact that none of the designs and developments achieved any real success. Franz Josef Popp had noted the facilities of Rapp Motorenwerke were ideal for engine production, having the necessary workforce and equipment. Popp lobbied hard to manufacture, by license, the 12-cylinder Austro-Daimler aircraft engine. Popp succeeded in convincing the Bavarian Army Administration and the Imperial Naval Office of the Imperial Austro-Hungarian Army Administration to order Rapp engines licensed through Austro-Daimler. On behalf the Austrian war Ministry, Popp was delegated to supervise the handling of the order in Munich. Popp was also the person who convinced Max Friz, an aircraft engine designer and engineer at Daimler, to come to Munich to assist in development and expansion. With Friz' arrival in 1916, the original Rapp designs were also worked on to create a "high altitude" aeroengine that would give the Imperial Army strategic air superiority in combat. 1917 marks the breakthrough by Friz and his team of engineers in developing the type III.

BMW Type III

On 20 May 1917, Rapp Motorenwerke registered the documentation for the construction design for the new engine, dubbed "type III". Friz' design, was laid out as an in-line six-cylinder, which guaranteed optimum balance, with few small vibrations. The engine was successful, but the real breakthrough came in 1917, when Friz integrated a basically simple throttle butterfly into the "high-altitude carburettor", enabling the engine to develop its full power high above the ground. This is precisely the reason why the engine, now dubbed "type IIIa", had unique superiority in air combat. Franz-Zeno Diemer, the pioneering aviator and test pilot for the company, sets a new world altitude record with a 32,000 ft flight in 1919 flying a DFW F 37/III with a BMW Type IV aircraft engine. September of the same year, Diemer set another world altitude record- this one for a passenger aircraft in a Ju F-13 powered by a BMW IIIa aircraft engine.

Rapp Motorenwerke changes to BMW GmbH

The decision by the Prussian Army Administration to order 600 units of the innovative high-altitude aeroengine, prompted reorganizing the legal structure of the company. The aeroengine developed by Friz had turned Rapp Motorenwerke into an essential contributor to the war effort virtually overnight. From the middle of 1917 onward, the business, which would probably have disappeared from history never to be heard of again, now enjoyed the undivided attention of the armed services and other governmental bodies. Large subsidies flowed in and the Munich company received well financed production orders. The recognition that Max Friz gained with his engine made it clear to all the senior managers that up to now Karl Rapp and his inadequate engine designs had held the company back from success. In Friz they now had an excellent chief designer on hand and were no longer dependent on Rapp. Therefore, on 25 July 1917 the partners in the company terminated Karl Rapp’s contract. The end of this collaboration had been coming for a long time. When Rapp’s departure was finally a certainty, another important decision had to be made. If the man who had lent his name to the company was now leaving it, a new name was naturally required. So, on 21 July 1917, Rapp Motorenwerke GmbH was renamed Bayerische Motorenwerke GmbH. It was thus the first company to bear this name and to use the abbreviation “BMW”. BMW AG acknowledges this date to be the official beginning of the company we know today.
The departure of Karl Rapp enabled a fundamental restructuring of BMW GmbH. While the development side was placed under Max Friz as Chief Designer, Franz Josef Popp took over the post of Managing Director. Until the end of the war, aeroengines remained the company's only product. The BBE aeroengine project was a big success under the designation BMW IIIa.