8 replies to this topic

[Christian]

Hi there

I am going to buy this ball mill for making black powder: http://www.harborfre...temnumber=46376

I am going to buy lead media from cooperman. What size would you recommend?

If you happen to know how many balls would be efficient too, please tell. If you need to calculate a lot of things first, dont worry - I am pretty sure I know how to calculate it :-). First I find the drums diameter. Next I find out how many cm3 one ball is, and that way find out how many balls it would take to fill half the drum. Am I right, or?

Thanks :-)
Christian

[mike_au]

First I find the drums diameter. Next I find out how many cm3 one ball is, and that way find out how many balls it would take to fill half the drum. Am I right, or?

Sort of, the balls won't stack neatly, the bigger they are the more air space there will be between them and the less you will need to fill a given volume. If you simply work out the volume of the jar and the volume of the media then you are on the safe side you will simply be buying more media than you need.

[spanner]

Here's what LadyKate has to say on those tumblers- she's GOOD, BTW The site is here: http://www.creagan.n...orks/index.html

"Harbor Freight-like tumblers take up to 18 hours to mill most powders sufficiently. This number is based on milling 12 different charcoals using 75-15-10 and pre-ground chemicals.
The mill media was .50 caliber lead balls and the weight of balls was 2.5 lbs. 100-200 g of composition (it varied a bit depending on what I was doing) was milled each time. Test firings were taken at 6, 12, 18, and 24-hour intervals. The test firings were trough burns and launches of 1.5" 35 gram dog food shells.
Most powders stopped noticeably improving after 12 hours but some required 18 to get to potential. Generally speaking, the harder charcoals seemed to take longer to mix to potential.
Cautions are: Don't overload the tumbler - the closer you come to 3 lbs., the closer you come to destruction of the motor.
Get spare belts (4" x 1/8" O-Rings work) - I destroyed three in doing the above experiments.
Advantages are: It is a cheap way to start if you don't want to build anything. Lloyd's mill designs are so superior for larger batches that it is almost laughable - but that doesn't mean you can't get results with these tumblers. I still use them to do small jobs and they work fine. These cheap tumblers are definitely for small batches with about 2.5 lbs. max
load weight (100-200 grams of comp) - but they do work for that." LK

[Mumbles]

I have a mill of that size. I use 100 1/2" lead balls, and this is under loaded. I'd suggest more toward 200. I can make around 200g at a time in 12 hours.

[cooperman435]

Christian if you look on the details for 17 and 21mm media it shows the volume taken up by 50 of them. I did this specifically to answer this question as the volume of your jar is (or can be) known and it wants to be half filled so you only need the volume of the jar and then half it.

A 2litre jar would need 1litres of media so :

17mm x50 balls is 0.2litres so roughly 250 balls in total
21mm x 50 balls is 0.45litres so roughly 110 balls in total

It also shows the weight to calculate the total charge of the mill in advance

Ive never had 50 of the 24mm or 26mm balls together in one place to measure the volume but will make them one day to check volume and weights too.

[Arthur Brown]

As a rock tumbler it will be most satisfactory using it's rated weight of lead then add 100 - 200g to mill. A drum half full of lead media risks being way over 3lbs


Note that the mill in the link is for 120v if you are getting Cooperman's media you are likely in a 230/240v

Edited by Arthur Brown, 21 January 2009 - 07:44 PM.

[Christian]

As a rock tumbler it will be most satisfactory using it's rated weight of lead then add 100 - 200g to mill. A drum half full of lead media risks being way over 3lbs


Note that the mill in the link is for 120v if you are getting Cooperman's media you are likely in a 230/240v

Thank you very much for letting me know about the 120v/230v problem. I did know about it, but I am certainly very happy that you said it . Luckily, I have a transformator that should be able to transform the power .

I will try with 100g of 17mm lead balls and see how that works out. Thanks everyone

[Arthur Brown]

Actually I'd suggest that you weigh out 3lbs of media which is about 1300g then see how much powder will just cover that.

[cooperman435]

serously guys there has been a great deal of stud done as to the correct method to charge a mill correctly and to deviate from this method HUGELY reduces the efficiency of the mill.

1/2 fill the jar with media of your choice.

add material to be milled until it occupies the voids between the media and JUST covers it.

The only exception to this would be if you were milling a material that quickly broke down to a smaller volume (such as magnalium hulls) which occupy a large volume at the beginning of the process but when powdered slightly shrinks in volume. In these scenarios it is necessary to experiment with your initial "overcharge" of material but the media stays the same.

Lowering the volume of media will ruin the effect, efficiency and speed of ballmilling. just reducing the media to 1/3 will double the time needed to mill to the same degree. This is why rock tumblers are pointless as they simply cannot cope with the required weight.