What am i doing wrong?(BP making)

[Stef727]

Then you will need the lead media, which ultimately will probably cost nearly as much as the mill.

 

I use ceramic media ( made specifically for ballmills) it costed me 8$/kg, and works at almost the same speed as lead (yes I also have lead so I know how fast lead mills).

http://www.pyrogarage.pl/img/other/cm20.jpg

Edited January 12, 2016 by Stef727

[MrB]

Haha så du hänger här med!

 

I'm like the ghost of Christmas past. You just cant get rid of me.

 

 

I don't have access to perchlorate, no, but i will leave flash powder and whistle for the future, when i have more real life experience in pyrotechnics.

 

Sounds safe. I wish you the best of luck.

 

 

 

I use ceramic media ( made specifically for ballmills) it costed me 8$/kg, and works at almost the same speed as lead (yes I also have lead so I know how fast lead mills).

 

Ceramic media is good, it's lighter, but harder. The problem with ceramic media is that i for one wouldn't dare to use it without proper paper-trail leading back to the manufacturer, that stands by their product and lets you know it really is spark-free. Milling BP with something that sparks, isn't stupid, it's a misplaced bomb, complete with armor piercing shrapnel. Nothing i will get close to. Now, there is ceramic media produced, that the manufacturer will go on record and say is spark free, but where "we" buy our stuff, we generally get second hand stuff, from unknown sources. I honestly don't know where PG gets their media, it's not stated on their site. It's also not stated anywhere who makes it, if it's spark free, spark resistant, or untested.

I'll stick to lead for BP.

B!

[WannabePyroPro]

I'm like the ghost of Christmas past. You just cant get rid of me.

 

 

 

 

Sounds safe. I wish you the best of luck.

 

 

 

 

Ceramic media is good, it's lighter, but harder. The problem with ceramic media is that i for one wouldn't dare to use it without proper paper-trail leading back to the manufacturer, that stands by their product and lets you know it really is spark-free. Milling BP with something that sparks, isn't stupid, it's a misplaced bomb, complete with armor piercing shrapnel. Nothing i will get close to. Now, there is ceramic media produced, that the manufacturer will go on record and say is spark free, but where "we" buy our stuff, we generally get second hand stuff, from unknown sources. I honestly don't know where PG gets their media, it's not stated on their site. It's also not stated anywhere who makes it, if it's spark free, spark resistant, or untested.

I'll stick to lead for BP.

B!

Thank you!

Is there much difference between mallmilling bp mixture and ballmilling each chemical, then mix it without any mill media?

[Arthur]

The whole reason behind milling BP is to incorporate the chemicals intimately. Even the tinyest speck of charcoal dust is like a sponge -what sort of sponge depends on the type of wood- milling pushes the fine nitrate and sulphur into these holes. which makes the reaction more energetic. Thoroughly soaking the charcoal in nitrate solution MAY just work or may not.

[MrB]

@ wannabe: What Arthur said is "yes" in response to your question.

 

Ballmilling the charcoal with half the KNO3, and then ballmilling the rest of the KNO3 with the S, and finally screan-mixing the two batches supposedly makes for a good compromise with increased safety, but if at all possible, get lead media, or a known none-sparking ceramic.

B!

[schroedinger]

B the barrel is actually better suited to the task then the cheap rubber barrels from lortone or normal pvc from a hardware store. I used such a mill for two years for everything before i switched to a homemade one with a bigger barrel and use that one only for small batches and charcoal. The barrel is still fine and i even didn't had to adjust the belt pressure once or fix anything else.

[lloyd]

I shudder when I read about these 'toy' mills with 1/50th HP fan motors, o-rings for belts, and associated with phrases like "adjust the belt".

 

C'mon... twenty-one years after my FIRST commercial mill was made, it's still running on the original, un-adjusted (ever!) belt, and original, never-replaced jars made from the 'cheap' plumbing pipe and fittings.

 

It's the same mill that went through the magnesium fire depicted in my booklet, and except for scraping off the char and re-mounting the two blown-through jar stops, it has never had any repairs necessary.

 

And, to be clear, it's not even in my possession -- I'm not 'baby-sitting' it. For the last fifteen years, it's been in every-other-day use in a commercial manufacturer's plant. I don't even get to supervise its use... it just plugs along.

 

One might spend $250 USD building a mill from all new parts. But, except for the plywood and bearings, one could almost certainly build one up from 'found' parts. I have a friend who just two years ago built a two-jar mill, including jars, lead media, and wood, for under $75 USD.

 

If you can afford to do any pyro at all, you can afford a robustly-made ball mill -- so long as you're willing to work for it a little.

 

Lloyd

Edited January 13, 2016 by lloyd

[MrB]

I've been meaning to get a Rebel 17, for as long as i can remember. (actually bought one, had it delivered, and it turns out the shipping company squashed it, wouldn't take responsibility, and the seller was reluctant to ship again, and refunded my cash.) Between that, and a Chinese "equivalent" there is a price difference of about 10%, and the Chinese can be had with free shipping, where as the cheapest i have found the Rebel for is another 100USD. The Chinese comes with variable speed, but also a lot more complicated electronics, that just will break at some point.

