6" suction/jet

[rookieminer]

Hello All,

I'm thinking about building a 5" or 6" dredge. I was wondering if anyone has seen or used a dredge with a combination suction jet? I was thinking it could be usefull if you were in shallow water where it was easy to lose your prime with a jet nozzle set up.
It seems like it would self prime itself whenever it sucked in some air. But I'm not sure if there is a problem with this setup, since I don't have much experience dredging. And I have never used a dredge bigger than a 3" suction.

Any input would be greatly appreciated.

rookieminer

[Aurum Flake]

You are gonna need a hell of a lot of water to run a 6, and if you make it a suction nozzle, you have a bunch of hose to wrestle around as well as costs. If you went combo (running both suction nozzle and jet tube at the same time), you'd have to have 2 been engines and 2 big pumps to run such a beast in addition to the extra presure hose. So, if you are working in such a shallow water area that you'd wanna use a suction nozzle, you'd burn up a pump trying to keep a 6 inch opening flowing water. A 4 factory inch machine moves about a 150 gallons a minute. Now, you try building a combo machine like your are talking about, without even looking up a chart, i'd guess bear minimum wild number off the top of my head would probably need 300 gallons to work in. Now, on top of that, if you are working in shallow water (probably recirculating your process water) the material would become so murky and gritty you would be mining blind and by brail (not much fun but can be done) but more importantly you'd be running that grit through your pumps and you'd eat them up quicker than a whistle.

Now, if you can get past mining blind, wrestling that hose, the risk to your pumps, throw in the fuel costs to run 2 engines like that for something that you can build one, or the other. Heck, for that matter, the price of the rig you'd build, you would be better off in my oppion to make 2 complete seperate getups that you could simply switch out depending if you are working shallow or deep water. BUT, i think a 6 is going to tire you out if you try and make a suction nozzle out of it and will be unhappy with its fuel economy and results.

Rule of thumb, suction nozzle = shallow water, jet tube = deep water.

Best of luck

[alaskaflounder]

I have some parts available for building a 5" like you want





Price negotiable or willing to trade for cool stuff.

[rookieminer]

You are gonna need a hell of a lot of water to run a 6, and if you make it a suction nozzle, you have a bunch of hose to wrestle around as well as costs. If you went combo (running both suction nozzle and jet tube at the same time), you'd have to have 2 been engines and 2 big pumps to run such a beast in addition to the extra presure hose. So, if you are working in such a shallow water area that you'd wanna use a suction nozzle, you'd burn up a pump trying to keep a 6 inch opening flowing water. A 4 factory inch machine moves about a 150 gallons a minute. Now, you try building a combo machine like your are talking about, without even looking up a chart, i'd guess bear minimum wild number off the top of my head would probably need 300 gallons to work in. Now, on top of that, if you are working in shallow water (probably recirculating your process water) the material would become so murky and gritty you would be mining blind and by brail (not much fun but can be done) but more importantly you'd be running that grit through your pumps and you'd eat them up quicker than a whistle.

Now, if you can get past mining blind, wrestling that hose, the risk to your pumps, throw in the fuel costs to run 2 engines like that for something that you can build one, or the other. Heck, for that matter, the price of the rig you'd build, you would be better off in my oppion to make 2 complete seperate getups that you could simply switch out depending if you are working shallow or deep water. BUT, i think a 6 is going to tire you out if you try and make a suction nozzle out of it and will be unhappy with its fuel economy and results.

Rule of thumb, suction nozzle = shallow water, jet tube = deep water.

Best of luck

Thanks for the reply,

I think your right about the 6" being a bear to handle with the extra hose attached to it. And I was aware of needing two different pumps, but I thought you needed two for a 6" jet set up anyway.
Any way I think a 6 will be to much for me to handle, and I appreciate you pointing out the flaws for me.
Do you think a 5" will be any better?

thanks again,

rookieminer

[rookieminer]

I have some parts available for building a 5" like you want





Price negotiable or willing to trade for cool stuff.

