a rotatable wheel on a mobile frame carries radially extending pairs of movable , opposed crop - gripping arms which are spring - loaded toward each other . brackets on each face of the wheel pivotably secure the arms . a roller on each arm moves onto and out of engagement with a cam on the frame with each rotation of the wheel , opening and closing the arms . preferably the brackets , springs and rollers have quickly defeasible attachment hardward for ease in replacing worn parts , like a readily accessible removable pin securing each arm spring in a cavity in the arm , and rollers having shafts with indents in which a spring - loaded lock removably lodges . in one embodiment a lone threaded member secures each bracket and also affords a base locator for the arm spring . a bracket is removable with arms still attached for ease in maintenance with access to the threaded member through the spring cavity .