Variable radius lever arm assembly

A lever arm assembly comprising a segmented lever arm able to curl and having a proximal end and a distal end, the lever arm carrying a drive connection at the proximal end for turning a driven member, the drive connection having a drive axis that is substantially perpendicular to the plane in which the lever arm curls, the lever arm being capable of being brought by an uncurling motion from a curled first condition to an uncurled, straightened second condition wherein in the curled first condition the lever arm is curled around the drive axis and the distal end is closer to the drive axis than it is in the second condition to provide a lever for turning the driven member, and when the lever arm is in the uncurled second condition the proximal end and the distal end are spaced further apart, to provide a longer lever for turning the driven member, wherein the lever arm comprises a plurality of blocks linked in a chain, each linked pair of blocks having a wall of one block of the pair that opposes and comes into abutment against a wall of another block of the pair when the lever arm is uncurled enough to reach the said second condition in use, the abutment of said wall of one block of the pair against said wall of another block of the pair limiting further deflection of the lever arm and thereby rigidifying the straightened extended lever arm for use as a lever for turning the driven member.