Slipper clutch

A slipper clutch (also known as a slider clutch or back-torque limiter) is a specialized clutch developed for performance oriented motorcycles to mitigate the effects of engine braking when riders decelerate as they enter corners.

They are designed to partially disengage or "slip" when the rear wheel tries to drive the engine faster than it would run under its own power. The engine braking forces in conventional clutches will normally be transmitted back along the drive chain causing the rear wheel to hop, chatter or lose traction. This is especially noted on larger displacement four-stroke engines, which have greater engine braking than their two-stroke or smaller displacement counterparts. Slipper clutches eliminate this extra loading on the rear suspension giving riders a more predictable ride and minimize the risk of over-reving the engine during downshifts. Slipper clutches can also prevent a catastrophic rear wheel lockup in case of engine seizure or transmission failure. Generally, the amount of force needed to disengage the clutch is adjustable to suit the application.

Slipper clutches have been used in most high displacement four stroke racing motorcycles since the early 1980s. Slipper clutches were introduced in the 1970s by John Gregory and TC Christenson on "Hogslayer" the most successful drag racing motorcycle of the 70s. Made of bronze sintered plates from an earthmover and a Rambler 2 speed transmission, the drivetrain let TC reach 180 mph in the quarter mile. Slipper clutches were also used in the Honda Interceptor 750 factory superbikes that same year. Before long, slipper clutches could be found in nearly every big bore four-stroke race bike, and notably (due to the cruiser-style and riding position) the 1983-1985 Honda Shadow VT750/VT700 models. Another street bike application was in the 1990-1997 Suzuki VX800. Slipper clutches are now gradually being factory installed on production motorcycles such as the Aprilia RSV Mille, Ducati 1198, Honda CBR1000RR 2008+, Yamaha YZF-R6 2006-2008, Yamaha YZF-R1 SP 2006 , Yamaha YZF-R1 2007-2009, Yamaha V-Max 2009, Kawasaki ZX-10R, Kawasaki ZX-6R, Suzuki SV1000 and GSX-R1000 2005-2007, Suzuki Hayabusa 2008, Suzuki RM125 2008, Harley Davidson V-Rod VRSC 2008, and are available as retrofit for many other models.

Slipper clutches have also been used to a lesser extent on automobiles, primarily those powered by motorcycle engines. They can also be found on racing remote control cars. Some experimental aircraft use a slipper clutch to protect the engine from shock in the event of a propeller strike.

One-way sprag clutches have also been used for the same purpose, but are generally not adjustable for disengagement force. Early Honda Shadow models used a design wherein a sprag clutch is connected to just half of the clutch friction plates, allowing the clutch to slip during heavy backloading sufficiently to prevent rear-wheel lockup, while still allowing moderate engine compression braking with the remaining friction plates.

See also

• Freewheel

References

(B1) EP 0854304 (B1)  "Friction clutch for vehicles"

External links

• Detailed history
• Background to semi-auto clutch
• A new back-torque limiter for high power motorcycles: functionality, design and development methodology