Design And Analysis Of Crankshaft Of A High-Power Motorcycle Engine

The crankshaft is the core moving part of the motorcycle engine.It consists of crank slider mechanism with piston and connecting rod to convert straight reciprocating motion of piston into rotation motion of crankshaft.The crankshaft of the motorcycle engine runs at a high speed of nearly 10,000 rpm,and the oil temperature is as high as 150 °C.In this high-speed,hightemperature harsh environment,the vibration and strength of the crankshaft are more demanding,and the crankshaft design and development has put forward higher requirements.This paper combines the engine development project of a certain enterprise to design and analyze the crankshaft of high-power motorcycle engine.The structure of the crankshaft directly affects the vibration characteristics of the crankshaft,the fatigue strength and the comfort of the whole vehicle.Therefore,it is very important to determine the structure of the crankshaft,which is related to the progress and effect of the whole development.According to the structural characteristics,displacement and power torque of the motorcycle,the crankshaft structure and size statistics and experience are used to determine the basic structure of the crankshaft and related key dimensions,materials,lubrication methods and other design elements.The crank mechanism is a composite moving part of high-speed rotation and reciprocating motion.Mastering the motion law of the crank mechanism and the force in motion are crucial for design analysis.The kinematic equations and motion mechanics equations of reciprocating motion and rotational motion are established,and the motion law and force condition are analyzed.The crankshaft is affected by the unbalanced inertial force,and then the unbalanced inertial force type and the first-order unbalanced inertia force are deeply studied.The effect of different dynamic balance and main inclination on the magnitude and direction of the first-order unbalanced inertial force is obtained.The crankshaft is the vibration source of the whole vehicle,and the vibration of the crankshaft directly affects the vibration level of the whole vehicle.The crankshaft vibration is caused by the unbalanced inertial force,so the unbalanced inertial force of the crankshaft is closely related to the vibration of the whole vehicle.By introducing the theory of rigid body striking center,the relationship between the unbalanced inertia force of the crankshaft and the vibration of the whole vehicle is established,and the influence of the dynamic balance of the crankshaft and the main inclination on the vibration of the whole vehicle is found.Then,by calculating the corresponding crankshaft dynamic balance and the main inclination angle,the state of minimizing the vibration of the whole vehicle is found.The crankshaft is the most important part of the engine,and its performance directly affects the stability and life of the engine.The modal analysis and strength analysis of the crankshaft are performed using ANSYS finite element software to ensure that the crankshaft performance meets the requirements for use.First,a three-dimensional model of the crankshaft mechanism was built using the three-dimensional software CATIA.Then the ANSYS finite element software is used to simulate and analyze the natural frequency and mode shape of the crankshaft structure,and the crankshaft and the engine are prevented from resonating in design.The accuracy of the calculated modality is verified by the prototype modal test to verify the accuracy of the crankshaft model.The strength analysis of the crankshaft is carried out,in particular the stress analysis of the spindle neck fillet for stress concentration.The durability of the crank mechanism is then analyzed and the durability of the crankshaft is verified by the endurance test of the prototype.Through the design analysis and test of the crankshaft of the motorcycle engine,the crankshaft structure satisfies the design requirements of the vibration,strength and durability of the crankshaft in the case of increased power.The combination of simulation verification and prototype test can improve the design capability and quality of high-power motorcycle engine crankshaft,reduce the repetitive workload,shorten the development time,reduce the development cost,and effectively complete the design and development of the crankshaft.