here's an article from Royal Manufacturing one of the three largest drywasher producers in the world
Here is the article that we wrote on drywashing. Hope you enjoy it and find it helpful.
Since the Southwest states are arid, a drywasher is the best choice for gold recovery. By using a drywasher, you can prospect in desert areas or most any area void of a nearby water source where the ground is absolutely dry. Without a drywasher, the prospector would need to transport all water needed to process his material making this method impractical.
There are 3 basic types of drywashers on the market today with each having its own Pros and Cons.
First, there is a Hand Operated Bellows Type (Puffer Type) This drywasher is operated by turning a crank or pulling a rope to activate a bellows. By forcing air from below and through the cloth of the recovery tray, light dust and dirt particles are slowly pushed over the riffles and eventually over the last riffle to fall off the edge of your drywasher. At this point the dirt is called tailings. Gold, however, remains trapped behind the riffles. If, however, you discover gold falling off the edge, then you are at too steep an angle. The Pros associated with these are that they can be easily built of wood with plans available on the Internet. These units can be built for less than $100. No gas or batteries needed. Manual drywashers produce virtually no noise. And theyre very light and easy to carry. Cons, however, are that it only works as long as youre cranking. This makes you more prone to develop crank fatigue. You cant feed and crank at the same time making the machine too slow. And, youre in the dust zone (breathing dust) whenever youre cranking it.
Second, there is an Electric (DC) Operated Bellows Type (Electric Puffer) This operates same as a manual machine except that an electric motor is used instead of the manual crank. The Pros of this type are that they produced low noise and have a longer lasting commercial construction. They have a no maintenance electric motor. And youre able to stand upwind of dust zone. The cons of this type are that the battery is typically heavy, a vacuum on the down stroke causes ultra-fine dust particles to fall down into the bellows area reducing their efficiency thus requiring the bellows to be cleaned out every few hours. And there is little to no vibration. Capacity is better than the manual machine, but not as capable as a gas blower operated machine. Price range is also mid-range ($450-$800)
The third type is the Gas Blower Operated This type is run by a gasoline operated blower. You can reduce the price of the unit if you run it using a leaf blower that you may already own. This machine has a greatly increased production capacity and there are many machines to choose from and different quality levels. Some machines even have heat induction which dries damp material as its being processed! With constant air flow, there is little dirt collected entering the recovery fan box as opposed to a puffer type. Greatly increased vibrations causes gold to settle much faster increasing recovery rate. Units with the recovery box not grounded can generate an electro-static charge, which causes fine gold to gather at the riffles.
The Cons of these machines are that they are extremely noisy. The constant whine is so distracting, that communication with your prospecting partner is very difficult. You might even have to develop hand signals to communicate! There are more components to carry into your site sometimes requiring a second trip. And lets not forget the engine problems Air filter clogs on motor air intake, hard to start when cold or stored for long periods of time. Price range is the highest ($500 - $1600)
When selecting an area for digging for gold, dig no closer than the drip ring of trees and bushes and confine yourself to the smallest practical area to reduce the environmental impact you have on the area. Beware location of local animals burrows and lairs as to not disturb their homes. Be especially attentive of tortoise burrows as they hibernate during the winter months when most prospectors actively drywash. Dont pick desert tortoises up as they will empty their bladder and loose needed water to survive. Refill holes you dig with tailings from the material you process. If you cannot refill completely, then leave the holes graded to at least 15 or less so tortoises can walk out. Also when digging, you will most likely run into all kinds of human left debris, while not a requirement, the conscientious prospector would take any debris that is processed in the drywasher home and dispose of it properly. Im continually finding shotgun shot, lead bullets, copper jackets and shotgun shells and cartridges. I always take this trash home to throw away.
When selecting a blower for your drywasher, you should opt for a 4-stroke over a 2-stroke. 2-strokes are less environmentally friendly, and you dont have to hassle with mixing oil with gas. Most people mix more oil than whats required, causing even more pollution. If you do decide to use a 2-stroke, premix your fuel and oil properly in your garage so you can clean up any spills.
If you have a 12 VDC drywasher, select a battery that is fully sealed so when it tips over, either in the field or in the back of your truck, you dont leak battery acid all over.
In short, a drywasher can move a large quantity of material in a short amount of time. And thats what gold prospecting is all about. Moving a lot of material to find a little bit of gold!!
By,
Robert Rieck
Royal Gold
www.royalmfgind.com