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Agent_34
08-17-2012, 12:15 PM
Does anyone know how deep the sluice boxes need to be if using the design criteria found in the Clarkson study of Yukon placer gold recovery? I have a fixed amount of space under my trommel and want to get as much sluice run as possible. The shallower I can make the boxes, the better. I am confident that 6 inches would be plenty. I would like to go as low as 4 inches and I think it might work. But I am concerned that I may not have as much freeboard as I would like if I go with 4 inches. I am primarily asking about the expanded metal section as I plan to have the hungarian riffle section out from underneath the trommel.

Thanks.

overtheedge
08-18-2012, 08:33 AM
I'll give 'er a try. As I recall the Clarkson study had the water flow at 200GPM per foot of width.

So I would assume the first thing we need to know is the maximum size of the classifieds coming out of the trommel. Next we nee to know how many GPM you are running as well as the height of your riffles.

From AMA 2012 Handbook:
Transporting Power of Running Water
Velocity (fpm) Particle size moved
30 fine sand lifted
45 fine gravel moved
120 1" pebbles moved
200 2"-3" cobbles moved
320 3"-4" cobbles moved
400 6"-8" cobbles moved

Minimum water depth needs to be about 2X the maximum particle size and about 2X the height of the riffles. That is the minimum water depth.

So if I did the math right, 1" deep in a 12" wide sluice with a water velocity of 30fpm is roughly 19 gpm. So 4" (X4) deep and a water velocity of 200fpm (200/30=X6.6) would be 19X4X6.6 = 501 gpm.

Hope this helps.
eric

DanAk
08-18-2012, 08:59 AM
My 24" box's have 6" high sides, and are plenty high for the water I am running, I use expanded metal riffles and screen to 1/2" the water level in the sluices only is about 1/2" deep while I am running material..

Agent_34
08-20-2012, 11:03 AM
Thanks to both of you for your responses.