between slots 64 and 74 while transmitting relative rotational movement from the back rod holding assembly to the front rod holding assembly as will be described more fully hereinafter rotation of the drum is performed by a drive motor 96 having a drive sprocket 98 connected by a chain 100 to a sprocket 102 on a shaft 104 front and back drive wheels 106 are disposed on shaft 104 and operate against the outer ring 60 and outer ring 70 transmitting rotational movement from the motor through the shaft to the drum additionally shafts 108 110 and 112 having idler wheels 114 operating on both the outer ring 60 and the outer ring 70 are disposed about the periphery of the drum to ensure proper alignment thereof fig9 illustrates a typical arrangement of a drive wheel 106 or idler wheel 114 with either of the outer rings 60 or 70 changes in the relative position or spacing between the inner rods 46 and outer rods 48 is accomplished through a spider drive mechanism 120 operated by a stepper motor 122 or the like an inner wall 124 is provided with a motor housing 126 attached thereto by fasteners 128 which may include bolts pins rivets welding or the like drive motor 96 may also be fastened to inner wall 124 likewise drive.