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BMW and the RS255 Kompressor

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BMW and the RS255 Kompressor
BMW and the RS255 Kompressor
Image courtesy of Bonhams 1793 Ltd.

German company Bayerische Motoren Werke GmbH, better known as BMW, came into existence in 1916. The company had originally been named Rapp Motorenwerke. To meet the demand for aero engines during the First World War, the company built a large manufacturing facility near to the Oberwiesenfeld airfield in Munich.

After the war, the company was forced to cease the manufacture of aircraft under the terms of the Versailles treaty. Drawing on the knowledge gained in making precision aircraft engines and components, the company turned its manufacturing capabilities toward industrial engines, agricultural machines, and even office furniture.

First BMW Motorcycles

BMW began the long journey toward motorcycle production in 1918 when they produced the M2B15 horizontally opposed boxer engine. The aircraft manufacturing plant also produced a motorcycle called the Flink (German for nimble). They also produced the Helios (from Greek mythology, Helius was the god of the sun) which used a longitudinal mounted BMW engine. The Helios was redesigned in 1922 by BMW.

1922 also saw the design phase of one of BMWs most important models – the R32 – finalized. Chief engineer, Max Friz, was responsible for the basic layout of a twin cylinder air-cooled boxer engine with a shaft drive and a double loop frame (some of these features can still be seen on BMW motorcycles today such as the BMW GS series).

Besides the engineering expertise of Max Friz and Rudolf Schleicher who joined BMW in 1923, the company also benefitted from sound financial guidance from Austrian industrialist, Camillo Castiglioni. Castiglioni became a member of the company’s supervisory board in 1922 controlling the financial affairs for ten years.

As with many early motorcycle manufacturers, BMW benefitted from their involvement with competition. Engineer and racer Rudolf Schleicher designed an aluminum cylinder head for the R37 which went on to win the German 500-cc championships in 1924 and 1925. Schleicher also won a prestigious gold medal in the International Six Days Trial held in the UK. Further updates to the BMW resulted in Josef Stelzer winning the German Road Championship on the R39.

In 1929 BMW introduced a supercharged (Kompressor in German) version of their 750-cc machine which was used by Ernest Henne to set a two wheeled world land speed record of 216 kms/hr. (135 mph). With further modifications, Henne went on to set many world records which culminated in 1937 when he set a speed of 279.5 kms/hr. (175 mph) with a machine that BMW claimed produced 108 hp. This record stood for fourteen years.

RS255 BMW

In 1939 Georg "Schorsch" Meier made history by being the first non-British rider to win the Senior TT in the IOM. Meier used a version of the supercharged boxer engined twin cylinder machine that had set so many land speed records.

The Meier machine was reputed to produce 55hp and weighed 138 kgs (304 lb’s) and is on permanent display in the BMW museum.

The supercharged BMW had many unique features, including the mounting and drive for the supercharger which was on the front of the engine driven directly by the crankshaft (the original design had the supercharger mounted atop the gearbox). Also unique to this machine was its tubular steel frame, as BMW street machines of the time used a pressed steel design.

The RS255 (RS stands for Racing Sports) used a foot gear change (a first on a BMW) and hydraulically damped telescopic front forks—something that would become commonplace on motorcycles. Interestingly, although BMW had spent considerable resources in designing and developing the telescopic front forks, the rear of this machine was still rigid.

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