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peluk
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Re: Fine Gold Sluice Design Help Needed ( 06:49:36 FriFeb 24 2017 )

(continued)
6)Sub surface sluices are eventually abandoned for surface designs. This is only from what I've seen and heard.The sluices in them are tilted to assist in selecting material from the flow. Yes,they are notorious for losing fine gold. You said you operated a subsurface sluice for an 8" dredge that did that as well..."but they were captured later in a surface sluice below"...? Did you catch all of them,some,or did you just find some fine gold in this "below" location?
9)You stated the subby will not plug because it is a subby sluice.It has no air,no slope,and it doesn't function like anything I am familiar with." Slurry velocity is constant throughout the length." The reason it functions like nothing I have seen is because it exists in your mind along with the constant slurry velocity. I don't believe it will work as I've stated and for some of the reasons but not all.
10) Other reasons this unit will be less than optimal in recovery are its flat attitude for one.There is no eddy created on the mat surfaces.There may be a rolling action but an eddy will be created by the water passing over an obstruction which will make it tumble. The eddy and attendant negative pressure or suction will be created when the tumbling water collapses at different speeds.In so doing it pulls heavies into the area beneath the riffle or rib.....as far as I can see.Being flat in its attitude,all that riffle mat will just be buried because it is a stagnant area with water just passing over it with little drawing effect.
The second point worthy of consideration is the point about hydrodynamics. It is the study of water flow isn't it? If the water is not restricted in its movement vertically as in a surface sluice,it's power can go wherever currents move it leaving areas of rest for mineral to be collected. Yours has no such area.But that may have to be sensed by "thinking in the flow" like a truck driver on a secondary road. He is one with his truck frame,wheel bearings and suspension. He feels their pain through his butt and treats them accordingly. You must think in the flow as a particle of flat gold and know what it is that produces the best rest area in that flow....assuming you want to come to rest.

That's all you get.Now it's up to you to decide whether you are going to fish or cut bait. In the end remember the rule "show me". Please see the receptionist on the way out.





  
Fleng
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Re: Fine Gold Sluice Design Help Needed ( 17:25:48 FriFeb 24 2017 )

Fleng,

You don't have to wait.

Take a box and fill it up with water and dirt.

Pump more water and dirt into it!

Then fine tune it. :smile:

- Geowizard

Geo-
Doesn't a jig work this way? I don't see any reason why a jig system wouldn't work underwater. Draglines system is a passive gravity system. If it were an active system with discharge some distance away it would avoid the mass buildup and slurry viscosity that peluk is concerned with.

Just discharge the bulk media of a common specific gravity and retain the high density. Use a sensor system to shutdown the process when flow is restricted, jig is overflowing, or the sand crater collapses.

Safety first.

  
geowizard
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Re: Fine Gold Sluice Design Help Needed ( 20:36:44 FriFeb 24 2017 )

Fleng,

I can show you a half-million dollar RMS Ross Jig plant that was flown into the interior of Alaska from Whitehorse, YT, Canada on three C-130 charter flights. Total cost - all in was about 1 million dollars.

Several Geniuses set it up and went broke. The plant was too "unstable" for all of the reasons that Jig plants fail.

It actually deserves it's own thread! :smile:

- Geowizard

  
geowizard
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Re: Fine Gold Sluice Design Help Needed ( 20:52:56 FriFeb 24 2017 )

Fleng,

The system proposed as the subby doesn't actually do anything.

Like I suggested, you can take a box, the dimensions don't matter - it's a box. Fill it with water and shovel in some dirt - call it a slurry. The outlet is at the top of the weir. When pumping begins, the box will overflow. The solids in the slurry will settle to the bottom. In a few more seconds, the slurry will flow directly across the top to the weir.

It's not a jig.

Will a jig work underwater? Who cares? Jigs work out of the water (sometimes) . The problems with jigs require a separate thread - not to confuse an already completely corrupted design discussion.

- Geowizard

  
dragline
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Re: Fine Gold Sluice Design Help Needed ( 22:34:15 SatFeb 25 2017 )

Geowizard,

You said: "I get it. It's a GAME."

Nope. It isn't a game. It is a design that evolves, i.e. changes. Please allow me to explain.

When I said that the Subby illustrated wasn't representative of my current design I probably should have elaborated on that point. While I do intend to illustrate my current "Subby" designs it is a bit early in the design effort for me to post illustrations. Sorry about that. Right now I'm busy performing calculations and exploring what might be the most efficient way to generate and deliver the power needed to make the hydraulic well-drilling-like dredge work. I'll try to give you an illustration soon, as in a week or two. But in the mean time I would appreciate your patience a little longer.

