79 posts in this topic

I have been studying the Reverse Helix Methods of gold recovery recently. I am impressed with the efficiency, compactness, and portability of these self-contained systems. It would be interesting to have open discussion on how well these work in actual practice. :)

 

- Geowizard  

Brent F. Myers likes this

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Todd and the gold rush crew on TV had some wiz bang reverse helix trommel last year. I am not sure if it lasted more than a couple hours before it broke down.

Personally, I see reverse helix systems as unnecessary extra complexity that in many cases (like Todd H) just leads to the loss of gold values.

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My take on the Gold Rush - Alaska presentation of "the Gold Machine" was - how much drama can we pump out of this - rather than demonstrating the technical advantages of the design. First - the delivery was delayed and Todd demanded it be delivered whether it worked or not...

 

Then the electric drive system was inadequate and needed replacement. That was a complete episode of drama in itself.

 

Finally they were getting gold! Then the helix came unglued internally and the system was not catching gold. So, they pulled the plug and didn't have anything to run gold! More drama!  :)

 

That wasn't a "real world" test of the reverse helix - it was a drama pump at the expense of Ray and "thegoldmachine". A later episode that covered the "what ever happened to.." questions, stated that thegoldmachine was taken to a nearby mine, repaired and it worked as advertised!

 

 

- Geowizard  

Ronald C likes this

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Sorry if you don't like my opinion but you asked for input. Minus the drama, the point is the Hoffman unit worked perhaps a few hours at best before it broke and required major work to bring it back to production.

Often small scale mining depends on keeping things simple. Your own operation this summer was about as simple as possible - just an oversized highbanker set up. Maximum simple and maximum ease of operation. Minimum of stuff to breakdown and stop production. I've seen a number of small scale operations that try to operate some sort of "better mousetrap" and spend the majority of their production season tinkering and repairing and not producing any gold. Adding a reverse helix to drag the material against gravity and the flow of the trommel partly to replace the sluice and concentrate handling systems adds complexity, much stuff to potentially breakdown, and replaces tried and true equipment known to work.

The other issue is what material you are using to execute the reverse helix. The tiny systems I have seen use plastic, which may be fine for occasional use by recreational level prospectors, but will not stand the abrasion of commercial level use. The Hoffman system used some sort of glued on rubber wiper, which again is not a good wear surface for gravel processing, You could execute the helix in metal, but it is costly to create and if you have any problems with it, the helix is not easily visible and you would need to do a major disassemble of the trommel to inspect or repair it. If there is a problem with it, you would not even know because for the most part, you cant see it. A sluice on the other hand is out in the open, easily inspected and easily repaired as needed.

I also have run small mining operations, and in my book simple and reliable as well as easy to inspect and repair are far more important than wiz bang better moustraps.

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Clay is what trommels are prized for.  The trommel can be tuned to completely dissolve the sticky stuff.  It does come at a steep price though.  I believe the GM 200 in the video requires a dedicated full-time operator,  there's several systems that need constant attention. 

 

I built an artisan trommel 5-6 years ago because I was going into a clay washing process.  I loved how it handled the job.  However I wasn't out in a remote location nor feeding with a loader.  I would use it again in the future.  My main complaint was,  I and the 2 other guys were always wet from the spray.

 

A vibrating water wash grizzly followed by an aggressive riffle design with a large recovery sluice might be reliable if built strong enough.  Strong is heavy.

 

Chris is correct in keeping it simple, no moving parts whenever possible.  If it can breakdown it probably will.

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I'm already sold on the trommel. I rounded up the barrels at the mine in August. A trommel is the plan. :)

 

 

Right now, it's just scratching out the design on paper, building a prototype at my desert fab shop and running it at my desert proving ground. If it will run for six months with me throwing everything I can at it including some Alaskan gold, then it should be able to be replicated up north.

 

- Geowizard

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So Geo - what are you going to fabricate the helix out of?

 

Glued Rubber? - wrong wont last.

Prefabricated plastic liner? - Wrong again wont last. Probably not available.

