My new ball mill

[Fly]

I just finished my new ball mill.I made it to use two 6''ID pvc tubes 9.5" long.I have used just one so

far & my, what a difference in time & volume I can mill.

 

Before I was using a single Harbor freight unit.Most I could mill at one time was 200 grams of meal

& it took about 6 hours to do a good job.It worked but small amounts & along time.

 

Now with this one I have made 500 grams in two hours & I can still get much more in there but have not

tried to see how much yet.We are talking one drum, & I made it where I can do two drums.

 

I did make it with two lift sticks.I'm telling you this thing is bitching!

 

Fly

[Mumbles]

That size can usually do around a kilo to 1200g. Be forewarned that too little material in there can cause excessive wear on the media.

[dagabu]

I think that is also what was decided to have set off the ball mill some months ago.

[Fly]

I think that is also what was decided to have set off the ball mill some months ago.

 

Why would that set off a ball mill?????

[dagabu]

Why would that set off a ball mill?????

 

Fly,

 

Take a look back in Passfire in the safety section, there is a bloke that blew a nice sized hole in his greenhouse because his ball mill failed in some way. the consensus was that he had under loaded the ball mill and the media was able to crash into itself unabated by the cushion of the materials in the mill and an ignition was created.

 

Either that or fairies started the fire with pixie dust, damn sprites.

[Fly]

Hummmmmmmmmmmmmmm sparks light BP Sooooooooooo ?????Well maybe there is more to this then

we know.

Fly

[Arthur]

There is a lot to be said for having several jars and maybe a couple of mills! The cheap 400g /1pound rock tumblers maybe take to long, to make too little, too slow BP,BUT when you need 10g of something passing 300 mesh then they are superb. Likewise some friends have a 50 litre mill jar simply for initial breaking of light charcoal.

 

 

Also if you work with Chlorate and sulphur then several jars and sets of media are needed to reduce contamination.

[Algenco]

Hummmmmmmmmmmmmmm sparks light BP Sooooooooooo ?????Well maybe there is more to this then

we know.

Fly

 

 

all the more reason to be certain your medium is non-sparking

[dagabu]

Hummmmmmmmmmmmmmm sparks light BP Sooooooooooo ?????Well maybe there is more to this then

we know.

Fly

 

Nope, I did not say a spark. Ignition by compression, diesel fuel is ignited this way, no spark plug is used. (glow plugs are used in the first few minutes until the temp can be brought up)

[ausgoty]

Nope, I did not say a spark. Ignition by compression, diesel fuel is ignited this way, no spark plug is used. (glow plugs are used in the first few minutes until the temp can be brought up)

 

Um, I would think the sort of pressure required would blow your mill jar to bits long before it even got close to ignition temp. Petrol engines typpically compress the air 8-10 times and they still need a spark plug to initiate combustion. Diesels are typically 14-16 times (14-16:1), this is a hell of a lot of pressure!

 

That being said, I would never trust a ball mill full of gunpowder, always cover it with something big and heavy if possible (keeps the noise down as well). Who knows what go's on inside!

 

When I tamp a rocket in a tube that is tight on the ramer I worry a lot about diesel ignition. I make a point of slowly pushing it with my hand until it is solid on the comp and the first blow or two are very light, so I can be sure all the air has gone.

[Updup]

Yep, the compression itself isn't what heats up to light somthing on fire, its compressing somthing quickly that generates enough heat to light somthing on fire:

 

[Fly]

I was going to reply to this, but it's just not worth my time.

 

Fly:whistle:

[Updup]

I was going to reply to this, but it's just not worth my time.

 

Fly:whistle:

 

Well you didn't have to say anything at all.

[Mumbles]

And neither did you updup.

 

The guy on passfire was Gary Smith I do believe. I don't ever recall hearing a defined cause, but I had other things on my mind at the time.

[Updup]

And neither did you updup.

 

The guy on passfire was Gary Smith I do believe. I don't ever recall hearing a defined cause, but I had other things on my mind at the time.

 

Thats true... Still, he started it XD

[pyroguy1960]

My two cents if anyone is looking for a new mill, I bought one of the octagonal inside ones with a nice neoprine lined barrel. I was amazed at how well it works....can mill BP very well in just an hour, plus it's very quiet.

[Updup]

My two cents if anyone is looking for a new mill, I bought one of the octagonal inside ones with a nice neoprine lined barrel. I was amazed at how well it works....can mill BP very well in just an hour, plus it's very quiet.

 

Really? I was acually wondering, since pyrodirict now stocks them, and they are on sale this week for only $99...

