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Post by RKC on Nov 12, 2008 8:39:53 GMT 12
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Post by RKC on Nov 12, 2008 8:41:06 GMT 12
From: Roscoe Sent: 11/07/2007 12:03 p.m.
Hi, Rob, it always makes an old dredger salivate when he sees a new machine getting put together.
I still think the old reversing header box is better in clay-bound gravels c/f the flared tube. Depends on the % of fines in the gravels, I guess.
What brand of compressor is he using?
On another note, I remember a few dredgers using pumps made by Brown Bros. in New Zealand. Were they a success? Are they still made?
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Post by RKC on Nov 12, 2008 8:43:10 GMT 12
From: RKCNZ Sent: 11/07/2007 1:46 p.m. G'day Rosco, This dredge is not the only one being constructed at present ready for the coming summer ... with summer only a few months away hopefully. I will let Coro answer any questions regarding his dredge which is to have its "sea trials" shortly. The point you raise about a "reversing header box" is something well worth discussing further and I'll try to find some time later to post about header boxes in more detail. But for now I’d like to mention that my personal preference is to use diffusers on 'Production dredges' … is your preference for header boxes or diffusers? Both header box’s and diffusers have numerous pluses and minuses and the selection of either on a dredge will depend on many factors (which we might go into later). One aspect of header box’s I should mention now is that their design is extremely important and the finer details must be got exactly right if they are to work. Also much will depend on whether the header box is being designed for a single sluice box or a triple sluice box. The Brown Bros pumps (if we are thinking of the same pump) were used on many recreational dredges in NZ in the late 80s and early 90s as they were easily purchased all over NZ (this pump was used on the Suitcase dredge i125.photobucket.com/albums/p71/auriferous101/suitcase_dredge_001.jpg?t=1184109365) and were an excellent pump for use on the smaller dredges. I haven't seen one in a pump shop for some time and I’m not sure if they are still being sold here. Next time I’m in a pump shop I’ll inquire about their present availability. Regards, Rob (RKC) |
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Post by RKC on Nov 12, 2008 8:44:31 GMT 12
From: Roscoe Sent: 11/07/2007 8:23 p.m.
Hi, Rob. By diffusers, I imagine you are talking about insertion rubber dampers, which I always used on both headers and tapered jets to keep down air entrainment. Clays have always been a bug-bear of mine as there seems to be a thin layer of flat or fine gold that adheres to the top section of clay beds. I rarely bother with a pure clay layer unless it is gritty. Using the usual parallel spray-bar setup in bank concentrators never seemed to do the job, even after recycling, so I rebuilt the spray curtain to include three cross spray-bars. Even so, puggy clay sometimes took two or three passes to completely break up. Most grey or white clay disintegrates readily, but that mongrel reddish-brown stuff just looks at spray jets and laughs. ;D
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Post by RKC on Nov 12, 2008 8:46:00 GMT 12
From: dr_edger Sent: 12/07/2007 3:13 a.m.
Brown Bros pumps?, Got one sitting in my shed at the moment that is supposed to be one, coupled to a brand new 6.5 hp Honda, now it’s a good unit, the 5hp motor being underpowered. Quite rare here. When Miners Den was at Drummoyne in the earlier 80’s they were selling a NZ made pump, it must be the same one, rough looking castings, poor machining and finish put me off buying one originally. If I can put a pic up maybe somebody can identify it?
The open impeller on the Dahlke was a bit of a surprise but then it would be a lot cheaper to make.
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Post by RKC on Nov 12, 2008 8:50:49 GMT 12
From: RKCNZ Sent: 12/07/2007 6:44 p.m. G’day Roscoe, What I referred to in the above post as diffusers is known by the more common name of “Jet Flairs” www.keeneeng.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=JFJN which are a replacement for header boxes. The history of diffusers (jet flairs) is interesting in that they were first used as long ago as the late 70s on the first Precision dredges that were manufactured, and were the invention of Pat Schofield who was the original and only designer of the Precision dredges. freelock.com/graphics/tomato.htm They were then copied by other dredge manufactures … and are now quiet common (as you are no doubt already well aware). There is a good illustration of a diffuser in the following photo of a 10" Precision dredge img.photobucket.com/albums/v172/Coochee/Eductor%20dredges%20and%20equipment/nzgoldZ_015.jpg?t=1184212344I prefer using diffusers rather that header boxes because diffusers can significantly improve fine gold recovery. The main disadvantage of using a diffuser is that the length of a dredge has to be significantly increased to accommodate the diffuser. Regards, Rob (RKC) |
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Post by RKC on Nov 12, 2008 8:52:14 GMT 12
From: RKCNZ Sent: 12/07/2007 6:53 p.m.
G’day Dr_edger,
The impeller on the Dahlke pump was a surprise for me also … it will be most interesting to see how it performs on Coros dredge!
I went into two pump shop here in Greymouth this morning and asked about the Brown Bros pump and as soon as I mentioned the pump is used in suction dredging they knew the pump I was referring to. However they did not have any in stock and said that if I wanted one I would have to supply them with the model number and they could then try to get it in. I had a look at the Brown Bros web site but could not see the pump we are referring to, although they had just about every other type of pump you could think of.
Regards,
Rob (RKC)
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Post by RKC on Nov 12, 2008 8:53:43 GMT 12
From: Roscoe Sent: 12/07/2007 7:01 p.m.
Hi, Doc, some of those early Honor-Bright clones of Keene pumps were pretty rough castings. I remember we had to turn up two impellers to even get them centered.
Hi, Rob, thanks for the Brown Bros info. I heard about them over the grapevine, but never saw one.
