1. A FRICTION DEVICE COMPRISING MEANS HAVING INTERENGAGEABLE FRICTION ELEMENTS ARRANGED TO BE MOVED THROUGH A PREDETERMINED DISTANCE WITH RESPECT TO EACH OTHER FROM A DISENGAGED POSITION TO AN ENGAGED POSITION; ACTUATING MEANS EFFECTIVE TO MOVE AT LEAST ONE OF SAID FRICTION ELEMENTS THROUGH SAID PREDETERMINED DISTANCE TO CAUSE ENGAGEMENT AND DISENGAGEMENT OF SAID FRICTION ELEMENTS AND EFFECTIVE TO MOVE AT LEAST ONE OF SAID FRICTION ELEMENTS THROUGH A DISTANCE IN EXCESS OF SAID PREDETERMINED DISTANCE UPON OCCURRENCE OF WEAR OF EITHER OF SAID FRICTION ELEMENTS; SAID ACTUATING MEANS INCLUDING AS A LEVER PORTION THEREOF TWO COAXIAL TELESCOPING MEMBERS BOTH MOVABLE WITH SAID ACTUATING MEANS TOGETHER DEFINING A PORTION OF A LEVER HAVING AN EFFECTIVE LENGTH; SAID TWO COAXIAL MEMBERS BEING RELATIVELY ROTATABLE WITH RESPECT TO EACH OTHER AND ADJUSTMENT MEANS OPERATIVELY CONNECTED BETWEEN SAID COAXIAL MEMBERS WHEREBY RELATIVE ROTATION THEREBETWEEN CAUSES THE EFFECTIVE LENGTH THEREOF TO CHANGE; SAID ADJUSTMENT MEANS INCLUDING A ONE-WAY MEANS INTERPOSED BETWEEN SAID TWO COAXIAL MEMBERS BEING EFFECTIVE TO RESTRICT RELATIVE ROTATION BETWEEN SAID TWO COAXIAL MEMBERS AS SAID ACTUATING MEANS MOVES SAID FRICTION ELEMENTS THROUGH SAID PREDETERMINED DISTANCE AND BEING EFFECTIVE TO CAUSE RELATIVE ROTATION BETWEEN SAID TWO COAXIAL MEMBERS AS SAID ACTUATING MEANS MOVES AT LEAST ONE OF SAID FRICTION ELEMENTS THROUGH SAID DISTANCE IN EXCESS OF SAID PREDETERMINED DISTANCE WHEREBY THE EFFECTIVE LENGTH OF SAID TWO COAXIAL MEMBERS CHANGES TO COMPENSATE FOR WEAR OF SAID FRICTION ELEMENTS.