whereby said piston shoes form multidirectional hydrodynamic bearing shoes for forewards and rearwards directed movements of said piston shoes by said curved face portions with said bearing face radii by {TAIL ~ the extension} of {HEAD ~ said curved face portions} equally symmetrical in both peripheral directions away from said middle between the front and rear ends of said respective face portion 
whereby said piston shoes form multidirectional hydrodynamic bearing shoes for forewards and rearwards directed movements of said piston shoes by said curved face portions with said bearing face radii by { TAIL ~ the extension } of { HEAD ~ said curved face portions } equally symmetrical in both peripheral directions away from said middle between the front and rear ends of said respective face portion
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