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GP Week : Issue 115
MOTOGP FEATURE >> particularly with the front-end washouts that plagued Stoner and Hayden last year, and are top of the list this year in Rossi’s development programme. But Ducati, bravely, remain committed to the course. As chief engineer and design guru Filippo Preziosi explains: “ We experiment, with new ideas, ideas which may become functional or not. We do not know beforehand. We test them here. And never as in 2011 our research lab has been, let’s say, so rich in the number of technicians.” This is a reference to the arrival of Rossi and help-meet Jerry Burgess, whose gifts of understanding and ‘surgical’ methods are expected to advance this and other experimental technologies at a speed no computer simul ation can imagine. “ We will learn more about the material, and we can change the stiffness ratios as we learn,” he added. Stiffness is the key. When the first monocoque chassis were essayed (Ossa, Seeley and others) in the late 1960s and early 1970s, the goal was the same as in cars: a stiff chassis that would allow the suspension to work accurately. For years afterwards, the principle prevailed. The England-based Suzuki team had some notable results with a chassis made from folded-and-glued Ciba-Geigy honeycomb sandwich material in 1984: tagged “the Cardboard Box”. But further carbon-fibre developments were nipped in the bud by the factory in Japan, which insisted on a classic aluminium chassis for its full-scale return to GP racing in 1987. But the bike had seemed promising. All the same, nobody followed suit. But it was only in the early 1990s that the penny really dropped about chassis stiffness. Yamaha had built an ultra-stiff chassis for Wayne Rainey. The sums all added up right, but the bike was plagued with what Wayne calls “chatter-bounce” in hard cornering. It was only after switching back to an older and more flexible chassis that the triple champion was able to get his 1993 season back on track. It was ultimately doomed, but when he had his terminal crash at Misano he had gained the lead of the championship for a fourth consecutive year. From this point the keynote of chassis design changed from stiffness to controlled flexibility. In retrospect, it seems obvious. It’s one thing to have scientifically designed suspension, like the Elf, which works impeccably when the bike is upright. But when it is leaned over at up to 60 degrees, the bumps strike at such an oblique angle that the suspension can no longer respond. To absorb bumps and keep on going, the whole bike must flex. But not so much that it can no longer contain its horsepower, and cannot run true in a straight line. Finding the right balance has occupied chassis designers ever since, and it is still as easy to get it wrong as ever. Ducati’s difficulty is redoubled because of the economy of their design. The other designers have the full length of the beam to play with. Revisions to stiffness can often be seen, with extra fillets welded on, or bonded carbon-fibre patches. Ducati have to find the same degree of flex control with their much smaller box. Tests after the Portuguese GP included a front chassis section with revised stiffness. Both factory riders liked it straight away. The next few weeks will see if it really is a step forward. Meanwhile, we can reflect that while failure might not be as painful, the best designers sometimes take as many risks as the riders themselves.