journalled in bearings in the mounting plates 60 and is of the same side to side width as the primary and secondary brushes 168 cm and has a medium knurled surface for engagement with the first conveyor belt 100 in the preferred embodiment the first fixed roller 68 is crowned that is has a diameter at its midpoint of about 7 6 cm 3 in that tapers to a diameter of about 7 cm 2 75 in at its opposite ends the crowned first fixed roller 68 assists in properly training the first conveyor belt 100 as is known in the art the first fixed roller 68 is driven by a hydraulic motor 70 through a chain and sprocket drive 72 shown in schematic form the first fixed roller 68 is driven at a rotational speed sufficient to drive the first conveyor belt 100 at a linear speed in a range of five to eight feet second in the direction shown the chain and sprocket drive 72 is additionally connected to the secondary brush 54 by a chain and sprocket drive 74 shown in schematic form to drive the secondary brush 54 in a counterclockwise direction at a tip velocity approximately equal to that of the primary brush 44 as described above additional fixed rollers include a second fixed roller 76 a third fixed roller 78 a fourth fixed roller 80 and a fifth fixed roller 82 rotatably mounted between the sides of the frame assembly 14 a sixth fixed roller 84 is rotatably mounted between a pair of mounting plates 86 that extend upwardly from the upper conveyor extension 30 and a seventh fixed.