|
|
Post by RKC on Nov 14, 2008 9:45:05 GMT 12
|
|
|
|
Post by RKC on Nov 14, 2008 9:46:03 GMT 12
From: dredgenz1 Sent: 17/09/2008 11:09 p.m.
Cheers Rob.
As you can see I use a triple sluice box on my 6", this fits between my pvc floats and can and will be lowered when I get round to some modifications. The motor can come down a little to. This dredge is purposely built for the area I work in. The pvc pipes come apart and are made to slot into each other, everything you see fits in the back of my 4x4.
In regards to HWS I've been told not to have the exhaust running directly over the copper tube because of the toxic gas it creates. Is this right? I'm building one soon. Trying to get as much info as I can. This is going on my 9HP Honda she is running a 350 Keene pump.
|
|
|
|
Post by RKC on Nov 14, 2008 9:47:11 GMT 12
From: RKCNZ Sent: 19/09/2008 4:07 p.m.
G'day dredgenz1,
Engine exhaust is certainly "toxic" but there is no potential health problem for a dredger by using the exhaust fumes to heat the copper coil in a HWS. What was probably meant when you were told about "toxic gas" was that the engine fumes should not come near a compressor that is used as a diving hooker. However, mixing the air from an engine exhaust with the air breathed in from a compressor is not usually a problem ... in most situations. Its only where there is no wind to disperse the engine fumes, such as when dredging in a steep sided gully or where trees overhang the stream, that there may be a problem with the fumes lingering. And if this is a perceived problem then an extension inlet can be attached to the compressor (http://www.keeneeng.com/Merchant2/images/air/T80G.jpg ). Its not something I've ever felt the need to do however ... but I would certainly consider doing it if dredging in a narrow gorge where the air could not circulate.
A 9hp Honda motor should put out sufficient hot air to run a coil HWS. And all the information you will need to build a HWS system is in the thread CONSTRUCTING A DREDGE HOT WATER SYSTEM.
The stream you are dredging looks most interesting! New Zealand South Island streams of that size are the waterways I find of most interest and if they have steep near vertical sides, like the stream in your photos, then they are of even more of interest to me. And if such a stream has old river bank workings, with stacked tailing's and tail-races, then you probably won't find a better river (provided a professional dredger has not been there before ).
There is a theory among professional dredgers that streams with steep near vertical sides have good gold in them because the miners of the 1800s could only use 'short' sluice box's when digging into the alluvial wash in the riverbanks and they therefore lost more gold from their sluice box's than in areas where longer sluice box's could be used. Its a theory I've always though was credible and some of the richest streams dredged in New Zealand have been streams with steep sides and river bank tailing's (such as parts of Lyell river which produced between half an ounce and 3 ounces, a day, to one dredger).
Regards,
Rob (RKC)
|
|
|
|
Post by RKC on Nov 14, 2008 9:47:45 GMT 12
From: theoriginaldanidor Sent: 20/09/2008 1:44 a.m.
Hi Rob,
Very interesting. Would you be able to explain to me why they were only able to use short sluice boxes in steep sided creeks?
Cheers
Dan
|
|
|
|
Post by RKC on Nov 14, 2008 9:49:40 GMT 12
From: RKCNZ Sent: 21/09/2008 2:48 p.m. G'day lloyd , I had a look for a photo I might have of a dredge that would illustrate, for anyone following this thread, the poor dredge design features I referred to above, however there are few modern dredges that have all the design faults I referred to above. But I did find a photo of a dredge that strikingly illustrates how dredge design has improved over the last 30-40 years. This dredge img.photobucket.com/albums/v172/Coochee/HOT%20LINKED%20PHOTOS/1963Otagodredge.jpg?t=1221957153 is one of the first, if not the first, eductor dredges built in Otago (1963) and could not better illustrate what I have been referring to. The photo was supplied to me by an Otago dredger of long standing who has an interest in the history of eductor dredging in New Zealand. Regards, Rob (RKC) |
|
|
|
Post by RKC on Nov 14, 2008 9:50:19 GMT 12
|
|
|
|
Post by RKC on Nov 14, 2008 9:51:13 GMT 12
From: RKCNZ Sent: 21/09/2008 3:19 p.m.
G'day Dan ( theoriginaldanidor ),
I'll try to do a drawing to illustrate the reference I made above to "short sluice box's", and I will post as soon as I get a chance to do the drawing. And, when I get the chance, I might make a post of how the miners of the 1800s hand worked the river beds and river banks and how it relates to modern day eductor dredging.
I've got some photos on a CD of richly auriferous streams in a gorge with steep sides ... but it might take me a while to find them.
Regards,
Rob (RKC)
|
|
|
|
Post by RKC on Nov 14, 2008 9:53:08 GMT 12
From: dredgenz1 Sent: 21/09/2008 7:51 p.m.
Hi Rob,
Cheers for your comments on HWS.
Yes the place I go has steep sides and old tailings.
You are right about the old timers having to shorter sluice boxes.Its one of my tactics to walk the banks up top first to find the old runs off the bank then start dredging about ten meters back from that.
The gold you see in the pan in my photos is a result from doing just that. 77 grams in two days work and 50 percent was found two feet from the bank and in three feet of water right under where the old timers sluice box would have been.
I find alot of gold this way.I'm going through the red tape with my council at the moment to get permit. In eighteen months gold dredging will be my full time job over the warmer months
I also bought a Minelab GPX 4000 on trademe a few weeks back, its not every day you see these on action here.
I found a 3.6 gram nugget second time out.This gives me something to do over winter. I have a very good place lined up for the gold detector near Springs Junction. DOC land its a shame you cant get a dredge in there.
Keep an eye on my photos they will change from time to time.
|
|
|
|
Post by RKC on Nov 14, 2008 9:55:02 GMT 12
|
|
|
|
Post by RKC on Nov 14, 2008 9:58:15 GMT 12
|
|
|
|
Post by RKC on Nov 14, 2008 9:58:56 GMT 12
From: RKCNZ Sent: 22/09/2008 6:56 p.m. G'day, An aspect of locating tailraces in the New Zealand South Island goldfields is that often the alluvial hand-miners of the 1800s would dig a tailrace into bedrock where they would then place their sluice boxs. And even though their wooden sluice boxs have long ago disappeared, its usually easy to accurately located where their sluice boxs would have been by finding a narrow channel dug into bedrock. Mostly, the miners of the 1800s would only dig down about a meter or less into bedrock, where the bedrock was hard and difficult to dig. But in places where the bedrock was soft they would dig tailraces as deep as 20 feet or so if it assisted the disposal of tailings. However, no matter how deep they dug the tailrace it would nearly always only be wide enough for one man to walk along. Typical tailrace: img.photobucket.com/albums/v172/Coochee/HOT%20LINKED%20PHOTOS/NewImagetailracesouthland.jpg?t=1222058671 Regards, Rob (RKC) |
|