When I told Peluk that "Perhaps it may be an unworkable design" I did so not because I thought it might not actually work. Given a bit more design development and testing I'm sure that it would work. The problem with doing that is that I have another similar design I'd like to pursue at the moment. Perhaps I'll return to that high banker design at a later date, or perhaps I won't. Basically the only thing I didn't accomplish with that high banker design was an illustration of a float actuated control mechanism that would reciprocally adjust the hopper and sluice jet systems so as to keep the water level of the hopper at an adjustable level. Hopefully you get that but should you not, oh well.

The current "Subby" design I am working on is intended to be used with a dredge, like the hydraulic well-drilling dredge I've been telling you about recently. I hope you can understand how this sluice design might differ from a high banker sluice. If you try to imagine the previous Subby but without the hopper, i.e. just a completely sealed system with an input and an output with a subsurface sluice in between, which should be a fairly simple concept.

Anyways. I'll get back to my calculations and post relevant information when I have it available.

In an age where instant gratification is the norm rather than the exception, I realize that I am trying your patience. I only ask that you defer any judgments about my motivations until I have a few more days (hopefully not weeks) to further develop these designs and post some more pretty pictures for you and the other forum members.

dragline

  
peluk
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Re: Fine Gold Sluice Design Help Needed ( 22:39:49 SatFeb 25 2017 )

In rereading my post,I see where some references might be too obscure. The reference to the obstruction stopping a force in motion refers to that 180 bend. It will play havoc with your flow...I think. A 90 degree sweep would cause 1/2 the problem probably. Either is an obstruction,not like a wall but for your purposes,it will at least alter the flow of material.

The reference to a driver and his truck(and I was thinking of a laden bellydump at the time, as I have when being in the seat) referred to the pellmell motion down a rutted road at speed. The rig is rocking a bit so you avoid the ruts as well as the potholes. An over adjustment that brings you to the shoulder can bring everything to an end. You think of yourself as being in a flow connected to the road by your aftersection as well as the relevant truck parts.
A driver could never make that 180 at that same speed.You'd have to slow down to a crawl temporarily,even for a 90. But you are expecting the flow of
material and water to just go through such obstructions in an unaltered fashion.That won't happen.

When you do or did a lot of different kinds of work,you can draw from what you observe.Sewer lines are of note,though they are not pressurized,neither do they carry sand. A 1/4" drop per foot will keep solids etc. moving. A 1/2" drop will start to leave material behind.If the pipe is cold that material can freeze. The last part is more important to the home owner or plumber and not necessarily important to a miner.

The laws of physics apply here as well as there.I run into them often, though I have not read of them as often.My biggest shock came to me years ago when I built a
rockerbox to mine the beach. It had a spraybar over the hopper tray so I could keep things moving with just me as the operator.

The problem was,the shaking packed the bed of the box and the flow went right over the packed material. Later,I found the rocker had not been considered ideal for the beaches here.It did better with creek run material. The gold on the beach is generally,as you have seen,too light to penetrate any buildup of sand though some may get buried.

The only other corrections I can think of are these. The slurry flow around the bends actually drops out material because of the different flow rates in the bend just as in a winding river. It would be affected by different principles as well in a closed system bend. Both opened and closed would result in buildup.

The last one I can't remember.It's tough getting old.




  
dragline
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Re: Fine Gold Sluice Design Help Needed ( 22:57:38 SatFeb 25 2017 )

One of the things I've been spending time on is performing calculations on the power requirements and demands for lifting a beach sand slurry. Since I'm familiar with Oregon beach sands and not at all familiar with Nome beach sands, I won't be making any inferences about the transplantability of my current hydraulic beach sand dredging concept anywhere else. From what I've seen of pictures and videos of dredges up in Nome I am fairly confident that the system I am currently working on would absolutely NOT work. Of course it probably wouldn't work on a lot or possibly mot Oregon beaches either. But for hopefully a lot of beaches that might be completely devoid of gravel, rock or cobbles (nothing larger than sand), I am optimistic that it will work as intended.

I have a couple charts that I've generated for two different trash pumps. The first which I already have purchased, a 6.5HP 208cc centrifugal trash pump capable of 16,000 GPH at zero head. The second pump that I'm evaluating is an 8.0HP 270cc trash pump capable of 25,000 GPH at zero head. Both are cheap pumps and should probably be replaced after a few hundred hours. But for the prototype development and proof of concept one or the other, or both, should hopefully be adequate.





My purpose in posting these performance charts for these pumps here is so the forum members that might be so inclined to use these data to validate, verify or follow along with my calculations as my project progresses.

