rotor shaft 98 projects from opposite ends of the casing and is journalled in bearings 102 103 supported on suitable platforms 104 105 mounted on the outside end walls 89 101 of the casing the rotor is driven by an electric motor 106 mounted on the outside of the casing adjacent the small end of the drum and coupled to the rotor shaft projecting from the bearing 103 by means of a pulley and belt transmission the motor 106 has a three groove pulley 107 fastened to its shaft and coupled to a similar pulley 108 fastened to the projecting end of the rotor shaft by v belts 109 as shown in fig5 the rotor 96 is located eccentrically of the rotational axis of the drum adjacent the upwardly moving side of the drum and in a position to intercept material lifted by the vanes 93 and falling from the upper region of the drum it is spaced from the frusto conical surface defined by the path of movement of the inner edges of the vanes so that there is a significant clearance between the rotor blades and the drum vanes and no shearing action is produced between the blades and the vanes for preferred operation the rotor is arranged to rotate in the opposite direction to the drum as indicated by the arrows 95 and 110 in fig5 in normal continuous use of the apparatus shown in fig1.