20 replies to this topic

[pjalchemist]

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Edited by pjalchemist, 11 December 2011 - 10:59 AM.

[maxman]

I cant answer any of your questions since I don't know that mill but 8 hrs seems an awful long time. 3 hrs should be plenty and indeed when I have used a mill 1hr makes very usable BP for lift etc. Take into account that milling dose have its dangers so the less time you can get away with the better. I think consistent BP is better than having the fastest. As I see it the only benefit in faster BP is you need to use a bit less for lift which might be an issue if you were in business and on a tight budget. 1lb core burner fuel does not need to be milled at all.

Stay Safe

Maxman

[Creepin_pyro]

I never tried using a tumbler for BP but I've heard it can take much (24 hours?) longer to achieve comparable results to a properly optimised mill. For the same money you could build a really nice mill.

[pjalchemist]

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Edited by pjalchemist, 11 December 2011 - 10:59 AM.

[maxman]

1lb core burner should be 60.30.10 screened a few times no need to shake at all. Fine tuning might be in order but if it wont fly then your chems aren't fine enough or your charcoal isnt good enough.

Maxman

[pjalchemist]

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Edited by pjalchemist, 11 December 2011 - 10:59 AM.

[Peret]

I had to google the tumbler because I'm not familiar with it. Seems it's equivalent to what we in the US refer to as a "Harbor Freight" tumbler, and since I have one I can answer.

The best literature on ball mills says the barrel should be half full of media. If you use half inch lead shot, this will take about 200 balls for a weight of 5 pounds. Unfortunately this mill is not man enough for the job. If you cut back to 120 balls (3 pounds) it will strain a bit but probably manage it, but milling will take a long time. 8 hours isn't too far off the mark. However, it will do better if you use a ceramic milling media, because hardness is a bigger advantage than weight. The gold standard is Zirconia M, 60% the density of lead and hard as diamonds. Half a drum weighs 3 pounds and does the job in an hour. You may need to take out a second mortgage to purchase it though. Alumina is cheaper and works fairly well. Even stream pebbles will work if you can't get anything better.

It is quite limited in the amount of powder it can mill at a time. The literature says the powder should disappear into the media and fill the spaces. That allows about 150-200 grams if the drum is half full, less pro-rata if there is less media. The milling action depends on the balls bashing against each other in a tumbling action, so if you overfill it won't mill at all no matter how long you run it. You might find the powder fluffs up and expands during milling, especially if you use a light fluffy charcoal, and at some point you can't hear the tumbling balls any more. When that happens it's over, no more work is being done. If it's not finished you'll have to split the batch in half and mill each separately. This is such a filthy nuisance that you quickly learn not to overfill, and in any case, half the charge usually mills in less than half the time so there's a net gain from small batches.

As Creepin_Pyro points out, this mill isn't inexpensive. I could buy four Harbor Freight mills for that price, or six during a sale. You could certainly make a much more capable unit yourself for the money, if you're any kind of handyman.

[dan100]

my jar is about 5" by 9" filled half full with ceramic baking beans that weigh 750g ideal comp weight is 100g [some comps vary in load]
a small mill should spin this easily you want to clock the speed as it will vary with different media [on mine anyway]
i expect lift quality bp in 3 hours where it is caked to the point of looking like stones. [too powerfull for 1 pounders]

dan.

[megabusa]

My mill is a 2.5L HDPE jar about 6" x 12" (from memory), in fact it is the storage jar that Cooperman sells.

I won't show a picture of the mill as it is a bit embarrasing !!! - It started out a few years ago as a quick fix & temporary measure, but it kept performing so well I have never bothered to make it more professional.

It is driven directly by a 24V motor that has attached to it a circular 'frame' or 'cage' that the jar slides into, so I can swap jars easily. The jars are held tight with a large 'jubilee clip'

It has variable speed, but it seems to work best at about 75RPM.

The media is about 130 22mm lead balls, cast using a fishing weight mould from eBay. These fill it to about halfway & it weights about 4Kg.

I mill for 1/2hr per 100g plus 1/2 hr, ie 500g would run for 3 hrs.

This gives very fast BP, in fact I am carefull not to run for too long as the BP quality decreases after a point due to lead contamination. This would be the danger of leaving it running all day.


I have given up milling my rocket fuel as it was on a knife edge, sometimes too slow, sometimes CATO. It was a bit exotic using different grades of charcoal etc.
I now use the good old 6-3-1 & it is reliable. The charcoal is milled to A/F beforehand in larger batches. The 6-3-1 goes into the mill for 10 minutes just to mix it & then I granulate it with 25% IPA in water, so it is less dusty when ramming.

Cheers,

Phil.

[dr thrust]

i bought the evans when i first started out, they use a tiny induction motor, that quite frankly isn't up to the job if your using lead media , if been told that if you let the motor free run for fifteen mins to "warm UP" this helps the motors efficiency i have a video of the evens v a homemade mill constructed from a pillar drill, £15 off a car boot, the video is old now and lots of people have seen it before but i think its still relevant.

http://www.youtube.com/watch?v=IqwdLXrdDLk

[Vic]

i bought the evans when i first started out, they use a tiny induction motor, that quite frankly isn't up to the job if your using lead media , if been told that if you let the motor free run for fifteen mins to "warm UP" this helps the motors efficiency i have a video of the evens v a homemade mill constructed from a pillar drill, £15 off a car boot, the video is old now and lots of people have seen it before but i think its still relevant.

Nice conversion of a pillar drill and one of the cheapest ways to make a decent mill without going over the top.

[dr thrust]

yep im a cheap-skate speed control for barrel size was a basic affair with the stepped pulleys, a good while back digger suggested a 3phase motor with digital inverter for the ultimate variable speed mill, cant remember the last time i used my mill, quite sad..

[megabusa]

cant remember the last time i used my mill, quite sad..

Used mine twice yesterday

[starseeker]

my jar is about 5" by 9" filled half full with ceramic baking beans that weigh 750g ideal comp weight is 100g [some comps vary in load]


dan.

Although baking beans are fine for single chems,they are not safe to mill any comps as they are prone to sparking,for using in a tumbler the cycleb ceramic media is very good,which are available from inoxia.

[dan100]

Although baking beans are fine for single chems,they are not safe to mill any comps as they are prone to sparking,for using in a tumbler the cycleb ceramic media is very good,which are available from inoxia.

really, i have raised this concern on another forum, i didnt go about it lightly ive read of ceramic sparking but why, i mean what type of discharge and how, is it an electric discharge? do you know what type of ceramic sparks?
sorry for the questions but i feel this is important and no one seems to know.
i can at least then find out what type of ceramic they are.
thank god i have only milled one batch, though it was the best ive seen it was only intended for inert milling and does such a good job in no time.

dan.