BMW R 2
The BMW R 2 , which appeared in 1931, was the second single-cylinder motorcycle model from BMW after the R 39 . R 2 was the first type designation from BMW, from which conclusions could be drawn about the displacement of the engine.
history
In 1931, after a four-year break, BMW brought a single-cylinder model back onto the market. Since 1928, motorcycles up to 200 cm³ could be driven without a license and tax-free in Germany. The R 2 was designed for this market , in which it was one of the most expensive motorcycles at 975 Reichsmarks . The R 2 sold more than 15,000 by 1937 contributed to the good reputation of BMW and paved the way for profitable mass production after the global economic crisis , which at the end of the construction period allowed a price of only 790 Reichsmarks. From March 1937, the successor was the BMW R 20 with tubular frame.
technology
engine
The small pushrod motor with hanging valves developed 6 HP (4 kW) in the first two series, later 8 HP (6 kW). It was already very advanced with a tunnel housing and axially installed crankshaft . This design was groundbreaking for the subsequent single-cylinder models and later newly developed boxer engines. The on-board voltage network by a 6V / 30W DC alternator powered located bottom left of the engine block. The battery is on the left behind the engine. The ignition is a so-called battery ignition. It is controlled by a camshaft operated breaker located in front of the engine in a cylindrical can.
drive
The R 2 had a manual gearbox with a drive shaft on the right side of the unsprung rear wheel.
BMW referred to the power transmission from the gearbox to the rear wheel as a " cardan drive ", the drive shaft as a " cardan shaft " and the gearbox on the rear wheel as a "cardan housing" - technically correct it was only a shaft drive of the rear wheel, as there were no cardan joints.
The gear housing was flanged directly to the motor housing. The input shaft of the three-speed gearbox was driven directly by the single-disc dry clutch in the crankshaft's flywheel. It sat in alignment with the main shaft, which drove the drive shaft via a hardy disk in direct extension. The engine, which was installed off-center to the right, resulted in a completely straight drive train in 3rd gear. The countershaft was under the main shaft. It was switched with a lever on the tank.
The kick starter was operated parallel to the vehicle's longitudinal axis and was located on the right-hand side - a sidecar operation was not intended.
landing gear
This motorcycle appeared in the then common BMW design, with a pressed and riveted sheet steel frame without rear suspension and the drawn short oscillating fork for guiding the front wheel.
The front and rear brakes are designed as half-hub brakes in accordance with the state of the art at the time.
Versions
Series 1 (1931)
The series 1 is particularly characterized by a more open valve train.
Series 2 to 5 (1932–1936)
The other four series built differed only in details, such as the shape of the tank, the exhaust system and the headlight mounting.
- Series 2 (1932–33) Encapsulated valve train, modified gear lever, from June 1933: friction shock absorber on the front fork
- Series 3 (1934) Amal carburetor (previously Sum carburetor), power increased to 8 HP, encapsulated alternator
- Series 4 (1935) smaller tank, modified headlights
- Series 5 (1936) modified drive ratio, wider rear fender with license plate holder
Technical specifications
Parameter | Data of the R 2, series 1 | Data of the R 2, series 5 |
---|---|---|
drilling | 63 mm | |
Hub | 64 mm | |
Displacement | 198 cc | |
power | 6 hp (4.4 kW ) at 3500 min -1 | 8 hp (5.9 kW ) at 4500 min -1 |
Top speed | 95 km / h | |
Empty weight | 110 kg | 130 kg |
Tank capacity | 11 L | 10 L |
See also
literature
- Erwin Tragatsch: All Motorcycles 1894 - 1981 . Motorbuch Verlag, Stuttgart 1997, ISBN 3-87943-410-7 .
- Andy Schwietzer: two-wheeled BMW R 2 . In: OLDTIMER MARKET . No. 3 , 2009, ISSN 0939-9704 , p. 26-33 .
- Udo Stünkel: BMW motorcycles typology: All series models from 1923 . Delius Klasing, Bielefeld 2008, ISBN 978-3-7688-2451-4 .
Web links
- BMW R 2. In: BMW History. BMW AG, accessed on December 24, 2017 (dossier of the BMW Group archive).
- Manual for BMW bikes, type R 2. In: BMW history. BMW AG, June 1931, accessed on December 6, 2015 (manual with pictures, 61 pages).
- Spare parts list for the BMW R 2/200 ccm, R 3/300 ccm, R 4/400 ccm motorcycles. In: BMW history. BMW AG, May 1942, accessed on December 6, 2015 (spare parts list for all series with pictures, 99 pages).
Individual evidence
- ↑ Advertising poster: BMW R 2. In: BMW History. BMW AG, 1931, accessed on December 7, 2015 (document in the BMW Group archive): "BMW - The new R 2 tax-free and driving license-free incl. Bosch light, Bosch horn, speedometer - 975 RM."
- ↑ High performance through quality and many years of experience, motorcycles R 2, R 35, R 5, R 6, R 12, R 17. In: BMW history. BMW AG, January 1937, accessed December 7, 2015 (prospectus).
- ↑ Price list No. 61. In: BMW History. BMW AG, February 1, 1937, accessed on December 7, 2015 (document in the BMW Group Archive).
- ↑ a b BMW R 2 Series 1 engine. In: BMW history. BMW AG, 1931, accessed on December 7, 2015 (photo in the BMW Group Archive).
- ↑ a b The new tax-free and driving license-free BMW R 2. In: BMW History. BMW AG, 1931, accessed on December 7, 2015 (prospectus): "Direct transmission through cardan shaft."
- ↑ BMW R 2 Series 1 engine sectional drawing. In: BMW history. BMW AG, 1931, accessed on December 7, 2015 (average engine and drive).
- ↑ BMW R 2 Series 1 construction drawing. In: BMW history. BMW AG, 1931, accessed on December 6, 2015 (technical overview drawing): "Type certificate"
- ↑ BMW R 2, Series 2a. In: BMW history. BMW AG, accessed on December 7, 2015 (dossier of the BMW Group Archive): “The time of the modifications cannot be determined by specific engine or chassis numbers. Also, these modifications were not necessarily introduced at the same time! "
class | Type | 1920s | 1930s | 1940s | ||||||||||||||||||||
3 | 4th | 5 | 6th | 7th | 8th | 9 | 0 | 1 | 2 | 3 | 4th | 5 | 6th | 7th | 8th | 9 | 0 | 1 | 2 | 3 | 4th | 5 | ||
up to 250 cm³ | Touring motorcycle | R 2 | R 20 | |||||||||||||||||||||
R 23 | ||||||||||||||||||||||||
Sport motorcycle | R 39 | |||||||||||||||||||||||
up to 500 cm³ | Touring motorcycle | R 32 | R 42 | R 52 | R 4 | |||||||||||||||||||
R 3 | R 35 | |||||||||||||||||||||||
Sport motorcycle | R 37 | R 47 | R 57 | R 5 | R 51 | |||||||||||||||||||
up to 750 cm³ | Touring motorcycle | R 62 | R 11 | R 12 | R 71 | |||||||||||||||||||
R 6 | R 61 | |||||||||||||||||||||||
Sport motorcycle | R 63 | R 16 | R 17 | R 66 | ||||||||||||||||||||
Prototypes, racing bikes | R 7 | |||||||||||||||||||||||
WR 750 | R 51 RS | |||||||||||||||||||||||
Military motorcycles | R 12 | |||||||||||||||||||||||
R 75 team |