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dragline
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Re: Fine Gold Sluice Design Help Needed ( 21:39:45 FriMar 3 2017 )

Joe,

Regarding your mention of an "Alaskan Curtain" flap, I have seen these in operation but haven't personally used one. Have you any experience with using these? Can you tell me what claims might be associated with using them?

If the overhead curtain were somewhat stiff but a little flexible like the curtains that I've seen I could imagine that one claim might be that they help to decrease slurry turbulence. I couldn't imagine that using a stiff curtain might increase sediment build-up in the riffles as Peluk is suggesting, but I would like to know more about these "Alaskan Curtains".

dragline

  
peluk
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Re: Fine Gold Sluice Design Help Needed ( 22:10:32 FriMar 3 2017 )

You are just going to have to produce this enclosed sluice and demonstrate the capabilities you speak of.

When you raise or lower the slope of an open sluice,you not only alter the speed of the flow,you alter the flow depth. When you raise it, with the pump pressure and available water the same,the depth of flow decreases.When that happens, and along with it,the point of impact of material in the flow changes along with the forces applied by the riffles being at a different attitude to the flow.

If you leave the sluice at that slope and increase pump pressure and water flow,the selection process is going to altered even more to where your gold will be back out on the beach.

Take a look at your photo of your ribbed mat and the gold content in the various grooves. It is pretty evenly distributed down the length of the mat. This is scary.

I have found this with Keene's beach mat as well if running at any kind of acceptable production speed. Although I am left with far less waste in the concentrate,gold is also found at the bottom of the mat enough to say,something has to be done. So,I follow the mat with a slick and then a field of expanded over moss over ribbed carpet. This is sufficient to allow me to say I'm satisfied with my recovery.

That puts me way ahead of your idea because I can observe and correct features of the flow in relation to my sluice and the catch medium I use.

The point in the process that I have to work on now is this. When do I stop,flush mats and start again.At what point have I reached the maximum gold retention capability before I start spilling it back on the beach. With cleanup sluices,you can easily observe this because everything is miniaturized.The mats collect gold only maybe 2/3 of their length.Recreating that on a larger scale at production speed is ideal.

For you and the enclosed sluice idea,a lot of the opportunity to observe recovery activity is not there let alone ease of disassembly for cleanup.

  
LipCa
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Re: Fine Gold Sluice Design Help Needed ( 23:03:19 FriMar 3 2017 )

Under water video cameras!

  
geowizard
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Re: Frog Fur matting? ( 23:38:53 FriMar 3 2017 )

Frog Fur mat?

I have a solution exclusively recommended for fine gold.

You've heard the expression "Fine as Frog's Fur"?

Why not? :confused:

- Geowizard
[1 edits; Last edit by geowizard at 00:03:17 Sat Mar 4 2017]

  
geowizard
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Re: Frog Fur matting? ( 00:16:21 SatMar 4 2017 )

LipCa,

It's a High Banker.

If the box is sealed, it works the same in or out of the water.

When you pump slurry into a box, the box fills with slurry.

The heavy solids in the slurry will begin to fill the box from the bottom - up to the top of the weir.

The solids settle initially as the box is filling. With 50 percent solids in the slurry, the solids will drop out immediately. Some of the solids will remain suspended.

The unfortunate situation is that some of - or much of the solids will fill the box.

My concern is that if the box becomes plugged, the box will pressure up and possibly explode.

Added;

I would hate to see dragline become an "Urban Legend". :smile:

- Geowizard
[1 edits; Last edit by geowizard at 00:19:02 Sat Mar 4 2017]

  
dragline
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Re: Frog Fur matting? ( 01:21:55 SatMar 4 2017 )

Geowizard,

Oh no! Exploding sluices! Wouldn't that be a spectacular sight to catch on video. I hear your concerns about sediment buildup which seems to be a common thread among other members here. Of course what sets my opinions apart in this regard is that I have built and operated a subsurface sluice previously. Conversely, I don't recall any other members of this forum having taken on that effort. If only Zooka were still here.
:sad:

So I hope you do not mind if I chuckle a little in response to your comments, opinions and predictions about slurry buildup or exploding sluices. Hopefully I can find the time this weekend to generate a design layout for my subsurface sluice box (fully enclosed from input to tails) that I intend to build and operate for this project.

However, I do not anticipate there is anything that I can do short of posting pictures and videos of a successfully operating subsurface sluice that will prompt either of you to change your minds. I will continue refining and updating my designs here on the forum just for the unlikely possibility that one of the forum's other members might understand the validity of my designs sufficiently to make observations or suggestions about my designs that I did not see and that prompt me to make changes or improvements.

dragline

  
geowizard
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Re: Urban Legend? ( 01:35:05 SatMar 4 2017 )

dragline,

There are many things I have NOT done. In the interest of self-preservation, I don't experiment with explosives. :confused:

So, you HAVE built one?

Then, pray-tell, armed with all of the facts and having built one, what design information do you need? :confused:

- Geowizard

  
dragline
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Re: Frog Fur matting? ( 01:51:10 SatMar 4 2017 )

LipCa,

Yes, I have thought a lot about the practical use of video cameras for other subsurface designs I have been working on over the years. One such design involves an in situ ocean floor semi-autonomous dredge and sluice. Of course such designs and contemplations are so far out of the ordinary as to be completely unsuited for discussion here on Alaska Gold Forum.

Interestingly, I have a half unit of 3/4 inch mold/release marine plywood that has been collecting dust in my warehouse for about 5 years now. You know, the kind of marine plywood that is engineered to build durable concrete casting forms that will tolerate many hundreds of castings. While this probably is not an ideal building material for my subsurface sluice I am guessing that it will hold together long enough to give me an idea about whether the results of my efforts will be on target with my performance predictions.

