The BMW Motorrad Concept R 18 – a purist, historically inspired version of
the big boxer – was presented by the BMW Group at the Concorso d’Eleganza in the
Villa d’Este at Lake Como in the early summer. Six months later, at the world’s
biggest motorcycle show – the EICMA in Milan – BMW Motorrad now presents its
second sensational concept bike based on a big boxer engine: the BMW Motorrad
Concept R 18 /2 (pronounced: “Slash Two”). It is the stylistic opposite of the
Concept R 18: a modern, dynamic custom cruiser with a performance appeal that is
somewhat rougher round the edges. As such, the BMW Motorrad Concept R 18 /2
demonstrates yet another potential expression of the Heritage concept, providing
an impressive example of the flexibility and wide-ranging customisation options
offered by this basic architecture.
“In contrast to the classic, elegant BMW Motorrad Concept R 18, the Concept R 18
/2 draws on its large boxer engine and frame to create a modern custom concept.
The Concept R 18 /2 is uniquely extrovert. Elements from the past and future of
BMW Motorrad merge here to create a captivating cruiser, making a powerful
statement: “It’s a highly emotional bike designed for active riding. At the same
time, the Concept R 18 /2 reflects the range of characterisations and customer
dreams that we are able to realise using the same backbone,” explains Edgar
Heinrich, Head of Design BMW Motorrad. A performance cruiser à la BMW.
The BMW Motorrad Concept R 18 /2 celebrates the fascination of cruisers in an
interpretation that is both sporty and modern. Minimalist handlebar trim
together with the deep, elongated proportions promises a dynamic driving
experience. The fairing, tear-drop fuel tank and seat form a flowing line that
finds its perfect conclusion in the shortened rear wheel cover. All body parts
are finished in Candy Apple Red metallic, an expressive red tone that highlights
the flowing movement on the side. This luminous custom red with lots of depth is
a real eye-catcher, changing from bright red to almost black depending on the
incidence of light. Another striking feature is created by the graphic lines on
the painted body parts, which extend from the side and top view of the fuel tank
to the wheel cover and are visually prolonged across the seat. These give the
Concept Bike a distinctive appeal. The large boxer at the centre.
As in the Concept R 18, the centrepiece of the BMW Motorrad Concept R 18 /2
is a large 2-cylinder boxer engine with 1800 cc, including modern air/oil
cooling and designed in a 1960s aesthetic. The engine is finished in a warm grey
tone and has a sporty look, with an integrated breast cover, valve covers in a
high-gloss black finish and a black frame. The engine badge bears the name of
the Concept Bike, adding a high-quality accentuation.
After “Departed” by the Japanese customizer CUSTOM WORKS ZON, “The Revival
Birdcage” by Revival Cycles in Austin, Texas and the BMW Motorrad Concept R 18,
the BMW Motorrad Concept R 18 /2 is now the fourth interpretation of the
large-volume BMW Motorrad boxer engine. Attention to detail.
As a genuine BMW, the BMW Motorrad Concept R 18 /2 not only features a boxer
engine, loop frame and tear-drop fuel tank, it also has a classic and elegantly
showcased universal shaft. The striking cast iron wheels with 19” at the front
and 16” at the rear create an equally discreet and dynamic dragster look,
authentically rounding off the bike’s overall appearance. Meanwhile features
such as high-performance Brembo brake calipers and Hattech stainless steel
tailpipe system reflect the close attention to detail with which the BMW
Motorrad Concept R 18 /2 was designed. Multitude of possibilities.
The BMW Motorrad Concept R 18 /2 puts forward a new interpretation of a
dynamic performance cruiser that not only taps into an area previously
unexplored by BMW Motorrad but also demonstrates the true versatility of the
“big boxer” platform. “After the BMW Motorrad Concept R 18, our aim with the
Concept R 18 /2 is to demonstrate how flexible the basic engine and suspension
are as a starting point for customisation, and how easy it is to authentically
realise different styles. And I have to admit: we were very impressed at how it
was possible to bring this boxer concept forward from the 30s via the 80s into
the 2020s,” says Bart Janssen Groesbeek, BMW Motorrad Vehicle Designer for the
Big Boxer Concepts.
Engine Overview
The highest-capacity 2-cylinder boxer engine of all
time.
The heart of the new BMW R 18 is a completely newly developed 2-cylinder boxer
engine – the “Big Boxer” – which has played a key role not just in the two BMW
Motorrad prototypes – the Concept R 18 and the Concept R 18 /2 – but also in the
custom bikes supported by BMW Motorrad, namely “The Departed” by ZON and
“Birdcage” by Revival Cycles. BMW Motorrad now presents this new, highly
distinctive engine in detail.
Not only in terms of its impressive outward appearance, but also from a
technical point of view, the new “Big Boxer” ties in with the traditional boxer
engines that were synonymous with motorcycles from Munich and Berlin-Spandau for
around 70 years, from the beginning of BMW Motorrad production in 1923 through
to the appearance of the air/oil-cooled successor: these were engines with a
clear design, created for optimum reliability and ease of maintenance, featuring
logically arranged yet powerful technology.
