I have been poking around the Queenstown area with a detector for around a year and have found a few spots in small creeks that have given up nice nuggets and I am thinking a small portable dredge is the shot to clean up the fine gold that is present also. What do you old wise hands recomend, do many guys use a detector and dredge together much? How does one get plans to build a small dredge?
As the streams in Otago you are detecting are shallow, you will require a dredge with a suction nozzle. The only other alternative is to use a dredge with a power jet, but then you would need to raise the water level in the stream so the power jet keeps its prime, and the only way to raise the water level would be to build dams.
The smallest surface dredges are the 2/2 ½ “ img.photobucket.com/albums/v172/Coochee/Papua%20New%20Guinea/7d466144.jpg?t=1208984638 which are too small to be of any use to anyone. A 3” would be a better choice. The heaviest single part of a 3” dredge is the motor, and a 3” dredge can be sufficiently powered by a 5/5.5 hp motor. A 5/5.5 hp stationary motor is a small enough size to be easily carried by one man. Larger motors can be difficult to get into remote areas … especially for one person working alone. I’ll go through some of the parts needed for a fairly conventional 3” surface dredge to help you decide if you might want to put one together yourself, rather than maybe buying a complete dredge from a mining supply store.
And, for anyone else who might want a suction nozzle, they sell the following sizes. 2” suction nozzle $80 each img.photobucket.com/albums/v172/Coochee/HOT%20LINKED%20PHOTOS/P1010002_2inchB-1.jpg?t=1208991819 3” suction nozzle $120 each 4’ suction nozzle $150 each 5” suction nozzle $230 each They can also make a 6” suction nozzle to order. Note: They only have one 2” and one 3” in stock at present. Also, the supplied nozzles don’t come with a reducer/spacer on the nozzle tip. However. It would be simple enough for anyone to weld on your own reducer/spacer (and the reducer/ spacer could then be to your preferred design).
A 10 or 15 feet length of 3” ID Eolo hose can be used. Information on the Eolo hose can be found in previous threads.
A basic sluice box is all you need and one can be made by cutting and bending a single sheet of aluminum. Don’t use thick aluminum as thick walled aluminium would considerably add to the overall weight of the dredge. A header box would be useful on the sluice box. However a header box might be difficult for you to design correctly and to build. If you could buy a second hand sluice box that would be the easiest way to go.
Basic Hungarian riffles made from mild steel are simple to construct by using steel strip that is cut and bent, and then welded. The carpet to go under the riffles can be No-mad carpet, which is easily sourced from most carpet stores in New Zealand . Un-backed No-mad carpet is preferable as its much easier to clean compared to backed carpet.
Lat flat hose can be used for the delivery hose, and its easily purchased. And lay flat hose can be rolled up so it is easily carried into remote areas.
You will need a foot-valve with a flapper valve so it can hold a prime when starting up.
The size of the floats will depend on the size of the selected sluice box. Making floats is basically just common sense. However, avoid using truck tyre tubes if possible as tubes get tossed around by a strong current and don’t sit particularly well in a strong current.
As you will be only working the small Otago streams, which are narrow, you could place the motor and pump on the river bank with the foot-valve in the water. And by not floating the motor you can significantly reduce the amount of flotation required.
There is another means to get fine gold from a shallow stream you might like to consider trying, and could be used when you have a stream that is too remote to get a dredge into … and that is by Sniping. You would not get as much fine gold as you would with dredging, but sometimes it can be the only way to get the gold, for numerous reasons.
I’ve always said the small streams of the Otago gold fields are a snipers paradise. But what has prevented sniping being more commonly used as a means of gold getting is that its very physically taxing and can therefore only be carried out successfully by fit young people.
To snipe a stream you will need a wet suit, face mask, crevicing tools and a sucker.
Sniping is preferably carried out in shallow rapids where the water is running fast and there is little overburden. And the method of working a stream is to submerge yourself by laying down fully submerged or kneeling in the stream, with your head underwater so you can see what’s going on (the most important part of successful sniping is to be able to see clearly underwater, while having both your hands free). You first remove what rocks you can by hand to locate the top of a crevice and then you fan the crevice with one hand. Fanning the crevice stirs up the lighter gravel which is swept away downstream by the fast flowing water to leave gold sitting quiet visibly on bedrock (the goggles magnify the gold so even small pieces of gold are clearly visible to the sniper). Often, not only chunky gold with some weight is visible, there can be a surprisingly significant amount of fines left in place on bedrock (if the fanning is done properly). The chunky pieces are easily picked up off bedrock, and to get the fines a sucker img.photobucket.com/albums/v521/NZGOLD/Equipment/P1010006bulb.jpg?t=1208992109 is used.