Anyways, back to the drawing board.

dragline

  
peluk
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Re: Fine Gold Sluice Design Help Needed ( 23:00:18 SatFeb 25 2017 )

Now I remember. The last point dealt with the results of the Canadian studies on the effects of slurry density on fine gold settling. I just can't recall the author at this moment.
Anyway,I read it and I recall really fine gold is not as abundant in the Canadian mining areas like the Yukon for example.They did experiments on the problem anyway. The findings were that a heavy slurry density greatly hinders fine gold settling and extraction. I found this to be very important up on Specimen Gulch outside Nome. It feeds into Anvil Creek I'm pretty sure.It was just downstream from the Caribou Bill claim that yielded a bundle.
My problems were two.The host rock was limestone and it went through the sluice like a thick light brown cream which floated a lot of flake gold right out with the flow. To compound that I couldn't see what was happening in the box because the flow was too silty for visibility.

The material and its gold content had been lost by a washplant so I was not the only one who experienced the problem.

Anyway,I'd stear clear of a dense slurry if you're looking to recover flake gold.

  
dragline
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Re: Fine Gold Sluice Design Help Needed ( 00:05:00 SunFeb 26 2017 )

Peluk,

I do hear and understand your good points about the potential problems with my designs. It may not be practical for me to explain why I am not concerned about these things, but please allow me to attempt to do so. While there are many more potential problems to consider I will attempt to tackle these four that you mentioned.

Complaint #1: 180 bends will significantly increase pressure loss, i.e. an increase in flow resistance or friction.
Response: For those forum members interested in this subject and are not afraid of a little basic math you might consider reading up on the Resistance Coefficient. I can tell you that I"m not worried at all about the increased resistance (friction) caused by these 180 bends because the pressure differences will be minimal at the flow velocities I will be designing for and I can easily compensate for those pressure losses by supplying only slightly more input pressure. I can say is that a completely enclosed sluice with a higher pressure at the head and a lower pressure at tails can be thought equivalent to head, i.e. this pressure difference is equivalent to a given head in inches or feet. When you think about the head to tails pressure difference with my 12 foot sluice being equivalent to 1 foot of head (example only), you can hopefully picture in your mind how this same 1 foot of head might be similar to the slope of your surface sluice (in air). If the total demand on increased pressure at a slurry velocity of 4 feet per second is 1 foot then the additional power necessary to lift a 50% sand solids slurry would be (12in*50%*(2.6g/cc-1g/cc))= 9.6 inches of head. Even if it were 2 feet of additional head (which it definitely isn't) it would only be an additional 1.5 feet of head which when you consider my pump is capable of putting out at lease 90 feet of head we are only talking about a few percent increase in total power consumption.

Complaint #2: 180 bends will substantially increase slurry turbulence or mixing after each 180 bend.
Response: True. That will be exactly what I expect to happen when the slurry with heavies on the bottom and lights on the top will have to fold back upon and under itself. Of course this condition is pretty much exactly where the slurry was when it entered the first four foot section before then encountering the 180 bend after 4 feet. Adding another 4 foot section will effectively double recovery. Adding a third, as I have presently penciled into my design, will increase overall recovery by 300% relative if I'd just gone to tails after four feet. My thoughts about this are that I'd like to build in that 300% increase in recovery if it is practical for me to do so.

Complaint #3: 180 bends will induce a buildup or accumulation of impacted sands over the riffles.
Response: I don't think so. I believe that there is nothing significantly different between a slurry moving at 5 feet per second over riffles with air over the top of the slurry versus a slurry moving at 5 feet per second over riffles with something that isn't air over the top of the riffles. In other words, I don't believe that the air over the slurry can magically make riffles perform any different than if that air were replaced by something else.

Complaint #4: While not directly related to the 180 bends, the riffles of a subsurface sluice that has a zero slope will no clear as readily as the riffles of a sluice at a 10 downward slope.
Response: The slope makes not difference whatsoever with the clearing of the riffles. Saying that it will because a sluice in air with a slope of 10 has buildup whereas a sluice in air with a 20 slope does not is completely irrelevant. The reason why the 20 slope clears the riffles while the 10 doesn't has to do with the slurry velocity. You know, that slurry velocity thing that originally prompted me to make this post and that not one forum member had any answers for me or seemed to have a clue why I would ask such a question?

dragline

  
geowizard
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Re: Fine Gold Sluice Design Help Needed ( 13:16:52 MonFeb 27 2017 )

dragline,

Gravity separation of gold has evolved over thousands of years.

Most of what we see in the art today is the culmination of all of the successes in the experience of mankind rolled into simplicity and reliability of operation.

Adding complexity and unreliability does nothing for the evolution of the art.

Because the public at large reads this forum and would become confused with a confusing perpetration of supposed working principles, I would caution anyone reading the content of this thread to look for content elsewhere that is proven to work.

You have been given advice on what to do and what not to do. You have continued to defend your design and posed unrealistic counter claims against the suggestions given.

