This torsion apparatus consists of a sturdy metal frame with two cast iron feet. A horizontal experimental rod (approximately 55 cm long and 5 mm in diameter) is fixed on the frame. One end of the rod is securely attached, while the other end is held by a heavy chuck at the center of a wheel. The wheel, connected to the chuck via a ball bearing, rotates freely in both clockwise and counterclockwise directions.
A wire, either plastic/metal with small hook is wound around a groove in the wheel, when weight suspended from its free end to apply torque, the angle of twist of the rod is measured at two different distances from its fixed end using pointers mounted on adjustable aluminum scales (graduated 30-0-30 in degrees).
A small mirror fixed to the rod adds in measuring the angle of twist accurately. The apparatus comes with two specimen rods (brass and steel) but does not include weights.