12 replies to this topic

[a2wpyro]

i am just about to place an order for the mini tumbler from manchester minerals.
it asks if i want like 700gs of agate mix or quartz. is this stuff nessesery or not?
i have also read the milling media post and noticed there was no links to any lead media sites for the u.k. i found thishere , it is located in germany, i havn't asked for a quote yet because i dont know what size media i need, can any one suggest what size for the "M.L.BEACH 900gm Mini Tumbler"
if so many thx

Edited by a2wpyro, 03 January 2004 - 06:40 PM.

[pyrotechnist]

Them tumblers are a rip off ask pyromaster he has one the media on that site looks ok I would suggest to make one your self than bye one from Manchester minerals they are to dear like ?70 and postage and packing you still have to pay that crap. Make one it?s a whole lot better to do that than bye one. :-)

Edited by pyrotechnist, 03 January 2004 - 07:31 PM.

[a2wpyro]

yeah i seen the prices they do seem expensive.
i have an old drill motor but im no good with electrics, and i have heard that drill motors tend to over heat when left on for long periods.
would an engine from a lawn mower be any good or would that be to powerfull?

Edited by a2wpyro, 03 January 2004 - 09:19 PM.

[alany]

I used the electric motor from a fan, which is obviously rated for continous use.

It is only 50W which means my mill is quite small, limited to 100 g batches or so, but that suits me fine for now. The gearing redution makes even a modest powered motor capable of turning the jar, but there is still only so much power there to be used, for the usual 6" diameter jars you need a fairly gutsy motor.

The other reason I chose the fan motor is because it is an induction motor, so it has no brushes to make sparks. This unfortunately means its starting torque is not all that great, so now and then I need to help the jar start turning, but that hasn't proved to be a big problem.

[Phoenix]

My ball mill uses a 170 Watt washing machine motor which I got from the local rubbish tip for about ?1.50. (In fact I think that was the only part I actually had to pay for). It works fine, I guess they chucked the washing machine as all its insides were coated with about 1.5cm of crusty horrible stuff.
Like the fan motor, it's an induction motor and is rated for continuous use. I've run it for about 14 hours at a time and no problems. It easily turns my mill jar, even with a 1kg of lead media plus 100g of BP (which is the heaviest combined load it ever has in).

Also, remember that a motor will generate heat when it runs, even with no load. On rec.pyrotechnics, Lloyd Sponenburgh said that most will heat up to 40 degrees celcius above the ambient air temperature. Even unloaded with a cooling fan mine gets too hot to hold your hand on.

[Stuart]

Mine is a window wipper motor. It also heats up to hot so it cant be held but thats only after and hour. Even geared up it still has enough jizz to turn four milling jars each weighing about a kilo.

Stuart

[adamw]

An Internal Combustion Engine to power a ball mill.... do you think that is a good idea?!?

[tajmiester]

The agate and quartz mixes are the powders used to tumble polish stones. When tumble polishing the media is the stone and the powder is replaced by a hard grit (agate or quartz) that is used to aid the attrition within the barrel, and so no it is not neccesary for milling pyrotechnic compositions.

Tris

P.S. Do you really intend to keep a lawnmower engine going for 12 - 24 hours strait?

Edited by tajmiester, 03 January 2004 - 11:29 PM.

[Pyromaster2003]

If i were you, id use that lawn mower engine for a go-kart! and find some smaller electric motor for your mill.

[Yugen-biki]

After making 2 ball mills I ended up buying a mill like the one foud on http://www.lortone.com/tumblers.html (3A). Not because of bad grinding action but due to noise! The first one I made use a electric drill motor and an old laserprinter. The second one used a industrial 3phase electrical motor and suplyes from the hardware store.
The important thing is to have the right number off balls and rpm in combination to the jar. This might be hard to obtain if you use a home made one.

[Phoenix]

Here's a formula I found for the correct RPM for a ball mill (not from LS's book, off a ceramics forum type thing):

"Revolutions per minute equals 54.19 / sq. root of R times 0.64 and 0.87. R is the
internal radius of the jar in feet. The two factors 0.64 and 0.87 establish the lower and upper operating limits"

For example, for my mill this is 54.19 / 0.577 x 0.64 = 60rpm
or 54.19 / 0.577 x 0.87 = 80rpm

I made my ball mill to these specs, but it seemed a little slow, so I turned a larger pulley for the motor to up the speed to 100rpm

I have found a way around the noise. I have a couple of cupboards under the bench in my shed, so in one of them I put a piece of plywood on a padded cushion, and drilled a hole through the cupbard so I can plug it in above the bench (I didn't feel like installing a socket inside the cupbaord). On its cushion, in its cupbard, in my shed the mill is inaudable from 10m away even empty, and if it's fully loaded with something soft like charcoal, you can hardly hear it standing right outside the shed.

[Yugen-biki]

My old mills were really loud! But I still use a piece of plywood on a padded cushion like you do.

[Steve]

Yeah, i've taken the the foam and cupboard idea after the noise got too irritating.