1. A MECHANICAL ACTUATOR COMPRISING A HOUSING HAVING A CAVITY THEREIN, A PISTON MOUNTED FOR RECIPROCATING MOVEMENT WITHIN SAID CAVITY, AN ACTUATING ROD MOUNTED IN SAID HOUSING IN PERPENDICULAR RELATION TO THE PATH OF MOVEMENT OF SAID PISTON WITH ONE END THEREOF EXTENDED INTO SAID CAVITY, A PLURALITY OF ROLLERS, EACH HAVING AN ANNULAR GROOVE THEREIN, MOUNTED IN SAID HOUSING AND CONFRONTING SAID PISTON, A COILED BIASING SPRING MOUNTED IN SAID HOUSING, EACH COIL OF SAID SPRING ENGAGING THE ANNULAR GROOVE IN EACH OF SAID ROLLERS, SAID ROLLERS ADAPTED TO BE MOVED INTO COLUMNAR RELATION TO EACH OTHER BY SAID PISTON WHEREBY SAID ROLLER ARE MOVED FROM A REST POSITION INTO AN ACTIVE POSITION TO ENGAGE AND ACTUATE SAID ROD OUTWARDLY OF SAID HOUSING, AND WHEREBY UPON RELEASE OF SAID PISTON FROM ENGAGEMENT WITH SAID ROLLERS, SAID SPRING WILL RETURN SAID ROLLERS TO THEIR REST POSITION.