Graphical statics a forgotten tool for solving plane mechanical problems.

Abstract

Graphical statics is an almost forgotten, intuitive drawing method for solving plane mechanical problems. It was already in use in the 19th century for biomechanical problems. It was still a standard method employed by civil engineers in the 1940s. Superceded by modern analytical methods, graphical statics disappeared almost completely. The method is restricted to plane static problems, but still remains a useful tool for visualizing, understanding and checking the actions of force groups occurring in modern biomechanical problems. After defining the basic mechanical terminology (body, motion, forces), the paper is written mainly as a teaching tool for immediate application. Many illustrative examples (sporting activities, functional forces in joints) help to clarify the difficult biomechanical content. For application, it must be assumed that the bodies investigated behave as rigid bodies under the action of the forces, but this does not prevent application of the method to deformable living bodies if specific static configurations of the bodies are considered. The application of the method requires a good anatomical knowledge and experience with the function of the musculoskeletal apparatus of living bodies. If reliable models are used, the method delivers quantitative results of sufficient accuracy. The paper may also help provide a better understanding of publications containing graphical solutions to bio-static problems.