The vertical spindle is free to rotate around its own axis. The crusher illustrated is a short-shaft suspended spindle type, meaning that the main shaft is suspended at the top and that the eccentric is mounted above the gear. The short-shaft design has superseded the long-shaft design in which the eccentric is mounted below the gear.
An impact crusher can be further classified as Horizontal impact crusher (HSI) and vertical shaft impact crusher (VSI) based on the type of arrangement of the impact rotor and shaft. Horizontal shaft impact crusher These break rock by impacting the rock with hammers/blow bars that are fixed upon the outer edge of a spinning rotor.