Reed you mention the sharp edges of the aluminum Gold Well. My question what's going to happen the Drop Well Vortex of the Gold Well sluice having 2" and 3" rocks tumble down the sluice or for that matter the 1.5" rocks you classified down to prior to running the concentrate through the sluice. Aluminum is soft and over time I would think that the Vortex's will become damaged. I suspect this is why Gold Well wants the end user to classify to 1/4" to control the size of material passing over these Drop Well Vortex cells.
There are sluices that have been in use now for several months on a daily basis. No appreciable wear is seen, and in fact they still have sharp edges. However, I do not know why you suggest that sharp edges are required, when they are not. That is a result of the machining process. If aluminum were NOT a suitable material for the sluice to be made of, I would have chosen another. Aircraft aluminum is used that has similar property to steel. 6061-T6 is used for the 6" units and 7075-T6 on the 12" units. I have had stainless steel screws strip out in the 7075 and not harm the threads, where the screw was trashed. I have also seen 7075 used in some cases in a machine shop to stamp out steel parts from sheet metal. The only step up from these grades of aluminum would be titanium and would be so expensive as to be affordable only by large mining companies.
In any case the aluminum is stronger than most mild steels that standard sheet metal sluices only 1/16" thick are made from. The plates on the Gold Well are 1/2" thick.
There are several effects in the spiral wells, one of the effects is a high pressure zone near the bottom of the pocket and a low pressure near the top edge. Watching videos and stopping on cloesup will reveal these as two little collections of black sand, one at the top just off center and the other at the bottom (just off center to the spiral well centerline in the outer ring.)
Another effect at play is the differential velocity across the varying depth of the pocket, one side to the other, which is not dependent of the sharpness of an edge. This effect would occur if the edges were fully rounded.
Thirdly, there are microscopic forces at play such as boundary layer effects and molecular attraction. The microscopic forces play more important a role than flow or pocket shape when it comes to microscopic gold. They are not large enough to see the forces of the flow of water due to the fact they are so small and they are caught in the boundary layers of the sluice.
Black sands are not what the sluice is designed to collect, and amongst black sands, not all black particles are equal. In fact if one views black sands closely under a microscope, the majority of the particles are merely dark and not black at all. The picture on the other thread showed the stratification of the pockets well. That was what the picture was intended for. Even large 'black particles' sat atop much finer gold and was not intermixed with it much at all in the spiral gold wells. In the slot riffles there was relatively little gold collection compared to the pocket volume, and the black particles were intermixed with the gold.
The Keene in the video collected virtually no gold, as stated in the video. I believe Reed stated in the end of the video that 'half dozen to a dozen micro specks' is all that the Keene caught from all the material put through the Gold Well that the Gold Well missed.
The indication in the manual to classify to 3/8" is simply that to get the absolute maximum theoretical gold recovery, that classification to that range would be ideal. Yet without classification it is nearly ideal recovery anyhow. Most of the users of the Gold Well simply run raw material or material classified down to 1 or 1 1/2" or so (tossing out obviously large rocks). A requirement of someone that wanted to process large rocks through the sluice, would be to have sufficient water and angle combination on the sluice to 'float' the rocks out so they just didn't sit there in the sluice. The sluice has a very low water requirement, but as seen in Reed's video, it will work just as well 'full to the rails'. In fact, also stated in that video, is they were trying to push it far beyond what was suggested for the sluice, and yet it performed just fine.
That is one of the features of the Gold Well, that it is not finnicky about water flow and angle to the same degree that other sluices are. It works well over a broad range of flow rates and angles with very little difference in performance, and thus ideally suited for a beginner who wants good results easily obtained. One of my customers (that the crew here blasted for posting) even tested one of his at 45 degees and it still caught the test gold that he put in it.
Aluminum is soft but the surface of all aluminum instantly oxidizes, and aluminum oxide (the same material used in that gray sandpaper you sand metal with), has a harness of 8. Most steels unless heat treated, typically run in the 6 range. But one characteristic that is little known about aluminum, is it's molecular attraction toward other metals. In fact aluminum alloys with gold, and this alloy is purple. That molecular attaction is a great thing to have down there in that boundary layer zone where the forces of the water flow are not acting strongly on the fine gold. The molecular attraction then becomes more significant and can add to the collection of fine gold, and one good reason that I would prefer to use aluminum over plastic. Plastic has no molecular attraction to gold. Only thing plastic attracts is WalMart shoppers... I doubt you will see my sluice in WalMart ... but who knows
