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Certainly dry washers can be home made. For many years nearly all dry washers were home made. In recent decades, maybe for the last 40 or so years commercial ones have been available and now prospectors have their choice to build one or buy one.

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The concept isn't new;

 

Commercial dry washers may go back more than 40 years - probably 5000 years. :)

 

Many miners in desert regions have used dry washers. It's likely that a few hungry fabricator types got busy selling dry washers and bellows.

 

Bellows have been around going back to the stone age.

 

- Geowizard

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I would really love to see the information you have on 5000 year old dry washers - but I am guessing you are just wildly speculating with no actual data or information on that matter. Winnowing is not the same as dry washing and I will agree with you that winnowing for gold was practiced in ancient times. Bellows for things like forges have also existed for thousands of years also. However putting the bellows together with a cloth lined dry sluice to create an air jig or dry washer as we know it here in the western US, was not invented until the second half of the 1800s. Fine woven, thin cloth that would let air pass evenly under a dry sluice was not possible with the technology of ancient times - and that kind of cloth is an essential item of the dry washer.Dry were used widely in the late 1800s in the southwest US, and also in Western Australia where they are called dry blowers.

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What Chris said.  There are lots of plans and threads on the various prospecting forums.  Some of the plans are drawn by people who could never make a living drafting and it's hard to interpret exactly what the designer has in mind.  There are some very good and reasonably priced commercial drywashers and although I'm an incorrigible DIY'er I think we should think twice before building one.  I've never built one from scratch but I've totally rebuilt a poorly made DIY drywasher that I got from a friend.  He either didn't follow or understand the plans.

 

Most DIY machines are wood, since many of us already have woodworking tools.  The main downside to a DIY wooden drywasher is that they are generally not as light and portable as an aluminum drywasher.  If someone has a sheet metal brake or other means of bending sheet aluminum, then a DIY aluminum drywasher might be a good project.

 

Building a drywasher is labor intensive and unless you already have the equivalent of a hardware store in your workshop, the price of parts adds up pretty fast.  Depends on your individual circumstances and inclination whether it's worth tackling. 

 

One of the main reasons for building one rather than buying one is if you have some ideas or improvements that you'd like to try.  Some areas that I think can be improved are:

 

Hopper Design.  It would be nice to have a larger hopper that will still feed the material evenly and in a controlled manner without either clogging or overloading too much material.  I think some of the earlier wooden designs were better than newer models.

 

Riffle Design.  I think there's room for improvement or at least experimentation in riffle design and spacing.

 

Vibration and Pulsing on Blower Drywashers.   This could be optimized. Some of the commercial models vibrate horizontally and a vertical vibration is better.

 

Flapper Valves on Bellows Drywashers.  I see numerous configurations, some with a large single flap, others with several smaller flaps and some earlier designs with a separate air chamber.  Seems like one or the other is better and some testing might be worthwhile.

 

Bellows Stroke Length and Speed.  Lots of different numbers being used and again some testing might be worthwhile.

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