Create a steel helix on the inside of the drum with welding rod? Steel is durable, but welding on drum steel is asking for trouble burn through holes will occur. weak spots will rust through and you will loose gold.

 

I'd suggest you will have enough of a headache creating and dialing in the trommel into your system. Make that works right and spend a year thinking about helix systems and if you are still really sold, try to build one for year after next. If you take on too much complicated new stuff all at once you will spend more time tinkering and fixing than you will in production.

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Chris - Yes, that's good advice and probably the best way to try it if that's the executive decision. As we invariably do with most of our " brilliant " ideas, we can always throw it away later or cut it up for spares.

 

Geo - I've just recently seen one for sale that's had very little use. I wonder why ? Not a huge Volume Model but if it could be snapped up at the right price it may well be a low-cost way of field-testing the concept. I'll chase up the Link and get back to you.   

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Somebody, somewhere can recognize a need here.

 

The plastic spiral wrap automotive wireing loom material needs to be up-sized.  The helix is built in.  It only needs to be a full-sized liner inside the structural drum.  Disposable and adjustable to fit most any size drum. There are some substancial PVC sheets available to heat form. 

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 "So, on the interior, add a cylindrical screen 10 feet long with a 15" diameter = 4 ft circumference x 10 ft = 40 ft screen surface."

 

- Geowizard

 

Geo ....

 That maybe be 40' of screen surface but not useable screen surface. You need to cut that figure

in half to be more realistic, even then you would be optimistic. 15" inner barrel is awful small to

try and stuff any yardage through on bank run material.

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Dick,

 

I agree. The reverse helix recovery systems can be ran in parallel as demonstrated with the Exrac-Tec HPC-30 where five systems are ran in parallel.  

 

I remember seeing a Mongolian/Chinese concentrator that used 100 gold wheels. :)

 

- Geowizard

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Is it TOP SECRET - like if you tell me you'll have to kill me? Like the CIA is monitoring the forum and my cell phone (no wait that's the NSA tracking my phone calls).

 

Or are you willing to share?

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Geo - In case you haven't already priced this one, here's the Link I mentioned - 

 

www.savonaequip.com

 

Under Used Equipment, scroll down to Trommels. It looks like it is in fact an Extrac-tec HPC10. You'll have to enquire to get the price. Volume will probably be too small for Ophir Production but it might make a half-decent Sampling Trommel if only the Reverse-Helix works efficiently enough in your Dragline Tailings. 

 

Good luck.

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I've designed and built a reverse helix trommel barrel out of UHMW and HDPE plastics.  The helix is cut from a 12" x 3/4" HDPE pipe sandwiched between a punched 3/16" UHMW inner screen and an 1/8" HDPE outer shell.  It was very difficult to manufacture so I'm not sure if I'll ever use it in my production model unless I can figure out how to assemble it more efficiently.  Also, changes in my plant design negate the necessity for it.  But it was fun to design and build. :)

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I am sold on reverse helix trommels.  At least for small scale stuff as my partner and I do in AZ.  We use the reverse helix trommel to run material when it's too wet to dry wash and also run the dry washer cons through it.  We have to run a recirc system and haul water.  cleanups of the silt from the reservoirs is a PIA but the gold recovery is very good.  We have checked the tailings from the output (good stuff) sluice and the waste tailings and found very little loss.  I attribute most if not all the lost to operator malfunction.  Although rated at a fairly high throughput (optimistic) it is easy to overload the barrel (bucket feed) if not paying attention.  

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Au+,

 

Good report! :)

 

I completed assembly of the trommel/screen and installed it in the outer cylinder yesterday.

 

Today, I am fabricating the hopper.

 

I will post photos soon!

 

- Geowizard

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Can you provide any information on your inside sprial cutter for the leads ?

 

I have a section of 12" x 1" blue PVC water pipe that I would like to cut leads into.

This is a mystery, I heard of others glueing leads into a pipe but cut leads look cleaner.

I have considered using a frame with rollers to turn the pipe while a cheap router on guides connected to a stepper motor is pulled through the pipe.

 

Anything is appreciated.

 

--Salto

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