BMW R 5

BMW R 5

The BMW R 5 was a sporty two-cylinder motorcycle in the 500 cm³ class from the German manufacturer BMW , which was completely redesigned on the market in 1936 and was trend-setting for motorcycle construction at BMW until the 1950s.

history

The BMW R 5 was created as a somewhat simpler “replica” of the 1935 factory racing motorcycles of the type 255. Instead of the DOHC racing engine with a compressor, a 494 cm³ OHV engine and the equipment required for road traffic such as lighting, horn and kick starter were installed. As the designer of both models, Rudolf Schleicher was in charge. The R 5 was presented as a series motorcycle at the motorcycle fair in Milan in January 1936.

In 1936 1502 units were built; In 1937 another 1,150 motorcycles were built.

technology

The frame is (unlike the sheet metal press frame of the previous models) made of oval and conically drawn steel tubes for the first time arcatom welded under protective gas . Thus the R 5 is the “prototype” of the BMW models up to 1955 (top model R 68). It defines the lines of the models from the 1950s. The fenders, tank and rims are made of sheet steel . The engine of the BMW R 5 is mounted in the frame with two quick-release axles. The mufflers are attached to the engine shaft and frame with clamps; they show the “fishtail” shape with a vertical slot outlet, which was common until the 1950s.

engine

The engine block , like the gearbox and the axle gear housing, is made of cast aluminum, the cylinders of gray cast iron. The longitudinally installed two-cylinder boxer four-stroke engine has bumpers ( OHV engine) running above the cylinders in chrome-plated protective tubes . The push rods move the rocker arms in the cylinder head , which in turn actuate the overhead valves. Like the two connecting rods, the rocker arms are mounted in needle bearings; the crankshaft runs in ball bearings . The engine of the R 5 has two "underneath" camshafts (they lie above the cylinder feet), which are driven by the crankshaft via a timing chain . The oil pump is located in the housing swamp and is a simple gear pump , the camshaft from the right by a worm - reduction is driven via an intermediate shaft. In addition to the lubrication in the crankcase, the engines of the R 5 also have oil fillings (to be checked and changed separately) for each cylinder head.

transmission

The flywheel on the rear crankshaft stub takes on the dry single-disc clutch . The clutch is operated with a thrust bearing via a push rod that runs through the hollow main shaft of the gear unit. The four-speed gearbox with dog clutch engagement is the first production BMW motorcycle gearbox with foot control, as it was previously used only in the BMW racing machines. In addition to the footshift, there is also a manual gearshift lever on the right side of the transmission, with which not only one gear further, but each gear can be selected directly and, for example, switched directly from fourth gear to neutral.

Ignition and alternator

The splash-proof encapsulated Bosch DC alternator type RD 45/6 2800 RS 15 with charge regulator sits on the engine housing under an aluminum cover that was ribbed from 1937 for better cooling . The ignition system is a Bosch battery ignition with ignition distribution via slip ring (VU 2 DR 7) with manual adjustment of the pre-ignition, driven by the left camshaft. The motorcycle cannot be started with the kick starter with an empty battery (or without battery). However, it can be pushed and then driven, since the direct current alternator, unlike a three-phase alternator, can generate electricity without a battery and the charge regulator is not destroyed in the process. The lead accumulator is attached to a bracket on the frame behind the gearbox.

Carburetor and air filter

The two slide carburetors are Fischer-Amal float chamber carburetors with a conical needle in the round slide. The wet air filter element sits on the gearbox housing from 1937 onwards, before two individual wet air filters were each attached to the carburetors: steel nets on which the dust sticks when the air is sucked in, which are washed out for maintenance purposes and then re-wetted with oil.

drive

The drive train consists of the open drive shaft (no cardan shaft , although it is so called, because of the rigid frame it does not need cardan joints) and the bevel gear on the rear wheel.

Chassis and chassis

The chassis is a double-loop tubular frame without a suspension of the rear wheel (rigid frame). The front telescopic fork was equipped for the first time with adjustable oil damping. For this purpose, an adjustment lever on the upper triple clamp can be continuously changed while driving, from hard to soft hydraulic damping.

Brakes

The R 5 is equipped with narrow half-hub brakes.

Trivia

The BMW R 5 served as a design template for the cruiser BMW R 18 launched in 2020 .

Technical specifications

Parameter	Data of the R 5
drilling	68 mm
Hub	68 mm
Displacement	494 cc
power	24  hp (18  kW ) at 5500 min -1
Top speed	140 km / h
Empty weight	165 kg
Tank capacity	15 l

See also

• List of BMW motorcycles

Web links

Commons : BMW R 5  - collection of images, videos and audio files

• BMW R 5. In: BMW History. BMW AG, accessed on December 21, 2015 (dossier of the BMW Group Archives). 

Individual evidence

1. ^ BMW Type R 5. In: BMW History. BMW AG, December 1935, accessed on December 21, 2015 (document in the BMW Group Archive): "Where can you find the highest speed, beauty, reliability and economy so ideally combined as in the new BMW type R 5?" 
2. ↑ Presentation of the BMW R 5. In: BMW History. BMW AG, January 1936, accessed on December 26, 2015 (document in the BMW Group Archive). 
3. ↑ Spare parts list for the BMW motorcycles R 5 -500 ccm Sport and R 6 -600 ccm. In: BMW history. BMW AG, April 1939, accessed on December 26, 2015 (complete spare parts list with pictures, 43 pages). 
4. ↑ Manual for the BMW motorcycle R 5 and R 6. In: BMW history. BMW AG, April 1937, accessed on December 26, 2015 (manual with pictures, 58 pages). 
5. ↑ ^{a b} manual for the BMW wheel type R 5. In: BMW history. BMW AG, May 1936, accessed on December 26, 2015 (manual with pictures, 61 pages). 
6. ↑ Official manufacturer's website. In: bmw-motorrad.de. Retrieved April 4, 2020 .