On graphical method of mechanical dynamics based on balance equation of rotating moment around moving point

Graphical method is an effective method to verify the results of analytical method. However, the research on graphical method of mechanical dynamics can not be carried out until the moment balance equation of rigid body rotating around moving point (practical equation A) is given in our open paper. The main reason is that the connecting rod is not a body rotating around a fixed point, and its moment balance equation contains too many unknowns. Practical equation A is derived based on the research idea of Fangyan equation. 1) Our 8 previous research results in mechanical dynamics were summarized. The instantaneous centre between two bodies is velocity instantaneous centre. After analysis, there is not necessarily acceleration instantaneous centre between two bodies. 2) A rotation moment balance equation (qualitative equation B) of a rigid body around a moving point was proposed based on qualitative analysis. 3) A crank rocker mechanism is taken as an example. The moment of rotation of a rigid body around the centroid (ordinary equation C) was practiced too. Practical equation A is as correct as ordinary equation C. Practical equation A makes the results of the graphical method of mechanical dynamics feasible.