# 30 gallon steel drum o.k. for ball mill?



## 924T (Oct 13, 2012)

I'm looking at building a ball mill out of a 30 gallon steel drum, with speed-controlled direct drive with an a.c.
motor powered by d.c voltage, with a speed controller [the a.c. motor being run by d.c. is not my idea, I saw
it here on the forum, liked it, double checked it with an electronics friend of mine who told me it's done all
the time, but I can't remember who posted that].

Is a standard steel drum heavy duty enough to use for a ball mill, or would it need to be reinforced in
some way?

I understand it'll be noisy, but I know enough about acoustics, and have a real time analyzer, that I can
identify the strongest frequencies generated when the mill is running, and design suitable countermeasures
to keep from driving the neighbors crazy.

Cheers,

Mike


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## butcher (Oct 13, 2012)

I think you may have that backwards.

You can run a DC motor, using diode or a diode bridge to rectify the AC current to DC.

It would be much more difficult to run an AC motor off of DC current without some type of converter which would be much more complicated than just a diode.


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## goldsilverpro (Oct 13, 2012)

I think that, if you use balls large enough to properly drop from the apex and crush the material, that thin drum will be severely beaten up in short order.The drum might last longer if you used it as a rod mill. I'm thinking 4 or 5 steel rods about 1.5" in diameter and about 4" shorter than the drum. May or may not work, depending on what type material you want to crush and the rotation speed. One place I worked rotated a 55 gal drum on rubber drive wheels with 3 or 4, 1.5"-2" rods to grind and blend silver ash with borax and soda ash, to prepare it for melting.


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## NobleMetalWorks (Oct 13, 2012)

924T said:


> I understand it'll be noisy, but I know enough about acoustics, and have a real time analyzer, that I can
> identify the strongest frequencies generated when the mill is running, and design suitable countermeasures
> to keep from driving the neighbors crazy.
> 
> ...



I owned a car stereo/alarm pager/cellular phone store in 1991. We were competing with our sound systems in IASCA for sound quality. I used to use low watts, to get the same exact effect as the big guys did without all the power consumption. I did this by using a product called "Dynomat"

http://www.dynamat.com/

So fast forward years later, here I am starting out of my garage with a lab and industrial equipment. Ball mills need to run through the night, so major problem. I don't want it to seem like I am demolishing cars in my garage. So I used Dynomat to create a sound barrier, just like I did in cars to keep the sound inside the car, so I wouldn't have to use more watts to push more power through the leaks. The stuff works so well that you can blast a car stereo and not hear very much on the outside. So I used it to wrap my ball mill barrel, on the outside. It also has another benefit, it sticks to the rollers better. All you hear is the dull sound of things moving around inside it, but you cannot even hear it outside the garage. All it takes to apply is a heat gun and patience. This might be an option instead of using expensive sound cancelling frequencies, less expensive I imagine also.

Scott


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## 924T (Oct 14, 2012)

butcher, 

You're absolutely correct-----------unfortunately, I did have it backwards. I was typing a little too fast for my own good.

Thanks for the correction!

Now I've got to figure out how to figure out what horsepower will be needed to turn the drum
to mill a 25kg load.

Cheers,

Mike


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## 924T (Oct 14, 2012)

goldsilverpro,

That is exactly what I was concerned about, the drum becoming deformed due to lack of wall thickness.

I've read in several posts months ago about several GRF members having heavy-duty inner liners in
their mill drums, but I have no experience or frame of reference with how one would source the
liner material, what it is, and how it would be installed.

I'm looking at milling CPU and/or BGA chips; I don't know if that's easier or more difficult on the drum than 
milling quartz ore?

I don't have any 1.5" steel rods on hand, so I'd have to go hunting for something like that.

I do have some polished steel rods from old HP inkjet printers (that the ink cartridge carriage rode on);
I'd have to measure them, I'm guessing they're maybe 5/16-3/8" diameter. I had a funny feeling that I
shouldn't take those to the scrap yard, and am now glad I hung on to them.

I see plastic 50/55 gallon drums available on ebay all the time------would those actually be a better choice
than steel?

Cheers,

Mike


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## 924T (Oct 14, 2012)

SBrown,

Hey, thanks for the Dynamat tip!

I was building and selling and renting p.a. systems back in the 70's and 80's, and it was always a challenge
to get the gain up high enough for the stage floor monitors (now that challenge is handled by computerized
sound processing systems----they even track the thermal stress the speaker voice coils are under when in
concert, and will temporarily back the wattage down a bit until the voice coil(s) cool back down into the 'safe' zone.

