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Whitworthone
#1 Posted : Tuesday, 16 August 2011 9:21:57 p.m.(UTC)
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How much head of water or hight drop would be required to pull gravel through to a sluice?
Would a long enough pipe have guts enough to suck and deposit gravel in a sluice lower down the creek?
Just wondering?
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East-Auck-Fossicker
#2 Posted : Tuesday, 16 August 2011 10:10:51 p.m.(UTC)
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Different rivers flow at different rates. If the little pebbles aren't rolling throw , too slow. If no black sand or sand at the back of sluice , slow down. If the river is running really fast you can put a large rock on top of your sluice . If you would like a DVD some how send me a mail address and I'll send it free.
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Glennl
#3 Posted : Sunday, 21 August 2011 9:06:41 p.m.(UTC)
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Hiya whitworthone, I recently spent quite a bit of time investigating and trialling a gravity dredge, mainly after seeing some pics on here from kiwijw. Are you talking about a gravity sluice or dredge? Threre are lots of clips on you tube but they don't seem all that efficient, sucking at the top and using corrugated pipe seems like a way to store the gold inside the pipe and not in your box, but they will work i guess. You can get somewhere in the region of 1.4psi/vertical metre of drop in the river. It all depends on how big your pipe diameter is, how steep your river is, how long you want to run pipe up stream for, will you reduce this to increase pressure and how you will funnel the water to create suction..ie: a power jet/suction nozzle...just making a non-motorised dredge. It's definitely possible, is a little labour intensive and take quite a bit of trial and error but is immensely satisfying once it's up and running. As an example, I had 50m of 100mm hose, 50m of 50mm hose, about 15m of drop in the river, a 50mm power jet and a 3m 50mm suction hose and it would bite, then swallow fingers!Some helpful info is available on http://goldfever.com/g_dredge.htm#layout
Good luck and happy digging
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Whitworthone
#5 Posted : Monday, 22 August 2011 9:48:28 p.m.(UTC)
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Thanks for the link, really good info. Brilliant!
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1864hatter
#4 Posted : Tuesday, 23 August 2011 11:19:14 a.m.(UTC)
1864hatter

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Glennl;4744 wrote:
Hiya whitworthone, I recently spent quite a bit of time investigating and trialling a gravity dredge, mainly after seeing some pics on here from kiwijw. Are you talking about a gravity sluice or dredge? Threre are lots of clips on you tube but they don't seem all that efficient, sucking at the top and using corrugated pipe seems like a way to store the gold inside the pipe and not in your box, but they will work i guess. You can get somewhere in the region of 1.4psi/vertical metre of drop in the river. It all depends on how big your pipe diameter is, how steep your river is, how long you want to run pipe up stream for, will you reduce this to increase pressure and how you will funnel the water to create suction..ie: a power jet/suction nozzle...just making a non-motorised dredge. It's definitely possible, is a little labour intensive and take quite a bit of trial and error but is immensely satisfying once it's up and running. As an example, I had 50m of 100mm hose, 50m of 50mm hose, about 15m of drop in the river, a 50mm power jet and a 3m 50mm suction hose and it would bite, then swallow fingers!Some helpful info is available on http://goldfever.com/g_dredge.htm#layout
Good luck and happy digging



Hey mate that sounds pretty good what kind of hose did you use? I find anything decent is quite expensive. Also do you mean you reduced the size of the hose half way down?

Cheers
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Glennl
#6 Posted : Thursday, 1 September 2011 10:03:02 a.m.(UTC)
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Hiya 1864hatter, I started off with just 50m of 50mm fire hose that I got from a ship I work on so was handy as is smooth lined inside so reduces a bit of the friction inside, but your right is a tad expensive. once I did some more thinking I added another 50m of 100mm layflat agricultural hose, was about $350 delivered from hamilton, and I got a 100-50mm reducer and brought a stainless powerjet from invercargill. The power jet is 50mm, and the fire hose connects to this before being stepped down in 3 stages to a 13mm jet outlet. the jet throws water about 10m and once sucking it is no different to a small water pump. I just need to fit a flow valve to control the speed and volume of flow as it is like a water pump on full throttle at the mo. Unfortunately my 100mm hose was nicked so am not going to replace it at this stage as now have a 5" dredge. The blue layflat hose is available on the net, cross country traders on trademe have about the best prices I have come across, cheaper than the pump shops in nelson even after the delivery costs. I have a video of it working, but I couldn't work out how to upload it onto this website. Know any farmers with trade accounts might be an advantage lol. Best of luck out there to all.
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