The problem here is to suck silt off the river bed and sort it in real time. I have split the machine into a top and bottom section for clarity. It looks like a mushroom with a lawn mower engine on top. Pull the handle and start accumulating gold. An upside down washing machine agitator is mounted in the center as a silt flinger.
Silt is sorted into size categories in the first pass.
In the second pass each size category is reflung to sort out the gold in them thar hills. A power rotary sluicer of sorts. The four handles around the perimeter help to control it in the water, like those two man post hole diggers you see at the Rent-All.