Is it rational?

When subjected to peer review that has been largely questioning and the subject of doubt, a rational designer would make the appropriate adjustments.

It isn't rational to continue to perpetrate concepts that are not accepted by those that are experienced in the art.

- Geowizard

  
geowizard
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Re: Fine Gold Sluice Design Help Needed ( 15:54:52 MonFeb 27 2017 )


Geowizard's TOP TEN;

Gold recovery solutions for the past Century.

#1:

PopandSons Fine Gold Sluice;

The Popandson Fine Gold Sluice, Design and Operating Guidelines
http://bb.bbboy.net/alaskagoldforum-viewthread?forum=2&thread=694
Powered By BbBoard - http://bb.bbboy.net

Work went into design for simplicity and reliability with documented field testing. It's in the TOP TEN.

- Geowizard

  
geowizard
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Re: Fine Gold Sluice Design Help Needed ( 16:00:25 MonFeb 27 2017 )

Geowizard's TOP TEN;

#2:

Cleangold Products:

http://www.cleangold.com/cleangold/products.html

This is the most NOVEL idea - it works! It's proven technology Worthy of US Patent and it is Patented Technology. Simple! Reliable! Get the Finest Gold!

A hearty SALUTE to Cleangold. :smile:

- Geowixard

  
geowizard
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Re: Fine Gold Sluice Design Help Needed ( 16:16:26 MonFeb 27 2017 )

Geowizard's TOP TEN;

#3;

Le Trap Sluice (Bank Robber);

Available from:

http://www.blackcatmining.com/mining-equipment/le-trap-sluice-box.cfm

This sluice does magic on fine gold! It has been widely discussed on this Forum.

It's Simple, Light weight, One working part, Easy to assemble and disassemble! :smile:

- Geowizard

  
dragline
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Re: Fine Gold Sluice Design Help Needed ( 17:35:54 MonFeb 27 2017 )

Geowizard,

While I appreciate your taking the time to offer your feedback, I do not believe that I have yet heard anything from you that might approach advice or an effort on your part to reach an understanding concerning my designs. Other than your statements that my designs won't work or my thinking is not rational I see no constructive effort from you to engage or evaluate my designs. From my perspective it seems obvious that you understand very little to nothing about design engineering principles or practices and you have little to no basis or justification for making such broad and sweeping judgments about me or my designs.

It used to be that we had forum members that were accomplished in the technical aspects of mining engineering or engineering principles in general, i.e. forum members that understood what slurry velocity was and also understood why it was important to measure and quantify this metric in relation to their gold recovery efforts. I guess those days are gone. Now it seems Alaska Gold Forum has devolved into a environment where ideas, innovation and discussions aren't welcome unless those discussions conform to the arrogant and narrow minded assumptions of a troll who's only purpose here seem to be to generate copious thread replies bent only upon hearing himself talk about his superior experience and knowledge.

dragline

  
dragline
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Re: Fine Gold Sluice Design Help Needed ( 18:31:46 MonFeb 27 2017 )

My next effort pertaining to my current designs involves an exploration of the practicality for making modifications to one or both of the cheap trash pumps for which I just previously posted performance graphs and specifications.

I want to consider the option of replacing the stock cast iron impeller with a slurry tolerant polyurethane impeller. Have any of you personally done this or have any of you used a trash pump such as I've previously described for the purpose of pumping slurry?



As things stand the solids handling capabilities of these pumps seem reasonable but I also understand that employing trash pumps as slurry pumps will significantly reduce the life expectancy of a few of the pump's components such as the impeller, shaft and impeller housing.

Here are the solids handling specs for the two pumps.
3" 6.5HP 208cc Trash Pump Solids handling: 9/16"
4" 8HP 270cc Trash Pump Solids handling: 3/4"

Assuming it might be practical to employ either or both of these trash pumps for pumping slurry my target classifying and/or screening of the input would be either a 1/4" or 1/8" input screen (but probably leaning towards the 1/8" screen).

Thanks,

dragline

  
Jim_Alaska
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Re: Fine Gold Sluice Design Help Needed ( 20:07:26 MonFeb 27 2017 )

Dragline,

All discussions are welcome here. As for lack of participation from forum members, please know that there is not the participation or views that there once was.

Some of the original members that had great knowledge and expertise have moved on, stopped visiting or died. Some just disappear for unknown reasons, like the member Steppgold.

Unfortunately this is the fate of all forums, they start slow, gain in popularity and then at some point die off. Eventually the owner closes the forums for lack of interest.

So please, continue posting away, you may yet get some information that helps. I know for myself, I have been mining since the 70's, consider myself knowledgeable and experienced, but have never thought of or heard of slurry velocities.

This may be another reason that other members have not posted, they just know nothing about it.



