Articles
Ducati/Rossi
It is the architecture of the Ducati engine which is restrictive in its nature in regards towards the swinging arm/chassis combination that makes it impossible for Valentino Rossi to find the perfect racing set-up. The highly positioned gearbox sprocket on the engine is detrimental to this, where the rear swinging arm is angled overly upwards. Such an arrangement is beneficial to rear wheel braking – of little impact on MotoGP bikes – and to traction, but at the expense of cornering potential.
To explain; on the apex of the corner, when power is fed in again, a loss of traction is experienced. With cornering forces compressing the suspension, given the excessive upwards angle of the swinging arm where the drive sprocket has to be positioned even higher, compared to a standard setting, to counteract driving forces extending the rear suspension under acceleration when it is already extended, the now higher than normal positioning of the gearbox sprocket in relationship to the swinging arm pivot point in conjunction with the top of the rear wheel drive sprocket increases the pull on the rear wheel/swinging arm reacting to remove the tire away from the tarmac as the power is applied to the compressed suspension. Loaded rear suspension does this in an unnoticed manner on most motorcycles but here the syndrome is magnified over so to affect cornering performance.
After the apex the Ducati reportedly drifts wide, where again engine architecture is responsible. The engine needs to be lowered in the frame to correct the above problem, further lowering the centre of gravity, where with it there is a loss of inward pull on the tilted over motorcycle to assist cornering. Further, the gyroscopic effect of the crankshaft, and all other rotating shafts, are more profound on the tire contact patches when they are closer to them with the engine positioned lower in the frame, again reducing cornering potential. All rotating shafts have a natural inclination towards forward straight-line travelling without wanting to deviate in any circular path or deviate with any tilting motion.
Raising the Ducati up is not the answer, borne out by the fact that when Ducati did extend the front telescopic forks the rear suspension wasn’t extended, where at the rear the rider seating position was lifted instead. Ducati cannot get around the predicament of lowering of the engine yet raising of the centre of gravity due to engine architecture within the given weight restrictions (i.e. keeping the design on or close to the minimum weight limit).
A heavier crankshaft is being devised at present to smooth out power delivery and hopefully massage the power in on the corners’ apexes in a less disruptive manner. Will this work? Yes and no. It will, with careful throttle response, allow a gentler feed in of power to reduce any sudden effect on the rear wheel that would pull it away from the track surface, but the gyroscopic effect of the heavier crankshaft is increased, again, in opposition to cornering performance!
(Robert Rae. 17/4/2011)