Thanks for the offer, but I have the means to make all of the components, except the pumps and engines of course.

rookieminer

[Aurum Flake]

Rookie,

You can run a 5 or a 6 on one pump, its just the price of pump and engine go up is all. More jets into the tube can cut down on rock jams.

There are alot of variables on the 5 vs 6 inch machine route. I'm not going to address those at this time.

Some people are probably tired of hearing me say this, but this is how i go at it. First, I find my dirt. Then i figure out how i'm gonna recover my values and what size my values are. Can i back my truck/trailer right to the water or am i gonna have to pack my gear in? How much and how far do i wanna pack it? Another thing to consider is how wide and deep is the waterway i wanna mine? How much overburden do i have to strip off at what depth to get to the pay later? What is the size of material i wish to recover in what quantities? How much waterway do i have to work (I.E. If i run a 6 instead of a 5 and get done quicker, am i gonna have to find a new place to mine sooner?) Do i have to mine at a depth greater than 20 feet? 40 feet? Deeper? Swift water, slack water? How large/strong/stout of a person are you to handle the hose? What type of stamina do you have? Have you spent many hours underwater on a hooka system moving rocks for an 8 hour day? Is the rock bottom up and down or rather calm and flat? Am i going to have helpers, or am i a one man mining show?

There are many other questions that i've forgoten to ask such as how much to spend, travel time, what do you expect to recover and on and on and on and on.

I said i wasnt going to address some of the 5 vs 6 inch machine route, but upon re-reading what i already typed above, it appears i did.

If you havent spent much time mining under water, i'd go buddy up with someone and do it for a day or more before you plunk down a bunch of time and money on your own gear. I'd sugguest reading anything by Dave McCracken (theres alot of free info AND videos on the Net). He's writen ALOT of material that will addres much of what i've already writen and more than i'd ever think to write. Makes me wish i'd thought of listing him first instead of me spending all this time.

Food for thought.

[rookieminer]

Rookie,

You can run a 5 or a 6 on one pump, its just the price of pump and engine go up is all. More jets into the tube can cut down on rock jams.

There are alot of variables on the 5 vs 6 inch machine route. I'm not going to address those at this time.

Some people are probably tired of hearing me say this, but this is how i go at it. First, I find my dirt. Then i figure out how i'm gonna recover my values and what size my values are. Can i back my truck/trailer right to the water or am i gonna have to pack my gear in? How much and how far do i wanna pack it? Another thing to consider is how wide and deep is the waterway i wanna mine? How much overburden do i have to strip off at what depth to get to the pay later? What is the size of material i wish to recover in what quantities? How much waterway do i have to work (I.E. If i run a 6 instead of a 5 and get done quicker, am i gonna have to find a new place to mine sooner?) Do i have to mine at a depth greater than 20 feet? 40 feet? Deeper? Swift water, slack water? How large/strong/stout of a person are you to handle the hose? What type of stamina do you have? Have you spent many hours underwater on a hooka system moving rocks for an 8 hour day? Is the rock bottom up and down or rather calm and flat? Am i going to have helpers, or am i a one man mining show?

There are many other questions that i've forgoten to ask such as how much to spend, travel time, what do you expect to recover and on and on and on and on.

I said i wasnt going to address some of the 5 vs 6 inch machine route, but upon re-reading what i already typed above, it appears i did.

If you havent spent much time mining under water, i'd go buddy up with someone and do it for a day or more before you plunk down a bunch of time and money on your own gear. I'd sugguest reading anything by Dave McCracken (theres alot of free info AND videos on the Net). He's writen ALOT of material that will addres much of what i've already writen and more than i'd ever think to write. Makes me wish i'd thought of listing him first instead of me spending all this time.

Food for thought.

