Specially designed apparatus for study and investigation into the stress and strain accompanying the torsion i.e., torsion modulus of rigidity of the substance. The apparatus consists of a two long metal mounting rods located vertically on a T-shaped assembly and are jointed at the top through another square metal rod. Three adjustable angle measure attachments, graduated in degrees, are located vertically along the lengths of the rods for measuring degree of rotation of experimental rod under torsion at the desired positions. The bottom T-shaped assembly has a circular drum on to which is connected the weight pan on its either side through lightweight cord. The cord wound on the drum, with the weight pan suitably loaded, provides the necessary torque to the experimental rod. Chuck is provided at the top as well as bottom with tightening screws to firmly hold the experimental rod. Complete assembly mounted on a heavy cast metal tripod base with leveling screws. Includes two experimental rods – one each of brass and steel.