Water flow in highbanker

[Explorer385]

Hi all,
Been a member for a couple of years and get wonderful information by reading the posts here - thanks to the many who post so much knowledge.
I have a small two tiered high banker which I got form detector den in Batemans Bay and have been trialling different water fow rates high banking for gold on the Mongarlowe and the Shoalhaven when I get a chance.
My question is: how do I determine an appropriate flow rate for water through the high banker? Secondly, how much angle should I run for the lower part with the riffles?

Thanks in advance
Terry

 

[Beagleboy]

What are the dimensions of your banker?

 

[Explorer385]

Its the Eldorado 2 tiered sluice from Detectaden. It is at my Brother-in-laws place at the moment so can't measure it but I guess it is about 900mm long on each tier. It has metal riffles over mesh and blue matting on the lower tier.

I have used it for gold (some minor success) however I think I may have been pumping a bit fast. Looking for some visual clues about appropriate flow rates also some advice about angles.
Thanks
Terry

 

[S.A_Stu]

Have you tried you tube atall mate? Hours of learning and dreaming on there mate...

 

[slowflow]

Terry, it is going to change with material. Usually about 20-25 mm of water over the medium is enough, but look to see the material is 'dancing ' in the riffles.
My sluice runs from about 8 to 15 degrees, it is not critical on the hog mats I run but level across the sluice is critical as is material movement. Less angle for clay. Pump runs at 1/4 throttle which is meaningless due to manufacture tolerances, if you want volume measurement use a big bucket, eg 55 litre and timer.

At Oallen I start at about 8 deg and around 30 sec to fill the bucket on a 12 inch wide sluice, then adjust for the 'dance'. The material has to clear from the riffles (30 to 30 seconds for a shovel in my case) or it can't trap gold. A pan or bucket at the end of the sluice to check for tailing gold content is useful. If there is a lot in the pan, lower and/or slow the flow. Most sluice are good for up to 80 or 90 % catch from my research/experience.

Good luck
Barry

 

[G0lddigg@]

these style of sluices rely heavily on angle and water so make sure you have a a good 20-30mm water at all times, make sure you have a bucket under the end when you shut down as they tend to flush out.

A good rule to use is shovel in some material and count how long it takes for your quartz to clear, 30 seconds is a good gauge as slowflow has said above. change on the day dependent on sediment, water quality and how much screen sized material gets through for each shovel.

 

[Explorer385]

Thanks Slowflow and Goldigg@ - that's very helpful. I must be going too slow with the water as I get lots of smallish pebbles and even some silt in behind the riffles when cleaning out. Have been getting a few specks of gold but nothing to write home about yet but I am pretty sure the bug has got me.
How often are you cleaning out.
Thanks again
Terry

 

[G0lddigg@]

clean out when your material looks too packed up or if there is too much ironstone buildup.

 

[Explorer385]

Another question if you will indulge me: are you pre screening what you feed into the high banker or straight from the ground to the highbanker using the inbuilt screen?
Terry

 

[slowflow]

straight from the shovel.
cleanout after an hour or so in a new spot to see if a move is required otherwise can run all day. Just don't let the sluice choke with material as you won't catch gold.

 

[Explorer385]

Thanks again for the info. Do you use wire or anything for scraping across the riffles if they start to fill up at the head of the sluice or do you just let the flow do the work and empty when full?

Terry

 

[slowflow]

flow should keep the riffles clear of fines, you may be retaining black sand. If your tailings have black sand thats OK unless you're collecting it. That and the gold should be about all your sluice retains when running well but mostly you will also have some other materials retained.

 

[Chewy]

Anyone collecting black sand? Um, I'll bite, why?

 

[Explorer385]

flow should keep the riffles clear of fines, you may be retaining black sand. If your tailings have black sand thats OK unless you're collecting it. That and the gold should be about all your sluice retains when running well but mostly you will also have some other materials retained.

Ah ha! So that tells me I am definitely running too slow. So much for originally thinking I was running too fast!
So it must be a combination of fluid dynamics and the weight of the gold that deposits the gold behind the riffles while still moving the other material through. Such as what happens in a fast flowing stream when water passes over an obstruction.
Simple concept but I was frightened to move water too fast as I feared losing any gold.
I shall try running much quicker next time and also pay particular attention to keeping it level from side to side.
Thanks a lot. I should have been smarter than this!
Terry

 

[mdv]

So it must be a combination of fluid dynamics and the weight of the gold that deposits the gold behind the riffles while still moving the other material through. Such as what happens in a fast flowing stream when water passes over an obstruction.

