is positioned proximate the distal end of a lever or bar 92 which is provided with a centrally disposed pivot or fulcrum point 94 about which the bar 92 may move in the direction of arrows 96 the axis 98 of reversing roller 34 is positioned at the other distal end of lever 92 and therefore is capable of moving in the direction of arrows 100 proximate the left distal end of bar 92 the push rod 102 of a cooperating braking mechanism 104 is affixed push rod 102 cooperates with a telescopic tube 106 which has affixed thereon at one end a braking material 108 that is adapted to cooperate with brake drum 86 and apply braking forces thereto in a conventional manner a spiral spring 110 is maintained in position on push rod 102 by support peg 112 the other end of spring 110 pushes against tube 106 permitting the braking material 108 to come into contact with drum 86 it is obvious that the braking forces applied to braking drum 86 are therefore directly related to the position of the axis 90 in lever or bar 92 in a similar manner on the righthand side of bar 92 proximate the distal end thereof the push rod 114 of braking mechanism 115 is affixed push rod 114 cooperates with a telescopic tube 116 which has provided thereon braking material 118 that is adapted to cooperate with and.