BMW R 42

BMW
BMW R 42
R 42
Manufacturer	BMW motorcycle
Sales description	R 42
Production period	1925 to 1928
class	Motorcycle , motorcycle with sidecar
design type	Tourer
Motor data
BMW M 43, air-cooled two-cylinder Boxer - four-stroke engine , flathead engine , mounted longitudinally
Displacement  (cm³)	494
Power  (kW / PS )	9/12 at 3400 min -1
Top speed (  km / h)	95
transmission	3 courses
drive	Cardan drive
Brakes	v. Drum brake, h. Cardan brake
Seat height (cm)	72
Empty weight  (kg)	126 (with sidecar 188)
Previous model	BMW R 32
successor	BMW R 52

The BMW R 42 was the second touring motorcycle from the German motorcycle manufacturer BMW.

history

development

On November 26, 1925, two years after the R 32 , BMW presented its successor, the R 42, to the public for the first time at the German Motor Show in Berlin . BMW continued the modular principle with this motorcycle. The chassis and gearbox with the basic engine were largely identical; The differentiation between sports and touring models was implemented using head or side-controlled cylinder heads and cylinders.

marketing

The price for the motorcycle in 1927 was 1,510  Reichsmarks (equivalent to 5,538 euros in today's purchasing power), which is 700 Reichsmarks less than for the R 32 . Lights, horn, speedometer and pillion seat were not included in the purchase price. Production ended in 1928 after over 6500 units; The successor was the R 52 , which was produced from July 1928 .

technology

engine

The engine with the designation M 43 was a longitudinally mounted twin-cylinder boxer - four-stroke engine with flathead engine .

construction

The motor housing could be divided horizontally. An intermediate gear above the crankshaft drove the camshaft one level higher, which in turn drove the ignition system on the next level. This gear cascade made the engine relatively tall for a boxer engine. The camshaft opened the valves via short slide tappets.

cylinder

The cast iron cylinders had removable cylinder heads made of light metal and radial cooling fins.

Carburetor

The carburetor, an in-house design by BMW, sucked in the air through the flywheel housing. The mixture quantity ("throttle slide") and mixture composition ("air slide") were set using two levers on the right-hand handlebar half.

ignition

A Bosch high-voltage magnet or an ignition generator were fastened to a platform above the crankshaft with a strap. The ignition was adjusted with a lever on the left side of the handlebar. The spark plug was in the removable cylinder head.

drive

The R 42 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 horizontally divisible gearbox housing was flanged directly to the motor housing. The three-speed input shaft was driven directly by the single-plate dry clutch in the crankshaft's flywheel. The output shaft drove the drive shaft via a hardy disk in direct extension. The housing of the bevel gear drive on the rear axle was filled with oil - the R 32 was still lubricated with grease. The gearbox was still filled with Stauffer grease. The kick starter was operated parallel to the vehicle's longitudinal axis; a bevel gear redirection was built into the gearbox housing for this purpose. This complex redirection was only given up in the successor series R 52 and R 57 .

landing gear

The chassis is a tubular frame without rear suspension, the front fork has a drawn short swing arm with leaf suspension. As with the R 39 , the rear brake was a so-called cardan brake that acted on the outer ring of the Hardy disc . The saddle height was 72 cm.

Technical specifications

Parameters	Data of the R 42
drilling	68 mm
Hub	68 mm
Displacement	494 cc
power	12  PS (9  kW ) at 3400 min -1
Top speed	95 km / h
Empty weight	126 kg (with sidecar 188 kg)
Tank capacity	14 liters

See also

• List of BMW motorcycles

literature

• Udo Stünkel: BMW motorcycles typology: All series models from 1923 . Delius Klasing, Bielefeld 2008, ISBN 978-3-7688-2451-4 .

Web links

Commons : BMW R 42  - collection of pictures, videos and audio files

• BMW R 42. In: BMW History. Retrieved on December 12, 2015 (dossier from the BMW Group Archive). 

Individual evidence

1. ↑ BMW presents the R 42. In: BMW History. BMW AG, November 26, 1925, accessed on December 10, 2015 (document in the BMW Group Archive): “At the German Motor Show in Berlin (November 26 - December 6, 1925), BMW is presenting the R 42, the successor to the R 32 " 
2. ↑ Price list No. 35 for BMW motorcycles: R 42, R 47. In: BMW history. BMW AG, 1926, accessed on January 4, 2016 (document in the BMW Group Archive). 
3. ↑ Udo Stünkel: BMW motorcycles typology: All series models from 1923 . Delius Klasing, Bielefeld 2008, ISBN 978-3-7688-2451-4 , p. 10-11 .
4. ↑ ^{a b c d e} manual for BMW wheels type R 42. In: BMW history. BMW AG, April 1926, accessed on December 13, 2015 (manual with pictures, 41 pages).