Canti-bounce clutches are the latest development that everybody is talking about in four stroke Moto GP racing. Here is how this rider-friendly technology works and why it is so much appreciated.
Basically, a pack of friction plates pressed together by springs is all that most bikes have to let us start off and change gear. Yet this simple component is assuming ever greater importance in high performance and racing motorcycles.
In Grand Prix racing clutch action is far more than just a subject of heated debate; it really can make all the difference between a great bike and a mediocre one. In performance road bikes the bounce-free clutch is still a luxury that only a handful of prestige models can afford to fit.
Yet thanks to the return of four stroke engines to GP racing this piece of technology is living a moment of glory. Nearly every team mechanic is working on them, because controlled clutch slip really does allow riders to make full use of the stopping power modern GP brakes can deliver. And not just GP bikes ... .
WHAT DOES IT DO?Basically, a pack of friction plates pressed together by springs is all that most bikes have to let us start off and change gear. Yet this simple component is assuming ever greater importance in high performance and racing motorcycles.
In Grand Prix racing clutch action is far more than just a subject of heated debate; it really can make all the difference between a great bike and a mediocre one. In performance road bikes the bounce-free clutch is still a luxury that only a handful of prestige models can afford to fit.
Yet thanks to the return of four stroke engines to GP racing this piece of technology is living a moment of glory. Nearly every team mechanic is working on them, because controlled clutch slip really does allow riders to make full use of the stopping power modern GP brakes can deliver. And not just GP bikes ... .
During fierce braking the combined weights of the bike and rider compress the front fork and lift weight off the bike’s rear wheel. Fierce braking is also normally accompanied by one or more changes down the gearbox to add maximum engine braking to conventional brake action and slow down in the shortest possible distance. As engines get bigger and the number of cylinders smaller, engine torque increases dramatically. Along with torque, braking power increases too. In extreme cases (like large twins and competition machines) the braking torque applied to the rear wheel can prove excessive, causing the wheel to lock even without the rear brake being applied. With very little weight on it, the rear wheel starts to bounce, causing man and machine to lose their trajectory and preventing riders entering bends cleanly and down their chosen line. Anti-bounce systems limit the engine’s braking torque by allowing some or all of the clutch plates to slip.
This is a valuable aid indeed for the racing rider, so much so that anti-bounce clutches are advancing in leaps and bounds on competition machines.
Yet anti-bounce clutch technology is not limited to competition motorcycles. Aprilia has long been using it on its RSV Mille sports road bike, and with great success too. The RSV Mille might be a production machine, but it is equipped with technology advanced enough for any GP machine. Aprilia’s faith in anti-bounce technology for road bikes has been amply vindicated by the fact that nowadays many other manufacturers are following suite and fitting their own sports models with anti-bounce clutches. Aprilia’s RSV Mille has had one since it was first introduced back in 1998!
P.P.C.: MAGIC INITIALS!
Potentially, there are many ways of designing and building anti-bounce clutches. Aprilia uses its own patented, ingeniously simple but extremely effective PPC (Pneumatic Power Clutch) system. Transmission through the clutch is controlled by a number of springs that push the clutch plates into contact with each other to create the friction necessary to transmit drive.
When you pull in the clutch lever, you compress these springs, allowing the plates to turn at their own speeds. The RSV Mille’s clutch springs are equipped with a small pressure-sensitive chamber that expands or contracts depending on the air pressure in the intake manifolds. The clutch is connected to the intake manifolds by a simple rubber hose. Whenever you close the throttle, the vacuum created in the manifolds is transmitted to the clutch spring chamber.
This causes it to contract and reduce the load on the clutch springs, allowing the plates a controlled amount of slip. Under conditions of rapid deceleration, the system permits just enough clutch slip to ensure that the rear wheel remains in very firm contact with the asphalt and that the bike decelerates precisely down the line chosen by the rider.
Imagine that you could keep your clutch lever under precision control even during the fiercest braking, to achieve just the right amount of clutch slip for maximum deceleration without bouncing at any time. Not even top race riders can manage such a feat, of course. Luckily, they do not have to. Aprilia’s technical genius and advanced technology does the job for them, and for you too.
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