BMW R 2

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BMW R 2 (1931) in the Ibbenbüren motorcycle museum

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

BMW R 2 (1931)

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)

Unrestored BMW R 2, Series 2a

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 hp (4.4  kW ) at 3500 min -1 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

Web links

Commons : BMW R 2  - collection of images, videos and audio files

Individual evidence

  1. 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."
  2. 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).
  3. Price list No. 61. In: BMW History. BMW AG, February 1, 1937, accessed on December 7, 2015 (document in the BMW Group Archive).
  4. 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).
  5. 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."
  6. BMW R 2 Series 1 engine sectional drawing. In: BMW history. BMW AG, 1931, accessed on December 7, 2015 (average engine and drive).
  7. BMW R 2 Series 1 construction drawing. In: BMW history. BMW AG, 1931, accessed on December 6, 2015 (technical overview drawing): "Type certificate"
  8. 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! "