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Post by oro e lavoro on May 17, 2014 22:54:48 GMT 12
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Post by oro e lavoro on May 17, 2014 23:05:41 GMT 12
buongiorno to all,still in the construction process for the 8 inch gravity sluice .Not knowing exactly the metall thickness for the riffles needed for 7 inch rocks hitting ,i ordered 3mm stainless steel,made a plan for my metal-man how to cut,bend and weld it. What happened? without giving me a call he ordered 2mm because he can,t bend the 3mm he says,cutted and bended and welded it. will the 2mm fall apart and what thickness you pro,s use for the 8 inch. Thanks in advance:emilio
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Post by lbd on May 17, 2014 23:47:58 GMT 12
The steel riffles in my 5" and 8" dredges are less then 2mm steel and survive okay.
She is looking good.
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Post by oro e lavoro on May 18, 2014 7:20:51 GMT 12
hi lbd, he,s a good metal men,just missed a phonecall. I ask because the riffles in the expanded metal section are welded only to the left and right side of the riffle frame,the 3 mesh support sheets are welded on top of the riffle lip so i,m afraid the weight of the rocks hitting will push down-forward the riffles.they are 65cm wide and 1 cm high , i wanted few as possible in that section for the finer gold,just enough to push down the expanded,so theres not much weight distribution. if i knew it would be 2mm i maybe let the middle support metal sink down to the expanded ?Are your riffles all covered with mesh or open area?
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Post by RKC on May 19, 2014 0:35:19 GMT 12
G'day oro e lavoro,
Your dredge is looking like its coming together well.
Riffles made from 2mm thick stainless steel will be much stronger than mild steel that is 2mm thick! So ... I can't envisage any problems arising from rocks hitting the riffles.
How large a screen you cover the riffles with will depend on the size of the gold expected to come from the river to be dredged. If its only fine gold that is expected to come from the deposit to be dredged then you can cover all of the riffles. If only some oversize (nuggets) is expected to be dredged, then only part of the length of the sluice box needs to be covered. When expecting nuggets I personally like to, at the very least, leave a few riffles uncovered at the head of the sluice box. By doing this you can immediately see if the area is producing nuggets (if you're not seeing them underwater). And the nuggets can be easily removed by hand when they appear, if the top riffles are left uncovered. Its worthwhile covering as much of the riffle area as practical because the riffles will run much more efficiently when covered with a screen. Rocks will collect between uncovered riffles and that will boil out the spot sending the gold further down the box.
The only reasons stainless steel is not more commonly used in gold dredges is that stainless steel weights more than either steel and aluminium, and additionally stainless steel is more expensive. Also its more difficult to fabricate. During the 1990s an Otago dredger who had a claim on the Arrow river used more stainless steel in his dredge than I have ever seen before or since. Its was all fine until he wanted to move his dredge with a small helicopter. The chopper had a great deal of difficulty lifting the dredge because of the weight.
Regards, Rob (RKC)
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Post by oro e lavoro on May 19, 2014 6:29:46 GMT 12
hi rkc,i asked for the covering because i was thinking that maybe covered riffles dont need to be very thick because the mesh protects them from the big stones.But now i,m calming down ,thankyou lbd and rkc.My problem is i maybe i will suck up more big rocks then you lucky new zeelanders,because i,m not allowed to use motors,which means also no compressor for air supply,so if i want to go deeper then my arm lenght i have to attach a tube to my nozzle and loosing control of the feed,or lower the water level in the pool i work when theres enough drop remaining which in some spots is may be possible.The sluice itself has to be adjustable in every section,beginning with the flare,i have no throttle,so when i got too much drop i can lower the flare tail,the riffle sections all changeable,because i,m travelling different spots.here within 2 car ours where i live its mostly fine stuff,with 2000-3000 specs needed to get a gram,-following your logic,all riffles covered and some open riffles at the end(you never now) in the few nugget spots in the country i cannot show up with this equipment,but in july and september i,m in italy where 2 rivers give flakes up to 5mm and little pickers(so far),Thats the spot with the blacksand problem i mentioned in earlier post. There i will follow your advice leaving a uncovered area at the head.