---
Jim_Alaska
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JOE_S_INDY
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Re: Fine Gold Sluice Design Help Needed ( 20:33:03 MonFeb 27 2017 )

Jim,

I can tell you that Dragline's string here has had me thinking and thinking until my brain was ready to explode -- just like his beach boring one did a few months ago. To be truthful, my engineering and experimenting experiences, like yours, suffers a bit from inactivity. I suppose there is only one way to 'fix' that -- exercising it a bit, and that is exactly what dragline has done.

Dragline has been a valued contributor here over quite a long time period. :clap: How many remember his experimentation on the "Saw Tooth" mats? In many ways those mats stand right up there, shoulder to shoulder with the now newer (not necessarily always better) extruded rubber mats which have, themselves, taken over from the domineering role that expanded over moss had fourty years ago.

Dragline, how did you ever do with that Saw Tooth design? Were you able to find a manufacturer to produce it for you? "Inquiring minds want to know" :doublethumbsup:

Inquirin' Joe
[1 edits; Last edit by JOE_S_INDY at 20:52:57 Mon Feb 27 2017]



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Wiser Mining Through Endless Personal Mistakes
 
 
dragline
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Re: Fine Gold Sluice Design Help Needed ( 22:06:01 MonFeb 27 2017 )

Joe,

I sincerely appreciate your kind words. Regarding my Sawtooth mat, yes I found an EPDM extruder in Ohio that was able to take on the manufacturing of my 4-TPI (Teeth per Inch) Sawtooth mat. The minimum order at the time was 750 Lbs bulk virgin EPDM so I went for it back in 2012.

As expected there were problems with the extrusion process owing to the difficulty in maintaining extrusion thermal uniformity across the entire width of the 6 inch extrusion die. But, the long story to short was that the manufacturer slapped on a smiley curved baffle on the input side of the die face that restricted flow into the center of the die and allow greater flow at the edges. The end result was that after a almost 200 Lbs of wasted and unusable extrusion the die process was dialed in and the Sawtooth mat extruded perfectly uniform.

For reasons that likely will not seem obvious to anyone, I wanted the extruded mat to be as thin as possible (less material and increased efficiency within a subsurface sluice assembly). Anyways I did net out about 500 feet of Sawtooth mat with the majority of which is sitting on some shelves here in my office.

I have sent out a lot of it for free to various miners for their evaluation but in general, I have found that the vast majority of miners don't understand it and don't have the skills or experience necessary to set it up and run it properly. But that's okay. I accomplished what I wanted to and now have an ample supply for my own use and for the use of a few of my Oregon beach mining friends.

I have been selling it on an unnamed auction site at a fairly high price and it does sell, occasionally, but my goal in doing so is not to make money but to allow the few miners who recognize something valuable here to have the opportunity to acquire, experiment with and use it. I also want to make sure that anyone that comes to possess it values it enough to read my instructions for its use and follows those instructions to the letter.

As a reminder, or as an introduction to new forum members, here is an illustration of the tooling die and manufacturing constraints.


Here is a photo of what the Sawtooth mat looks like with beach gold in the riffles.


Here is a photo of what the Sawtooth mat looks like in perspective.


dragline
[1 edits; Last edit by dragline at 22:12:55 Mon Feb 27 2017]

  
JOE_S_INDY
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Re: Fine Gold Sluice Design Help Needed ( 03:15:31 TueFeb 28 2017 )

Timothy,

I think that that is the first time I have seen the final product you created. It seems to work mighty fine on that beach Gold - and that beach Gold is a tough nut to crack. I spent a lifetime one month in '04 or '05 on the beach in Nome. Just long enough to learn great humility when it comes to panning out very fine Gold sizes. Well done.

I noticed the casual reference (you might have heard me shouting) to a sub surface sluice assembly. So, through a compendium of thoughts I think we have returned to the thrust of this string.

In using (I assume) the saw tooth design in this sub surface sluice box (I have actually started calling it an 'enclosed sluice box') has the capture rate come up to expectations?

Never having seen much on the 'saw tooth' design, how do you find it best employed? Do you have certain drop in degrees that work best? How about water flow - high, low or medium? Slurry particle size ranges? Other systems (Le Trap, G-1, Gold Hog and such) have "sweet spots" that, in a given set of circumstances, produce astounding results compared to many of the older systems. Is that testing part of this experimentation?

Does the "Enclosed Sluice Box" favor the saw tooth matting?

Just a metric bunch of questions on a relatively unknown design to me.

Joe
[1 edits; Last edit by JOE_S_INDY at 06:29:23 Tue Feb 28 2017]



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peluk
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Re: Fine Gold Sluice Design Help Needed ( 00:57:25 WedMar 1 2017 )

Dragline,thank you for addressing my questions about your design. They were just musings because generally,I have no real visual of your finished product or the riffles/mats on the
base of the tubes. You are confined to a 0 degree slope.That part is clear.

