Hi Chris, I had thought of the fill creeping to one end but thought that could be overcome in a non-industrial unit, by inclining the trays by hand until it works, or seeing that the unit would normally be loaded by shovel, shovel it back to the other end. This wooden structure was already well on in manufacture when I saw the thread, had it not been I would have suggested an other way, as you mentioned a drum screen. How about this. Buy an old cement mixer and either cut patches out of the drum and replace them with bolted in or welded in mesh, or if you have the time and patience, drill lots and lots of holes through the drum and use that as your sifter. You would need patience because the would have to be a great many holes to drill. One advantage of using this system is that the left over rubble can be tipped into your wheel barrow in the same way as the cement was.