Bowling ball and cement mixer?

[Harold_V]

Readers,

I got an email from one of our new readers, who prefers to not post. He (alaska jack) said he's using a bowling ball in a cement mixer to grind chips. Might be worth a try for those that are stymied.

Harold

 

[LeftyTheBandit]

I'm off to the pawn shop to buy a bowling ball. I'll have to rent the mixer. I'm setting up a 376 cpu batch and I want to dust them up before ARing them. I love these off the wall ideas Woohoo.

 

[goldsilverpro]

If you're using anything but a mixer made of heavy duty steel, you'll end up with dents. I did the same thing many years ago, using large bolts and nuts, and produced a very dented mixer, although it did work quite well. I would think twice before renting the mixer, because you may end up buying it.

 

[Shecker]

An article in the California Mining Journal referred to the bowling ball approach as a means of breaking black sands for the liberation of fine gold.
Something to think about.

Randy in Gunnison

 

[viacin]

how about getting a old dryer, silicon all the holes up, taking out the heating element, throwing in your scrap and about 10 lbs of 1/2" ball bearings Seen it on mythbusters when they were trying to tenderize meat.

 

[Harold_V]

I'm of the opinion that it would be a waste of time.

You can get considerable insight on the proper action of ball mills by doing a little research. Velocity is critical---as is ball size. Otherwise, all you do is wear things out by attrition. Assuming you used a ball large enough to do any work (½" is woefully lacking in size), you'd destroy the dryer in moments.

The idea of a ball mill is to carry the charge, balls and all, towards the top of the mill, then drop them just before hitting dead center. It's the dropping that does the crushing. Anything less is very inefficient. Too small of a ball charge and the balls don't do anything.

The mill pictured, below, was made of steel pipe, with a wall thickness of roughly 3/8". The largest balls used were 2" diameter.

Harold

 

[viacin]

Geez, this exists in a commercial form? Now I can just see two rednecks sittin on the front porch coming up with this idea a hundred years ago.

"hey, what if we took a bunch of rocks and balls and spun dem around real fast in a drum. I bet it would crush dos rocks up real nice."

"yep, 'hey baby, bring me the dryer!'"

lol. But seriously, I wish I thought of it, it's a great invention.

 

[LeftyTheBandit]

Harold;
Coming from you I would expect nothing less. Quick question bout your rig.

Do you feed items into the hopper I see top left of the picture?
Does the hopper lead to a screw mill? Feed into ball mill?

I also see that there is a ramp that leads into a scrap box. Does the ramp transfer the mill or does the grind'ed material just flow down the ramp? Is the ramp even part of your mill?

Regards
Richard

 

[butcher]

I Have used my cement mixer with rock different sizes , with water to puverize ore (rock) to mud (fine powder) works great takes alot of time , I wouldnt do it dry. it is hard on an old cement mixer after weeks needs lil repair,and very noisy, My closest neighbor about a mile away thought i was playing the drums day an night, have not put my ceramic chips in it as it splashes and will have loses and these are harder to come by and higher percent gold than ore,am now building a ball mill from propane tank, motor bearings ect.will have gasket on door to keep dust down. also have been breaking my circuit boards up or band saw them, cleaning ferrous metals off,example cut circuit board around connector or gold bearing part, (if for electronic reuse or sell to another pile), this i have been treating in acid peroxide (strong on the peroxide) at first 32%,once almost all base metals dissolved and any flakes settle i save this mud, then my stripped boards get aqua regia treatment or HCL/Bleach to get last of gold of course I have to deal with tin and lead copper ect, to get to my silver and gold. yes viacin us redneck miners been doin it.

 

[Harold_V]

Do you feed items into the hopper I see top left of the picture?

Yes. The ball mill, along with an agitation tank, were built to process a specific lot of ore. I had only four 5 gallon buckets of the stuff, but recovered over 40 ounces of gold. The ore had a head assay that ran about 325 ounces/ton. I say about, because with such a high grade ore, you can get various assay returns, which proved to be the case on the few I had run. So then, the ore, which was crushed to ½" minus, was loaded in the hopper to be fed slowly to the ball mill. It was a continuous operation, not a batch run.

Does the hopper lead to a screw mill? Feed into ball mill?

I designed a feed wheel that had two small buckets. The gear motor you see in the picture reduced speed considerably, then I used the large and small gear belt pulleys you see to power the wheel. I don't recall the RPM now, but it was quite slow. Maybe 10 rpm. The ore was dropped from the wheel into a large funnel/elbow assembly that ran a seal against the ball mill to prevent losses.

If you noticed, there's a cylinder behind the hopper. That contained water that was re-circulated after settling. The water was discharged through a nozzle in the elbow, washing the material into the ball mill. I had a small valve that controlled the volume of water that entered the ball mill, which also regulated the amount of time the solids would stay in the mill. The ball mill sat at a slight angle, to compensate for the large intake than discharge diameter. That was an added feature, when I discovered the original small intake was problematic.

For the record, lime was introduced to the ball mill on a regular basis, to insure that the pH was higher than 9½. The ore was a sulfide, plus likely had tellurium as well. Cyanide alone did very little, but oxidizing with bromine solved the riddle instantly.

I also see that there is a ramp that leads into a scrap box. Does the ramp transfer the mill or does the grind'ed material just flow down the ramp? Is the ramp even part of your mill?

By now you likely understand that the ramp transferred the slurry to the container, where it was classified. I had a fine screen that separated particles that were not fine enough to process with cyanide. They were returned to the mill for a little more punishment. Very little didn't make it through the first screening. To minimize large pieces being discharged, the discharge trunnion had a series of round rods that ran across the bore, preventing anything larger than 1/8" from leaving the ball mill. I had to make the classified size that large because I extracted quite a bit of gold that was up to that size, but nothing larger.

The ore was spectacular----showing bands of gold in areas---although the gold was quite fine in general. Much of it was just a gray looking area, but was gold. A particle magnified @ 400X was totally pocked with tiny bits of gold. It was for that reason that I crushed the ore so fine--so it would all be exposed to cyanide for extraction.

Should any of the readers ever get near my location, I still have samples of the ore, a gift to me from the owner of the ore that was processed. It's a sight to behold! 8)

Hope this answers some of your questions. Feel free to inquire if you have more.

Harold

An added comment.

The chute was made of copper. I originally had hoped to recover the majority of the gold by amalgamation. Turns out the gold wouldn't cooperate. A piece of the recovered gold would float on mercury, and not wet. The solids that I recovered yielded something like 30% gold. It is for that reason I think the ore contained tellurium. I have no way of knowing, not being a chemist