6" subbie dredge

[principedeleon]

Hello guys..
I have built a 6" subbie with my 8hp Honda engine and i have been very please with the results even tho i feel i dont have it fully functioning how i would want ..

I have more then enough suction but my sluice box just cant clear the riffles has if there would be air inside the sluice box.



I dont know exactly how could i achieve something lightweight but yet efficient.
I have seen this trap which im not sure how well it work but it sure could help me avoid clog ups in the sluice box..
Or could i build a 2" jet and run the half inch material through a sluice box up on the surface ..

 

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[kcm]

I'll take a crack at this one - but first have to ask this: What size gold do you generally find in your area? Are you in an area of overly-fine gold, or somewhere where you might even land a 1/2 oz. or larger nugget?

Next question - what size pump do you have? How many GPM's?

If looking for really fine gold, I like the general idea in your last photo, with the rod running inline with the water flow. However, I would have terminated the rods at the end of the tube and then add a layer of expanded metal over the rods, formed to the shape of the rods. Then at the end of the tube, I would leave the end open except for a ridge that rises maybe 1/4" to 1/2" higher than the expanded metal. That would allow ALL larger material to work out the end of the trap without clogging up. Gold being heavy would ("should") drop down in the low-pressure area between the rods. However, don't think you'd need that many rods - probably only enough to work as spacers for the expanded. Could even choose to put some miners moss under the rods if you're worried about losing any gold.

If in California or other area where it's possible to get a 1/2 oz. or larger nugget...have been thinking about this while writing the first part. I think a similar setup would also work for this, but you'd be limited to the size of gold saved according to what will readily fit through the expanded. Might be better to have a 2-stage system in this case. Have an area that ALL material flows over, but traps the very fine gold (as above), then have a nugget trap for the REALLY good stuff!

My thought on this is, how are you keeping the unit laterally level? If you use "rods", as in the first section, and if the unit turns, then you'll lose some of your catchment capacity. Turn the system more on its side and you may start losing gold. So you'll have to have a system for keeping the unit from rolling to one side or the other, as well as keeping it relatively level lengthwise. Maybe have the unit suspended from a surface float? But then what happens where the water is too active? ...Am starting to see some of the thinking that went into the Bazooka dredge systems.

Well, that's all I have. Keep in mind that I'm not even a novice - just someone with a long-held interest in prospecting!! So hopefully this will be a good start for some of the more experienced folks to jump in.


EDIT - Only told of using a tube design, but I would personally prefer a boxed design. Guess I got tunnel-visioned on that last pic.

EDIT #2 - With the expanded metal, I would think it should be set so that it helps water to flow into the miners moss and flush out the lighter materials. In the attached pic, water should flow bottom to top (assuming the pic loads properly).

 

[boaraxa]

Perhaps where the hose attaches to the sluice its set to high & most of the flow is going over the top rather than clearing the riffles ?

 

[winners58]

hang it under some floats so you can adjust and keep the angle, maybe a over-under for the fines
or an area for a sump to pull the fines to another sluice possibly on the surface.

About Subsurface Suction Gold Dredges

.
http://www.detectorprospector.com/steves-mining-journal/five-inch-subsurface-dredge-mills-creek.htm

 

[winners58]

I see, you're going from a 6" hose to a 12"x12" box the water is just expanding too much and not able to keep moving at the right speed.

you can calculate the cross section area of the hose is 3.14 x 3^2 = 28.27 and the area of the box is 12^2 = 144
I know it doesn't take into account the volume and flow, looks like you'll have to experiment to get the right proportions.
I think that's why they used to make them like a suitcase. you want the water to slow down but how much?
.
maybe you could have it taper down.

 

[principedeleon]

I'll take a crack at this one - but first have to ask this: What size gold do you generally find in your area? Are you in an area of overly-fine gold, or somewhere where you might even land a 1/2 oz. or larger nugget?

Next question - what size pump do you have? How many GPM's?

If looking for really fine gold, I like the general idea in your last photo, with the rod running inline with the water flow. However, I would have terminated the rods at the end of the tube and then add a layer of expanded metal over the rods, formed to the shape of the rods. Then at the end of the tube, I would leave the end open except for a ridge that rises maybe 1/4" to 1/2" higher than the expanded metal. That would allow ALL larger material to work out the end of the trap without clogging up. Gold being heavy would ("should") drop down in the low-pressure area between the rods. However, don't think you'd need that many rods - probably only enough to work as spacers for the expanded. Could even choose to put some miners moss under the rods if you're worried about losing any gold.

If in California or other area where it's possible to get a 1/2 oz. or larger nugget...have been thinking about this while writing the first part. I think a similar setup would also work for this, but you'd be limited to the size of gold saved according to what will readily fit through the expanded. Might be better to have a 2-stage system in this case. Have an area that ALL material flows over, but traps the very fine gold (as above), then have a nugget trap for the REALLY good stuff!

My thought on this is, how are you keeping the unit laterally level? If you use "rods", as in the first section, and if the unit turns, then you'll lose some of your catchment capacity. Turn the system more on its side and you may start losing gold. So you'll have to have a system for keeping the unit from rolling to one side or the other, as well as keeping it relatively level lengthwise. Maybe have the unit suspended from a surface float? But then what happens where the water is too active? ...Am starting to see some of the thinking that went into the Bazooka dredge systems.

