Anti-Hop Clutches are popular for bikes above 400 cc. They offer the advantage of better driving stability in lower gears and during down shifting. The currently used designs of such clutches are having different constructions with complex geometry parts and almost 30% more number of parts (compared to standard clutch) are used in some designs to achieve the desired 'Driving Assist' and 'Coasting Slip' effect. The production process used, demands for specialized tools for manufacturing the complex geometry of parts and the price of the clutch assembly is more than double as compared to standard, equivalent design of multi plate wet clutches. These type of clutches are commonly known as - Anti Hop Clutch or Slipper Clutch or Assist and Slip clutches. To achieve same performance benefits with simpler design, less number of parts with a Flexibility to alter the Assist and Slip effect to suit the application, Endurance Technologies Ltd. developed a new concept. The simplicity of design and enhanced effect of Assist and Slip is experienced on vehicle trials. Further the design can be optimized to meet the expected performance and durability targets of the intended application. In this paper the details of concept clutch construction, Mathematical models developed, Performance and durability measurements taken on the vehicle are summarized which is trademarked as Endurance Variable Torque Clutch (EVTC). The evaluation of different variables on performance is discussed and to achieve the performance within a narrow tolerance band the special design considerations utilized are elaborated. For achieving better ergonomic effect on Clutch lever, the clutch uses a pair of diaphragm spring which is assembled so as to inherently reduce the variations in clutch performance over the life span. Due to above advantages of design, the EVTC cost is approximately 65% of popular Slipper clutches, while achieving better or equal performance and durability. Compared to standard (Non Slipper) design of clutches, this clutch has indicated 100% improvement in road endurance life due to operation in optimum working pressure on Friction Plates. The modularity of this design also provides the possibility of adapting the same clutch configuration on vehicles with varying capacity (say 150 cc to 250 cc) with change of only friction material and machining parameters of assist and slip affecting helix angles, reducing the development time. Above benefits increase the feasibility of implementation on lower capacity engines, especially to suit the sporty type riding habits of end users.
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