drive 34 and 34 driven 34 elements in the upper drive assembly are used somewhat interchangably herein inasmuch as the element driven by the drive shaft is also the drive element for the driven element a power takeoff which in turn is the drive element for the drilling unit to impart torque to the drill string 34 drilling unit 34 means all the equipment near the upper drive assembly such as the elevator swivel etc which are raised and lowered by the traveling block and 34 lower drive assembly 34 includes the rotary table and the power takeoff to rotate the drive shaft whether a sprocket chain drive a pulley belt drive or a gear as part of a drive train which uses the rotary table as the power source fig1 illustrates a platform 10 on which a derrick 12 of the conventional type and size is supported for drilling and reaming operations to be conducted located within the derrick are three sections of drill pipe 14 connected together as unit above the platform illustrating the manner in which drilling or reaming in triples is accomplished as described in the krasnov application supra the line of travel of a drilling unit 16 with its upper drive assembly 18 and rotational axis of the drill pipe are in the center line of the derrick and moved vertically by a traveling block 20 in the conventional manner this center line is the main or drilling axis and denoted as 22 the platform 10 and derrick 12 may be located on a floater i e ship or semi submersible or a offshore platform stationary or movable for drilling a well or may be part of a land based rig for drilling an onshore well an easy break out.