so many questions about dredges and whatnot

[truckguru]

Hello all, I'm a new member to the forum but a long time watcher.

So, I've finally gone off the deep end and have decided to build a dredge and seek my fame and fortune in the frozen north (sometime in the next 2 years, leasing and permits).

I have multiple questions regarding dredges and the math associated with them.

lets start simple,

equipment for pumping water

A. keene p1500 pump x2
B. Yanmar 40 hp diesel x2

When pumping 1200 to 1500 gpm of water thru 2 pumps, can the intakes be split off of each foot valve and run a double or tripple intake feed for shallower water? depth of the creek maybe a little shallow in spots and I'm hoping this is the work around for trying to suck up a heck of a lot of water without causing air cavitation in the system.

design and theoretical operation

1. how to properly size a sluice box for a dredge (yes I've read the post about sluices) however a dredge sluice runs a bit differently. So, What is the proper math to calculate size for a dredge sluice size based off of volume and flow rates assuming running at 50% pump capacity lets say a 6" intake (see below)?

2. For the suction side of life, I've been thinking about a 6" suction nozzle (just because I want to be able to suck start a 3406), 20 to 25 foot of hose then a jet log, flare, sluice. Whats the math for feeding the jet log so it doesn't loose prime?
2b. will the suction nozzle provide enough water volume to the jet log so it will not loose pressure if the nozzle is removed from the water? I'd like to hit a bank from time to time.

3. I will be scabbing on part of a hydrovac system to blast thru hard pack (2700 psi) with the various tips available dislodging material should be no issue. has anyone tried this?

4. from most of what i've read a 12% slurry rate by volume is what should be going down the box, what happens at say 15% or 20%

5. If I've completely missed the mark, please say so. At the moment I may just be completely mad as a hatter and twice as ugly.

Dream your dream and take your shot. Your death bed should only be surrounded with love and memories, NOT regret.

 

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[Reed Lukens]

Just dig out the foot valves by hand before starting up, then start up with the suction hose at the foot valves to make a hole for them. It just takes a few minutes. You don't need or want a suction nozzle on a 6" because you'll use too much energy to work it that can better be used tossing rock, etc.

There's too many variables to start into sluice box design without more input. What are you using for riffles, how many boxes, etc. Look up the Promac Industrial 8" triple dredge design, that will give you a good idea of where you want to start.
https://m.youtube.com/playlist?list=PL39A9E7B702FF1B8A

 

[Phil]

"If I've completely missed the mark, please say so."

1. Stop trying to reinvent the wheel. If you are going to build from scratch, research the dredges available.........then duplicate the design.

2. Get a claim, then design the the sluice box. Specifically, if your claim is known for producing nuggets, I prefer a single stage sluice because you can turn up the pump and move more material without losing gold. However, if you are going after 200 mesh gold, you need a long three stage box with the pump turned down so you don't blow gold out the back.

3. If you want to work shallow water, buy a 4" dredge with suction nozzle.

Lastly, and most importantly, big equipment moves big material. If you don't know what to look for, all you are going to do is move a LOT of worthless material. You would be better off starting with a small dredge, pay your dues, learn the ground, THEN upgrade to a larger dredge.

 

[RTR]

As you said..."lets start simple"....Dig some test holes... do some panning ...then go crazy,before spending Big $$$s

 

[russau]

And when you are new to dredging , NEVER , NEVER , NEVER raise the suction nozzle out of the water to do anything while running !!! If you do this you'll stop the suction at the nozzle and blow your material out the back of your dredge ! I've seen this happen many times and it aint pretty !

 

[truckguru]

Ok, got it! I missed the mark trying to reinvent the wheel. Consider this idea shelved.

Looks like I'll be going a slightly different route with a off the shelf unit until permits have gone thru then it'll be a shell dredge and d11.

 

[Jason in Enid]

Ype, dredges are stupidly simple contraptions, but like everything, the devil is in the details. Being able to move gravels is one thing, catching the gold in those gravels is a whole new ball of cats. If you want to build a dredge, you should start by buying a small (4 inch) used dredge first. Spend a season with it. You will learn the ins and outs of exactly how to dredge and how to tweek water flow and sluice angle and play with different collection methods. This also lets you dredge test holes around your property to check for amounts and size of gold. Then you can spend ALL your free time researching dredge building, design theory, sluice concepts and matting choices. Trust me, theres a LOT of info to digest. Then you can spend all winter sourcing materials and building your dredge. Plan on several weeks of adjustments when you do get your dredge into use. Guaranteed it wont be 100% the first time you use it.

 

[principedeleon]

now in days there is veryy little virgen ground specialy in gold bearing areas.. having a understanding about if the area is heavyly mined is a good idea to know before hand because you dont want to be dredging others tailings...

another thing is when you are not sure where a dredging cut was left you might leave behind gold lefted probably by others..

so having someone who have had time in and out of a river mining will help you more then a 20" dredge.

prospecting is the most important of mining .. if you dont have a clue where to be mining is best to go most lightest dredge possible depending on how large is the river or creek...

 

[N-Lionberger]

Even with suction nozzles where you won't lose suction prime by popping it in and out of the water whenever you do so you rob your sluice of water, the riffle vortexes collapse and your cons are flushed out from under, restart of full flow scours it out. If you need material off the banks just wash it down with a blaster hose.