Wednesday, October 1, 2008

Placer Mining Equipment: the Gold Trommel

Used Commercially and Recreationally

The gold trommel is a specialized piece of placer mining equipment that is most commonly used in commercial gold mining operations. When employed commercially, trommels can be quite large in scale and are often powered by large diesel or electric engines.

However, many recreational or small-scale placer gold miners swear by these gold-grabbing workhorses and use them extensively. I myself have had limited experience running trommels, but I do know they can be extremely efficient and very effective at recovering fine gold. Additionally, the larger-sized models can handle impressive volumes of gold-bearing gravel when operating at peak efficiency.

Trommel Components

As with all types of motorized mining equipment, trommels will vary somewhat from design-to-design, but all gold trommels will feature most of the following components:

Metal Frame (including wheels and tow bar or hitch): the frame is the trommel's metal "skeleton" and supports all the other trommel components. Invariably, a set of wheels is mounted on an axle at the bottom of the upper end of the trommel and a tow bar or hitch is in evidence at the opposite end (in larger models).

Hopper or "Feeder" Chute: auriferous material is "fed" (poured, shoveled, or dumped) into this square or rectangular "box" attached to the upper end of the trommel.

Rotating Drum or Cylinder: the trommel drum or cylinder is typically constructed of high-grade aluminum, stainless steel, or expanded metal with openings ("screen") in it typically running 1/4 inch to 1/2 inch and is mounted at a downward angle deemed most efficient for gold recovery. The drum's rotation or "spin" can be powered by a number of sources, including small gasoline engines, batteries, "plug-in" electric motors, or large diesel engines (most commonly used in commercial operations).

Drum Side Panels and Tray: the panels prevent material from escaping from the sides of the turning drum and the tray forces or directs gold-bearing material pushed through the trommel screen holes in and downward toward the sluice box.

Sprayer: trommel sprayers come in various forms, but the most common is a length of perforated PVC or metal piping that is fixed in place near the top of the drum but independent of the drum's rotation. Water is fed into the piping via a pump and length of hose, or less frequently, by gravity.

Sluice Box: the trommel sluice box sits below the rotating drum and is usually just a shorter or truncated version of the hand-carried, commercially manufactured metal sluice boxes on the market.

Tailings Tray or Chute: the tailings tray or chute is attached to the lower end of the trommel above the sluice box mount and directs waste material away from the drum and sluice box.

Assorted Motors, Belts, Hoses, Pumps, Pulleys, etc.: These components can vary from model-to-model, but are part and parcel of most gold trommels.

How the Trommel Works

1) The trommel is first set up at or near the auriferous material to be processed.

2) It is then energized, the motor begins turning the rotating drum, and the water sprayer is activated.

3) Material is fed into the hopper box and directed into the angled and constantly turning drum.

4) The sprayer then washes or "cleans" dirt and mud from the material as it tumbles round and round inside the drum.

5) Any pieces of material (rocks and gravel) larger than the drum screen hole size will eventually be forced down the drum into the tailings tray and out, forming a tailings (coarse tailings) pile at the bottom of the unit.

6) The remainder of the gold-bearing gravel will fall into the sluice box below, where hydraulic action traps the black sands and gold while allowing the remaining waste to flow out the lower end of the box into additional tailings (fine tailings).

7) The entire process is repeated until the sluice box requires "cleaning."

8) The trommel is then shut down and all the black sand concentrates and gold are flushed from the sluice box into a container (a 5-gallon bucket for most recreational miners).

9) The concentrates are then panned or run through a concentrator (spiral wheel or blue bowl) and the gold recovered.

That's essentially it.

Advantages: trommels are very efficient gold grabbers and even extremely fine or flour gold in the micron range can be recovered consistently using a properly constructed trommel that is set up for peak operation. Additionally, like a highbanker, trommels can be set up anywhere near the source of auriferous material, as long as water can be pumped or "fed" into the drum unit and there is a power source to operate the unit.

Disadvantages: one of the main disadvantages to using trommels is their overall lack of portability. Unless they are a "mini" model, they typically cannot be carried or "packed in" to remote areas but must be towed to an accessible gold site using a standard vehicle or an ATV. Additionally, they require tools, spare parts, gasoline or diesel fuel (in fuel models), batteries, and the like. But, as I stated earlier, those miners that use trommels swear by them.

If you are (or have been) a gold trommel user and are willing to share your views and experience on using this nifty piece of placer mining equipment, drop me a line. I'd appreciate hearing from you.

(c)  Jim Rocha (J.R.)  2008

6 comments:

  1. Good job, I am collecting parts to build a 4' trommel to use on my bench/bar claim in Alaska. I am planing on powering it with an isuzu 4 cyl diesel engine. Right now I use a sluice box and grizzley, the clay robs gold, hence the trommel solution. The Hitachi EX200 and Cat D6 and 6" Gorman Rupp Detroit 3-53 finish up the setup. A trommel and 5 ton 6x6 dump truck are in the works. Happy prospecting and trommeling! Jay.

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  2. Jay thanks so much for commenting and for providing specific info on your trommel and operations up in Alaska. Your info may help some of those out there interested in using a trommel. If you see this comment can you contact me via e-mail please? (jr872vt90@yahoo.com) Thanks again for your support of the blog! My best, J.R.

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  3. Hi JR,
    I've been using a Gold Claimer trommel for several years now. It was used in the San Pedro mtns for 20 years or more with very good success. I bought it used and had to replace a few parts, but it's working very well for me. The only complaint I have is that the feed hopper is fairly high of the ground. I hope I can find a conveyor feeder to solve that problem and use a bobcat to increase production.
    Rattlesnake Jim

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  4. Thanks for the info on the Gold Claimer Jim. Your comments and expertise are appreciated. J.R.

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  5. For all you trommel builders. I built one a few years ago and love it. One thing I noticed with some constructions is the drive wheels are turning away from the trommel. Wrong, they should turn into the trommel. Better traction that way. Chain drive an gears work even better.

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  6. Thanks for the great piece of info Larry. Your expertise and knowledge are appreciated. Jim

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