This is how Hammy got most of his gold, including the 15 ounce crevice he found. He did sometimes use a dredge, but the dredge was actually of most use to remove overburden so he could hand snip the gold left in a crevice. He used a Suitcase dredge, which is a dredge that’s woefully underpowered and does not have enough suction to lift any chunky pieces off bedrock following the removal of the overburden.
Great info Rob. On another matter concerning compressor's for diving. I have been communicating with a guy in the states who is selling a motor/compressor set up on ebay for shallow diving. eg. Cleaning the underside of boats or gold dredging. The gold dredging got my attention. cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150239170224
I asked him if I could hook the compressor up to run off my dredge motor & so do away with his motor & the weight of freight. He said it was designed to be direct driven & to operate it off a pulley & belt would flog the bearing out prematurely & the compressor wasn't designed to be used as such.
I mentioned to him that I had a compressor that I used to use for powering my air powered nail guns that run at 120 psi & the compressor would go much higher, that i no longer used the compressor as I now use the paslode gas powered nail guns (I'm a builder by trade) I had never consided using this as a diving compressor because of the oil lubrication in it. He said there is an oil called monlec oil that is paraffin based so is breathing air safe & you can also run any water air separator to remove any oil that may get into the line.??????
What are your thoughts on this Rob, do you think it would be safe ?
Thanks for the information. I will have a shot at sniping in a couple of spots before I get too excited and build a dredge, they seem to add alot of comlication to the equation, with a detector I can cover a lot of ground with minimal equipment. It appeals it in simpicatilty. But for every oz of nuggets there is a lot more in fines, however some spots seem to have no fines, can,t even get a colour in the pan but have produced some nice nuggets. What precentage of nuggets too fines does the Arrow have in your experience? Remote back country streams in the Wakatipu, have many been dredged, and how do you go about sampling a small stream to see if its worth the effort to haul a dredge in?
The compressor you are considering purchasing from the States looks good and is reasonably compact, except for the air reservoir tanks. The fact that it can be picked up with one hand is in its favour. The only problem seems to me is that it uses oil.
Direct drive compressors are excellent as they are compact, and there was a oil-less compressor sold back in the 80s called the Happy Hooker that was direct driven and small enough to be easily lifted. I did a search on the Internet a few years ago to see if it is still being sold but my search did not turn up any compressors by that name.
Its simple to make a Hooker using a small compressor such as the Thomas T80 powered by a Honda 2.2hp motor and connected by a fan belt. Using a fan belt is not the perfect solution but it is simple … and is doable!
Your mention of using “monlec oil that is paraffin based so is breathing air safe” reminded me that I was told, back in the 80s by a Australian compressor manufacturing company, that they used an edible oil in their cast iron compressors, which, they said, meant they could be used as a Hooker diving compressor. I didn’t like the idea then and still don’t like the idea. However, its probably worse to breath in the aluminium dust from a cast aluminium Thomas compressor (I’ve mentioned previously in the forum about using a filter at the outlet on a Thomas compressor) than breathing in an edible oil.
Sniping for gold from the streams of Otago, should not be underestimated as a means of getting significant amounts of gold, and you really should give sniping a try … and its great fun!
Sniping has always been popular in Otago and there is an interesting historical photo in Hammy’s book taken at the “Jewellers shop” (the junction of the Shotover and Moonlight Creek) in … I think, the 1950s, which shows a guy in a wet suit with a hooker for diving.
A great number of the streams around Queenstown are presently under claim (Mining Permit) but in the back country there should be enough streams still unclaimed to keep you busy. Poaching from mining claims is developing into a very sensitive issue in the Queenstown area.
During the 90s an American miner regularly visited Otago in the summer and autumn months to exclusively snipe for gold. And sniping was his speciality which he had perfected to a fine art. I only wish I had taken some photos of him in a stream – or better still a video. He would jump into a stream and lay horizontally on the water surface with his head always underwater. And to look down on him from the river bank he appeared as if he was dog-paddling in the water (without going forward). However, what he was actually doing was using ‘both’ hands to throw rocks behind him, while always keeping his head underwater so he could see what was occurring (he was able to use both hands to shift rocks as he was supported by the buoyancy of his wet suit). He would ‘not’ throw the rocks far, just far enough to get them out of the way. And when he was in the water he would be going flat-out! (it was exhausting just to watch).
He had learnt over many years to make every move count and there would be no wasted effort when he was working.
An example of wasted effort is often seen when inexperienced guys are in a river moving rocks. They will typically pick up a rock with both hands, raise their heads out of the water and often stand up, and then look about to see where to throw the rock. And they will then heave the rock as far away as they can.
