Abstract: Apparatus for inserting prefabricated drain members downwardly into underlying earth which includes a vertically extending mast that supports an elongated earth penetrating mandrel. The mandrel is adapted to receive a prefabricated drain member for movement with the mandrel down into the earth to insert drain members. A drive is mounted on the mast for driving the mandrel into and out of the underlying earth and the drive includes a rotary drive gear that engages the mandrel and a motor for driving the gear. A vibrator is mounted on the upper end of the mandrel for imparting vibrations to assist in its penetration into the earth. A flexible torsion drive coupler couples the motor to the drive gear for driving the drive gear and for also isolating the motor and the mast from vibrations imparted to the mandrel by the vibrator.