Terry

Exactly.

Riffles and obstructions cause a low pressure zone where there is a vertical force pushing all material downwards to the bottom. But gold being relatively much heavier will not be so easily agitated (by turbulence) upwards off the bottom. Lighter material will be more easily agitated upwards where the horizontal forces coupled with the upward agitation will then push the lighter material over the riffle.

 

[Twapster]

Hey Terry, don't ever be afraid to ask and also to try different methods. There is no right answer and what works on one sluice may not work so well on another........everyone has their preference on the equipment they use and after a while you get a "feel"of whats working on your machine. A lot also depends on the ground you are working and you learn to adjust.....how much gold if any im blowing out the end........and in fact in the higher clay areas im more excited when I find gold in the tailings...a few specs means my banker will be full of the good stuff. These days I rarely put a pan on the end because im confident of what im catching. I know blokes that spend way too much time checking what they've lost, id rather keep shovelling and those extra few buckets more than make up for the spec or two I blew out the end.

I have also found that lightly rocking my banker is a good trick to clear some material. The gold doesn't float away like the light stuff it tends to stick to the bottom even with a bit of jiggling to clear some build up. The important thing is don't stop and start the flow too much....easiest way to blow gold out the end. Also you may think the water flow is fast, it is often too slow. Having said that, fundamentally gold is way heavier than most. If I end up with a full pan for cleanout I''ve prob been running too slow. I aim for about half to 3/4 of a cleanout pan after running for about an hour, and then I take a rest and pan it out.

The true pros will go all day without cleaning out, but I tend to need my gold fix to keep me motivated thru the day as it can be hard yakka sometimes. Seeing some nice gold keeps my spirits up for the next lot of shovelling!!

Don't be afraid of loosing gold, concentrate of the basics and you will catch most of it........as they say, no one gets it all. :lol: :lol:

 

[G0lddigg@]

great advice offered from our members, i'll only add that with a vortex the greater the force the greater the force if that makes sense. Alot of people freak out when they see how aggressive i run my water but with the right angle that water creates the perfect environment for stratification and exchange by riffles. as twapster has pointed out rocking your banker a bit can really help loosen things up

worth watching a few goldhog videos, while not directly associated with your setup the core principle of fluid dynamics is the same.

skip to 28.20 to see the most relevant which is scrubber mat, it acts very similar to a standard riffle design but with further advancements in smaller riffles in series.

[video=480,360]https://www.youtube.com/watch?v=kSbx3I_OrMA[/video]

 

[Explorer385]

Thanks for the clarifications guys and yes I will ask questions because that's how we learn.
So if I understand what you mean by "the more force the more force" bit is that the greater the flow over the riffle, the less pressure in the area directly behind and below it, therefore a combination of that lower pressure and the weight of the gold combine to drop gold into that area and, once there, there is insufficient flow to dislodge it?

Then, by extension, the added protection of the moss or carpet material combined with the disturbance to flow caused by the expanded metal grill serves to trap smaller particles that have been carried out over the riffles?

If that's roughly how it works then I am beginning to understand the dynamics.

I am happy (even at my age 56) to spend a day on the shovel and do so eagerly, it would be nice to know that my chances are good of getting a bit of a return in the form of some gold.

Be keen to spend some time with others who knew what they were doing.

Terry

 

[Explorer385]

great advice offered from our members, i'll only add that with a vortex the greater the force the greater the force if that makes sense. Alot of people freak out when they see how aggressive i run my water but with the right angle that water creates the perfect environment for stratification and exchange by riffles. as twapster has pointed out rocking your banker a bit can really help loosen things up

worth watching a few goldhog videos, while not directly associated with your setup the core principle of fluid dynamics is the same.

skip to 28.20 to see the most relevant which is scrubber mat, it acts very similar to a standard riffle design but with further advancements in smaller riffles in series.

[video=480,360]https://www.youtube.com/watch?v=kSbx3I_OrMA[/video]

Thanks v much. A picture is worth a thousand words and video even more. Just watched about 6 mins from 28:20 and very very informative. Will watch more of those and learn.

Terry

 

[G0lddigg@]

i think you get the gyst now you can go and dig to china if you have to