Show - Elliniko Athens 3/2006
These are some highlights from the motorbike exhibition
that took place at11-19 March in the former Athens airport at Elliniko.
The following is not an explicit presentation of the exhibition,
just some photos and comments from some bikes and technology highlights
that attracted our attention.
One of the most important technical aspect of the exhibition was
the duolever front suspension system of the new 4 cylinder BMWs.,
K1200S/R. Even though many independant constructors and inventors
preceeded BMW these are the first mainstream models that are widely
avaliable to the public with such a suspension design. Its appearence
may look similar to that of a conventional telescopic fork but in
principle it is very diffirent. It uses a double wishbone system
and an articulated pivot to separate the suspension movement from
steering imput. With carefully selected wishbone sizes and angles
the designer can choose the amount of squat and dive thus adjusting
the behaviour of the chassis when accelerating, braking and the
general stability of the bike.
It is impressive that even standing still over the bike and pushing
it while holding the brake lever the bike has a minimal dive (but
it dives nevertheless) and at the same time in purely vertical movements
the suspension moves freely.
Although the primary target for the MT-03's design was the controversial
look, the rear coilover's position has engineering benefits as well.
This actually is a very good packaging solution, especially for
narrow one or V-2 cylinder engines. The coilover is closer to the
centre of gravity and it is also more protected from dirt and mud
than usual enduro bikes suspensions. Its kinematics also favour
a very gentle path of almost vertical forces to the coilover vecause
of the bigger lever that the pivot creates thus eliminating the
need of a complex floating links arrangement.
The new KTM LC8 Super Enduro is the latest version of KTM's V2 engine
combined with this tubular trellis frame. The very broad spectrum
of bikes that uses this engine/frame is very impressive. It is used
not only in competition dirt track applications like this particular
Super Enduro and the Adventure Rally bike but also as a purely street
bike at the Super Duke version which face the direct competition
of superbike derivatives like the Aprilia's Tuono. Of course these
bikes aren't identical but the sumilarities and the almost identical
core elements like the engine and the frame are more than the diffirences.
Aprilia SXV/RXV 4.5/5.5.
These new Aprilias are the first in their class using a two cylinder
engine. The new V-2 is very powerfull (maybe too powerfull in the
550 version) and it is also quite compact. Although the engine is
the attention seeker of these bikes the chassis is also a very interesting
piece of engineering .It consist from two parts, at the front there
is a tubular wireframe which supports the headstock of the front
suspension and at the rear there is a cast aluminium part with internal
ribs. We assume that the main reason for this design is to infuse
a flexibility in specific planes at the headstick region to make
the bike more controllable while the rear stiff section supports
rigidly the engine and frame eliminating any unwanting oscillations.
The ZX10R continues the long tradition of Kawasaki's sofisticated
air intakes (ram-air as it calls them). In the later models (ZX10/6/14)
a NACA inlet that gradually increases its apperture is used. In
the previous generation of Kawasaki's sportbikes with the ZX12R
(look at the photo below) as the most recent example there was a
different approach. An inlet duct protrudes from the fairing in
order to receive air that is outside the boundary layer. Both versions
are positioned in the front of the fairing's nosecone in order to
maximise inlet's dynamic pressure. In the new ZX10R, as seen in
the photo tha NACA inlet is shaped with a raised lip where it meets
the fairing in order to reduce the turbulence that exist in the
boundary layer and to feed the engine with a more homogenous airflow.
Polaris/Arctic Cat ATV tracks
Polaris and Arctic Cat presented in their stands tracked versions
of their big ATVs. The Polaris ATV used tracks made also by Polaris
while Arctic Cat had after market Tatou tracks. Both track kits
are bolt-on and very easy to mount and they give the ATVs exceptional
off road capabilities.The pressure that these tracks excersise to
the ground is very small enabling them to flow over soft terrain
(like snow or mud) while their very long ground trail can surpass
gaps and rocks without bouncing or wheel stuck. Friction and losses
have a huge impact in the speed and acceleration but these are vehicles
for a very specific use and at any time they can convert very easy
to normal ATVs.
Tatou's track kit seems lighter and there are versions avaliable
for off-road cars and even for minivans.
In both cases the ATVs have a double wishbone independant suspension
fron and rear. The rigid rear swingarm that many atv's and most
quads use in the rear axle wouldn't be the ideal solution because
these tracks need to be as vertical to the ground as possible and
double wishbones providing this optimum kinematic path are much
better suited. A rigid swingarm is depended a lot on the rear tyre
destortion for traction and these tracks wouldn't co-operate easily
The Buell XB series bikes aren't new (apart from the Ulysses version),
however they are very interesting and packed with inconventional
engineering and ingenious details. Apart from the belt final transmission,
the use of the frame and swingarm as fuel and oil tank respectively
and the low mounted exhaust a detail that is often is neglected
and only been taken as a design eccentricity is the rim mounted
single front disc brake.
Because of its huge size, one disk produces enough stopping power
and because the forces act mostly at the perimeter of the wheel
the wheel doesn't need to have a great torsional stiffness thus
it can be very light. The rear wheel is much heavier because apart
from the torque of the engine it has to sustain also the torsional
forces of the rear conventional brake.
The importance of the front discbrake to the overhaul dynamics of
the bike is that although the wheel is very light its rotating inertia
increases dramatically when the speed rises. So as the bike moves
faster the front wheel becomes more and more stable and this combined
with the very steep castor angle and small trail of the frame produce
a very agile bike that is stable enough at high speeds.
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