The BMW WR 750 was a
supercharged racing motorcycle
Motorcycle racing (also called moto racing and motorbike racing) is the motorcycle sport of racing motorcycles. Major varieties include motorcycle road racing and off-road racing, both either on Race track, circuits or open courses, and track ...
from
BMW with two-cylinder, four-stroke
flat twin engine
A flat-twin engine is a two-cylinder internal combustion engine with the cylinders on opposite sides of the crankshaft. The most common type of flat-twin engine is the boxer-twin engine, where both pistons move inwards and outwards at the same ti ...
starting production in the year 1929.
History
The idea to equip the flat twin engine with a supercharger came from the designer of the BMW R 37 race bike, Rudolf Schleicher.
[ But after his departure from BMW, the concept was transferred to the racing mechanic Josef Hopf, closest confidant of Rudolf Schleicher, and the BMW works driver and German Champion of 1926 and 1927, ]Ernst Jakob Henne
Ernst Jakob Henne ( – ) was a German motorcycle racer and racecar driver.
Henne was born in the village of Weiler, near Wangen im Allgäu. His father was a saddlemaker. In 1919 Henne was apprenticed to a become a motor vehicle mechanic. H ...
. The first engines ran on the test bench in 1928.
Races and record attempts
The WR 500 and WR 750 could not break the dominance of the English brands in the international racing.[ Success came with the next generation of supercharged BMWs, with the Type 255, which went on the hunt for records and racing successes beginning in 1935.
]
Record runs
The first official world speed record for BMW was set by Ernst Jakob Henne on a WR 750 on 19 September 1929 with over the mile with flying start. The record runs with the bumper compressor engines were continued until 1934.[
]
Design
The ''Werksrennmotorräder'' ("works
Works may refer to:
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* Samuel Works (c. 1781–1868), New York politician
Albums
* '' ''Works'' (Pink Floyd album)'', a Pink Floyd album from 1983
* ''Works'', a Gary Burton album ...
racebikes", initialized WR) WR 500 and WR 750 designs were derived from the R 37.
Engine
The engine was a longitudinally mounted flat twin
A flat-twin engine is a two-cylinder internal combustion engine with the cylinders on opposite sides of the crankshaft. The most common type of flat-twin engine is the boxer-twin engine, where both pistons move inwards and outwards at the same ti ...
four-stroke engine
A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directi ...
with overhead valve
An overhead valve (OHV) engine, sometimes called a ''pushrod engine'', is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with earlier flathead engines, where the valves were located b ...
s. The compressor was located between the seat and gearbox and in the first version was driven by an additional open parallel shaft next to the magneto with a right-angle bevel gear
Bevel gears are gears where the axes of the two shafts intersect and the tooth-bearing faces of the gears themselves are conically shaped. Bevel gears are most often mounted on shafts that are 90 degrees apart, but can be designed to work at othe ...
linkage.[ Thus, the compressor shaft ran transversely to the direction of travel. The boost pressure was up to 2 ]bar
Bar or BAR may refer to:
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* Candy bar
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depending on application. The tank was shortened compared to the series motorcycles to make room for the compressor. The single carburetor was located behind the compressor.
Starting in 1930 there was also a version with chain-driven compressor. The chain ran behind the cylinders under a highly modified engine cover, and drove the compressor shaft lying parallel to the direction of travel.[
]
Drive
The WR 750 had a manual transmission with shaft drive on the right side of the unsprung rear wheel.
Suspension
The front fork utilized a leading link fork, suspended by two leaf spring
A leaf spring is a simple form of spring commonly used for the suspension in wheeled vehicles. Originally called a ''laminated'' or ''carriage spring'', and sometimes referred to as a semi-elliptical spring, elliptical spring, or cart spring, i ...
assemblies. The brakes were considerably enlarged and improved from those furnished on the production motorcycles.
See also
*List of motorcycles of the 1920s
A ''list'' is any set of items in a row. List or lists may also refer to:
People
* List (surname)
Organizations
* List College, an undergraduate division of the Jewish Theological Seminary of America
* SC Germania List, German rugby unio ...
*List of motorcycles of the 1930s
This a listing of motorcycles of the 1930s, including those on sale, introduced, or otherwise relevant in this period.
Motorcycle
* Abendsonne
* Acme motorcycle (1939–1949)
*AJS Model E (1925-1939)
*AJS S3 V-twin
* AJS Silver Streak
* AJS V4
...
*List of motorcycles by type of engine
List of motorcycles by type of engine is a list of motorcycles by the type of motorcycle engine used by the vehicle, such as by the number of cylinders or configuration.
A transverse engine is an engine mounted in a vehicle so that the engine's cr ...
*Motorcycle land-speed record
The motorcycle land-speed record is the fastest speed achieved by a motorcycle on land. It is standardized as the speed over a course of fixed length, averaged over two runs in opposite directions. AMA National Land Speed Records requires 2 passes ...
References
External links
{{Forced induction motorcycles
WR 750
Land speed record motorcycles