You stated in response to my 3rd question.... "Complaint #3 -Nothing significantly different between a slurry moving 5' per second over riffles with air over them(open top sluice) versus a slurry moving 5' per second over riffles with something that isn't air over the top of the riffles"...that is to say,an enclosed sluice.
My feeling is that your response does not take into consideration that in an open sluice,the upwelling turbulence from the riffles causes pull and lift on the material being sorted and assists in that action. In your closed system,the upwelling action or turbulence is hindered by the overhead column of water whipping along in a steady stream with no possibility of distortion or displacement due to its weight and pressure on the bottom of the tube. As mentioned before,material can only fall out of the flow and build up along the bottom.

Your attention to Complaint #4 seems to be the point at which I just have to say "good luck" and I look for ward to the finished product.

  
peluk
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Re: Fine Gold Sluice Design Help Needed ( 01:18:35 WedMar 1 2017 )

Geo,I see you have posted "Geowizzard's Top10" recovery tools here but you have also started another thread in the Forum titled "Geowizzard's Top 20". Because you included a product in the "Top 10" that doesn't work and which I want to comment on,I'll go to the new thread for that purpose. Besides that,I want to see how or if Dragline will conclude this design discussion on his request for a "Fine Gold Sluice Design Help Needed" request. It may only relate to his particular design idea and its improvement. Actually,the plastic impeller idea might be better addressed in a new thread.The topic night attract others interested in it specifically.

  
geowizard
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Re: Fine Gold Sluice Design Help Needed ( 01:49:28 WedMar 1 2017 )

peluk,

I decided to start another thread.

No problems, I appreciate the input. :smile:

- Geowizard

  
dragline
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Re: Fine Gold Sluice Design Help Needed ( 19:56:54 ThuMar 2 2017 )

Joe,

Thanks for your comments and questions. I have played around with the 4-TPI Sawtooth Mat in conventional air sluices enough to achieve good results compared to other similar mats such as Vortex and Clean Gold. However, I have not as yet incorporated the Sawtooth mat in a Subby (Enclosed) sluice or done any testing with that specific configuration.

The last time I build and operated a Subby (enclosed) sluice was for an 8 inch dredge that I operated for few summers back in the late 1970's, which seems like a lifetime ago at this point. Whether or not the Sawtooth mat is more efficient or superior to its competitors is irrelevant to me at this point. I have seen it perform on par, sometimes better and sometimes worse, than what I consider to be its direct competitors, the Vortex and Clean Gold mats.

The problem with arriving at conclusions about any specific mat's performance relative to other mats concerns the fact that no mat is ideal for all setups and conditions. In other words, the Sawtooth mat might outperform the Clean Gold mat under certain flow velocity and pre-classification situations and yet underperform that same mat under different conditions.

The point I'm trying to make here is that my efforts to design and manufacture the Sawtooth mat that you see illustrated and in the photos has less to do with it's performance against the competition under just any conditions, but it has everything to do with the Sawtooth mat's performance under very specific conditions that are somewhat unique to my intended applications for it, i.e. a subsurface (enclosed with no air) sluice.

Regarding...

1. Competition: I do not consider Le Trap, G-1, or Gold Hog to be competitors for this mat. If you are considering using any of these other mats vs. the Sawtooth mat please forget about using the Sawtooth mat. The Sawtooth mat is not a general purpose placer gold mat because it is not intended to capture coarse gold or anything approaching pickers. While it probably would do okay at coarse gold I'm not prepared to evaluate its performance with coarse gold or make any claims about that performance. While there are similarities between Gold Hog extruded EPDM mats and the Sawtooth mat, i.e. they are both EPDM, both 6 inches wide, and both make claims to capture fine gold, there really are very few similarities or overlap concerning the use of Gold Hog mats or Sawtooth mat in practice. I might have more to say about that later but not having tested the performance of Gold Hog mats vs. the Sawtooth mat I'm going to avoid expressing opinions about that.

2. Capture rate expectations vs reality: Yes, the capture rate for extremely fine gold with the Sawtooth mat is competitive with Vortex and Clean Gold mats under a verity of conditions such as you might expect would be appropriate. I can't say it is either superior or inferior to these other mats owing to the fact that as you vary the conditions one mat or the other will be at the top of the heap or the bottom. Again, the Sawtooth mat offers me the flexibility of my overall systems design that the other mats could not possibly offer and for that reason it is superior for my specific needs.

