Abstract: A mobile screening apparatus includes a horizontal rotary drum preferably fed by underflow from a prescreening device that is reversible endless belt of screening grizzly bars. The belt reverses for expelling oversize material caught between bars. Force needed to turn the drum is monitored, as a way of controlling drum feeding by the prescreening device, for preventing protracted over-filling of the drum. The screening drum includes an outer peripheral cage of longitudinal bars, at least some of which preferably are movably mounted. A set of wires is circumferentially wrapped about the bar cage, with sufficient flexibility to permit the wires to locally elastically flex away from the bars sufficient to pass slightly oversize material and facilitate cleaning of debris lodged in spaces among the bars and wires. Brushes help dislodge lodged debris.