Thanks for the reply, they are all very good points that I should be considering. As for spending some time under water with someone experienced, I think that's a great idea. If I get any extra time this year I will be sure to post it on here. I would be willing to work/help someone just for the experience. As for strength and stamina, I would say I have average to above average strength, and I make up for anything I lack in strength in stamina.

thanks again,

rookieminer

[mendoAu]

rookieminer,
With your attitude and willingness you shouldn't have a problem locating someone willing to "show you the ropes". I'd suggest that during the dredge season to drop by the campgrounds and mining shops with some fliers and pass them around to anyone that looks like they have a dredge. I'd never turn anyone away that wants to toss rocks for nuttin. But I'd also be reluctant not to split the finds. With the right person the learning curve to be a "dredge tender" is fast. A wetsuit and a good back will take you far.

[overtheedge]

Unless you have an awful lot of overburden to move, stay away from larger dredges.

The reason is all about physics and economics. Dredges larger than 2-2.5" require a lot of water to move the 1-2" rocks down the sluice. Without a large classifier section, recovery of -8 mesh is very low at best. It is the smaller gold that pays the bills.

A well designed 2" combi will do well down to -40 mesh with high recovery and acceptable recovery down to +80 mesh. The key is, was and will always be classification prior to the sluice box. The multi-stage whiz-bangs being peddled are gimmicks to mine the miners. The problem is that these in-sluice classifiers are far too short with not enough open area. Any attempt to open up the classification area by using screen robs the over-sized area of water.

My 2" home-made dredge and 2.5" Keene crashbox have 1/4" gravel plant screen on the nozzles. Of course there is nothing larger than 10 mesh in my area. Most of the time, I use a 2" siphon dredge with occasionally a small 2-cycle pump for priming the siphon or siphon assist. The lower water usage gives me a 90%+ recovery to 80 mesh and acceptable to 100 mesh where it really starts to poop out.

Here in Alaska, the most popular size of recreational dredge is the 4". Several years ago in a side by side test, my little toy 1" recovered more than the 2.5" being operated less than 15' away from the same skim bar. And he moved probably 5-8X the material. The difference was due to classification. There is pretty much nothing larger than 10 mesh in this area with most of the weight in the -30 +60 mesh range. Any attempt to move 1-2" rocks and recover small gold (-10 mesh) in the same sluice doesn't work.

Don't fall into the trap of larger is better. It is all about what stays in the sluice. You can get acceptable recovery if the dredge dumps into a real washplant. But a real washplant isn't very portable.

Others have already pointed out the problem of economics. High start-up costs and much higher operating costs. Remember that you have amortization and replacement/maintenance costs that come with operating. Then a 5-6" isn't very handy for week-end dredgers. You have transportation and set-up/tear-down time to consider. Not counting wrestling a 5-6" nozzle and hose for a few hours a day. The average week-end dredger forgets the physical demands needed to operate for 6-8 hours a day. Then to take full advantage of a 5-6", you need to consider the cost of diving; hookah set-up and dry suit.

Hope this helps.
eric

[rookieminer]

I agree with you, on all points.

I have been doing some research and thinking, and I have came to the same conclusions you pointed out. I also agree about the combos on the market. I purchased one a couple years ago, and I was not satisfied after the first trip out. Since then I have made several modifications to it. The biggest problem being the grizzly below the crash box, the piece of garbage aluminum punch plate they used lost atleast 25% of the fines before they even made it to the sluice.

I've also came to the conclusion that the two main problems that slow me down are rock jams, and moving all of the 2" to 5" rocks out of the hole by hand. The simple solution to this problem I came up with (atleast I hope it works), is to shovel the rocks into a metal milk crate and dump it out. I figure it's an easy way to get rid of most of the rocks that are likely to cause a rock jam, and for the most part will reduce the overall average size of the material I'm dredging out. I figure that shoveling them will be a lot faster than removing them by hand, also easier on my hands when the waters real cold. If I get rid of most of the rocks that are likely to cause a problem, I think I will be able to leave the nozzel sucking in the bottom of the hole most of the time, while I shovel out the rocks.

Thanks for the reply,

rookieminer