BMW R 37

BMW
BMW R 37, exhibited at the AvD-Oldtimer-Grand-Prix 2011
R 37
Manufacturer	BMW motorcycle
Sales description	BMW R 37
Production period	1924 to 1926
class	Motorcycle , motorcycle with sidecar
Motor data
Two-cylinder Boxer - four-stroke - gasoline engine , installed longitudinally
Displacement  (cm³)	494
Power  (kW / PS )	12/16 at 4000 min -1
Top speed (  km / h)	115
transmission	3 courses
drive	Cardan drive
Empty weight  (kg)	134/184 (with sidecar)
Previous model	none
successor	BMW R 47

The BMW R 37 was the first sporty motorcycle from BMW .

history

development

Steering head with nameplate

During the development of the first BMW R 32 motorcycle , work began in parallel on a considerably more powerful sports model. As early as the beginning of 1923, a prototype was running with valves arranged in parallel in the partially encapsulated OHV cylinder head - and like the touring model without a front brake.

The young designer Rudolf Schleicher developed encapsulated light metal cylinder heads that have shaped the image of all BMW motorcycles to this day.

On December 10, 1924, 14 months after the R 32 , BMW presented the R 37 sports model to the public for the first time at the German Motor Show in Berlin .

With this motorcycle, BMW specified the modular principle for the coming model generations. The chassis and gearbox with the basic engine were largely identical; the differentiation for the displacement classes with 500 cm³ and 750 cm³ was achieved through modified cylinder bores . Touring models had side-controlled valves, sports models head-controlled. The R 37 as a sports model - even referred to as a “racing model” in a price list - had V-shaped valves hanging in the heads, which were operated by a camshaft via bumpers and rocker arms on roller bearings .

Sporting successes

Even before it was introduced as a new sports model, the R 37 achieved its first successes in numerous national competitions in 1924.

Participation in the following races is documented:

• Big Solitude Bergpreis 1923: Use of a prototype with steel cylinders by Hans Soenius
• Eifel race 1924: Franz Bieber (winner)
• Ruselbergrennen 1924: Franz Bieber (winner)
• Grand Solitude Bergpreis 1924: Franz Bieber, Rudolf Schleicher, Rudolf Reich (winner)
• Hindelang-Oberjoch Race 1924: Rudolf Schleicher
• Ettaler hill climb 1924: Rudi Reich in a BMW R 37 with a sidecar

Rudolf Schleicher won the first gold medal for Germany at the International Six Day Race in 1926 with the BMW R 37 he had developed ; at the same time it was the first international motorsport success for BMW.

marketing

According to the BMW price list, the price for the motorcycle in 1925 was 2,900 Reichsmarks - 700 Reichsmarks more than for the R 32 ; Lights, horn, speedometer and pillion seat were not included. Production ended in 1926 after only 152 units; The successor was the R 47 presented at the end of 1926 .

technology

engine

Bumper motor; clearly visible: footrest instead of the footrest that will later be used

Kick starter parallel to the longitudinal axis of the vehicle or transversely to the installation position of the engine, to the right of the clutch lever with cable holder

The engine with the designation M 2 B 36 was designed as a longitudinally installed two-cylinder boxer four-stroke engine with OHV valve control .

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.

Compared to the R 32 with the same displacement , the new cylinder heads almost doubled the output. The cooling has been improved by the cooling fins of the cylinders now arranged in the direction of flow.

During the course of production, the exhaust system was changed and extended to over the rear axle.

Carburetor

The 26-mm three-slide carburetor, a proprietary design by BMW, drew the intake 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 using a lever on the left half of the handlebar.

drive

Drive shaft of the R 37 with Hardy disc - not yet a "real" cardan shaft; the three-slide carburettor is clearly visible

The R 37 had a manually shifted 3-speed gearbox, the upper end of the gear lever was on the right side of the 14 liter tank. The drive shaft led to the unsprung rear wheel on the right-hand side of the vehicle and therefore had no joints . Nevertheless, BMW referred to the power transmission as " cardan drive ", the drive shaft as " cardan shaft " and the housing of the deflection gear on the rear wheel as "cardan housing".

The horizontally divisible gearbox housing was flanged directly to the motor housing. The transmission input shaft was driven directly by the single-disc dry clutch in the crankshaft's flywheel. The output shaft drove the drive shaft via a hardy disk in direct extension.

The kick starter (starter lever) was actuated parallel to the vehicle's longitudinal axis; a bevel gear redirection was built into the gearbox housing for this purpose. This complex diversion was abandoned four years later on the R 52 and R 57 .

landing gear

The sidecar compatible chassis was the same as that of the R 32 : a double loop tubular frame without rear suspension, the front fork is a drawn short swing arm with leaf suspension.

