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Classifying for the drywasher


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I would think it would depend on the type and size of your drywasher and the material you are digging. Not a one size fits all kind of deal IMO. That said, I think 1/4 inch is about right if you want to take the time to classify rather than just shoveling directly into the hopper of your drywasher. It is my feeling that feed rate and angle of the riffle tray is more critical than size of material within reason. Operating a drywasher efficiently seems to be as much art as science. lots of observation and practice to get it right. A continuing learning process as experience is accquired. I am sure others with more experience will post their observations and recommendations.

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I took some 1/8" or 1/4" wire mesh, cut a piece out to fit the top of the dry washer classifier, then simply shoveled it on top. Can fill bucket and pour on top also. in either case you still have to use your hands to prod the dirt through. I find classifying using screens on a bucket to be onerous and time consuming. I find some areas don't need any classification at all.

http://www.louispage.com/blog/bid/10206/Do-You-Need-Wire-Mesh-With-Small-Openings

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I try to keep my feed rate low thinking that too much too fast is a bad thing. But the angle of the riffle tray is what I wonder about sometimes, I have seen steep angles and not so steep angles. Some folks use a low angels when processing wet sand they say it help to dry the sand out, I don't know if does or not. I would think a low angle riffle tray would slow things down a bit and allow for the capture of smaller gold fragments. So I guess my question comes down to "Is there a preferred angle for dry washer riffle trays?"

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I'm with SLNugget - I classify to 1/4 in prior to running through the drywasher. I know many don't classify, but I do. I believe it helps me to remove a few of the many variables that effect my drywasher set-up. It assists in allowing a lower speed on the motor and a flatter angle on the tray due to not having to try and move larger material through the tray.

Gaius -

I also use only enough angle to keep the material moving through the box. I look for the "chocolate waterfall" over the riffles. I like to be able to see a little, I said little, shine off the riffles as the dirt rises up and over the riffle. This is what took me a while to learn ---> one angle does not fit all conditions. I learned that what I was looking for was not the perfect angle for all, but the propper angle for the current conditions that gives me the dirt flow I discribed above. On occassion, I will have dirt so moist that I have to run a steep angle to keep it moving. When this happens, I run it through the 151 once to dry it, then I flatten the angle and run it a second time for my gold recovery or a pack up and go home and wait for dryer conditions.

Hope this helps,

-Joe

Edited by campbell954
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I have been using a wire oval basket with a nice long handled (generally used for wok's frying) to classify. The screen has various sizes the largest being about a 1/4 inch or so. I set my dry washer up so I get a nice even flow of material over the riffles, but I usually don't see any shine off the riffles. The last couple of trips I have been placing the riffle tray angle a little flatter in an attempt to slow things down a bit. I take along 4 buckets 3 to hold what been classified for the dry washer and the other holds what I pull out of the dry washer. Plus I catch the dry washer run off and run it back thru the dry washer. I'm not sure what the right answer is for the blower motor speed so I have been playing with the speed, I'm thinking about just leaving the speed alone.

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You must run a metal detector over your +1/4 inch rock pile. My girlfriend is wearing a nugget today that came out of my +1/4 rock pile. The nuggets found in your +1/4 inch rock are usually too clay/dirt covered to find without a metal detector.

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If you have a classifier on top of the hopper, I don’t believe in classification prior to dry washing. I have done it before, but it chews up a lot of time. The top of the hopper has something to classify to. I’ve classified to 1/8” before and the flow can be adjusted smoothly so that the hopper door doesn’t clog up. If I classify to bigger, then the hopper door gets clogged with +1/8” material, but a coat hangar opened up can fix those clogs without slowing down production. The hopper on top of my drywasher is either 3/8” or 1/2" expanded metal. The rocks bigger than that just fall to the ground.



Classifying to smaller than the hopper takes chews up a lot of time. It can slow my production down from digging and processing 3 or 4 buckets an hour to 1 bucket an hour.



If I’m moving material to the dry washer, I will classify it to ½” first so I only lug dirt that will go through the dry washer.



The material we’re working now seems to find about one +20 mesh piece every couple of buckets and a few smaller specks per bucket. This is from wet washing and we’re still honing the drywasher. Dry washing moves so much more material so 50% of 20 buckets is better then 98% of 5 buckets.


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Chrisski (and others)

How often do you clean out the lower riffle tray? I've heard every two or three buckets you should clean out the lower riffle tray.

At what speed do you run the blower motor?

I'm assuming you built a classifier for the top of your hopper, what did you use for materials and did find your materials at Lowes/Home Depot?

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The hopper on top of my drywasher is either 3/8” or 1/2" expanded metal. The rocks bigger than that just fall to the ground.

I had a 151 with the expanded metal on top. I was very surprised with the large size of rocks,etc that were able to go through that classifier. The wire mesh screen took care of that and improved my yield at the same time. The adage "haste makes waste" also applied to my situation when dry washing.

