Faster Production Speed

[Admiral Crunch]

I've been lurking a bit through the sluicing section and there are some mighty impressive home built boxes and setups on display here. In the never ending quest for knowledge about all things related to sluicing, I am stumped on a few issues and figured why not ask a much more knowledgeable community.

A bit of background, me and a friend completed our first season of prospecting on the the san gabriel river in southern California last year and are chomping at the bit to continue what will likely be a lifelong obsession . We have met a few really cool people who were willing to share some tips and have tweaked our gear with those suggestions in mind. We are currently running a 3' jobe sluice with a custom extension/auto-classifier I built out of sheet metal and 1/4" hardware cloth. Basically up to version 4.0 after trying a number of prototype versions made of wood using different sized screens. This was built over the winter and we have not tried it yet so this may alleviate part of the issue we are struggling with.

This brings me to the main sticking point of production speed. It seems like it is extremely easy for one man digging at a moderate pace to overload the box. While not the strapping young lads we once were, we can still move the gravel pretty good. I have read more flow or velocity (increased box angle in the absence of 'natural' velocity) is the key to higher production speed but too much will blow the gold right on through. Our experimentation with angles seems to be hit and miss. 1" of drop per foot of box isn't even going to cut it in our usual spots so we increase it beyond that to possibly unreasonable angles. It seems as if there is a theoretical maximum feed rate for a given box at a given GPM of flow before you start losing gold.

With all of that out of the way, any suggestions for getting the production speed up? It would be nice to have a setup that say 1 or 2 men could fast and furiously shovel material into all day. I am toying with the idea of building some kind of modular long tom that could be quickly assembled on-site but don't know if this would address the issue of overfeeding even with increased flow. Should we just not fear the extreme flow required to clear the riffles in a timely manner? Or is it unrealistic to expect a 3 foot box to cope with a fairly brisk feed rate? 20-30 seconds between shovel fulls is not that great. I could see that for a home cleanup box where you are gently feeding in concentrates but I do not like having to slow down while on the river. When you are feeling it, might as well go for the glory

 

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[KevinInColorado]

Wider sluice for more material. Too steep WILL mean you are losing finer gold.

How about bringing two sluices to the river?! I have seen one guy alternate shovels back and forth between two. Get two diff styles of sluices if you do this to give more versatility to your collection of gear...maybe a fluid bed or molded plastic drop riffle style (angus Mackirk) for example.

 

[Admiral Crunch]

Interesting, for some reason I was stuck on the idea of a secondary box after the jobe (in line) but kept coming to the conclusion that it would only buy a few more shovel fulls before plugging up and that really doesn't solve the problem.

I ended up grabbing a 1x10x5' and 2 1x6x5' from home despot's scrap pile for a total of $4 with intent of making another box. You have certainly given me a few good ideas. After seeing the old timers using long toms of varying lengths, going wider than 10" or side-by-side and alternating shovels never really dawned on me for some reason

Also the drop riffle is kind of intriguing. I was aware of their existence but had not done the homework on overall effectiveness vs hungarians. Seems its time for another prototype and technique tweak.

 

[Astrobouncer]

Look into fluid beds man. Raised riffles sluices process material slow, its just how they work. Drop riffles are a little faster but still way slow compared to a fluid bed. I have a punch plate drop riffle sluice and it sits gathering dust most of the time for one of my fluid beds. A well setup fluid bed is about like running a back packable highbanker, except you do have to shovel out from behind it.

 

[Admiral Crunch]

Thanks for the info Astro. I was not aware of this concept but after some quick googlefoo, think I get the superficial details. So I saw your mini passive version and build pics and REALLY like the idea of going that route if possible.

You are depending on the lighter material to 'boil' out of the trap at the end? Do you maintain the taper to prevent a static water column from forming and refusing to spray out the bars in the trap? I am not opposed to grabbing a pump and motorcycle battery, but passive is very intriguing since we have to backpack our gear in potentially up to 5 miles. The gears are turning upstairs which is great, just a few details to work out.

Is there an optimal ratio for the under-chamber opening for lack of a better term? More specifically if, for the sake of discussion, you were going to build the bed so you could place a 10" x 36" sluice on top of it and discharge into the bed as a secondary trap how tall would you build the inlet assuming 1/2" or 3/4" pvc for the agitator nozzles? And one more question, how long of a screened off runout would you build beyond the end of the box (the area that overloaded-so-still-gold-bearing-sluice-tailings can fall into)? I'll post some pics once the build under way if anyone is interested. Looks like goodyguy has a pretty mean machine going on his design too with the funnels down low. Plenty of ideas going around, but a starting point would be nice.