shaft 46 is driven by the engine 13 through a drive train not shown the endless belt feeder conveyor 28 is of the chain belt type and includes conveyor chains 51 52 carried by the shaft 46 and the drum 47 a series of transverse slats 53 are attached to the chains 51 52 which move in the direction of arrow 54 to convey crop material the idler drum 47 is floatingly mounted relative the side walls 41 42 of the feeder housing 22 by a pair of shaft supporting tensioning mechanisms 56 57 which are opposite images of one another the idler drum 47 is rotatably mounted on a transverse axis 58 by a nonrotating shaft 59 the drum is rotatably supported by a pair of anti friction bearings 61 62 on the laterally opposite ends of a main or central shaft portion 63 the central portion 63 of the shaft 59 also carries a pair of retainers 73 for the idler drum support bearings 61 62 the central shaft portion 63 terminates at its opposite ends within the lateral space between the side walls 41 42 of the feeder housing 22 and within the lateral spacing of a pair of tensioning support arms 66 67 of the tensioning mechanism 56 57 a pair of axial extensions 68 69 are mounted on laterally opposite ends of the central portion 63 of the shaft 59 by cap screws 71 as shown in fig3 and 5 the inboard parts 74 75 of the extensions 68 69 extend through openings 76 77 in the free ends of the support arms 66 67 and outboard parts 78 79 of the arms 66 67 are in vertically confronting abuttable relation to upper and lower stops 81 82.