Expressions of excitation forces
Instantaneous speed fluctuations of thermal engines. Excitations applied to the crankshaft

With the knowledge of the above kinematic characteristics, we can study the equilibrium of the connecting rod and piston. The piston is considered as a point mass on the axis of the connecting rod. In the Galilean reference frame (O, x, y, z), finding the liner force on the piston and the crankpin force on the connecting rod involves projecting the three dynamic equilibrium equations onto the axes of the reference frame. These equations are derived from the fundamental principle of dynamics applied to the piston and connecting rod respectively.

With the exception of the gas pressure force, whose single component is given a negative sign, all forces are assumed to have...