I wonder why more pumps weren't made with slinger bars on the back of the impellers instead of seals. The six Everflo pumps ( from Marino Pumps) we used never leaked more than a slow drip.
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Post by RKC on Nov 12, 2008 8:54:43 GMT 12
From: Otago_MinerNZ Sent: 12/07/2007 7:15 p.m.
Very nice looking dredge indeed Coro, look forward to hearing the results from the trials.
Interested in these diffusers, only dredge I have worked with had a header box. Will do some research before asking any dumb questions!
Thanks for posting these pic's Rob, great information for a beginner like me!
Cheers,
Hamish
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Post by RKC on Nov 12, 2008 8:55:38 GMT 12
From: RKCNZ Sent: 12/07/2007 7:33 p.m.
G'day Rosco,
I still have two of the old Honor Brite pumps ... they would have to be the worst dredge pumps imaginable. They have a gap of about 1/4" between the impeller and the casting and had such poor performance I only used them a short time before replacing them. I don't know why I've kept them all these years ... they might however come in handy for something one day.
Regards,
Rob (RKC)
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Post by RKC on Nov 12, 2008 8:58:26 GMT 12
From: dr_edger Sent: 13/07/2007 2:34 a.m. Brown Bros Pump. The one I have was originally supplied by H.Blake, Orange with his dredges. He claimed they were Brown Bros pumps and were cast in Orange, this is a obviously a furphy to put buyers away from where they were sourced from; nobody in Orange has ever heard of them being made there. The pump was originally blue, the inlet 2.5 ins. Now fitted with a camlock, outlet 2 ins. Now fitted to an ideal 6.5 Honda. Despite the rough looking exterior it is a dammed good pump now. Will put up a picture later. The pumps on the Brown Bros website (Australian?) are not the same as it is an entirely different manufacturer, an easily made mistake and why you wont find them there. Honor Bright pumps, later on became the Eldorado's Pumps, yes the fit was terrible and I have had to re-machine quite a few of them in the past, the same with the Jessie. To overcome excessive impeller clearance I machine the inside of the housing true and press in a plastic ware ring for zero clearance, this stops the recirculation of the outlet back to the inlet, this improves the performance considerably, so don’t chuck out those old pumps, give them to me!  Hi Otago Miner, what is the width of your header box? (diffuser as Rob calls them) 4 or 5 ins inlet? it looks identical to the one I have from G.W. of Jessie but have never got round to finishing it off. Artificial grass for matting, yuck Dr.edger. |
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Post by RKC on Nov 12, 2008 8:59:51 GMT 12
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Post by RKC on Nov 12, 2008 9:11:11 GMT 12
From: Roscoe Sent: 13/07/2007 2:12 p.m.
Dunno about these full-width diffusers or flares, as they must slow down the passage of oversize rocks, leading to scouring and re-mixing of the gravels. Which kinda defeats the purpose of stratifying and putting fines at the bottom level. We toyed with sucking the bottom level out on its passage through a smaller ratio flare, and putting it through a separate sluice, but never got beyond the planning stage. Gold King or Treasure Emporium had the right idea of dumping oversize in front of the header, but might have complications in shallow water.
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Post by RKC on Nov 12, 2008 9:12:00 GMT 12
From: Roscoe Sent: 13/07/2007 2:15 p.m. Might be an idea to save those HonorBrite pumps for an eventual Dredger`s Museum. Y`know, where youngsters can come and see what the dinosaurs did.  |
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Post by RKC on Nov 12, 2008 9:15:49 GMT 12
From: RKCNZ Sent: 13/07/2007 4:16 p.m.
G'day Roscoe,,
I remembered last night that Ron and Greg at Prospectors Home used to sell a replacement impeller for the Honor Brite (HB) pumps. I should have bought two back then when I had the chance (probably none around now) and got some more work from these pumps rather that have had them sitting in my garage for years gathering dust. They were such poor pumps I would have never sold them second hand as I would have been ripping-off some poor sod .
The replacement impellers Ron and Greg sold were much larger than the original HB impellers and therefore the gap was much less (solving the biggest problem unique to these pumps). They also had much bigger vanes ... but the downside of that might have been that more HP (Horse power) would be required to run them.
Another problem with those HB pumps is the way they were designed to connect to the engine. The 1" engine shaft needed to have a thread cut on it, or an extension on the shaft with a thread on it ... both presented problems. The Jessie pump system of attaching the pump to the engine is the best method I've seen on dredge pumps as they could be attached in minutes to a standard engine shaft, with no mucking about and wasted time. I was told recently by a Kiwi dredger who bought a Jessie pump from Miners Den about a year ago that Miners Den has changed this and there is now some other way they have devised to attach the engine to the Jessie pumps. I'll have a look at his Jessie pump next time I see him and find out how the pump attaches to an engine.
One incident that really pissed me of at the time (on the issue of attaching motors to pumps and Miners Den) was when I bought an engine from Miners Den in Melbourne (in the 80s) and told them it was to be used to run a dredge pump ... and it was being sold by them as a dredge engine! But when I got it back to Big River and went to attach the pump I found there were no threads cut in the holes in the body of the motor. And apart from being mightily pissed of with Miners Den I was also a little annoyed at myself for not checking and noticing their omission prior to leaving Melbourne with the engine ... however, the bottom line is that Miners Den should never have sold it without it being ready to attach to the pump. As luck would have it Lubo was with me at the time and he had thread cutting tools and cut the threads for me, thus saving me a trip back to Melbourne and a couple of days of lost dredging time (Lubo was always very generous, and if I did not thank you at the time Lubo, I will now ... thanks).
Regards,
Rob (RKC)
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