Experimental pure bending conditions are difficult to obtain when large deformations and displacements are required. In this work, a new principle using two universal joints is proposed and developed to enable such pure bending conditions. This principle has been applied to design an apparatus suitable to test small size samples (such as wires of diameter < 1mm) at small curvature radii (≃ 5mm) and to specifically provide small size samples moment-curvature relationship. This article underlines and validates the abilities of this new apparatus by performing and analysing tests on samples made of well-known material.