In many contemporary images, friction shock absorbers can be seen on the front swing arm.

Wedge block brake on the rear wheel with a long foot control lever

The rear wheel was decelerated by a foot-operated wedge - block brake that acted on its own brake rim; the front brake had a drum diameter of 150 mm.

Technical specifications

Parameter	BMW R 37
drilling	68 mm
Hub	68 mm
Displacement	494 cc
Compression ratio	6.2: 1
power	16  hp (12  kW ) at 4000 min -1
Top speed	115 km / h
Seat height	72 cm
Empty weight	134 kg (with original sidecar "S 38" 184 kg)
Tank capacity	14 l

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 37  - collection of pictures, videos and audio files

• BMW R 37. In: BMW History. BMW AG, accessed on December 30, 2019 (dossier of the BMW Group Archives). 
• Spare parts list and boards for the BMW sports bike Type R 37. In: BMW History. BMW AG, 1925, accessed on January 4, 2016 (spare parts list with pictures, 23 pages). 

Individual evidence

1. ↑ prototype 500cc OHV 1924. In: BMW history. BMW AG, 1923, retrieved on December 10, 2015 (photo in the BMW Group archive): “1923 - Head-controlled sports machine based on the R 32 with steel cylinders and cast-iron cylinder heads (predecessor of the R 37). Was only successful on a winter trip due to cooling problems. "  
2. ↑ Cylinder head of the R 37, combustion chamber. In: BMW history. BMW AG, 1924, accessed on December 11, 2015 (photo in the BMW Group archive): "The first R 37 cylinder head, labeled by Rudolf Schleicher."  
3. ↑ BMW presents the R 37, the first sports model from the BMW brand. In: BMW history. BMW AG, December 10, 1924, accessed on December 12, 2015 (text in the BMW Group Archive): “At the German Motor Show in Berlin (December 10-18, 1924), BMW presented the R 37, the first sports model with light alloy Cylinder head and hanging valve control. "  
4. ^ Solitude 1923, Hans Soenius in a BMW R 37. In: BMW history. BMW AG, 1923, accessed on December 16, 2015 (photo in the BMW Group Archive): "First start of the BMW R 37 with steel cylinder on the Solitude 1923"  
5. ↑ Franz Bieber, winner of the 1924 Eifel race with a BMW R 37. In: BMW history. BMW AG, 1924, accessed on December 16, 2015 (photo in the BMW Group Archive): "Franz Bieber after his victory"  
6. ^ Ruselbergrennen, winner Franz Bieber. In: BMW history. BMW AG, September 21, 1924, accessed on December 16, 2015 (photo in the BMW Group Archive): "Franz Bieber wins with the 500ccm R 37"  
7. ↑ BMW R 37 with Rudi Reich. In: BMW history. BMW AG, 1924, accessed on December 16, 2015 (photo in the BMW Group Archive): "Winner at Solitude 1924"  
8. ↑ BMW R 37 with Rudolf Schleicher. In: BMW history. BMW AG, 1924, accessed on December 16, 2015 (photo in the BMW Group Archive): "Hindelang-Oberjochrennen"  
9. ^ Rudi Reich in a BMW R 37 with a sidecar. In: BMW history. BMW AG, 1924, accessed on December 16, 2015 (photo in the BMW Group Archive): "Beim Ettaler Bergrennen"  
10. ^ Rudolf Schleicher's victory in the six-day race in 1926. In: BMW history. BMW AG, 1926, accessed on December 12, 2015 (text in the BMW Group Archive).  
11. ↑ Price list No. 28 for BMW motorcycles R 32, R 39, R 37 and the sidecar S 38. In: BMW history. BMW AG, 1925, accessed on December 10, 2015 (document in the BMW Group Archive): "BMW Renn-Modell 1,9 / 16PS"  
12. ↑ Udo Stünkel: BMW motorcycles typology: All series models from 1923 . Delius Klasing, Bielefeld 2008, ISBN 978-3-7688-2451-4 , p. 10-11 .
13. ↑ BMW R 37 technical drawing of the M 2 B 36 engine. In: BMW history. BMW AG, accessed on December 15, 2015 (document in the BMW Group Archive).  
14. ↑ ^{a b} manual for BMW wheels, type R 32 / 37. In: BMW history. BMW AG, December 10, 1925, accessed on December 15, 2015 (manual with pictures, 23 pages).  
15. ↑ R 37 and racing driver Köppen. In: BMW history. BMW AG, 1926, accessed on December 15, 2015 (photo in the BMW Group archive): "Racing driver Paul Köppen, Berlin, with his R 37 and victory wreath."