With its OHV valve drive along with a separate engine and transmission
housing, the new “Big Boxer” has the same structural features that distinguished
the very first BMW Motorrad boxer engine, which at that time had laterally
controlled valves. The highest-capacity twin-cylinder boxer engine ever used in
motorcycle series production is a 1 802 cc engine, resulting from a 107.1 mm
bore and
100 mm stroke. The engine output is 67 kW (91 hp) at 4 750 rpm. The maximum
torque of 158 Nm is already available at 3 000 rpm. More than 150 Nm is now
available from 2 000 to 4 000 rpm. This ensures enormous pulling power and – in
conjunction with a generously sized flywheel mass – exemplary running smoothness
as well. These are the benefits of this level of performance and torque during
riding. The maximum engine speed is 5 750 rpm, while the idling speed is 950
rpm.
Air/oil cooling, vertically split engine housing and triple plain bearing
crankcase.
The new “Big Boxer” is air/oil cooled, has large ribbed cylinders and cylinder
heads and weighs 110.8 kg including gearbox and intake system. It has a
vertically split aluminium engine housing.
Unlike the classic air-cooled 2-valve boxer engines made by BMW Motorrad,
however, the “Big Boxer” crankshaft, forged from quenched and tempered steel,
has an additional main bearing at the centre, which was necessary due to the
enormous cylinder volume in order to prevent undesirable bending vibrations of
the crankshaft.
Like the crankshaft, the two connecting rods with I-shaft are mounted on
plain bearings and are likewise forged from quenched and tempered steel. They
accommodate cast aluminium pistons with two compression rings and an oil wiper
ring. The running surface of the light metal cylinders is coated with NiCaSil.
Lubricating and cooling oil is supplied by a wet sump lubrication system with
a two-stage oil pump via sleeve-type chain driven by the crankshaft.
Classic OHV valve drive with two camshafts as in the legendary R 5 to R 51/2
combined with modern 4-valve technology and dual ignition.
Although the new “Big Boxer” has four valves, dual ignition, a modern combustion
chamber architecture, intake manifold injection and the BMS-O engine management
system for the best possible torque as well as optimum consumption and
emissions, it uses the classic OHV configuration for its valve drive – as was
the practice pursued by BMW Motorrad over a period of some 70 years.
When developing the valve drive for the “Big Boxer”, BMW Motorrad engineers
were inspired by a very special engine design in the history of BMW Motorrad –
in keeping with the Heritage concept: the 2-cylinder boxer engine of the R 5/R
51 (1936 – 1941) and R 51/2 (1950 – 1951), the latter having been the first BMW
motorcycle with a boxer engine after the Second World War. In contrast to other
OHV designs by BMW Motorrad, this engine – highly valued by connoisseurs – has
two camshafts driven by the crankshaft via a sleeve-type chain.
As in the historical role model, the two camshafts are also positioned to the
left and right above the crankshaft in the “Big Boxer”. The advantage of this
“twin camshaft boxer” is the shorter pushrods. This also makes for reduced
moving masses, minimised deflections and lower linear expansions. A generally
stiffer valve drive with improved control precision and higher speed stability
is the consequence of this more elaborate construction.
Fork rocker arm and manually adjustable valve clearance compensation via
adjusting screws as in the traditional BMW boxer role model.
In the traditional BMW Motorrad boxer design, the two pushrods actuate one
pushrod per cylinder side for the intake and one for the exhaust side, guided in
a sealed pushrod tube on the top of the cylinders. The two intake and exhaust
valves in the cylinder head are actuated in pairs via fork toggle levers.
In contrast to today’s widespread engine technology, valve clearance
compensation is not effected by means of hydraulic elements, but – as was the
case in most classic air-cooled BMW two-valve boxers for decades – via one
adjusting screw with one lock nut for each valve. As was formerly the case in
the classic 2-valve boxers, valve clearance adjustment (0.2 – 0.3 mm) in the R18
“Big Boxer” is also achieved very quickly. The valves are made of steel, with a
disc diameter of 41.2 mm on the inlet side and 35 mm on the outlet side. The
valve angle is 21 degrees on the inlet side and 24 degrees on the outlet side.
Constant mesh 6-speed transmission and self-reinforcing single-plate dry
clutch with anti-hopping function.
As in most BMW Motorrad boxer engines for decades (with the exception of
vertical-flow, air/water-cooled boxers since 2012), a single-disc dry clutch
transmits the torque generated by the engine to the transmission. For the first
time it is designed as a self-reinforcing anti-hopping clutch, thereby
eliminating unwanted stamping of the rear wheel caused by engine drag torque in
the event of hard downshifting.
The constant mesh 6-speed transmission is located in a dual-section aluminium
housing and is designed as a 4-shaft transmission with helical gear pairs. The
gearbox input shaft with lug dampers drives the two gearbox shafts with the gear
wheel pairs. An output shaft is provided to bridge the distance and reverse the
direction of rotation. A reverse gear is available as an optional extra. This is
driven by an intermediate gear and an electric motor and can be shifted
manually.
Open secondary drive based on the classic role model.
As in all BMW motorcycles with boxer engines, torque is transmitted from the
gearbox to the rear wheel in the R 18 via a propeller-shaft or universal-shaft
drive with universal joint, shaft and rear-axle drive with bevel and ring gear.
The propeller shaft and universal joint are examples of fascinating classic
motorcycle technology since they are nickel-plated and open, as was commonly the
case in BMW Motorrad models up to and including model year 1955. A so-called
tripoid joint is applied on the gearbox side for the purpose of length
compensation.
Any corrections or more information on these motorcycles will be kindly appreciated.