Kinematic Properties of Tripode (Tri-pot) Joints

The geometry of tripode (also called tri-pot) joints or shaft couplings is simplified by folding one side onto the other, and the kinematic properties are obtained. Due to a built-in orbital motion, a tripode joint cannot be used alone between two shafts of fixed axes; therefore it cannot directly be compared with a typical CV (constant-velocity) joint. Yet it is shown that: (a) if its shafts are kept parallel to a fixed plane a tripode joint transmits equal rotations as other CV joints do; (b) if one shaft axis is fixed and the other shaft axis has a fixed point, input and output angular velocities slightly differ, with a cycle of three times shaft speed; (c) to transmit rotation between two shafts of fixed axes, a tripode joint must be incorporated with another tripode or CV joint or a mechanism. In this case deviation between input and output angular velocities can be made very small or even nil.