2003-08-11 20:09:50 UTC
me and my friend are making our very first ball-mill. I've done a lot
of googling and reading, and decided to make a mill, that would look
something like this:
Here's a little demo:
You can see the two separate milling sections. The lower section is
supposed to be used for "safe" milling (separate chems or non reactive
compounds), and the higher section for milling oxidizer+fuel mixtures
like BP. Both can work at same time, without interference. Separate
motors with remotely controlled variable RPM will be used. These will
be placed inside the box, under the higher milling section. So much
for the mill itself. Any comments or ideas for such construction?
Now about the jar. So far, I have found (and bought) a 11cm diameter,
25 cm length PVC tube with end caps. However, after some Googling in
rec.pyrotechnics, i found out that milling would take about 8 hours.
Is it correct? Now I'm trying to find PVC tube of diameter of ~15 cm
(very hard to find ;( ). Would it make the milling process faster? I
mean I'm not sure what diammeter jar shall I use. 15cm somehow seems
to be a better option (faster & more space), however harder to find.
The media: in case of 11cm dia jar, I'd use 12mm dia/20mm length
cylinders; in case of 15cm jar - 15mm dia/25mm length cylinders. I
intentionaly haven't mentioned the metal yet, I'll talk about it
later. The question here that bothers me, is are such sizes of media
suitable for such jars? I've found lot's of info about making ball
mill's, however didn't find the way for calculating the the size of
media according to the size of jar. I've only found a formula to
calculate the RPM of a mill.
The metal of the media: since I couldn't find balls of any suitable
metal larger than 8mm, I'm making my own cylinders. Probably lead.
Gonna drill some holes in wood, poor molten lead and wait for it to
cool. Found it in some ones post here. Brilliant idea! Yesterday I
came up with another idea: take copper tube, fill it with molten lead,
and cut into cylinders after cooling down. However, today I found out
that I'm not the first with such idea. Someone has already mentioned
it here, and someone else said it ain't gonna work (the lead would
become loose inside, and milled powder would be trapped between Cu and
Pb). Maybe anyone has tried to do it? I know Cu is bad for milling
some chems, but I'd use it for BP only. Or how about using Al tube
instead of Cu?
So overall, I'll repeat the questions that I don't know or could not
find any answers to:
1. The construction of the mill (I know it is a very big topic, maybe
just some ideas or smth ;) );
2. Would increasing jar's diametter from 11 to 15 (or even more) cm be
a wise decision? Would the milling be faster? Would the powder be
3. What would be the optimal dimensions of milling cylinders for a 11
or 15 cm dia jar? Or even better, how to calculate them according to
the diammeter of jar?
4. Has anyone tried to use copper (or some other) tube filled with
5. And last question: what is antimony? ;) I believe it's some kind of
metal, right? Where it is used in everyday life? I want to harden my
lead, but dunno where to get that antimony stuff ;)
Any comments or suggestions are welcome and highly appreciated. Thank
you in advance. RoCkaZ