Subsurface Gold Dredge Mods

[sjmpainter]

Been working on the Subbie and added grizzly bars to the sluice. Hopefully this will help with my material hogging issue.

[deathray]

Nice work man!

[Lanny]

That really is great looking work! Shoot an update when you try it out. I'd love to know how it does.

All the best,

Lanny

[Steve Herschbach]

Really nice work. I always wanted to try that but I also had some concerns. I will relay those to you to keep an eye out for. Here is an ideal riffle vortex per Clarkson at http://emrlibrary.gov.yk.ca/ygs/mining_technology/placerrecovery.pdf

The riffle is not the main gold recovery device, it is the carpet. The first thing I ever did in a subbie is replace the stock carpet with miners moss.

The riffle exists to drive gold to and into the carpet. To do this the vortex must be vigorous enough to keep the riffle open and the carpet exposed to the flow. A very common error for newcomers running a hand sluice is to think they are running too fast and the gold will wash away. So they run the sluice too level or too slow. This allows the space between the riffles to fill and pack, and actually lose more gold than if the sluice were running faster/steeper. Counter-intuitive to what many people think faster or steeper can be better.

Or faster/steeper can go too far, in which case you then have carpet scouring. The flow is too aggressive, scouring out everything between the riffles and blowing the gold out.

The proper solution can only be arrived at through trial and error as different gravel shapes and sizes play into it. The bottom line is adjustments should be made to try and get as near as possible to the ideal vortex pictured above.

A subbie has a very deep riffle for a reason. There is supposed to be a very aggressive flow and in turn that flow keeps that riffle open and working properly.

Therein my concern. If thin rocks get down between the grates and then try to boil back out, only to be stopped by the rails, material could be trapped and build up, leading to riffle packing.

Not saying it will and not saying it won't, but be on the lookout for it. I always wanted to try what you are doing and you have done it far better than I would have. The only real question is - does it really work? I know people who have done similar things and they say it does, the problem always being nobody ever runs serious comparative tests running the same material twice so frankly nobody ever really knows. They are in a poor spot, getting gold, then make the change, get in a better spot, see more gold, and think "aha, my idea worked" and then it just stays that way. Being lazy I ultimately just figured Keene made it that way for a reason and left it open.

I always wanted to have a swimming pool divided with a wall in the middle. Put ten yards on one side with two ounces calibrated gold in material. Dredge it all over to the other side of pool, check results. Put gold back in material, change riffles, dredge it all back to other side of pool, check results. This is the only halfway scientific way I can think of to get seriously good test results. The second best would be to make up calibrated lead loads on an ounce each, varying size ranges carefully the same in each load. Run one batch through while dredging in the wild to check recovery with one riffle set, then use an identical test batch to compare on another run with different riffles. The thing it would be hard to adjust for would be that the material itself would probably vary in each run but if you picked a big gravel bar with fairly homogeneous material this could be minimized.

Simple deal is just run that puppy and go back and check those riffles constantly to be on the lookout for riffle packing.

Good luck, great detailed work, thanks for posting!

[sjmpainter]

I contemplated this for a long time. Really I am unsure how this will affect the riffle area and I come to the same conclusion. Do it and see what the result is. If it works great if not cut it off and go back to the standard riffle.

Don't know if it is apparent? but I did put some thought into the placement of the grizzly. First I used 1/8 inch bars set at 1/2 inch spacing and raised them 1 inch off the riffle. My hope here is to not disrupt the flow of water and destroy the vortex. I really hemmed and hawed on the height but settled for the 1 inch. It is hard to tell but if you look down the tube the bars are in line with the bottom of the tube. This should make for a pretty straight shot out the back.

I tend to hog material and dredge for long periods of time before checking the box. And I can't count the times I have looked to see a flat stone wedged in there. That is the primary driver to the bars. Let's hope it solves that without creating a new issue.

I do run miners moss in the box just left it out for the pictures. I will end up testing some GolHog UR matting in this. Other test I have done with the UR warrant a look see here as well.

I plan to set up to do video clips of dredging this year and I will make it a goal to get something posted for you. I can see this is of intrest to you so plan on a clip of this in operation.

Anyway thanks for the info.

[Steve Herschbach]

I think the placement of the bars is brilliant. Every similar mod I have seen has bars welded right to the top of the riffles. Yours being more open I would think would be less prone to packing.

I am adding video uploading capability to the forum along with the upgrade, would love to see them.

[minerdude]

I built one about 10 years ago , they work good, if you  glue a  bubble level to the top of the sluice and,keep it level. I see you are able to adjust the box, up or down that is a must.. The spacing between the bars seem to far apart( they look like 1", we had ours at about 3/4" center to center If my memory serves me. Most of the gold will be in the first 3 riffles if level . I also built a 6" subbie as you call it (like the name") and ran it with 2- 6.5 Hondas with a power jet, not a nozzle. I wish to this day I had kept it, but sold it to a friend of mine who used it to make a living with it for a few years. Your frame and floats, are they from a full size 4" or did you get the smaller floats? I used my 6" in about 12 ft of water. You do need good floatation for that I used a 6" floats.

[sjmpainter]

minerdude, my 4 inch subbie is set up with Keene 2 1/2 inch floats and that seems to be perfect. The bars are closer at 1/2 inch and the first riffle is open but for the pictures I have a piece of punch plate blocking the view.

I plan to test run this thing at the end of the month so really interested in comments at this point.

I will get some pictures posted tonight of a second sub-surface dredge I am building right now. I would really like feedback on this one as it is a six inch with a twist.

Steve - How is the video uploading addition to the forum? I got a GoPro last week and plan to spend a bit of time next week in Hawaii getting the ins and outs understood.

 

 

[Steve Herschbach]

I have not done anything formal yet but you can just attach an mp3 or mp4 file as an attachment in a message as John has done here

I will get a video section done soon so this is more an interim step. Upload limit I think is 25MB so if you have huge files still need to use YouTube

 

[minerdude]

   I would like to see them both the  6" for sure. I will be in Anchorage this Monday. Maybe we can get together. We tend to dredge in way faster water than most, so flotation for us is a must and also the drag factor   We have changed the blue hoses to the power jet to a black hose with spiral metal, As the blue hose is not really a pressure hose.  They tend to start out as a tiny leak, next thing you have a sprinkler system and duct tape begins. The hose is not as floppy in the water and can be formed in a smaller radius up to the pump. The two hoses can form a rams head .And it lasts longer and is way cheaper to replace if need be. We have not had any leaks yet in two years.

     I know the 6" subbie  can be powered with an 8hp motor pump using a" y" pipe splitter like Daulke did for the dual power jet. Since the 6" tube was so long you can put the power jet right on the intake . Most of the time the dual motors do not need to run full throttle..