3. Inclination (slope): There's no magic slope that is optimal for the Sawtooth mat although you'd probably find that a slope in the range of 10 to 12 might work well for your application. With that said, there are very specific flow velocities that are optimal for a given set of conditions just as would be expected with any other mat. One thing you absolutely must consider is the requirement for pre-classification of materials. If you are not screening your input materials you'll probably get good results with 20 mesh coarse gold but absolutely dismal results with 60 mesh gold and finer. When working with beach gold I don't have to pre-classify (in most situations) because 100% of the sand and gold I'm digging would easily pass thru a 16 mesh screen. The only things I can tell you with certainty is that if you are wanting to recover 80 mesh minus gold (down to 325 mesh) and your not on an Oregon beach you're absolutely going to have to pre-classify to either 8 or better yet 16 mesh and you are going to need to run at a slurry velocity between 2 feet and 4 feet per second.

Again, I didn't design and manufacture the Sawtooth mat so I could sell it and make a profit. The only reason I'm selling it is on the unlikely chance that someone might have a use for it and provide me with some feedback on it's performance. The only reason the Sawtooth mat exists is because it is the optimal mat design for a few projects that' I'm working on involving subsurface (enclosed) sluice designs.

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Re: Fine Gold Sluice Design Help Needed ( 22:02:34 ThuMar 2 2017 )

Here is a somewhat related project that I am working on with the 4-TPI Sawtooth mat that includes 3mm x 1.5mm N50 magnets. have the magnets on order but haven't constructed this Sawtooth mat modification.

As most of you are probably aware, gold is not magnetic per say, but it is both diamagnetic and paramagnetic. If you don't know what these words mean or how these phenomena may be employed in gold recovery you might want to Google or go to YouTube and watch some videos on this rather interesting subject.



One might ask the question...

If gold isn't magnetic, how can magnets help recover gold?

Answer: While gold is not magnetic in the classical sense, it is both diamagnetic and paramagnetic. What this means is that gold encounters resistance when passing thru a strong magnetic field such that the gold particles decelerate relative to the slurry around it allowing additional time for the gold to drop out of the slurry and enter the riffle eddies below.

You'll notice that the positioning of the N50 magnets is at an incline with the riffles such that the edge or corner of the magnet projects upward and closer to the slurry than the flat center of the magnet. This tilt of the magnet is important because it projects the magnetic field's centripetal divergence into the slurry causing rapid deceleration of the gold. The flat edges and flat areas (of centripetal convergence) of the magnets are not nearly as effective as the edges because these flat areas have no diamagnetic effect on the gold.

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Re: Fine Gold Sluice Design Help Needed ( 23:33:11 ThuMar 2 2017 )

Peluk,

I appreciate your comments. While you haven't altered my opinions or raised my concerns about the performance of a subsurface sluice relative to a conventional in-air sluice you have made me think more deeply about the physical and hydrodynamic forces involved which is a good thing.

Your comment: "My feeling is that your response does not take into consideration that in an open sluice,the upwelling turbulence from the riffles causes pull and lift on the material being sorted and assists in that action. In your closed system,the upwelling action or turbulence is hindered by the overhead column of water whipping along in a steady stream with no possibility of distortion or displacement due to its weight and pressure on the bottom of the tube. As mentioned before,material can only fall out of the flow and build up along the bottom."

Response: Since water is a relatively incompressible liquid there won't be any bouncing effect caused by the riffles and propagating up to the surface. But there may indeed be a wave effect at the surface caused by the riffles when the dimension of flow length between those riffles is significant relative to the depth of the slurry. My point here is that all of the sluices you're used to dealing with have relatively shallow slurry flows relative to the horizontal span and riffle depth and under such conditions the slurry will rise and fall with each riffle. Of course this same effect would occur with the 4-TPI Sawtooth mat as well if the slurry depth were 1/8 or 1/4 inch which might be typical for a fine gold in-air conventional sluice. My 4-TPI Sawtooth mat has just 1/4 of an inch between riffles and the depth to which the slurry could fall into that riffle is probably much less than 1/16 inch for an in-air sluice. With such a narrow riffle spacing you just are not going to see a whole lot of reciprocal wave action at the surface of a slurry that is more than 1/2 inch. But what if the slurry were 2 inches deep passing over these same 4-TPI riffles at the same slurry velocity with air over the top of the slurry? Your reasoning would have no choice but to say that there would be build-up regardless of how fast the slurry is progressing because there is no wave induced turbulence that somehow is bouncing between the surface and the riffles and somehow this effect is essential to riffle clearing. I apologize that I just don't see any justification for that reasoning.

