TORSION S3-1 SUMMARY Shaft: In engineering the members of which deformations are mainly torsion Such as transmission shafts in machines drill rods in oil-drilling rigs etc Torsion: Resultant of the external forces is a force couple and its acting plane is perpendicular to the axis of the shaft. Under this case the deformation of the rod is torsion B A O5 §3–1 SUMMARY Shaft：In engineering the members of which deformations are mainly torsion. Such as transmission shafts in machines, drill rods in oil-drilling rigs etc. Torsion：Resultant of the external forces is a force couple and its acting plane is perpendicular to the axis of the shaft. Under this case the deformation of the rod is torsion. A B O m m  O B A 