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Multi-plate wet clutches used in motorbikes transmit the torque by friction under pressure between driving and driven Plates. The life & performance of the clutch for the friction material used, depends on amount of energy generated during clutch slip, amount & uniformity of heat dissipation amongst the plates and surface texture of mating surfaces. Above parameters if not properly considered during design stage may lead to higher temperature of rubbing surfaces. Higher temperature further reduces the friction coefficient and increases the wear rate of friction material leading ultimately to lower torque capacity of clutch. The temperature rise in a wet clutch is the balance between amount of heat generated and the amount of heat dissipated by oil flowing through clutch. The maximum amount of oil is limited by the requirement of clutch drag torque, Which decides the quality of neutral finding and gear shift feel on vehicle.

In recent years with the advent of technological advancements, engine power & torque levels per unit engine displacement volume in motorcycles are showing significant increase. These powertrains however are prone to Torsional Vibration issues. The severity is even more with single cylinder engines. The Torsional Vibration Damper System (TVDS) in clutches has become critical as it plays an important role in isolating these torsional vibrations. Thereby increasing the lifespan of the critical powertrain components. The major challenge with TVDS is, it must transmit the high torques on one hand and effectively keep the high pulsations in torque away from the rest of drive train on the other. These are conflicting requirements & often result in a design compromise. Further this is revealed only at full vehicle testing. Thus it requires the full vehicle functional prototypes to be ready for first level evaluation of TVDS.

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.

Automotive clutches form the most important component in the drive line which acts both as torque transmitter and as a fuse. Testing clutches, in the vehicle assembly, poses certain limitations. In this context the automotive clutch, as a component, needs to be evaluated to determine various performance parameters like wear, load loss, slipping torque, slipping time etc. to meet desired design, performance and durability requirements. It is very important to simulate engine and vehicle conditions in terms of operating environment, speed and load accurately while evaluating above parameters. This creates lot of challenges to design and develop a test rig capable of evaluating complete clutch performance. Very limited options are available for such test rigs worldwide. In India, no manufacturer provides such indigenous test rigs. Developing an indigenous, cost effective clutch test rig was the need of the hour.

Most of the studies on judder and rattling in power train with multi plate wet clutches are focused on the slip-stick phenomena of the friction materials, lubrication used, thermo-elastic behavior of friction materials, tribology considerations, boundary layer, asperity contact theories and so on. In this paper, a different approach for problem solution is presented. This is based on the concept of mutual matching and differences seen in the behavior of mating components under different assembly boundary conditions, since a very small proportion of mass production exhibits judder and rattling. The clutch and the engine components are assembled in random orientation about the axis of rotation. The probability considerations are extended to explain the basic, root cause of variation on problem occurrence and inconsistency of problem repeatability, even though all the components are within design specifications.