The American sniper used to say that he could move, by hand, just as much gravel as could be moved if he was using a 3” dredge.
He once took 11 ounces out of the upper Arrow right under Hammy’s nose … which Hammy would not have been too pleased about.
If you had a chance to ask any of the guys who mined around Otago in the 80s and 90s if there was any gold left in the streams, I could guarantee you they would nearly all say the gold is gone. Nevertheless, gold somehow keeps coming out of Otago streams. For example, Hammy missed the 8 ouncer that the guy from Southland (who was on his Christmas holidays!) sniped from the Arrow a few years ago. And so on.
Building a dredge would “add a lot of complication to the equation”. But, if you should find a good spot when sniping and then find the gold continues into ground with too much overburden to move by hand, the “equation” will be different and my guess is that you will then have no hesitation about getting a dredge.
I couldn’t agree more that the “simplicity” of using a metal detector to sniff out gold is one of the best reasons to use a metal detector for gold getting. Another reason, which particularly appeals to me, is that metal detecting can be done alone and you never have to deal with the difficult personality issues that often accompany working with someone else when gett'n' gold.
What has killed off many Production Dredging projects for gold are the difficulties that seem to inevitability arise when a group of men work together on a dredge. The weirdest aspects of human nature appear when three or four, or often even just two, men work on the one dredging project. I could fill a book with stories about dredging projects coming unstuck because of stupid bickering and the change in personality that comes over some people when they see significant amounts of gold in front of them.
I’ve also seen some partnerships, of usually only two men, that work very well. And the dredging projects that have been successful are most often those projects where the men can work harmoniously together. But, the important point is that the ‘successful’ partnerships are between men who knew each other very well ‘prior’ to commencing a dredging project and have a track record together. An example I saw in the 90s was two men who had met and worked together in a meat processing works and knew each other from then. Anyway … when they were both retrenched from the meat works they decided to then go dredging. They went in as equal partners and when dredging they would spent the day taking turns underwater on the dredge, so they were sharing the work equally. Good partnerships not only make the dredging easier, but, each can support the other in the inevitable difficult times that require self discipline … such as when its cold and raining, or when the gold is not showing up. Or when its both cold and wet AND gold is not showing up!
If there is one thing in particular I’ve learnt, is that to be successful at gold getting you have to get the priorities right, and focus on what really matters, which is wrestling the gold from its hiding place.
One solution that can work, to avoid the usual disagreements among dredging partners, is for a claim owner to employ men to dredge rather than have everyone as equal partners. This can and has worked in New Zealand … however a few potential problems can still arise. Commonly an employee will dredge happily for only a month or so, on a dredging project, until one day he decides there is nothing to this gold dredging game and he should be dredging for himself . He then leaves to get his own dredge (thinking he knows it all when he actually knows virtually nothing). And there is the ever-present potential for an employee to steal gold. One such instance I was told about was when an employee was caught when the claim owner saw gold fall out of a glove as the man he employed left the water after a dredging shift. The employee must have been grabbing any gold he could while underwater and hiding it in his glove. And this could have been going on for … who knows how long. Needless to say, the claim owner and the employee then each went their own way. Once such a breach of trust occurs, there is no way the two could ever work together again.
Also, employees need to be supervised so that they don’t breach any of the claim conditions, as the claim owner is the one who has to answer to the authorities for any breach of conditions (and pay the fines for). The potentional for a breach of claim conditions is one of the main reasons why claim owners can't let just anyone on their claim to dredge.
There is no rule relating to the “percentage of nuggets to fines”. Some areas can have only fines and no nuggets, and other areas can have only nuggets. And the additional complicating factor these days, is that all the areas you will be prospecting around Otago were mined in the late 1800s, with many mined again in the 1980/90s. BTW: The miners definition of a nugget is a single piece of gold that can be thrown in the air and caught.
These days the only way to “sample” (prospect) a stream is to mine it! You can forget about using a pan to prospect a stream, as you will not learn anything ‘conclusive’. Pans are mostly used these days by hobby fossickers who are only looking for a little colour. The only use dredgers have for a pan is to further concentrate the concentrates from a dredge sluice box. BTW: The best pans for panning off dredge concentrates are the large Kiwi steel pans (available from many hardware stores). There is always a lot of very the heavy black sands in dredge concentrates and if you try to use one of the black plastic pans you will find it will bend with the weight and it is then impossible to pan correctly.