Rather, my contention is that all of the effects that you are describing are detrimental to fine gold recovery. In other words, the turbulence that is induced when the slurry falls and rises between riffle crests is a bad thing because it isn't the turbulence that is essential to fine gold recovery efficiency or riffle clearing. Instead, it is the eddies behind each riffle prominence that provides a reverse current where by the forward velocity of gold contacting that reverse current can be slowed sufficiently to drop out of the slurry and be retained in the riffle. My understanding of how riffles work apparently differs markedly from your own. My understanding tells me that turbulence is the enemy of fine gold recovery and the more we can do to design a sluice and riffle system that minimizes turbulence the more efficient that system will be at recovering extremely fine gold. Everything that I have studied about efficient fine gold recovery suggests that slurry laminar flow is good and slurry turbulence is bad. My advice for you is to try not to think of the eddies behind riffle prominences as turbulence. These eddies are established by the riffles for the purpose of presenting counter currents to the slurry flow that will grab and slow the gold sufficiently to drop out of the slurry and turbulence outside of these counter current eddies is a very bad thing.

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Re: Fine Gold Sluice Design Help Needed ( 02:19:21 FriMar 3 2017 )

The most important feature( or the most unconventional) of your proposed sluice is that it is without any slope.When you used that sawtooth mat you had a slope in the sluice. So,for you, it remains to be seen what will happen in your sluice with the sawtooth mat with zero slope.

How an closed sluice with a slope will operate,I can't say.I believe without a slope to it you can expect it to plug up.

In an open sluice,upwelling currents or turbulence are easily altered by raising or lowering the sluice to find how the riffles respond and collect.Depth of water can be adjusted as well as current speed. These are generally not adjustable in a closed sluice even with a slope.

  
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Re: Fine Gold Sluice Design Help Needed ( 03:39:26 FriMar 3 2017 )

"But there may indeed be a wave effect at the surface caused by the riffles when the dimension of flow length between those riffles is significant relative to the depth of the slurry"

What surface? I thought this was a closed system?

  
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Re: Fine Gold Sluice Design Help Needed ( 03:46:07 FriMar 3 2017 )

Peluk,

Yes, you bring up completely valid points and inferences pertaining to in-air sluices where the slope is set higher or lower so as to vary the slurry velocity. By increasing the slope you increase the slurry velocity thereby increasing the scrubbing effect on the riffles and increasing the reverse current eddy size and reverse stream velocity behind and below the peaks of the riffles. Increasing or decreasing the throttle on the pump that supplies the slurry from a suction dredge to the subsurface sluice accomplishes the same exact thing, i.e. an increase or decrease in slurry velocity.

Slurry velocity is not a complicated thing but as you are aware many miners with 40 or more years of experience running suction dredges or huge washplants have never given a thought to the metric of slurry velocity let alone actually taken the time to measure it. Devoid of any reference or experience of dealing directly with slurry velocity miners may experience difficulty understanding that by adjusting the slope of their sluice they are indirectly adjusting their slurry velocity with a very similar if not identical result as when I adjust the throttle on my pump.

I have mentioned this before but just to reiterate the point, I positively affirm the point that I could design a subsurface (fully enclosed) sluice with an uphill slope and it would perform more efficiently than either a downhill or zero slope sluice. The reason this is so get's back to Geowizards fixation on upward flows necessarily being elutriation columns by definition. While not all upward slurry flows will result in a separation of heavies from the lighter specific gravity materials, when you place riffles beneath an upward sloping subsurface sluice you will definitely increase the fine gold capture efficiency owing to the added elutriation effects. This is because when the slurry travels up hill the tendency will be for the heavies, gold included, to lag behind in the flow and more easily be captured by the eddies.

While I have never seen or heard of a design for an upward sloping subsurface sluice/elutriation column the potential exists that some enterprising miner may come along and build such a novel thing and patent it (assuming that it hasn't already been patented).

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Re: Fine Gold Sluice Design Help Needed ( 03:56:52 FriMar 3 2017 )

LipCa,

Yes, my design pertains to a subsurface (i.e. enclosed) sluice. Some members here and I are having a discussion pertaining to the potential performance differences between an in-air sluice (with air over the top of the slurry) and a subsurface sluice with something other than air over the top of the slurry.

Some members here are convinced that a subsurface sluice will clog up and accumulate sediments over the top of the riffles because the riffles as I have design them are level and not downward sloping. Since I have an understanding of slurry velocity and have built and operated a subsurface sluice previously I know both intuitively and from experience that a level subsurface sluice will not accumulate sediments when the slurry velocity is adjusted properly.

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Re: Fine Gold Sluice Design Help Needed ( 15:34:04 FriMar 3 2017 )

Dragline,

To be the devil's advocate here:

A situation that seems to touch on the "Enclosed" aspect could be an "Alaskan Curtain". The flap that is suspended over riffles to "quiet them down" and get the slurry to more closely follow the profile of the riffles.

Joe



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Wiser Mining Through Endless Personal Mistakes
 
 

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