Anti-hopping clutch
An anti-hopping clutch (in Anglo-Saxon countries: slipper clutch or back-torque limiter ) is a special clutch that was originally used in motorcycle racing and has also been used in street-legal sports motorcycles for a number of years , which only partially transfers the braking force of the motor to the rear wheel when coasting .
General
When braking hard before a curve and at the same time shifting down quickly, the engine brake acts on the rear wheel. This can be enough to lock the rear wheel, which is relieved by the dynamic wheel load distribution . The hopping, jumping or stamping of the rear wheel described with the English word hopping can occur, which can result in the complete loss of grip or traction . The loss of grip of the rear wheel, especially when cornering when cornering, makes the motorcycle unstable or even uncontrollable. In the worst case, the rear wheel slipping sideways leads to the rider falling.
An anti-hopping clutch prevents this reaction of the engine brake on the rear wheel and thus enables more safety in normal traffic and better lap times on the racetrack. However, there are also racing drivers who consciously refrain from using an anti-hopping clutch because they have integrated the effect of the engine brake into their driving style.
application
The technology is preferably used on large-displacement motorcycles with a few cylinders (e.g. Ducati 1098 , Aprilia RSV Mille with 1000 cm³ V-Twin, various Supermoto models), since the torque of the engine brake is strongest on these and therefore the hopping effect is most pronounced. It should be mentioned here that anti-hopping clutches are more important for larger V2 / V4 engines . With the constant further development of motorcycles, it can make sense nowadays to use an anti-hopping clutch for four-cylinder motorcycles with less displacement (e.g. Yamaha YZF-R6 with 600 cm³).
Honda installed an anti-hopping clutch in the VF1000F (SC15 / 16) model as early as 1984. The Honda VFR 750 R / RC 30 sports motorcycle also had an anti-hopping clutch. Kawasaki was the undisputed leader in R4 engines with the introduction of a suitable slipper clutch from 2003 onwards. Since 2005, all Kawasaki athletes and super sports models have had this type of clutch. The remaining Japanese manufacturers followed suit. In the meantime, BMW has also installed such a clutch in some of its motorcycles (e.g. BMW R 1200 GS K50 ).
The anti-hopping clutch combines the functions of a normal motorcycle clutch with that of a roller freewheel. In contrast to the simple freewheel, which suddenly separates the power transmission in one direction, with the anti-hopping clutch only the contact pressure of the clutch linings is reduced in pushing mode or, in the event of a strong braking torque of the engine (e.g. in the event of an unintentional engine failure), it is completely eliminated resulting in a "soft" release of the clutch. In the same way, the pressing force starts again softly when the driver accelerates again. This avoids unwanted load change shocks and the handling of the motorcycle remains controllable. The torque required to separate the power flow can be adjusted on some models. However, there are also other systems (e.g. Aprilia RSV Mille, Buell 1125R ) that separate due to the negative pressure created in the intake tract .
literature
- Patent EP0854304 : Friction clutch for vehicles.