Abstract: Apparatus and methods for measuring strain and torque are described. The apparatus, which is used in the methods, usually includes a thin walled cylinder within a thick walled cylinder, the cylinders being fixed together at their ends only, means for vibrating the walls of the thin walled cylinder and means for indicating the frequency of vibration. As torque is applied to the thick walled cylinder and therefore to the thin walled cylinder, longitudinal strain appears in the thin walled cylinder and the frequency of vibration changes. Thus an indication is obtained of the applied torque or of strain in a test member applying the torque.