Newbie - Gravity dredge info needed

[Caminochaos]

Hello everyone! I have been panning and sluicing for 12 years or so and looking to get a little more creative. I have been doing a lot of research on gravity dredges due to the fact that a gas powered dredge is out of reach for me money wise the gravity dredge might be a good temporary solution.

I have the concept of how to make one and it seems that a simple Big-O dredge is the most popular. However I have heard that the fines get caught in the ripples quite a bit. I like the idea of being able to carry a flexible hose to my spot because carring 100' feet of PVC pipe would be tough through brush and hills 1 or 2 guys.

My questions:
Is have any of you tried other types of hoses or pipes that are a little easier to handle? OR
Is there an easy way to clean out the ripple inside the Big-O pipes?
OR
Are there inserts or sleeves you can buy to line the inside of the Big-O?

I am looking to go cheap on this.

Thanks for your help.

 

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[patches63]

not sure what a big-o dredge is,but yestertday spent more on large diameter utility water line,than a pump would cost brand new. 80 psi line (poly) is also much harder to pack than an engine pump on a ledge frame pack.and weighs in close to same weight.g-dredging takes volume plus head.rare are areas where 100 foot of pvc will suffice.deposits beneath waterfalls come to mind.40 foot drop per mile of stream has been said to be optimal for deposition of values.heavier the values/steeper the optimal grade.thus,serious ops need lots of gravity line.start at about your venturi diameter X 2 if not in california,would re-consider the pump option.honda engines with modern mining pumps are actually easier.having said that,a successfull gravity unit would be the cats whiskers.would need 12V air i suppose,or what point.hope this helps,keep us posted.

 

[Hoser John]

12v air=$1,000+ and weighs a bloody ton ,lookn' for a reliable unit for years that'll last more than a hour or so-tons a au 2 u 2 -John

 

[Caminochaos]

Thanks patches....but I am looking for a cheaper solution.

 

[kiwi jw]

My Gravity Dredge Set Up:

I used 2" PVC pipe with some green flexi hose at the top end, like a vacuum cleaner hose & pipe set up. This I use at the top where the hole is that I am wanting to suck out.

The 2" pipe runs from there down hill to where my home made sluicebox is with home made headerbox that has an old fridge tray in it for classifing the material to less than 20mm before it carries on thru the sluicebox. Much like a highbanker set up. So any material larger than 20mm just falls out the front. The bonus of pre-classifing the material is you dont need to keep on coming down & check for possible rock blockages in the headerbox or riffles. Plus it improves the fine gold recovery as you dont need as stronger water flow to wash the gravel thru the box as you would to wash thru rocks of say 2".

To get the whole thing running, I block the bottom end down in the sluicebox with a tennis ball. Go up to the top end & fill the pipe from the sluicebox all the way up to the top flexi hose with water. Make sure the top flexi pipe hose end is in the water, Usualy jammed under a rock or in a crevice. Then I race back down to the sluicebox & pull out the tennis ball, & hay-presto you have a dredge operating with no noise & no operating cost factor.

Then its just a matter of going up top & vacuuming out the rock pool. You have to manhandle large rocks out of the way plus any other cobbles that wont go up the nozzel. Sometimes it involves ropes & winches to move the bigger rocks but thats all part of the fun. I made an underwater viewfinder out of a 300mm length of 150mm diameter pvc stomwater pipe with some glass siliconed in the end. I can hold that in one hand & view what im doing in the water with the suction pipe in the other. You can sometimes see the bigger bits of gold as you suck em up.

Gold found on this attempt

Happy hunting

JW

 

[jimmygoat]

Pretty cool set-up Kiwi. And it looks like it works too. Sweet.

 

[Jack Hamilton]

Do you have a nozzle on your hose or do you just use the hose? I was also wondering if there would be a way to use a dredge nozzle and the gravity line, but keep the sluice closer to the operation.

 

[kiwi jw]

Hi there, When I first set this idea up my aim was to run a 2" suction nozzle. But I very soon found out that that was not going to give any where near the pressure to run a nozzle. You would need a lot more fall & bigger pipework, like they did in the old days to run their hydrolic monitors, to get the required squirt to run a nozzle or power jet. I just ended up using the syphone suction to do all the work. Just like syphoning petrol but on a bigger scale & longer pipe work.
I have done the same thing with a 4" pipe. Works a treat.

JW

 

[Caminochaos]

Very nice set up Kiwi!

Have you guys used just drainage pipe (Big-o) and no PVC? I've heard that it works great as long as you have no low points in it for thing to get caught in.

I was thinking of using a 4" black drainage flexible pipe and make the opening smaller with duct tape or something so that larger material doesn't get sucked thru.

 

[kiwi jw]

I just used my 4" dredge flexi hose with the steel suction tip that is slightly reduced at the opening, taped the flexi hose to the pvc that I used a heat gun on to flare the opening a bit bigger so the flexi hose would fit inside it. If the drainage coil has those deep spiral ridges I would give it a miss. They will cause a lot of friction slowing the water up plus any gold will get traped in those grooves & never make it to your box. Only to fall out when you carry the piping some where else. Unless you carefuly shake the shit out of it to make the gold fall out in a controled manner.

JW

 

[Astrobouncer]

That's a great setup and definitely something I would be interested in trying. What is the smallest diameter tubing you think would work in a setup like that? I noticed they had lots of smooth smaller tubes at lowes would something like 2 inch be ok if you made a hardware cloth screen to keep out 1/4 inch and bigger rocks? Or is that just too small?

 

[TerryC]

Just like syphoning petrol but on a bigger scale & longer pipe work.

JW

Boy can you tell HE'S from down under! I like the setup! I have a source of water about 100 feet above where I need it. Hmmmm, now where was that pvc pipe?! I really like your setup. Thanks! TTC

 

[kiwi jw]

Hi guys & thanks for your comments. I wouldnt go any smaller than 2" pipe other wise you may as well just shovel the material. The smaller you go then of course the more material you physicaly have to man handle. No different to any dredge set up. That is why I stepped up to a 4" pipe as that could move a heap more material.

Happy hunting

JW

 

[Caminochaos]

Kiwi,

Did you use any adhesive to connect the PVC?

The only reason I ask is I'd like to disassemble it at the end of the weekend to take it back home and think that it would be a real pain to take back apart once put together. I guess I could use duct tape. I'd like to get your thoughts on this matter.

Thanks,
Joel

 

[Goldwasher]

hey kiwi... so u run pretty much the same diameter pipe/ hose the whole way? and what would you say your length to drop ratio has to be for minimum suction needed to move material.looks like you have pretty good drop to work with...i bet you can leave your stuff set up without being taken unlike where most of us here live...id just keep addin on......and on.........

 

[Caminochaos]

I have good news. I was able to get some 3" conduit pipe for free. Pretty much an unlimited amount also. I will be trying this in a few weeks and I'll let you guys know how it works. I have yet to see the pipe so I'm not sure how I'm going to connect it but it will be fun figuring it out.

 

[auferret]

The pvc conduit sold around here has one end flared so the next one will fit inside it. No connectors needed unless you start cutting them. I'm not sure how those joints will hold up to the pressure at the lower end.

 

[strickman]

duct tape ,at the very least.might need more.

 

[Caminochaos]

Yeah, I thought abou the flare end situation also. I going to pick up the pipe this weekend so I'll be able to figure something out once I see it.