[helix]

The reason for G Smiths ball mill ball mill explosion was put down to the lift bars which were on the large side combined with a severely undercharged mill. The consensus was that the large lift bars caused the media to be carried to the top of the jar and drop onto the comp below eventually resulting in ignition of the powder. I recall that the action was likened to that of a hammer mill as opposed to a ball mill.

[Updup]

The reason for G Smiths ball mill ball mill explosion was put down to the lift bars which were on the large side combined with a severely undercharged mill. The consensus was that the large lift bars caused the media to be carried to the top of the jar and drop onto the comp below eventually resulting in ignition of the powder. I recall that the action was likened to that of a hammer mill as opposed to a ball mill.

 

Thanks, so if it was a hammer like action that (we think) caused this, would should we think about hammering BP based foutains and rockets? As I'm sure a ¹/₂" ball (Maybe bigger), falling 6 inches or so would make a fraction of the impact a simple 8oz hammer would make.

 

Unless each impact generated some heat?

[helix]

Thanks, so if it was a hammer like action that (we think) caused this, would should we think about hammering BP based foutains and rockets? As I'm sure a ¹/₂" ball (Maybe bigger), falling 6 inches or so would make a fraction of the impact a simple 8oz hammer would make.

 

Unless each impact generated some heat?

 

 

 

The energy dissipated between 2 media surfaces could actually be quite high as the area of contact between these would be very small resulting in the possibility of very high pressure being imparted on the powder; this coupled with the large number of impacts "could" have created favourable conditions for ignition in G Smiths mill. I think Gary was also using ceramic media but I might be wrong.

 

Pounding BP seems to be less dangerous when you consider how many years this procedure has been carried out and the number of rockets etc. made but there are still accidents that occur - pinching comp on a rocket spindle is probably the biggest problem.

[Mumbles]

Thanks, so if it was a hammer like action that (we think) caused this, would should we think about hammering BP based foutains and rockets? As I'm sure a ¹/₂" ball (Maybe bigger), falling 6 inches or so would make a fraction of the impact a simple 8oz hammer would make.

 

Unless each impact generated some heat?

 

You're missing the point completely. It's not a hammering action, it's the pinching action that occurs in a very localized spot. In rockets and fountains the force is applied over a broad area. At most you're generating a couple hundres to few thousand PSI. Force is mass times acceleration. In this case, it's not acceleration of speeding up, it acceleration of going from maximum speed to zero. In a rocket or fountain there is a much slower deceleration as the composition compacts and cushions the impact. In a ball mill, that time is on the order of milliseconds not tenths of seconds. I can put up some arbitrary math, but Lloyd S. showed that a ball mill impact can easily generate over 30,000 PSI. The idea with a properly charged mill is that all the impacts are somewhat cushioned, and when undercharged there will be more direct ball to ball strikes, and more pinching action.

[Fly]

Mumbles I'm not in dispute tonight.I know you know your stuff.But why is it, I can not get BP to ignite with

a three LB brass hammer when I hit it on a one inch thick steel plate.

 

I have tried this more than once.No kidding this hammer I made years back & has a 1018 steel handle that

is very heavy with no give.It's hard for me to comprehend a .500 dia lead ball setting this thing off on PVC.

 

Hey I'm open to any come back to what I'm missing here.I don't want to blow my shop & self up or

anyone else for any reason.

 

But I'm sorry I just don't get this.

Fly

[helix]

Fly,

 

your mill jars probably fine so long as the lifter bars are not going to permit your media to be carried on the surface of the bar to a height above the comp from which it can drop onto the media/ powder below.

 

I'd agree that its hard to ignite BP by impact. If you put a little BP on a smaller area such as the head of a nail or something similar and hit it then the probability of ignition would be higher as you would impart more pressure on the powder however I don't know how many times you would have to try to get an ignition - I'd guess the likelihood of it igniting would still be pretty low.

 

 

[Mumbles]

For me, it's the media wear and not the possibility of spontaneous ignition that keeps me from under charging a mill. I really don't know if the impact theory is really true, but there is definitely a difference between hand ramming rockets or fountains and high impact scenarios such as yours with the hammer and isolated possibilities in a mill.

 

I personally thought that Gary's mill leaked powder and shorted out the motor, but I'm having trouble finding any real conclusions in the thread.

[Fly]

Well buddy that is what I think.The motor on mine is located below the drum as a lot of them are.We know

motors have brushes that produce sparks.

 

Who really knows for sure what happened.I do think I will most likley make a cover over the top of my motor.Tomorrow

I'm going to pick up some thin wall stainless steel tubing & cut it into one inch peaces & fill them with

lead to stop the wear thing on the media.

 

Fly