Abstract: A yo-yo variety reciprocating drive for long stroke, well pumping units, which employ a flexible element as the operative link between the winding drum and the polish rod of the well pump. Reversal from an upstroke to a downstroke is cushioned by mechanism which provides a power source off dwell period of predetermined duration during the aforesaid stroke exchange and is adjustable to control the length of stroke of the pumping unit. A velocity control senses the velocity of the polish rod during such dwell period and re-energizes the power source when a predetermined velocity is achieved following reversal of direction.

Abstract: A motion compensator for disposition between an offshore support structure and an offshore well structure movable with respect thereto comprises a compensator assembly interconnected with the support structure and the well structure such that relative movement between said structures will cause movement within the compensator assembly, and a position indicator including a cam assembly for measuring the relative movement within the compensator assembly, and a transducer operatively associated with the cam assembly for translating its measurements into a signal.