Portable dry washer grizzly

[arizau]

Background and inspiration first. My recently received Whippet dry washer has a diamond pattern (about 1/4" narrowest opening width) expanded metal screen above the hopper. I am currently working an old rocker box tailings pile (virtually all fairly loose thus easily screenable material) as my feed source but, with my current feed, there is probably an equal amount of gravel and fines that goes through the grizzly. The Whippet (and probably all dry washers) hates excess gravel in the feed and that is what I was getting by running what I was digging! I have been screening to minus 8 mesh since my first outing and that is a real butt kicker as we all know and it limited me to about 5 gallons of feed per outing since it has been overly hot for one and then there is the over 90% gravel sized and bigger source material which I have to dig then screen classify before feeding! I thought I was stuck with screen classifying until I thought "Why not a grizzly"? Traditional made of metal (?), nope too heavy...so I came up with this idea, make one from wood.

This is what I plan to do: Glue a frame* onto a piece of 48"X18"X1/4" peg board and table saw evenly spaced kerfs through the peg board alone and then partially rout the kerfs so they are rounded/channeled at the opening but only 1/8" (saw kerf width) at the exit. This will still leave random 1/4" peg board openings but the majority of the material that passes should be almost all minus 1/8". I know I could use solid hard board but I think the additional openings will actually benefit the overall efficiency of the grizzly. I also plan to bias the frame so that the effect is to have slightly slanted kerfing so as not to allow material to skid straight down between the kerfs and encourage the smaller particles to slide diagonally down the channels and give them time to fall through the openings if they are small enough. I know that this will not be the most durable grizzly but will probably last most or all of a season and maybe more. I don't have the slightest idea if this will work yet but if it does, I am sure I will be able to produce more minus 1/8" feed with less effort.

*I will probably have to add some cross bars too to minimize flexing of the peg board.

 

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[KevinInColorado]

Since I have a whippet too, I'd love to hear and see how this goes!

 

[1637]

i use two of the same size screens on top of each other ,then offset them to adjust the size,you can change it for different ground.
thanks brad

 

[arizau]

i use two of the same size screens on top of each other ,then offset them to adjust the size,you can change it for different ground.
thanks brad

After your post I changed my mind and will try offset wire mesh first. At the least, it will be lighter.

 

[1637]

my keene 12volt puffer came with 1/2 and most of time i likes about 3/8.i also use this on my shaker table.
brad

 

[N-Lionberger]

Is the screen on the hopper not replaceable?

 

[arizau]

The hopper screen is permanently attached expanded stainless. Probably most feed sources are high percentage dirt and sand mixed with a fairly low percentage of gravel(?). For that I am sure it is fine but my feed source is mostly mixed gravel with probably less than 10% minus 1/8" hence the need for additional classification to keep from filling the tray with a heavy load of gravel.

 

[N-Lionberger]

Thats kind of lame, maybe you can modify it? I have a few different screens I swap out on my homemade wood puffer.

 

[arizau]

I could have fashioned a screen overlay for the grizzly which is, by design, pretty small to begin with. The fold up screen I built has over 2 times the screening area, is over 1 1/2 times as long and is only slightly heavier than the bucket and bucket screen I was using. It should be self clearing and, with the longer screen run, it should maximize screening. It attaches easily to the Whippet for backpacking. Now all I have to do is wait a couple of months for my prospecting area to dry out again since the area gets almost daily rains during our monsoon season which just started.

 

[KevinInColorado]

Pics?
Your fellow Whippet users are interested!

 

[arizau]

Pics?
Your fellow Whippet users are interested!

I took one picture with it folded up and attached to the Whippet and will take a couple more of it opened and will post them when I figure out how to get them off my cell phone and attach them to a post.

In the mean time visualize this written description........The frame and legs are formed with about 3/4" square wood pieces. I made it so that it folds up like the legs on a tv tray with the exception that it is not hinged from the center but about 6" down from the top. The leg set overlaps the top of the frame so that it can be folded flat (3/4" thick). I over lapped and twist tied together two pieces of 1/2" mesh and secured it to the frame. Over lapping changed the opening sizes to a little less than 1/4" (not quite as small as it may ultimately have to be for my current feed source but plenty good for more normal feed). I also attached a strip of heavy duty plastic sheet to the portion of the leg set that extends above the screen to form a barrier that opposes the screen thinking that that may help to keep the feed from flowing down the screen while still stacked up. That piece might not last long but it is easy to replace and lighter than a sheet of wood.

 

[arizau]

Our Arizona monsoon rains have subsided somewhat so I decided to take the screen out to test it and to see if the rocker box tailings piles I have been working was dry enough to work. It ended up that the material in the pile(s) was easy to screen and seems to be workable/dry washable even though it is still a little damp....I came to the conclusion that since the piles are of previously washed material it has not/does not clump up into clods and mostly separates into individual particles as it slides down or through the screen so it should dry wash ok once it is screened. I brought home a sample of the washer box tails material and another from the screened oversize pile and found gold in both. I was a little surprised to find that, from those samples, the gold found in the rocker tails had the largest pieces found but, at that, they were still all minus 30 mesh (I think a testament to the fact that rocker boxes work well but if there are the means, sluicing is best)*. I expected to see similar size gold in both. I will concentrate on rocker box tails for now but I suspect that the coarse tails does have some larger gold/pickers or maybe even some "chispas" (nuggets that are mostly rock) but those are probably better found by metal detecting.

Why am I processing tailings? I'm old, there are dozens/hundreds(?) of remote but easily accessible (by foot) and fairly loose tailing piles with proven gold and most importantly, in situ placer gold in this area must be water processed due to being encased in a type of hard clay like dirt and there "ain't no water in sight"!

Time to get busy.

*The old timers had to haul water for miles by burro so they did the best they could. Some of what they lost, I plan to recover.

 

[arizau]

I now have had the opportunity to use the screen on a couple of outings. My Whippet really loves the smaller feed. I probably averaged running about 15 to 30 gallons (or more?) of fresh dug feed (picked, dug and screened until I pooped myself out...at 75 it ain't easy any more) but I also re ran all of it at least one more time and after cleanups I am averaging about 0.28 grams recovered/outing. Gas money, yahoo! That to me is pretty good but could be much better if I can just manage to dig more or run across a few pickers. All the gold is 50 mesh and down with many pieces under 100 mesh. Love the Whippet.. On my last outing I kept the cleanups of fresh and re run feed separate and have concluded that I do not need to do that with the rocker box tails that I am currently digging since the gold recovered from the re run was less than 0.01 grams. In the meantime I am out of commission with a recent knee injury but hope to get out again in a couple of days.

I also purchased a gold cube tray, cut it in half and made a mini cube. Boy does it make the cleanup easier. I catch most of the gold on the top tray from which I did not remove the vortex mat. I re ran the tails and recovered 0.07 more grams and suspect there is even more gold in those tails.