Hey there, OC!
... on modifying my 10" wide 30" long river sluice. I guess the best way to approach this is from a historical standpoint - and then kind of put a spin on everything based on any personal knowledge 'stuff' that might have accumulated, through trial and error, over the years.
In-stream sluice boxes are very dependent on stream flow and volume - and as such need to get 'down and dirty' quickly to be able to recover the Gold during the few seconds that the slurry spends traveling through the box. Any free Gold (not stuck / cemented to gravel with clay) will drop blindingly fast. That is for any sized pieces, minute to large, in the water-thinned slurry.
Back in "the olden days" the "Carpet" really was carpet and the riffles were anything that presented a dead spot for Gold to drop and be caught into. Not very efficient - but then it was all virgin ground to work. Catching the large and disregarding the small sizes of Gold meant that for that time era it was all that was wanted. Rocks, logs, rail road rails and angle iron all ""worked"" to the standards of the time.
Then Clarkson, Polling and others in the Yukon came up with a better idea. Expanded over Miners' Moss with MUCH better recover percentages. Even scaling that concept down to smaller sluices (like "The Pop and Sons") was much, much better.
Then, of course, the Le Trap (and later the G-1) came along and turned recovery into just drops for the Gold to fall into - allowing the lighter materials to just wash through. No carpets and no expanded metal but needing no more volume than a single shoveler can produce. (also able to be 'flooded' with too much material being shoveled in
)
Then the Keene Wonder Mat came out just about the time that Gold Hog began production with it's ongoing program of mat development. Gold Hog mats require a fair amount of water flow - but with careful selection the mats can can work quite well in-stream. They handle an amazing volume of material but
do need a certain volume and speed of water.
Now, each and every "improvement" has it's good and not-so-good sides. In the realm of small in-stream sluices that are relatively simple to operate pretty much comes down to:
One time costs
Efficiency in recovery
Volume of material processed over time with the water conditions to process it
The ability to process the material to leave just the Gold and other heavies in the box
The convenience, volume of concentrates and the speed of cleanups
Everyone has their personal preferences based on what works for certain (their own specific) circumstances. Usually an "Old Salt" decides to experiment with the newer "stuff" and progresses only to a point of comfort based on individual circumstances and successes. Dredgers have very different needs from in-stream guys, and so, to stay focused on in-stream sluices, there are a few (OK, Hoser did mention 1,000 styles of expanded
) different combinations that
could work for you.
Shoveling directly into your sluice box means that there will be a wide range of slurry sizes. To add a variable you need to determine how much water and the flow speed you'll be able to get going through the box.
In my opinion the riffle over flattened expanded over Miners' Moss is the easiest and most forgiving to use over a wide range of in-stream circumstances. Pretty good (but not exceptional) recovery.
To me, the "Hand Wringing" over 'migration losses' under the metal riffles' just hasn't been a demonstrated problem. Yes, a little water goes under the riffle's bottom edge - however there isn't the flow / pressure to blast the Gold along through the protected areas on the back side of the riffles. I feel that a 100% seal under the riffle is unrealistic and not really needed - especially considering that another riffle is
right behind the one before it.
As a practical test of this idea - watch a piece of Gold in water flow on an uncarpeted and unprotected sluice floor (or on, say, a Miller Table). Just as in a stream bed the Gold is difficult / slow to move (if it wasn't all the Gold would have been washed into the oceans a long time ago).
Again,
In my opinion if you have the luxury of pretty good water volume and quite a bit of speed, the Gold Hog mats would be the way to go. A little expensive to buy (one time expense), they also require internet research to decide which styles you should buy, how to install and then use them. it takes effort on this new technology - *but* - once set up they are the best (again my opinion) for any style sluice box. Recovery is exceptionally good for all size Gold and it has the ability to process as much material as a single shoveler can (reasonably) put through it. Clean-up has a very low volume of concentrates and is really fast. By just saving the concentrates in a bucket to keep on going will result in processing a lot more material over your shoveling day. Investing viewing time in the Gold Hog videos is something that I
highly recommend (good general information usable by anyone using any sluicing equipment)
As an aside - save that bucket of concentrates until the end of the day and then slowly re-run it through the box on your last run of the day. If you have a good set-up you will re-recover -*
all*- the Gold and further process / pass through almost all the lighter materials (like black sands) through the recovery areas
and out the back.. If you are unsure about this procedure just save all the processed-through-the-box concentrates on that last run. Pan them separately and see the results.
Joe
