Effect of Crank Pin Center Offset on the Piston Movement Characteristics

  • Iesam J. Hasan


The system of the crank, connecting rod and piston, is a critical system of engines and compressors. The main objective of this work is to study the piston movement characteristics (displacement, velocity, and acceleration), with inline and offset types of the piston path concerning the crank pin. The dimensions of the crank and crank-pin offset were assumed as ratios of the connecting rod length. The effect of the offset on the piston behavior was investigated.    

The piston movement line offset has an apparent effect on the piston movement characteristics, where the displacement, velocity, and acceleration are decreased from IDC to the maximum point, and increase from maximum point to the ODC concerning the inline condition. Similarly, the offset changes the point at which the piston changes the movement direction, and change the point at which have (zero) and (maximum) velocity and acceleration. The angle of the crank at (IDC) and (ODC) are not equal to zero when the piston is at the offset condition. All these offset effects have led to changes in the timing of the patterns of motor and compressor stroke time.