BMW R 2
The published in 1931 BMW R 2 was after the R 39, the second single-cylinder motorcycle model BMW. R 2 was the first type designation of BMW, it could be concluded on the cubic capacity of the engine of the.
- 3.1 Series 1 (1931 )
- 3.2 Series 2-5 ( 1932-1936 )
History
1931 BMW launched after four year break a single-cylinder model on the market. Since 1928 motorcycles up to 200 cc without a license and tax-free could be operated in Germany. For this market, the R 2 was designed, in which she was one of the most expensive motorcycles with 975 Reichsmark. The R and 1937 more than 15,000 sold 2 contributed to the reputation of BMW and paved after the global economic crisis the way for profitable mass production. Successor was from March 1937, the BMW R 20 with tubular frame.
Technology
Motor
The small bumper engine with overhead valves has in the first two series, 6 HP ( 4 kW), later 8 hp (6 kW). He was already running very progressive with tunnel to be built in housing and axially crankshaft. This design was the way for the subsequent single-cylinder models and later newly developed horizontally opposed engines. The on-board voltage power is supplied by a 6V/30W DC alternator is on the left bottom of the engine block. The battery is located behind the left engine. The ignition is called a battery ignition. It is controlled by a camshaft actuated by the circuit breaker, which is located in front of the motor in a cylindrical can.
Drive
The R 2 had a manual transmission with drive shaft on the right side of the unsprung rear wheel.
BMW described the power from the transmission to the rear wheel as " shaft drive ", the drive shaft as a " propeller " and the gearbox on the rear as " gimbal " - technically correct, it was just a shaft driving the rear wheel, as there was no universal joints.
The gearbox was mounted directly on the motor housing. The input shaft with 3 courses was directly driven by the single-plate dry clutch in the flywheel to the crankshaft. The output shaft drove a Hardy disc in the drive shaft to direct extension. With the right eccentrically mounted engine resulted in 3rd gear a completely straight driveline.
The kickstarter was operated parallel to the vehicle longitudinal axis and was positioned on the right side - a sidecar was not provided.
Landing gear
This motorcycle appeared in the then current BMW design, with a pressed and riveted steel frame with no rear suspension and the solid short tuning fork for keeping the front wheel.
The front and rear brakes are made to the then state of the art as a semi- hub brakes.
Versions
Series 1 (1931 )
The series 1 is particularly characterized by a more open the valve train.
Series 2-5 ( 1932-1936 )
The other four built series differed only in details like the shape of the tank, the exhaust system or the headlight mounting.
- Series 2 ( 1932-33 ) enclosed valve train, changed gear lever, as of June 1933: friction shock absorbers on the front fork
- Series 3 (1934 ) Amal carburettor (previously Sum carburetor ), but with 8 PS, alternator encapsulated
- Series 4 ( 1935), smaller tank, changed headlights
- Series 5 (1936 ) modified drive ratio, wider rear fender with license plate holder