Disclosed preload mechanism for a memory alloy wire actuator having a rotating element to rotate about a pivot and a first contact point to couple to the actuator. Contraction of the actuator displaces the first contact point so the rotating element rotates from a first to a second position. The preload mechanism has a bias element with a first end coupled to a second contact point of the rotating element and a second end pinned relative to the pivot. The bias element has a line of action extending between the second and the first end and having an offset distance that is the minimum distance between the line of action and the pivot. The offset distance has a first value when the rotating element is in the first position and a second value when the rotating element is the second position, the second value being smaller than the first value.