a trailered , short stroke reduction grinder including a telescoping , multi - stage push ram and hydraulic grinding head which are operable from seat mounted joy sticks in an enclosed operator cabin . collected reduction materials are pushed to a grinding channel defined between multiple arcuate , sizing screens and the rotating grinding head . a hydraulic shear bar controls the entry of the material to the grinding channel . the grates of the sizing screen are arranged to provide a plurality of reduction apertures of progressively increasing size and differing geometric shape . a single hydraulic motor and belt drive linkage control the grinding head and permit forward and reverse operation . high density plastic slide bearings at cross supports of a discharge conveyor support a ribbed belt .