Abstract: A rig mounted compactor is provided. The rig mounted compactor comprises a shaft rotatably arranged to cause vibration of the rig mounted compactor with a first amplitude and a second amplitude by means of a first weight and a second weight and a hydraulic motor arranged to drive the shaft. The first weight is eccentrically fixed to the shaft, and the second weight is eccentrically arranged at the shaft. The second weight is clutchable between an idle mode when driven in the direction, and a rotatable mode when driven in the direction. The second weight is arranged to idle with respect to the shaft in the idle mode. The shaft is arranged to cause the first amplitude of the vibration by the first weight in the idle mode, and the second weight is arranged to rotate synchronously with the shaft in the rotatable mode to cause the second amplitude of the vibration.