Well, that's all I have. Keep in mind that I'm not even a novice - just someone with a long-held interest in prospecting!! So hopefully this will be a good start for some of the more experienced folks to jump in.


EDIT - Only told of using a tube design, but I would personally prefer a boxed design. Guess I got tunnel-visioned on that last pic.

EDIT #2 - With the expanded metal, I would think it should be set so that it helps water to flow into the miners moss and flush out the lighter materials. In the attached pic, water should flow bottom to top (assuming the pic loads properly).
View attachment 1337311

Its possible to find a 15Gram nugget or larger .. We have found a 7gram as the larges around the area ..

I really dont understand completely the concept of expended metal over the rods..

The grizzly rods was used attach to a sump that the material was pumped to a surface 4" sluice.. If not mistaken..

But i dont know exactly how it really works. Since i have most of my understanding on a surface dredge .

I was thinking if theres a back pressure that pushes the material up to the sluice or a small jet that suctions the material to the sluice ..

 

[kcm]

When writing that post, the "sole" purpose of having the rods under expanded was to support the expanded, allowing room for small material to drop out. If the expanded is strong enough, could just as easily be supported along the edges.

 

[principedeleon]

Perhaps where the hose attaches to the sluice its set to high & most of the flow is going over the top rather than clearing the riffles ?

Its about 2.5" high .. But about a 1.5" from the rubber waffle matting which i place at the head of the box.

I

 

[principedeleon]

I see, you're going from a 6" hose to a 12"x12" box the water is just expanding too much and not able to keep moving at the right speed.

you can calculate the cross section area of the hose is 3.14 x 3^2 = 28.27 and the area of the box is 12^2 = 144
I know it doesn't take into account the volume and flow, looks like you'll have to experiment to get the right proportions.
I think that's why they used to make them like a suitcase. you want the water to slow down but how much?
.
maybe you could have it taper down.
View attachment 1337411

How low could i have it if there is about almost 6" rocks passing through the box.
I believe the height of the sluice is about 10 - 11 inches .

 

[kcm]

How low could i have it if there is about almost 6" rocks passing through the box.
I believe the height of the sluice is about 10 - 11 inches .

You're saying there's an almost 6" depth of "smaller rocks", right?

Could you post a pic of the exiting end of your box please?

 

[winners58]

on my keene sub it was a 4" in with an exit of 6" you have the riffles and possibly some screen but you still have to allow for 6" rocks from the hose
in this drawing it has an area of low pressure then narrows to eject and keep the material moving.
http://www.wvminers.com/wp-content/uploads/2012/07/uwdredge.pdf

on my example of a 4" sub; 4" area = 12.56, 6" area = 28.27 see what I'm getting at, it just needs to be fine tuned and dialed in.
maybe narrow the exit down to 8" tall minus the riffles, you could test it with some styrofoam blocks glued in the roof over riffle section.

 

[principedeleon]

These are the measurements i made mine from .. The sluice box is flared and the height is around 9-10" .

Would reducing it by just a inch would make a huge difference ?

 

[Timberdoodle]

Hi P. Nice job on building a Trev Alty suitcase dredge. Keep in mind that this type of submersible is designed to run on a down-tilt angle and is not meant to fully clear out all the gravels from the box as the entire box works like a semi-fluid bed. It works good on larger gold but not a good choice for fines. As long as your not plugging up in the sluice-box don't worry about it becoming loaded up with gravels.

 

[principedeleon]

But the riffles aint working right and the gold is to me exiting out the sluice ..


I ran it with some air in sluice and it was to me working better .. But i want to have it running the riffles with a vortex going on ... But i dont see much room for making it more efficient by lowering the height of he box ..


Maybe there a better sluice box option ?

 

[Timberdoodle]

The problem with most subbies is that to move 6 inch rocks through the sluice means you have a minimum height (based on nozzle size) and maximum width to keep the material moving and not jamming in the sluice. This means alot of velocity and turbulence and you end up with water depth and water speed that keeps much of the fine gold in suspension and it never gets to riffle height for processing/collection and out the back it goes. The larger the subbie and the more velocity required to move the larger rocks. Trev's design uses more of a balance of material lift driven from the incoming flow to remove/replace material like a fluid bed and the riffles are more like collection areas than well designed vortex processors.

You may want to try running it with downtilt and let the results at the end of the day speak for themselves, but only if your not in fine gold country.

A well designed underwater classifier with a separate sluice passing minus 1" will certainly outperform on fine gold, but now size increases and things get more complicated. The "dragon" on Bering sea gold used a similar method.

 

[bill-costa rica]

looking at all the pictures and talking about subbies I feel like I hace stepped back in time about 10 , 15 years

 

[russau]

Bill what ever happened to your 10 inch dredge? I would love to tow that up the Misery River for some suction time!

 

[bill-costa rica]

its still here . I cant use it. its sitting in the trailer waiting for someone to buy it.

 

[Jason in Enid]

Bill what ever happened to your 10 inch dredge? I would love to tow that up the Misery River for some suction time!

Can you imagine the gravel you could process with someting like that up on the Ark headwaters? Man, you could work that river bank to bank and 30 foot down!

 

[russau]

its still here . I cant use it. its sitting in the trailer waiting for someone to buy it.

IF you were ONLY a days drive from me , we would be talking!