Thanks, Bob. The actual concept occurred to me last August, but I'd been working on dry gem recovery for about 8 years, building 8 or 10 different designs. As it turns out, you can't recover gems dry. A physics phenomenon called "Granular Convection" aka "the Brazil Nut Effect, prevents it. So I built this for that purpose (not being aware of GC), and when it didn't work for gems I tried it for gold, and it worked great. A few bugs to work out, and it's now a pretty nice little wet/dry gold machine that can be built in almost any size. I sell the 18" unit for $550 + shipping, with a solid body of HDPE corrugated pipe. That model weighs 19lbs. The one I use myself is a skeletonized version that sells for $650 + shipping. It only weighs 11lbs. I'm amazed myself at how well these perform.
They only draw about 1 amp, so can get by with a fairly small battery pack, and when used wet, they require very little water...just enough to keep the material on the diaphragm sort of soupy. Water has no impact on the recovery...that's all in the mechanical action.