When I was once dredging a river claim (paying a tribute to the claim owner) I was disappointed with the gold I was getting, so I decided to walk upstream (into unclaimed ground, above the claim boundaries) to do some prospecting with a long-handled shovel and pan. I spent a few hours panning numerous dishes of the wash which was taken with the shovel from the river bed, and I could not get a single colour. So, that was enough to completely discourage me and I went back to the claim and dredged there for a while longer (wasting valuable time at the height of the season). Anyway, for complicated reasons I don’t need to detail here, I later put my dredge in at the spot I had earlier “prospected” unsuccessfully … and I got on to excellent gold immediately! I ended up taking many, many ounces from an area my “prospecting” indicated I should not have bothered to put my dredge in. If it had been a remote area I probably would not have dredged it and the gold would still be there today. Basically, it was only because I could easily put my dredge in, that I disregarded the “results” of my “prospecting” and actually put my dredge in to determine conclusively if gold was there, or was not there.
Rob has asked me to mention the compressor I bought from Bob. I looked at a few when I was in the States, and found that for dollar for dollar this is the best, in my opinion. Rob has included the photo of the unit, a very nice piece of equipment.
So below is some info for anyone who is thinking of getting a compressor. The Dahlke Compressor. This compressor utilizes three sealed lifetime lubricated ball bearings, that do not need lubricating at all. This unit uses a composite self lubricating piston and is shrouded with a cooling fan to aid in the dissipation of heat. All O rings are temperature preformed rings, to allow the correct seat surface. Fitted is a load valve to minimize any back pressure to the piston when starting the motor. I am not sure if this is a common feature on other compressors.
The knurled knob is the only adjustment to the compressor. This is the pressure relief valve. The compressor comes with three tension springs. The springs are color coded, Yellow 20-50 PSI, Red 51-100 PSI, and Silver 101 - 150 PSI. The unit will produce approximately 3.3 CFM and is of course regulated by the engine RPM. This oil less piston compressor will produce 3.3 CFM at 1725 RPM shaft speed. With these settings available, simple adjustment can be made with engine RPM, especially if diving to depth where the unit is good for two divers working to 40 - 50 foot depth. Pretty impressive for a cost of around NZD 400 depending on the exchange rate. It runs very smooth and quiet. I hope this is what you are looking for re specs, I have used my dredge now (It is brand new) 3 times and with the set up I have built it works superbly. I was concerned that because of limiting myself to a lower HP motor I was going to loose considerable power, but it seems to be OK, as I tried the unit connected, and disconnected and no real drag to speak of.
I was also asked to mention the hose that I use. In the States I use the standard Clearflow, external ribbed, suction hose.
To get that over here would cost a considerable sum, even importing it from Aussie. So I had a good look around here. I came up with (Rob had a photo of the hose I use on his photo bucket) A hose known as HD PU Ducting Hose. (Hose Supplies, Mt Maunganui 07 5727070, or CHCH 03 343 6058). They make these hose´s in various thicknesses. You should go the thickest as this gives good rigidness under water in relatively swift conditions, is very strong, they blast wood chips at high pressure through this hose, is steel ribbed, clear, with a relatively smooth bore internal. If anything it is wavy inside, but not at all excessive. The salesman tried to puncture the hose with a screwdriver, and could not. It is easy to handle, like carry through the bush, and does not collapse when your son trips over it and lands on it!! .If you shop around you can get this hose, which I have (127mm) at under $75 per meter. They have off cuts up to 20 foot in some instances, but most commonly up to and between 15 - 18 foot. Unusual I know, but that is what I came across. In these lengths the price is very negotiable.
So their you have it. I hope this all helps. Sorry for the delay in writing, but as usual very busy. I am off into the bush for 3 days next week, so if any further info needed expect a delay. Rob, I will contact you soon, head off to the States in 5 weeks, away for 3 months.
Yep, running a 5 inch with a 6.5 HP Motor. Does the job very well. Again all Dahlke parts, and with using the 5-6 and 8inch in the States worked my own design re flare box etc. You know how it is, trying to save everything you can!!
Off to the States dredging, working with the guys in Northern California, and will probably go bush for a few weeks on my own, still good potential up there. Interesting how the Americans operate, you will see dredges where good access is to the rivers, but to hump your gear to a remote spot, you will never see a soul, just the wildlife.
I am at building the sluice box stage and have looked at a few designs on the net and I'm thinking a classifier over riffles with more riffles further down box is a nice simple design.
My question is what height should the riffles be under classifier be, am going for Hungarian type and what height should the riffles be further down the box? I'm using nomad matting, if its unbacked should anything go under the nomad?
I'm using a 6.5 hp motor with a proline hp400 pump, which is designed for this motor, naturally its a 4'' dredge. thanks for any help