is displaced along the guide surface 11 of the first subassembly 1 fig3 illustrates the progression of the piston 30 in fig2 a u2013 2 j the right piston 30 was resting against the contact area 20 of the second subassembly the guide surface 11 of the first subassembly is shown as multiple black lines indicating eleven snapshots over time as the right piston is moved along the guide surface 11 as the piston 30 progresses to the left each black line shows at the right hand end a progressively shorter distance of the guide surface 11 relative to the piston indicating that at that stage the first subassembly moves faster than the piston that is it moves underneath the piston resulting in a ration of translation of the movement of the first subassembly into the piston movement of less than 1 at a certain point during the relative rotation between the two subassemblies the guide surface 11 and the surface 21 of the second subassembly form a confining guide path for the piston so that the piston 30 is forced to move faster than the first subassembly while progressing toward the idle piston thus resulting in a ratio of translation of first subassembly movement to piston movement of greater than 1 in idle position see for example the left hand thrust piston in fig3 the.