But in regard to your video camera suggestions, I'm planning on building the top, bottom, input and tails sides out of the marine plywood. But the two lateral sides I'm planning on building out of acrylic sheet, probably 3/8 or 1/2 inch. As long as I have my cell phone on me I will be taking videos of the slurry interactions with the riffles thru the acrylic sheet. While not nearly as informative as looking down into the riffles of an in-air sluice, the side view of the riffles should allow me to estimate slurry flow velocity and gather data regarding riffle clearing at various ranges of velocities.

dragline

  
dragline
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Re: Frog Fur matting? ( 02:27:10 SatMar 4 2017 )

Geowizard,

Your question: Then, pray-tell, armed with all of the facts and having built one, what design information do you need?

Response: I need exactly the same thing that prompted me to start this thread. I wanted to have a discussion with one or more miners that had experience with quantifying and interpreting the metric of "slurry velocity" as it pertains to fine gold sluice design and operation. In other words, I was hoping to hear feedback from miners such that they would tell me for their washplant, and with a given distribution of gold mesh sizes and at a given pre-classification the slurry velocity they found optimal was, for example, 5.5 feet per second or whatever.

What I built and operated my subsurface sluice for a few summers back in the late 1970's I operated at slurry velocities that ranged from about 5 feet per second up to a maximum of 13 feet per second. But the gold I was dealing with was fairly coarse from the north fork of the middle fork of the American River in California. I occasionally setup a surface in-air sluice at tails to see what I was loosing and I determined that my losses began picking up above 8 to 10 feet per second. But again, that was fairly coarse gold the size of a Buick compared to the beach gold I'm dealing with presently.

I've heard reports here on Alaska Gold Forum from beach miners in the past that have the opinion that their Beach Box sluices operated well at slurry velocities between about 2 and 3 feet per second. Other beach miners have indicated 4 or 5 feet per second. But having so few data points for reference it is difficult for me to nail down and target what I believe might be an optimal slurry velocity.

The problem with aiming too high, i.e. 6 feet per second, is that I might be blowing out the majority of my fines at full throttle. With such a situation I will be forced to reduce to half throttle whereby the riffles will be operating most efficiently but the overall productivity will be half of what it could have been if I had more data and had guessed 3 feet per second was optimal at full throttle

If I aim too low and I'm only achieving a slurry velocity of 1.5 feet per second at full throttle I risk the dreaded riffle buildup problem that you and Peluk are so concerned about. But no matter what slurry velocity I choose as optimal I'm going to have to also pick a depth and throttle setting that I "guess" will allow the greatest flexibility over a wide range of slurry solids percentages at a given dredge depth.

If you have understood what I have said here you will probably conclude that establishing the optimal power setting on the pump for most efficient recovery isn't going to be easy and that is why I was hoping for more data.

But I can tell you that the riffles of my Sawtooth mat on Oregon beaches don't seem to start clearing optimally until about 2.5 feet per second and that beyond 5 feet per second I'll see gold reatained further down the length of my Sawtooth mat suggesting the likelihood of loses. But 12 inch wide or 16 inch wide beach sluices set up in small streams, rivulets and freshets probably are not a very reliable way to nail down optimal slurry velocities. Since there are, or were, a lot of miners here with a broad range of experience operating large washplants under various conditions I was hoping for feedback and more data.

dragline

  
peluk
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Re: Fine Gold Sluice Design Help Needed ( 05:01:10 SatMar 4 2017 )

Dragline,until Joe gives you his thoughts on the dampening flap at the head of the flow,these are my observations. I don't recall saying the flap might lead to buildup in the riffles. That hasn't happened to me. What I may have mentioned is the negative pressure that the flow encounters at its(the flap's) bottom,downstream edge.It is only important if you had flake gold riding the torrent out of the hopper. Before it had a chance to settle out of the flow,it could be riding mid-depth and upon passing under that edge,the release of constraining pressure could have a lifting effect and hold it in suspension longer. It's just one of those things that makes me gnash my teeth before I go to sleep.

What I have observed with different materials used as flaps are varied. First,I use the flap to break any surface bubbles ideally, and somewhat flatten the flow. If the mat is too heavy,sand and water will build up behind it and spill out around the edges. That calls for cutting back on water flow to see if that cures the problem. If it does and the mats or whatever are selecting gold,I can stay with that.

I have used lots of materials such as visqueen,canvas,and plastic tarp.Clear visqueen will show the bubbles forming into a larger bubble and seeking the highest wrinkle on the
bottom side of the sheet. I am forever experimenting with these dampers.I usually have a slick at the top of the box before the flow hits the field of mats or whatever medium I've chosen. Flat gold,if you have a lot of it,has to be catered to. Solid shapes are already on the bottom early on.



  
JOE_S_INDY
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Re: Fine Gold Sluice Design Help Needed ( 09:04:19 SatMar 4 2017 )

So, OK, I'm back!

An Alaskan Curtain is a moderately flexible sheet of material which rides on the top of the water, creating a hybrid to the Air or Solid covering to the water flowing over riffles. The best material seems to be something that mimics a flat piece of inner tube, Of course, inner tubes are getting harder and harder to find - but we all know it's "flexibility factor".

The flap that I spent the most time around was on a friend's commercial operation. "Hung" over the moss expanded just downstream of the slick plate and before the small riffle sections it took the splashing and surging of the shaker plant and "trained" the water to be smoother and flatter under the curtain as well as after it ended.

The discussion of water or air overhead of the slurry going over the riffles brought it to mind. Having seen it used for 2 or 3 years gave me the impression that it didn't slow the water / slurry down much if any but rather flattened the laminar flow somewhat while going over the moss / small expanded and going into the short riffles.

Joe




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Wiser Mining Through Endless Personal Mistakes
 
 

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