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Thread: Gravity Dredging

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  1. #1
    us
    Mar 2012
    Northern California
    Gold Bug 2, GP 3000
    609
    389 times
    Prospecting

    Gravity Dredging

    Has anyone here tried gravity dredging? From what I've seen around on the internet it can be just as good as gas powered dredging depending on the circumstances. If anyone that has tried it sees this post how long did you make the hose and what size was it? I want to experiment with g-dredging but I'm not sure where to start. I'd like to try it out in small creek although I'm not sure if it would be possible to downsize from what Ive seen people do in videos at the river. Here's a link to a video of some guy that did it successfully but didn't get gold because he never hit bedrock..

  2. #2
    us
    Mar 2003
    Redding,Calif.
    4,017
    2417 times
    All Types Of Treasure Hunting

    Re: Gravity Dredging

    2 ways to do it. 100+ foot of hose with at least 10' of drop or oversize hose then reduce at suction end and you then suck. Trying to run a jet is just too wimpy of a pull but not done yet. Been testing and developing the Oates inductor to be posted for all to see for "free" after done and copyrighted so no one can produce and mt your wallets but for miners to own use for themselves. Then you are engine free and good to go LEGALLY IN KALIF-John

  3. #3
    us
    Mar 2012
    Northern California
    Gold Bug 2, GP 3000
    609
    389 times
    Prospecting

    Re: Gravity Dredging

    What if you had a shorter hose like a 50ft one and still have a 10ft drop? Would it not work because you need it to be really long?

  4. #4
    us
    Northern California

    Aug 2007
    'South' Texas
    XLT, GMT, 6000D Coinmaster
    2,771
    1466 times
    All Types Of Treasure Hunting

    Re: Gravity Dredging

    N8, I believe that would be 100' of 4" inside diameter of hose. "I do not know what I'm talking about here" but I think that to get the same amount of energy, from gallons of water, down the hose in a shorter length that the drop would need to be about doubled. Hoser will correct me on this, I hope, but in any case the amount of drop would need to be greater. Oh, the straighter you can keep the hose the more efficient your operation will be or, the more kinks and right angles the less efficient your operation will be.....63bkpkr
    Out searching w/GMT & friend under my arm

  5. #5
    us
    Mar 2012
    Northern California
    Gold Bug 2, GP 3000
    609
    389 times
    Prospecting

    Re: Gravity Dredging

    63, I think you're right about having to double the drop with a hose half the length and that is probably a lot harder to do... You would probably have to be dredging at the top of a waterfall or something.. I guess I'll stick with building a custom hand dredge. I've been looking around on the internet on how to build one that has two check valves on it so that you can pump the material back out into a bucket or even a sluice through a hose. -N8

  6. #6
    us
    Mar 2003
    Redding,Calif.
    4,017
    2417 times
    All Types Of Treasure Hunting

    Re: Gravity Dredging

    Still playing games with pic resizing here and still lousy results bummer-what you must take in consideration is a bit complex=weight of water--velocity--angle of drop,hose size,gallons per foot in hose,drop height and on and on. Big hose reduction before the suck hose is the biggie-a 4" hose runs a 2 1/2 suction tip at 50' with 10' of drop and 8' of 2 1/2" hose ok fed into a standard sluice box with hungarian riffles. Mod/hungarians testing in progress.-John

  7. #7
    us
    Northern California

    Aug 2007
    'South' Texas
    XLT, GMT, 6000D Coinmaster
    2,771
    1466 times
    All Types Of Treasure Hunting

    Re: Gravity Dredging

    Ahh, computers, pictures, videos and such - when they work life is beautiful when they do not you get a headache or two. 63bkpkr
    Out searching w/GMT & friend under my arm

  8. #8
    us
    Gold Dredger 2nd Generation

    Dec 2010
    N. Cal - Born & Raised
    426
    64 times
    Prospecting

    Re: Gravity Dredging

    Hoser, if you need some help with the pics drop them over and I'll fixem up and post or send back.
    Gravity dredging just ain't the same for me, just can't live without my pumps.

