Hi Garry & Graeme, Thanks for your comments. I kind of liked the concept of it & how it is modeled on the bends of a river & the way the curves & bends of a river concentrate material. I agree that it would be a bastard of a thing to make. The best time to check out a river for possible gold locations & to see the back eddies & such is when a river is in full flood. They behave in a much different way when in flood & hence moving & depositing gold. You will notice towards the end of the first footage how the bubbles on top of the water are back peddling against the main current. Just like a river in flood & this is where the gold & heavies are going to drop out or get sucked & tucked out of the main flow. Interersting I think.
Garry....in the 2nd footage they have quite a velocity of water going down the box & I dont think bigger stones would build up & the heavies & black sands would just concentrate on the down stream side of the bends, like in a hungerian riffle. It would get to a stage when you would have to clean out the build up. I reckon you could shovel into it as fast as you could with no problems.
Sluice boxs are strange things & no one box is going to be perfect at trapping all types & sizes of gold. A dredge box needs a certain velocity of water going down it just to wash on the bigger rocks, let alone the finer material & smaller gold. The bigger your dredge the stronger the water flow needs to be to wash on & out the bigger rocks. This isnt good for saving the finer gold. Just like with a river sluice. If you are going to just shovel directly in to it then you are going to need a stronger flow to wash on the bigger material with out having to stop & man handle the bigger bits out of it. Again this isnt good for fine gold recovery. Riffle height & spacing comes into this equation as well. Depending on the size & shape, mass & density of the gold in the material being worked then the sluice box really needs a size & spacing of riffle to suit.
If the gold is fairly small then I use a riffle height of no more 12mm & spaced at about 80mm.
The material is usualy classified so nothing bigger than 10mm is going down the box & I have a fairly gentle water flow.
Just enough to wash on the waste material with out me having to rake it on & out the box.
This works very well at saving finer gold & of course bigger bits if they are present.
If I shovel directly in to the box then I use a longer box, 1200 long, same height riffle but spaced closer together at about 40 mm
My 4" dredge box is a different kettle of fish with 30mm riffles spaced at about 50mm. With a reasonable amount of water going down the box to wash on the bigger stones it still traps the black sand pretty well but I am sure would be losing some fine gold.
Happy hunting
JW :)
