your thoughts on expanded metal (catwalk) on a sluice

I have read in a gold book that expanded metal on top of your miners moss but under your riffles will blow out gold??
I guess you need the riffles to lower the turbulence of the water to catch gold but if you have expanded metal under the riffles wouldn't water flow a little under the riffles causing it to blow fines out. I get what there saying now I am confused as 90% of highbankers/ sluices have riffles then expanded metal the carpet.

what are your thoughts??

Everyone will say all sorts of things mate, your best answers will be personal testing. I love expanded mesh and dont doubt its abilities in any way no matter what the setup. Its also true that any gaps can blow gold out, but with riffles and mesh, both hold the gold in the matting very well. If gold creeps out of a main riffle eddy, the mesh will stop it. Theres no perfect sluice or mat for all jobs, usually best to have a sluice you can add and remove modifications per zone easily. Im pretty confident that the gap ander the riffles would blow gold backwards as well, not down the sluice as the eddy current is always throwing the gold to the rear corner of a riffle. In saying this.. a soggy sock and a bit of twine would also catch gold.

What Atom is saying is true.
Also you can over complicate an issue.
It all actually comes down to the operator and how you work it.
My Take.
Don't put the mesh under the riffles.
Put it between the last few riffles.
That way, You have low pressure zones continually under your riffles
promoting a fluid bed and the cat walk sitting in the direct flow also
sitting on matting will enhance the same effect as well.
Like a Wal Banker, You have your cat walk sitting flat on the aluminum
and once the fluid bed forms, will trap fine gold very well.
I have a set of riffles designed and built like this and they work very effectively.
I will put up a photo of them later if you wish.

Its down to the operator mate! Don't set your pump to full blast and don't have you angle to steep!
If the expanded mesh has carpet underneath then no wash out at all should happen! Again its down to you!

Some, US systems that have both mesh and riffles sold in our aussie shops don't even have a lip to hold the carpet down! So the gold goes under and straight out!
Could be one of those systems talked about in the book?

Man you guys are fast! lol

Thanks for the quick reply's guys.
Tathradj a pic will be great.

I do normally run a little river sluice after the highbanker to heap catch the blow out gold. the river sluice has only expanded metal.

ben2363 said:

Thanks for the quick reply's guys.
Tathradj a pic will be great.

I do normally run a little river sluice after the highbanker to heap catch the blow out gold. the river sluice has only expanded metal.

Click to expand...

Do you ever catch anything in the second sluice?

Not too much I hope.

My 2 cents.......

I use ribbed v matting as a base
Then miners moss on-top
Expanded mesh across the top of that :8
and metal riffles to finish and lock it all in

The riffles are attached to "swing arms" that are bolted on at the rear of the sluice and fold down across the top of the sluice and lock in at the base with a wing nut and a bolt, with this design I have found that all the matts and mesh are compressed by the riffles just enough to stop washouts

As AR said expanded metal or the riffle (some designs) will push material up your sluice. A good read on the subject is:

http://www.hecklerfabrication.com/files/sluice-build-partIII-2.pdf

Read also the Poling and Clarkson research referenced in the document.

Riffles on top of expanded in my opinion compete against each other creating a gold loss due to the fact neither work efficiently together as they would have acting independently, which might be what your book is referring to.
Jon

first time running with the 2 sluices I didn't even get a spec of gold on the second sluice but the second time I got about 7 fly poo specks.
blisters that's for the link good read.

I welded some flat onto the mesh as a riffle at about 3" spaces, then sealed the bottom holes with stickaflex to stop water going underneath; works great with miners moss or mat underneath.

That pic was the first attempt, I made the gap wider to allow the water to ripple better.
Cheers LL

smart thinking limpalot

Sorry for delay but here is my riffle setup for my Wal Banker.
Have a carefull look at them.
What I do is take the original's out and these just sit in the sluice.
You have to be a little careful on amount of water and material
you are processing.

The actual riffles vary by a few degrees and distance apart, not much again
with the first one set more upright to act as a nugget trap and smooth the
fluid bed before hitting the combo.
Also, The riffles sit a little above the mat causing a slight pressure
wash under the riffle to keep black sand from compacting.
I have never found Gold after the 4th from the right.
Water flow is from the right to the left.
Have Fun.

thanks heaps Tathradj

Hey Tath, just curious why you have the expanded mesh if no gold ever gets that far?

Occ Panner, That is for Gem Stones and any wayward large Nuggets that find their way down
the sluice.
Actually been thinking about taking the first one out as it does nothing but trap ironstone.

Ha ha, but then the second one will trap all the iron stone.