Dry Blowing vs Winnowing

[Goldfreak]

Before the invention of the dry blower people used to sometimes "winnnow" for gold in a similar way they still do in many parts of the world for grain. My question is why a dry blower is more efficient ? Could winnowing be refined to match the dry blower ? ( I am thinking of dropping from a greater height, controlling cross air flow, particle size etc etc ) please give me your thoughts and save me making some likely useless contraption.

 

[grubstake]

Winnowing grain involves the separation of relatively heavy, consistently-sized grains from extremely light husks, which is relatively easy, as the grains fall straight down but the husks act like little sails, tending to catch the breeze and drift away.

However, winnowing for gold would involve the separation of heavy, unevenly-sized gold from a mixture of quite heavy, unevenly-sized rock and soil particles. I'd imagine that's a very much tougher proposition, as only the small dust particles will readily blow to the side.

 

[mbasko]

https://www.goldenpipeline.com.au/the-scheme/need-for-the-scheme/dryblowing/
From the above I gather modern dryblowers were developed from the "winnowing" dry blow method.
To me the advent of "mechanical" dryblowers is more efficient due to the added wind from the bellows or blower rather than relying on the natural drift of the lighter material i.e. by using the bellows or blowers more material could be processed at one time (size of operation dependent) & heavier material (but still lighter than gold) can be removed.
To match that my thoughts would be you would need a long drop & plenty of natural breeze.

 

[Goldfreak]

Would small particles get moved as much as large particles of equal density by a cross breeze ? I am starting to think much of the dry blowers efficiancy relies on the short puffing action having much less effect on high density particles due to not having enough time to overcome the inertia of the heavy bits. Sorry if I stuffed up the physics terminology

 

[mbasko]

With modern dryblowers the efficiency would also come with the ability to set it up or tune it in for optimal results in different areas.
You can adjust the air flow & recovery tray/riffles angle to suit the material your running + the gold being captured in a specific area.
As far as set up goes my knowledge is very basic. Hopefully someone like @Nightjar will see this & explain it better.

 

[Moneybox]

The Winnowing would work quite well if you could control the breeze direction and velocity. Both change too much in a short period of time for this to be a reliable recovery method. The dryblower works on the same basic principal plus a bit of extra assistance from vibration. The main difference is that we have total control over the airflow velocity and volume and we can direct it to where our material is passing through. It's still a challenge to try to get the correct air flow vs soil flow. The dryblower is the best we have in desert environments but it's highly inefficient on some particle sizes and soil types.

 

[Grey Panner]

Before the invention of the dry blower people used to sometimes "winnnow" for gold in a similar way they still do in many parts of the world for grain. My question is why a dry blower is more efficient ? Could winnowing be refined to match the dry blower ? ( I am thinking of dropping from a greater height, controlling cross air flow, particle size etc etc ) please give me your thoughts and save me making some likely useless contraption. View attachment 8617View attachment 8619

I have never used a dry blower but on one occasion, in a bone dry creek bed when we were short of water, I tried winnowing.
I fed the pay dirt from shoulder high into a ground level pan. The wind was patchy and tended to be frustrating. After some considerable time I had collected quite a bit of concentrate.I took this awayand wet panned it later. I obtained several grams of gold but I have no way of knowing how much, if any, I lost during the process.
Winnowing certainly works but you need a steady strongish breeze when working with gravel.

 

[Nightjar]

Have mentioned in another post
Somewhere around early 90's we did a comparison between continuous air and bellows type dry blowers, the bellows/ puffer design won hands down.
The main comparison was we re-ran tailings from each machine back through opposite machines. The continuous air rarely picked up any gold from the bellows tailings, where as the bellows retrieved a surprising amount of gold (fine) from its opposition.
These weren't one off tests, they were over a month period.
Here is a little info on the patented bellows.

https://www.google.com/search?clien...lYBHUk1BGAQBSgAegQIBxAB&biw=360&bih=612&dpr=3

 

[Nightjar]

Regardless of which dryblower you prefer, both have to be set up correctly to be efficient.
The bellows machine riffle we found worked best set at 21° angle. This came about by using shotgun pellets in feed, when we retrieved all 10 pellets we new the set up was near perfect. From there on machine wasn't altered. What I did with mine was set it up at home on a known level floor. Anchored a two way spirit level to a horizontal frame then set the 21° with the riffle.
Out bush set up machine with the level centered, then knew the riffle was at correct angle.
Saw many instances where owners just dragged them to surfaces they wanted to blow, sometimes on a steep slope?
My original dry blower was a Falcon, manufactured here in Perth. Four of us fed it by hand, an hour at at a time.
At alater date I built two scaled down models, sold one, so effectively mine was free and lost count of the ozs it found.
Age caught up with me and swinging a Garrett then later the Minelabs was an easier option than swinging the banjo.
Sold with some regret, the blower went to a VERY happy prospector.

 

[Nightjar]

Four photos of the downsized dryblower I built following the larger Falcon design.




I'm holding a little slug found in top screen of the Falcon.

 

[Nightjar]

Miniature 12V bellows I built, still take this one away to satisfy needs if detecting gets boring.


A 12V gold wheel I built.



A homemade sluice for the end of a days dryblowing clean up.

 

[Nightjar]

At the end of a hard day, cold beer or three coming up.



Wish I could have fitted this one on my trailer to bring home and rebuild.



My mates home built dryblower.

 

[davsgold]

excellent story and pictures Nightjar, very well done, and very well built gear for the job at hand

cheers dave

 

[Stingray]

A more refined form of winnowing is yandiing. I was lucky enough to be shown this art by a couple of old aboriginal women. These ladies were able to work the yandi dish so that the gold ended up in a little pile at one end of the dish. Incredible skills. Note the brush for sweeping out the cracks.

 

[kev205]

I have never used a dry blower but on one occasion, in a bone dry creek bed when we were short of water, I tried winnowing.
I fed the pay dirt from shoulder high into a ground level pan. The wind was patchy and tended to be frustrating. After some considerable time I had collected quite a bit of concentrate.I took this awayand wet panned it later. I obtained several grams of gold but I have no way of knowing how much, if any, I lost during the process.
Winnowing certainly works but you need a steady strongish breeze when working with gravel.

I did have a wiper motor on this for a short while but didn't like taking a battery and didn't like listening to the "clack clack" noise all the time so reverted back to the hand operation