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GP Week : Issue 42
>>MOTOpreview Honda’s mainly-for-show skeletal chassis on the final iteration of the old oval-piston NR500 of the 1980s to several lower-end attempts in the 250 class. None achieved much. One reason was yet to be fully understood, but became clear with later (1990s) experiments by Yamaha with ultra-stiff front suspension. Ultimate chassis stiffness may be an ideal on four wheels, but it doesn’t work like that on two. Too much stiffness damages cornering performance, and with modern grippy tyres induced chatter and bounce problems that persisted until Wayne Rainey went back to a previous and more flexible chassis. In simple terms, a motorcycle chassis needs to flex to make up for the loss of suspension movement when it is leaned over by more than 60 degrees. The difficult part is getting it flex in the right way. For instance, you want the chassis to resist bending under braking, but to offer compliance when it is leaned over. And not too much compliance, for then the power will make it tie itself in knots. This where Ducati have been able to combine recently acquired understanding of the effects of chassis flex with one of the great advantages of carbon fibre. As their statement explained: “Choosing to utilise the carbon-fibre composite technology … means that, on the one hand, one can mould the piece into the desired form without incurring enormous equipment costs and, on the other hand, vary levels of rigidity and torsional characteristics can be attained simply by altering the type, the number and the directional orientation of the carbon fibres, using the same equipment.” The effect so far has been signal. One has only to look at Stoner’s domination on lap times in testing and at the first race to see that. His own view is that “the GP9 is the best Ducati there’s ever been”. More to the point, the new bike has solved a problem he had with it ‘pumping’under power … most especially when combined with the new carbon-fibre swing-arm. And the engineers have only just begun. They either got it sensationally right first time, or there is even more to come. Ducati’s statement gives some details. “In testing carried out up until now theGP9 guarantees greater precision and stability in braking and on entering corners. “We maintain, however, that only by using to race … will we be able to properly evaluate the potential of this technical solution.” Showing an undiminished commitment to the principle that “racing improves the breed”. Two questions remain. The first is whether carbon-fibre chassis construction, still very costly, will ever have any relevance for production bikes. The second is whether Ducati’s innovation will trigger a round of copy-cat engineering from Japan. And just one more. Will Ducati continue with the carbon-fibre, or have they already moved on already? The experimental cast aluminium ‘stressed airbox’ tested pre-season at Jerez suggests that having established the stiffness ratios required, Ducati can now replicate them in production- friendly cast metal instead. 37