riffle question

[Russ ECV58]

hey all,
I was thinking of getting the dredge riffle setup for my A52. my thought behind this was, with the taller riffles, I'd be able to run a faster water flow which would allow me to run larger/more material through it, maybe even catch a little more gold. I'll still be using it as a hand sluice, not as a high banker or power sluice. so my question is, have any of you ever tried anything like this, and if so how did it work? would I be smart to just leave well enough alone, and keep it as is?

 

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[Hoser John]

I'd leave it alone myself as you aren't gonna approach dredge velocity unless in the rapids anyhow. If you go to dredge modified hungarians remove the wire from the box as it prevents the knife edge bottom from sealing, not like the L of a sluice riffles seal. Then you gold collects right where it should but with no seal it just goes out the end from riffle to riffle-John

 

[Russ ECV58]

Thank you John, that's exactly the kind of answer I was looking for. I didn't realize there was a difference in the way the riffles sealed to the matting. Since fine gold is what I normally find, I think I will leave it as is.

 

[Kruzman]

Riffle height is based on the size of the material you want to retain, not water speed or depth.

 

[Goldwasher]

Riffle height is based on the size of the material you want to retain, not water speed or depth.

Kinda

 

[junker2k]

Riffle height is based on the size of the material you want to retain, not water speed or depth.

You might want to rethink this statement.

 

[Goldwasher]

As a rule of thumb for good recovery you should classify your material to your riffle height or drop.. 3/8 inch riffles...classify to atleast 3/8....riffles are a set feature the water volume and speed changes based on the waterway.You will mainly change your headflow and angle based on situation.To make sure your sluice is concentrating properly and if you classify to 3/8 and your riffles are 3/8 you should will get very decent recovery.

 

[Goldwasher]

dredges and powersluices have bigger riffle sets because of the increased amount of material they will handle with less classifacation.

 

[Goodyguy]

Riffle height is only one part of the equation. The taller the riffle the greater the water flow needs to be to keep the material moving down the sluice without building up between the riffles no matter what size the material is classified to. Of course larger gravels are going to need even more flow than sand sized material but all things being equal taller riffles need more flow to work properly than shorter riffles.

The shorter the riffle height the smaller the material should be classified to, and the smaller the material is the slower the flow needs to be and the flatter the angle of the sluice needs to be.

For best results run all the same size material at a time. An example would be to run all 1/2" material by itself, then all -1/2" to +3/8" then all - 3/8" to +1/4" and so on. The reason why is because when the sizes of the material being run are all close to the same it's easy for the sluice to sort out and retain the heavies.

For example, if you run all 1/2" and smaller material at the same time and if a 1/2" rock weighs the same as a small flake of gold and the flow and angle of your sluice are set up to wash 1/2" gravels out then it's also likely to wash out the same weight flakes of gold. (not to mention that larger gravels can also dislodge small pieces of gold as they travel down the sluice) But if you are setup to run all 1/2" material and nothing smaller, then no way is a 1/2" nugget of gold going to get dislodged or washed out by those lighter 1/2" gravels. Same thing when you are setup to run all 1/4" material and so on down the line.

Proper spacing between the riffles is often overlooked by the manufactures due to cost cutting priorities. According to scientific studies, to create the most efficient sorting vortex between the riffles, the distance between the riffles should be no more than twice the height of a riffle. Examples would be: 1" tall riffles should be 2" apart. 3/4" tall riffles should be 1-1/2" apart and 1/2" tall riffles should only be 1" apart.

Studies have shown that a sluice with riffles spaced too far apart prevents a vortex from forming between them causing too much scouring of material resulting in fine gold losses. Conversely, riffles spaced too close together will result in too much buildup of material between them also causing gold loss.

Everything must work hand in hand for the most efficient gold recovery to take place. You must have the proper water flow and angle for whatever height and style riffles your equipment has, and run material that is properly classified for that system.

Ok, no one is going to take the time to do all that classifying as in my examples above, but hopefully those who are new to this will gain some insight as to why classifying is an important part of recovering the smallest flakes and specks of gold that really can add up over a season.

For most prospectors it's usually a trade off, save time by not classifying and run material as fast as possible and accept the loss of some fine gold by making up for it by running a greater volume of material. That's fine when you're on some good gold but where I'm from you need all the specks you can get.

Go for the Gold
GG~

 

[Doitlaynstyle]

"Examples would be: 1" tall riffles should be 2" apart. 3/4" tall riffles should be 1-1/2" apart and 1/2" tall riffles should only be 1" apart. "

"Studies have shown that a sluice with riffles spaced too far apart prevents a vortex from forming between them causing too much scouring of material resulting in fine gold losses."

GG as usual you practically quote just how I remember reading it while I was researching it when I went to build my riffles. However these points are not exactly true with all types of riffles. With my Branson Riffles the reason why they failed when they were called Clarkston riffles was because they were usually spaced based on that science. However it has been proven that at 1.5 times height doubled between the riffles allows the dual vortexes the room to function properly. To your credit again when learning how to run my setup I found that 1 foot of drop over 4 feet seemed extreme but it runs perfectly and doesn't miss not even one fine flake of flour gold. I am attaching a photo of the principle BUT I am not going to describe the ONE key trick to making these riffles work the best that they possibly can. (EDIT) THAT SHOULD READ 3" OF DROP PER FOOT. 4" WORKS TOO BUT ITS A LITTLE STEEP AND I HAVEN'T FULLY TESTED IT YET.

 

[Goodyguy]

GG as usual you practically quote just how I remember reading it while I was researching it when I went to build my riffles. However these points are not exactly true with all types of riffles. With my Branson Riffles the reason why they failed when they were called Clarkston riffles was because they were usually spaced based on that science. However it has been proven that at 1.5 times height doubled between the riffles allows the dual vortexes the room to function properly. To your credit again when learning how to run my setup I found that 1 foot of drop over 4 feet seemed extreme but it runs perfectly and doesn't miss not even one fine flake of flour gold. I am attaching a photo of the principle BUT I am not going to describe the ONE key trick to making these riffles work the best that they possibly can.
THAT SHOULD READ 3" OF DROP PER FOOT. 4" WORKS TOO BUT ITS A LITTLE STEEP AND I HAVEN'T FULLY TESTED IT YET.

Thanks for the heads up

Let me get this straight, are you saying to achieve two properly functioning vortices between riffles that the spacing should be 1.5 times the height doubled?
So 1" riffles should be spaced 3" apart angled 15 degrees and maintain a 3-4" drop per foot if you want two smaller vortices instead of one large one? And does the flow need to be slower or faster or the same to achieve the double vortex?

Also what advantage does two smaller vortices have over one larger one? And are you referring to a modified Clarkson with the 1/2" lip or the original angle iron where the lip is 1"


Example below from the Clarkson study showing original angle iron riffles spaced too close and too far apart to create a vortex.




Example below from Clarkson study showing modified riffle with proper drop and spacing to create a vortex.



I'm pretty sure you have seen the Heckler study as well http://www.hecklerfabrication.com/files/sluice-build-partIII-2.pdf

But I have not heard of Branson riffles can you tell me more about them?


Thanks in advance,
GG~