  9. #9
    us
    Mar 2003
    Redding,Calif.
    4,017
    2417 times
    All Types Of Treasure Hunting

    Re: Gravity Dredging

    Just tried yet again with tnet editor--now 4 systems and even my *&^%$# post disappeared-hahahaha I HATE COMPUTERS,BUREAURATZ AND CDFG---John --thanx much GW ,as always ol'friend,have ol'bud comn' to town to party down as he don't like snow dredging anymore--more ol'dogs like me but very 'puter savvy to assist at least and I promise not to call at 4am blitzed best call I've gotten im many MANY years

  10. #10
    us
    Jan 2012
    Tuolumne County
    Tesorro LST
    126
    111 times
    Prospecting
    I know this is an older thread but the gravity dredge may be the answer to working my claim here in California, the creek I am on has a steep grade and would accomodate a gravity dredge no problem. Watching the above video, has anyone ever checked at how well the drainage pipe catches gold? I would assume, much like a culvert, the 'riffles' are meant to clean themselves, that's why the riffles are rounded in the culverts. If that is the case, I don't think you could dredge for too long before the gold worked itself to the end of the hose. If it does catch well, can you really get it cleaned out without a bunch of hassle? If all I have to do is carry around '100 feet of drainage hose, that would make my life a lot easier. My idea would be to buy smooth lined hose and put the sluice below me, but again, if the hose catches most of the gold, I wouldn't have to carry the sluice.

  11. #11

    May 2005
    St. Louis, missouri
    3,151
    753 times
    Hey Hoser! dont worry about them computors!!! they are just a passing fad and will go away and we will go back to paper and pencil if ole obama has his way much longer!

  12. #12

    May 2012
    691
    233 times
    All Types Of Treasure Hunting
    I'm sorry, if you're carrying around one of these

    Click image for larger version. 

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    Is one of these really that much more of a burden?

    Name:  folding-backpack-sluice-box.jpeg
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  13. #13
    us
    Mar 2003
    Redding,Calif.
    4,017
    2417 times
    All Types Of Treasure Hunting
    Look inside of hose prior to buying as MUST be smooth bore as if inside is like that outside you'll plug up extremely ez and with hose that is NOT clear your in for a loooooong hastle-I just use my sluicebox for recovery also as gravity is not extreme high pressure like dredging and trying to run a s/n or pj is a folly with gravity---John

  14. #14

    Jul 2006
    91
    41 times
    i have done a bit of gravity dredging like what is seen in the video, its very hard to work with the 4" big o tube. you will quickly fine yourself exhausted from picking up and filling that water filled hose. they now make it in a 3" that may make it easier to maneuver. i also used a sluice box at the tail end. most of the fine gold was in the sluice and nuggets and pickers stayed in the tube.
    last time i set mine up i had about 30' of tube going over a 8' waterfall. it was to powerful and started to crush the tube at the intake.
    i have read online that you need 100' of tube and 10' drop but i have done it with as little as 25' and 4' drop and got good results.
    the suction is very powerful, you have to be careful not to get your hand sucked up the intake.
    the bad part about the big o tubing is it is very thin and you will get pin holes in it from dragging it on the rocks. the holes will cause air to get into the system and end up with a lack of suction. still working on a patch for them, thinking pvc glue or melting plastic into the holes.
    gravel rock plug ups can be avoided by not sucking up to much at once, its easy to want to move that gravel as fast as it will take it, but slower is better.
    cleaning it out is not easy. you have to pick the tube up vertically and hit it to dislodge the gold and black sand into a bucket.

    the good thing about the tubing its about 50 bucks for 100'.
    also its very lightweight and you could pack it into remote areas.
    its nice to dredge without that constant noise from an engine. you can hear the bigger rocks and gravel making there way though the tube.
    the biggest hole i dredged was about 4' deep to bed rock by 6'x4' with mask and snorkel. that took about 4 or 5 hours by myself.
    i was so tired i had a hard time walking back to the truck.
    nugget hunting with a detector is so much easier.

  15. #15
    us
    Sniper

    Aug 2012
    Redding
    Eyes - Nokta FORS Gold - Fisher Gold Bug II
    1,152
    528 times
    Prospecting
    I had thought about this but in reverse, never thought to put it into a sluice! lol

    I have been wanting something to help move overburden so I thought about grabbing the same tubing showed and building a large sheetmetal intake on it to help bring natural water pressure to me to help move overburden while sniping.
    I lost track after the idea when Fish and Game told me I could do it with a motorized pump but still funny to see how well this works as a dredge. :P

    I am going to have to give this a try now.
    Head in the water, butt in the air.
    Now I know why ducks do it!
    Underwater Sniper n00b

 

 
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