Chen et al. [65] developed novel ci

Chen et al. [65] developed novel circular arc helical gears (CAHGM) with pure rolling.Based on the meshing principle of space curve meshing, the parameter equations of the concave-convex circular arc profiles were established.A pair of CAHGM was manufactured via rapid prototyping technology.The contact ratio equation and the theoretical kinematic performance were validated.The gears have a large backlash which is harmful to the forward and reverse drives.Chen et al. [66] and [67] also developed pure rolling helical gears with convex-to-convex meshing type and pure rolling rack and pinion mechanism.Geometric design, meshing performance, and mechanical behaviour were presented.Parametric equations for contact curves and for the tooth surfaces were derived.A numerical comparison of contact stresses and bending stresses between the modified involute gearing and the new gearing was made.With new gearing, the maximum bending stresses are significantly lower, and the contact stresses are 1.5 to 2 times higher.The maximum contact stress can be decreased by increasing the tooth number and face width and decreasing the helix angle.Properties of pure rolling gearing have not yet been experimentally researched.