Thaks to all
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Post by lbd on May 19, 2014 21:15:58 GMT 12
The last section of my sluice box has un protected riffles and I regularly feed it 150mm to 180mm rocks without any problem
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Post by oro e lavoro on May 20, 2014 5:26:39 GMT 12
do you recommend steel rods on the riffle lips? Are they there to prevent flat stones to collect between, (saw a video from boaraxa) and reenforce the riffles? They help?What thickness stainless steel you recommend and what distance between them?
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Post by RKC on May 21, 2014 10:26:51 GMT 12
G'day oro e lavoro, Adding some steel rods to hold the riffles secure is well worth doing and has no downsides other than it will add a little extra weight. And it will help to keep the larger rocks from collecting between the riffles and boiling out the area between the riffles. There would probably be some information on riffle spacing in this thread ... golddredgingforum.proboards.com/thread/104/building-small-dredge?page=1An example of a dredge built where the gold expected will be fine gold ( imageshack.com/a/img844/8610/867n.jpg ). Just about all of the riffles are covered in this sluice box. Regards, Rob (RKC)
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Post by oro e lavoro on May 22, 2014 7:22:24 GMT 12
buongiorno rkc and everybody,thankyou for all the information,i do this dredge paycheck after paycheck and your forum and input helps me even though i,m no pro (and cannot develop to beeing one in my enviroment)saving money and time,reducing building errors and testing ,i,m a little bit behind my timeplan and probably won,t get the flotation done for this summer,but i got different spots where i can dredge without it,just need my 78 years old father,shoveling away the tailings.
emilio
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Post by RKC on May 22, 2014 9:08:05 GMT 12
G'day oro e lavoro,
Good luck with the project! Looks like you're having fun with the build.
Be sure to post photos of the finished dredge when its done.
Regards, Rob (RKC)
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Post by oro e lavoro on May 23, 2014 6:31:03 GMT 12
I would be glad to do so
thanks again
emilio
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Post by oro e lavoro on Jun 19, 2014 9:30:05 GMT 12
Hi together,little progresses going on. Adjustable flare and a open riffle section with rods done...and look what was laying in front of my grandmothers balkony..over 30meters of 8 inch polyurethane quality gravel suction hose.Its used by dredge /pump trucks that are very en vogue around here,for roofing or instead of backhoes in roadconstruction etc.Its around 218 nz dollars per meter,ouch! One question ;can i mount the clips on the sheet that crosses over the sluice and the hook on the bended edge of the sluice? thanks; emilio
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Post by RKC on Jun 22, 2014 14:03:05 GMT 12
G'day oro e lavoro, Its coming together and looks good! I'm not sure I understand your question about mounting the "clips". If what you are asking is to do with securing the riffles inside the sluice box then it should be fairly straightforward. Securing the riffles is no problem ... its just about common sense. However ... what you have to consider apart from that is how to make the riffles easily removable. On a lot of the company manufactured dredges the riffles are secured permanently in one spot and at the other end are clipped down. The riffle tray then swings up so the carpet can be removed. However I think a better way is to be able to completely remove the riffles so they can be set aside from the sluice box while cleaning out the box. On the dredge shown in the links below you can see an example of how the clips are positioned on a sluice box. imagizer.imageshack.us/v2/1024x766q50/856/mgho.jpgimagizer.imageshack.us/v2/867x649q90/849/ep2g.jpgRegards, Rob (RKC)
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Post by oro e lavoro on Jun 22, 2014 23:23:31 GMT 12
hello rkc,nice to hear you.Yes,in my four inch sluice i have that system,one end of the riffle frame bar is jammed under a female screw and the other end is clipped down,so i can remove the entire frame, but i have no bended sluice edge on the four inch,now on the 8 inch i have this bended edge nd that creates a obstruction for the clips.I saw on a 8inch keene they solved that problem with distance plates,or others just cut gaps in to he bended edges for the clips,but i dont like to cut the rolled edges ,because i will use 6 pairs of clips to have all different riffle types changeable for the different rivers ,gold and blacksand contents,it would leave a emmentaler-cheese looking like sluice edge. So i was thinking to try to interchange the position of the clip-parts,mounting the clip on the bar and the hook on the bended edge.Wanted to know if there any problem arising with that system ,cause its always done the opposite way. Thanks:emilio Attachments:
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