Abstract: A pneumatically operated percussion apparatus for compacting soil, or other material. The apparatus includes a gear case that supports a percussion unit that is adapted to engage the soil to compact the same. A pneumatically operated motor is mounted on the gear case and air is supplied to the motor via a manually-operated "deadman" valve unit. A centrifugal clutch connects the output shaft of the motor to the percussion unit. The air flow to the motor is controlled by a governor to obtain a substantially uniform rotational speed for the motor output shaft.