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Blaf

Ball-Mill

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I would just like to say this: Guys, you should see my home-made ball-mill. It's a real beauty....and Imean it.

Blaf

p.s. If I ever discover how to post an image of it, I'd do it right away...

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Here we go....the first image shows how my mill looks standing on the floor. Construction is made of aluminium bars and ABS plastic sheets of 3mm thickness. Looks nice, doesn't it?
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The plastic jar is of 1 liter capacity and has been made of PVC water line tubing. The other one I use much more often is smaller than this one and red coloured. Rotation speed is little more than 60RPM which I found quite appropriate. Since I've got a regulated power supply I can always adjust voltage and rotation speed accordingly...but 12V works fine.
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Here you can see two shafts that rotate simultaneously due to the rubber belt linking them. The parts come from an old, broken Xerox photo-copy machine (thanks guys!).
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The motor can been powered by 12V car-battery or regulated power supply. Transmission is cog-wheeled with approximately 1:2 ratio.
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The same detail from another angle.
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Hope those links work well. Questions and suggestions are welcome!!!

Blaf

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Very nice ball-mill!

Where are you going to operate your ball-mill? Wich media are you going to use? And do you have a remote switch-off button?

I changed your post a little bit (image urls).

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And where did you get the motor from?

Wouldn't big fan motors make nice motors for ball mills?

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Thank you Gamekeeper for flattering! And here are answers to your questions:
As a matter of fact I'm operaitng my ball-mill for one year now and it works quite fine. The motor heats very little and only if the jar is 2/3 full of media and chems. Currently I use glass marbles for charcoal and sulphur and steel balls for nitrates and chems alike. I've got lead balls too (I purchased it at fishing shop) and used it only once to grind KNO3...I didn't like it because they were too messy so I've put them aside for future use. Well, as regards to remote switch off button, I haven't done anything yet...at the end of feeding cable I soldered a chinch socket so that I simply plug or unplug it from appropriate female socket. Just for informational purposes – the lenght of my mill including motor is little more than 30cm while width is 15cm.

As for the motor Pk, it comes from another source. I'm not sure which one because I just picked it up from one of my carboard boxes containing various mechanics. I did not calculate anything (motor runs at 200-300 RPM) and the final RPM outcome was a stroke of pure luck. You asked if fan motors would be good for this - I don't really know but they seem to run at much higher speeds and they have no significant power, just rotational inertia, which itself is not enough. On the other hand, if you can find a nice transmission with rotation ratio of say – 1:20, well, then I'll give it a try.

Blaf

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I recently made a ball mill, now I must find a proper jar.
Is PVC ok for the job, isn't there a threat of static electicity?

And another question, can BP be ball milled (of course with lead media), wouldn't it ignite when the lead balls crush it?

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Yes, BP can be ballmilled, I myself use PVC too and haven't got any problems yet, make sure you wetten te BP very little, that way you will minimise the threat of ignition.

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I use portions of grey water drain tubing. They come in standard diameters and pieces I made my yars from are short intersections which can be ended (and sealed) by appropriate end caps. Ends of those intersection tubings come equipped with rubber O-rings so when you press end cap in it's water and air sealed....I should post an image of it so that you can see it in all its beauty. I'm not sure what material they're made of but I had no problems so far. As for BP milling, I do that with glass marbles of some 15mm diameter...no sparks here for sure.

Blaf

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Black powder doesn't detonate to begin with. Atleast not in small amounts. Detonate means for the gasses released faster than the speed of sound. Making it a high explosive. Low explosives such as black powder and (according to the scientific community) flash powder deflagrate. I don't believe I've heard of BP igniting from static electricty, but if you are worried about it, just buy some anti-static aerosol spray. I think it's sold as computer and electronic cleaner or something like that.

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Duvel, this link you posted is very interesting indeed. The man has done everything within his power to light BP with static charge, but nothing happened. And even more, he explains very logically that it's almost impossible in real world as Carbon has certain conductivity and therefore does not have suficient resistance to generate heat. Sounds good to me...which doesn't mean I'll use steel bearings in my BP milling...I'll keep using my marbles anyway.

Blaf

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So that means that there is no need to wetten the BP, if using non sparkling media?
I think steel media made sparks differ from those made by static electricity, so you mustn't use steel for BP milling.

Blaf, can you tell me more about your marbles, where did you get them and what size are you using?

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Hello kv!

As for me, I never wett my BP while milling...at least I never tried so far. But whichever way you do it, consider the fact that this simple comp is (beyond certain extent) shock sensitive and heavy, sharp blow could potentially set it off. That's why I almost gave up using steel balls, they just idle for now. You asked for marbles - well, I got mine in so called China Shop (seven-eleven kind of shop in USA) almost for nothing. Half of a kilogram for as little as 2 Euro. Mainly, they're of 15mm diameter and there were two dozens of larger ones of 25mm diameter. I use them for almost everything now except for charcoal milling...

Blaf

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Finaly,after searching in several shops, I have found glass marbles.
Because of the upgrade on my ball mill I didn't have the opportunity to try them in, so I'm curious about the efficiency of them...

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Wetten your composition, or whatever, in your yar gives a big mess..
I did it.. the meal powder sticked on the balls (glass).. I never do it again!

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That could be very annoying.

And I think that wet-milling is less effective, because the balls stick to each other and don't crush the meal as good as it is done in dry-milling.

I searched in the net about ball mills and I found that usualy the speed of the barrel is 65-80% of the critical speed.
Here is the formula tu calculate the CS:

Hope someone will find this useful...

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Well, it's so easy to convert centimeters into feet, that I don't bother looking for a SI standard formula.

CS=76.63/ sqrt of (C/30.48 )
where C=centimeters

1foot=30.48cm

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There is a difference between dry-milling and milling with a very little water, I don't know the english word, but in dutch it is 'vochtig' so perhaps Duvel or someone else can translate it, but I don't think you still get a mess like milling with very much water.

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vochtig-damp, humid, moist

But what are the positive things of wet-milling, isn't dry-milling better, or you are thinking about saftey?

In which milling proces smaller particles can be made, damp or dry?

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The biggest advantage of damp milling is that you composition won't ignite by static electricity. When your dry milling works as well as you wish, you'll get very fine dust in your ballmill, and you might know how dangerous a dust explosion can be. When you mill with a very little water the mix won't produce dust in you ballmill but will be stuck together just enough for safe milling. I think that's the most important thing about it - safety.

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Should it help to put your yar away (for an hour or so) after dry milling,
so the dust can sink to the rest of your compo?

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Do not argue about something so trivial guys.

Wett your mixtures if you want but do not use excessive amounts of water as to prevent sticking to your media. Your meal should be just crumbly - that's the right consistency.
I dry mill my meal, never sprinkle water over it and use only glass marbles as milling media. No sparks, no strong friction, moderate rotation speed and have no fear. As for pyrophoric properties of dust (I never experienced one so far!), there should be slight concern about it. To prevent rapid introduction to Oxigen (this is just if you are Safety Freak) you can always drill a small hole in your jar's end cap and tihgten a self-threading screw there. As your milling is over, leave the jar for a few minutes allowing dust to settle down and then unscrew it slowly to expose your meal to controlled flow of Oxigen and nothing bad should happen.

Huh, too much talking here...

Blaf

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