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Bike 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.

BMW K1200S/R

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.

Yamaha MT-03

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.

ΚΤΜ LC8.

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.

Kawasaki ZX-10R.

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.

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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

Buell XB12R

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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I.K. Erripis 170306

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