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i just add a piece or 1/4" hardware cloth over the riffel tray.

Some locations have fine gold and not enough smaller dirt to run through the dry washer well...

Too many rocks and it will starve and the riffel tray will load up with worthless rocks...

It all depends on hat the material your processing is like and what the gold is like....

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I’m by no means an expert, I’m still honing the method each time I go out, but here’s what I do….







I have a Gold Buddy Colt which is the medium of the three smaller gold buddies and the classifier is expanded sheet metal. I’m not sure if the size is 3/8” or ½”. Home Depot lists it on the website as in store, but I’ve never seen it. It is just like the expanded sheet metal you see sitting on top of a the carpet on a sluice box. The hopper is set up at 45 degree angle and I just shovel the dirt on or pour from a bucket and the bigger rocks fall to a pile on the ground. The expended metal is tough enough to last, whereas the wire sheets would eventually wear out.



I’ve tried to build my own classifiers with ¼” wire screening, but it’s been a disaster. I tried to put the wire over the bottom of a five gallon bucket I cut out and putting the top of a five gallon bucket over it, to make it look like a bucket classifier, but it fell right apart after cutting my hands. I’m not very handy, I don’t have a lot of tools, and whenever I try building something by myself, I end up spending more than I would have if I bought it new or used. This wire sheet may not be strong for continued production to put on top of a dry washer.



I’ve tried to price making my own sluice at Grainger, but materials are more than a new sluice.



I used to use a Gold Cube, and classifying down to 1/8” took up to one hour per five gallon bucket, so I am trying to concentrate on running more material by classifying less.



I run the blower motor enough so the material slides smoothly down the lower tray and I set the hopper door so that the material leaves the top two riffles visible as it flows down. For my small four cycle leaf blower I bought at home depot, this comes to a little more than ¾ of idle. I’ve heard of some people that run the blowers at idle, but I have a smaller leaf blower and I think they may have a 3.5 HP or 4.5 HP blower that was built specifically for dry washing like you would attach to a larger dry washer like a Keene 151. After watching the material go down the riffles for a while, you can see the material get aerated, and even see the lighter material float to the top, so it becomes understandable how the material gets fluidized. It took me months of watching before I finally understood.



I’m still experimenting with emptying the bucket, so I’m trying with 5 buckets in production. Most of what I do is sampling, so I empty every bucket and run it separately. For sampling, if there’s gold in the sand, the dry washer will pick it up. I’m just not sure of the recovery rate. For production, I used to run two buckets, but I’d bring home so many tailings, I am trying to trust my equipment more and I now run five buckets.



I’m convinced that when I find a spot for true production, I’ll have to move hundreds of buckets of material to get on ounce of gold. If I find a spot like that, I can’t be emptying the riffle tray every two buckets, and I can’t be classifying down to 1/8” for hundreds of buckets. Running hundreds of buckets with a drywasher will take days of dawn to dusk labor. I bet this will fill up several five gallon buckets of cons emptying every five buckets. It’ll take me days to go through those cons, so I don’t need twice as much material.



I wish the desert washes I work in ran with water. With a dredge, I could move the amount of material I want to.



The spot my partner and I work now is just enough to keep coming back, but not enough to go into true production mode.






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I always try to use my time best when out digging. I'm spending gas, and energy to get out there so I try to make the most of it while I'm there. I feel like classifying, and then running the dirt through the drywasher ( essentially classifying twice) is pointless and is time you could spend running more material. Bottom line is, once you've found a gold bearing spot, the more you run, the more gold you get. So no sense wasting time because like Chrisski said, it will take hundreds of buckets to get that ounce. Put whatever screen size is best for you on your drywasher. I also think classifying and throwing out all the bigger rocks as soon as you dig them also costs you gold. I like to get a big pile of loose material together, enough to get a good run out of ( around ten buckets is good for my drywasher). Take out all the biggest rocks but leave anything two inches or smaller in your pile. While I'm digging and getting my pile together, I make it a point to flatten it out and walk over the dirt I want to run as much as I can. This smashes all those clods up, and grinds some of the dirt stuck to those bigger rocks off. I try to knock as much dirt off all the rocks that will be classified out so any gold that's stuck to them doesn't just get tossed over your shoulder as soon as you take a rock out of the ground. Some days I will spend the first 3 or 4 hours just digging and getting a runnable pile together. Then halfway through the day I put everything up in my car except for the shovel and drywasher and I know all I have to do for the rest of the day is run that pile of loose dirt. I like this method because after digging and walking back and forth across that pile of dirt all day, it really breaks up all the chunks to free up that trapped gold.

Edited by King
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Just shows to go ya, there are as many methods as prospectors! I think I like the walking back and forth on the dirt all day to break it up. Anything to make it easier. :)

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