So, being a bit of a dinosaur, I hadn't heard of Dynamat-----I read the product overview PDF, and it looks like a well
designed product---------I'll have to download the technical specs PDF, because I'm now curious as to what
material(s) they're using to get the job done.

Very interesting stuff, and certainly a lot simpler (and hopefully cheaper, er, more cost effective) than doing a real-time
frequency analysis and then doing all the recording studio type design to kill the selected problem frequencies.

Thanks again,

Cheers,

Mike


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## goldsilverpro (Oct 14, 2012)

924T,

I can't see the 3/8" rods doing much unless, maybe, you had about 50 of them. Also, they're probably too short for a 30 gallon drum. If they worked their way cross-wise, it would be a problem.

______________________________

If I were to ever make a simple ball mill, I would use about a 30" section of large diameter (say, 20"), heavy wall, steel pipe, with ends welded on it. I might make it a bit shorter but I would still make it at least 20" in diameter for a decent ball drop distance (I've seen pictures of ball mills that were about 4' in diameter and only 12"-18" wide). I would want it to be at least 1/4" thick, but 3/8" would be better, especially for the end pieces (maybe even 1/2" for these). A fairly large (say, 8" x 12" - for easier material clean-out) door can be made from a piece of the same pipe (has the same curvature). The door hole in the pipe would have bolts (at least 1/4", probably 3/8") welded around the perimeter with matching holes (slightly oversize) in the door. I would weld a handle on the door. I would use a thick rubber gasket (say, 1/4"-3/8"), with matching punched bolt holes, between the mill and the door. Wing nuts and washers could be used on the bolts. It would be mounted on a heavy frame and possibly chain (heavy) driven with heavy duty bearings on a large shaft. There would be enough room under the mill to dump the contents into a fairly large bin. To get the balls to drop from the apex, the proper rotation speed should be calculated, using well known formulas, before building the drive mechanism. I would probably use at least 2" balls. It would be extremely noisy. Ear plugs or earmuffs are necessary. You can buy acoustic blankets but they aren't cheap. A small acoustic room could be built. The Dynomat sounds interesting.

There are many other styles one can make but that is about the simplest. I've never made a ball mill but have seen and used several homemade ones like the above description. They all worked well.

To me, the keyword in making a good ball mill is "heavy-duty". Better to overbuild it than underbuild it. To me, it's something you can't fudge on. No plastic and no thin metal. Big balls.


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## 924T (Oct 15, 2012)

goldsilverpro,

Those are some excellent specifications, and some great advice----thanks!

It sounds like I'd better hold off on building a ball mill for a while, and do it right the first time,
and the mill will last many years.

Cheers,

Mike


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## 4metals (Oct 15, 2012)

I've seen and used mills made of large diameter pipe, the trick is steel pipe not cast iron. cast iron is brittle and the balls may shatter it.


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## 924T (Oct 16, 2012)

goldsilverpro and 4metals,

As fate would have it, I was talking ball mills with an electronics friend of mine today (he used to maintain the control
systems for the local LaFarge cement plant, and they have a humongous ball mill(s) there), and mentioned that I
had no idea where I would find 20" diameter steel pipe around my area------------he's pretty certain he knows where
there is some, so I might just have a shot at building a durable mill, sooner than I had anticipated.

He said that the industrial ball mills he's seen have had triangular steel plates welded to the inside of
the drum--------------have you guys ever heard of anything like that?

Cheers,

Mike


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## 4metals (Oct 16, 2012)

What he refers to triangular steel plates are likely angle iron welded down to the cylinder to form a pyramid shape along the length of the drum. These act as lifter bars to lift and drop the balls on to the charge to increase the ability to make powders by lifting and dropping the balls in addition to the normal grinding action of the balls.


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## Jimmy (Jan 21, 2013)

I used to design, build and operate all of my mining equipment.
Ball mills dont crush the material by dropping balls on it. The material is crushed between the balls. That is why you need small balls. Otherwise large pieces of material will get stuck in the voids between the balls and never get crushed.
If your ball mill is running fast enough to crest the balls, It wont last long.
The shell liner is not there to crush material against. It is there to keep the balls from destroying the shell. Most companies these days dont use maganese steel liners much anymore. They use Urethane rubber liners. They are not cheap, but if you need them I can make them. But unless this is a contionous operation, I would just plan on replacing the drum often.
If you want a real ball mill, let me know. I have plenty of them. :lol:


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## shaftsinkerawc (Jan 21, 2013)

Can you post some pictures and prices in the For Sale section? Do you have any in Alaska?


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