a take up pulley 132 to double pulley 122 the pulley 132 is supported by an arm 133 pivotally mounted at pivot 134 to a frame member not shown and loaded by an air cylinder 135 in turn pivotally mounted to a stationary frame member not shown by a clevis 137 the cylinder 135 is pivotally connected to the arm 133 by a clevis 139 39 on a piston arm 139 the endless belt 130 is also used to drive guide roll 38 on dancer arm 40 this is best seen in fig3 after passing over pulley 122 belt 130 passes around a stationary pulley 150 over a first pulley 138 coaxial with and fixed to dancer roll 38 on shaft 39 down and around a stationary pulley 152 over another stationary pulley 154 down and around a second free wheeling pulley 140 coaxially mounted on shaft 39 with the dancer roll 38 on arm 40 and over a width of double width pulley 142 coaxial with and fixed to guide roll 42 since the pulleys 138 and 140 turn in the same direction and at the same speed i e film speed they may comprise a common double pulley referring back to fig2 from pulley 142 the belt 130 continues over pulleys 144 and.