38 replies to this topic

[willdee]

At the moment I dont have a ball mill,
I will perhaps make one in the future but at the moment there is none available.

What I do have is a treadmill (Running machine) would it be possible to just set the machine on slow and place the container containing BP and some heavy bearings onto the belt of the treadmill.

I will then prevent the container from rolling off, now it should just sit against the treadmill belt and rotate??

Sorry for the rubbish description but I hope you get the Idea

[Creepin_pyro]

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Edited by Creepin_pyro, 20 September 2011 - 04:46 PM.

[Atom Fireworks]

Yea that could work well but as mentioned its a good idea to have it outside away from people and any obstructions. Ide give it a shot, 5 mins in a drum will lead media is better than half hour with a mortar and pestle.

[Mortartube]

A used rock tumbler from ebay would be better as it's small enough to opersate remotely. I use one with a drinks container like this as a jar/

http://www.whitefurz...l.php?ref=F0310

It is half full of lead media cast into cylinders and will 100g of good BP (fast enough for lift when pressed into a puck and granulated) in 10 hours. You can split the milling times into 2 x 5hr sessions or whatever you like. You will need a machine that takes two small polishing jars to get the drinks container on. The single ones are too short. The original jars are too slow and take forever to produce good BP.

If it slips, a few heavy duty rubber bands around the small end will give it grip.


You need something like the 3lb double barrel model here,

http://www.ukge.co.u...ne-Tumblers.asp

and order 2 or 3 spare drivebelts. They last a long time but it is annoying when they break and you don't have a spare.

I realise these are not as efficient as a well designed ball mill but they will bring the chance of good BP into your scope. They may seem expensive but they are well made and will last for years.

[whoof]

What is considered to be the best ball size for BP please ?
Marble size ?

[Atom Fireworks]

What is considered to be the best ball size for BP please ?
Marble size ?

Depends on the size of your mill. Mines approx 5/6 inch mouth size by 7 inch long and i think ime using 18mm lead balls and it makes very fast and usable bp in 3/4 hours of milling its very efficient and cost me 40 quid to make and 30 of that was on a speed controller !

[Mortartube]

And the media is considerably quicker if it's cylindrical and not ball shaped, huge difference in surface area.

[Atom Fireworks]

And the media is considerably quicker if it's cylindrical and not ball shaped, huge difference in surface area.

Hi mortar tube, ime not nit picking here just going to ask do you have any facts about that or is it a myth? The way i see it is balls will all fit snugly together rolling and crushing the mix as well ans tumbling and impacting upon it. With cylinders i can see allot of the new found surface area actually doing diddly squat because of its ireegularity in shape as opposed to balls.

Again ime not having a pop i would just like to understand how the theory goes with regards to the two types.

Jay

[Potassium chlorate]

A ball always has a smaller surface than a cylinder with the same diameter. For example: a ball with the diameter 20mm has the surface area 4πr²~4*3.14*10*10mm²=1256mm², while a cylinder with the same diameter and height has the surface area 2 π r h+2 π r²~2*3.14*10*20mm²+2*3.14*10*10mm²=1884mm2 . Simple maths. In addition the more irregular shape of the cylinder (the ball is the most regular shape there is) makes it much more likely that a cylinder will follow the rotating barrel 180^o and then fall down on the composition, while this might not be the case with a ball.

Edited by Potassium chlorate, 21 June 2011 - 08:23 AM.

[Atom Fireworks]

Hmmm i think the balls rolling over each other is better for grinding fine compositions even finer, maybe cylinders are better for getting the inital chunks of charcoal ect.. down to size. I think its down to personal preference unless anybody has got hard evidence?

[cooperman435]

Id agree with dumper.

Milling isn't about surface area of the media but a combination of contact points and force of impact

Yes cylinders have a greater surface are but by that reasoning they have a lower weight to surface area ratio so each individual impact is less, also the irregular shape suggests a less regimented falling pattern and uneven impacts.

I suppose there's a ying and yang but my money would be on balls being overall better.

The shape also lends its self to reducing damage to the media better

Edited by cooperman435, 21 June 2011 - 10:16 AM.

[crystal palace fireworks]

Interesting differs of opinion here, both have there merits, I guess factors like speed of drum, size & weight of media, size of ball mill drum, and amounts of comps to be ground/crushed are equally important, that said, I would have thought that cylindrical media would have a greater surface area to crush comps more quickley, and given the more irregular shape of a cylinder (to occassionally tumble on its end) to randomly crush irregular or larger peices of comp better in the scale of things = reducing milling time with the added benefit of shortening the long term damage to the media itself,

Although I could be completely wrong!

Edited by crystal palace fireworks, 21 June 2011 - 11:10 AM.

[Atom Fireworks]

I think some kind of experiment may be in the pipeline here, using the same mill, same chems ect and same milling times see which type of media works best?

[whoof]

I think some kind of experiment may be in the pipeline here, using the same mill, same chems ect and same milling times see which type of media works best?

Would it be possible to substitute solder or pewter for lead ? (easier to cast)
Any material conflicts ?

http://www.mine-engi...ing/rodmill.htm

May be of interest.

Edited by snert, 21 June 2011 - 12:54 PM.

[Mortartube]

I only have personal experience to guide me. I recast all of my spherical media into cylindrical media on the advice of a knowledgeable chap in the industry. I would say it has reduced my milling times by over a half and I get a better end product regarding fineness.

This is using the same mill, jar and speed.