Speed up your gold processing work and increase gold recovery with the Mountain Goat Reverse Helix Trommel. This machine is rightly named because it can eat almost anything and is light enough to carry up a mountain!
The Mountain Goat Trommel is a reverse helix system built on the same principle as the huge mining trommels used by large mining companies all over the world, but this is light and portable.
The reverse helix system came from the Archimedes Screw Pump invented over 2,000 years ago by the mathematician Archimedes.
The Mountain Goat is efficient because the spiral riffles inside of the tube turn and bring the heavy materials up to the high end of the tube while allowing the lighter materials to flow out of the back of the tube as tailings. This system makes the trommel completely self-cleaning, which eliminates the need to break down for clean-up as is necessary with sluice box type equipment.
The spiral riffles in the trommel tube are ¼ inch deep and spaced ¾ inch apart. We suggested your placer material be screened to ½ inch or less even though rocks as large as ¾ inch will pass through the tube. There is a nugget trap at the low end of the tube which should be checked regularly for nuggets larger than ¼ inch.
The front legs of the trommel are adjustable to increase the pitch but we found that the factory setting is the best for getting fine or flour gold. The factory setting has the front legs about 1 inch longer than the back legs. Tests have shown very little loss of fine gold at this setting when a wetting agent such as Jet Dry is used in the system.
The Mountain Goat can be used in a large tray, such a mortar mixing tub, with about 5 gallons of water which is then recirculated by a 750 gallon per hour pump. It can also be used directly in a stream.