Ball screw assembly

A ball screw assembly includes a screw shaft along which is formed a first helical groove; a nut along which is form a second helical groove; the first helical groove and the second helical groove cooperating to define a track, a plurality of balls arranged in the track and configured to move along the track in response to relative motion between the screw shaft and the nut such that rotational motion of the screw is translated to linear motion of the nut via the balls and vice versa. The assembly also includes a bypass shoe arranged between the nut and the track and spaced from the track by a predetermined preload X, wherein when a load applied to the nut exceeds the predetermined preload, the bypass shoe engages with the track such that motion of the screw is transferred to motion of the nut via the shoe and bypasses the balls.