a piston and cylinder unit for a gyratory crusher including a cylinder having an upper piston carrying the crusher head and a lower piston dividing the interior of the cylinder into a hydraulic chamber and a gas chamber . the hydraulic chamber is selectively chargeable with hydraulic fluid to adjust the crushing gap between the crusher head and the bowl of the crusher , and the gas chamber is connected in communication with a pressure relief chamber within the lower piston to provide an accummulator within the unit accommodating the momentary displacement of the crusher head by noncrushable materials moving through the crushing gap during crushing operations .