(In reality i would probably go for 4 3Kilo ones, or 1 5, 2 3kilo ones, rather then 1 7kilo version, but for the sake of argument.) The argument that is made is that the rebels pretty much are immortal, unless you leave them out in the sun, which will degrade the "belt", and, if exposed, the liner. As i said before, for what ever irrational reason, i always discarded the clear plastic, Chinese units, as inferior, but, are they, really?

If it was between one of these, and a harbor freight tumbler, i'd say go with the Chinese one, every day.

 

 

If you can afford to do any pyro at all, you can afford a robustly-made ball mill -- so long as you're willing to work for it a little.

 

I could, quite easily. But it also makes little sense in buying a product that you don't know enough about to say if it's worth the extra investment, or not. If you had to suggest an "off the shelf" mill for a hobbyist, with a "capacity" of somewhere between 3 and 10 kilo. Which one(s) would it be?

Preferably available with 230-240v 50Hz drive, and in EU, or at the very least with a shipping option to get it here...

B!

[lloyd]

Mr. B,

Sorry, I'm a hardcore case: I ONLY recommend building one from scratch, even if you don't use my design (but please, please use my speed and HP recommendations). The gang I hang with at FW.com and Passfire.com have a couple of mills they recommend, but I don't know if they're available in the UK.

 

But the most common "advanced amateur" solution is to build the mill from scratch parts and buy the larger, rubber-lined steel Rebel jars. The hex design and rubber liner improves milling efficiency over my round PVC jars.

 

Lloyd

[OldMarine]

Lloyd, I don't think I've asked you yet about the hobfir mill I have. It has the proper speed and uses what I assume to be your jar design. Opinion?

[lloyd]

I think early models had only a 1/8HP shaded-pole induction motor with little starting torque, had only an imitation of a 'belt' (although later ones had a v-belt), and has vastly undersized, flexible rollers.

 

Other than that, it's a great mill! If you have a very late version, it might have better of everything.

 

If you cannot make it start itself while you're remote to the mill, run at about 70-90rpm with a 1-gallon jar loaded with 29lb of lead and 1Kg of powder, and finish a load of BP from raw ingredients in 2-4 hours, then it lacks in power, belt tension, or speed.

 

Typically, under-powered or o-ring-driven mills tend not to be able to handle proper full charges without being manually 'kick started'. That puts the pyro in extreme danger. Read my article about our deliberately exploding a ball mill jar, on FW.com and Passfire.com. <shrug>

 

Hobby fireworks is not in business anymore, either. Where'd you get it?

 

Lloyd

Edited January 14, 2016 by lloyd

[OldMarine]

I ordered it on eBay. The seller's handle is hobfir. Here's the link:

http://www.ebay.com/itm/351622825001

[lloyd]

Yeah. 1/8HP split phase motor (can't start itself reliably with a full load). Has a 3L v-belt (good). Rollers are thin compared to the loads they'll manage over the life of the mill.

 

If you can find a 1/4HP capacitor-start motor (or larger) to properly fit it, you'd be better off with that. With a full jar, you need that extra starting torque.

 

If the mill won't start itself when you turn it on with 30+lb in the jar, then you have to hand-start. That's not good practice, and in the case of a power failure/restart, if the motor isn't impedance-protected, it could burn up without being hand-cranked again.

 

You know all this stuff Patrick! You make/made your living working with motors like the one on there!

 

Lloyd

[MrB]

Mr. B,

Sorry, I'm a hardcore case: I ONLY recommend building one from scratch, even if you don't use my design (but please, please use my speed and HP recommendations). The gang I hang with at FW.com and Passfire.com have a couple of mills they recommend, but I don't know if they're available in the UK.

 

But the most common "advanced amateur" solution is to build the mill from scratch parts and buy the larger, rubber-lined steel Rebel jars. The hex design and rubber liner improves milling efficiency over my round PVC jars.

 

Lloyd

 

Someone (BB) gave me this "recommendation" to end up with the right speed for any size jar:

 

265.45/((J-M)/2.54)^(1/2)*.65

 

Where J is jar inner diameter, and M is milling media size.

I suspect that it's not perfect, the last post in the thread is him stating he rearranged the formula to provide a more reliable output for metric, but he never did post a different .vbs, and i quite frankly missed the post at the time when it was made, so i didn't ask about it. For all intents and purposes the current one seams to do quite well.

My personal .vbs was edited a bit so i remember who to give credit to, and where to find the post. (His contribution is a nice 3 lines. Mine is a hackjob taking one of his lines, and turning it in to 8, just so i get a yes/no, which pops up the forum thread in your default browser... The things we do to preserve our dignity.)

 

On building... I admit defeat. I have a huge workshop at my disposal, but it all comes down to my ability to actually fabricate something that looks ok, feel and acts reliably, I am anything but a fabricator.

If i were to make, and print out the blueprints, i could probably have one of the employees knock it out in 20 mins, which at least would mean the build was solid, but i'm not convinced in my ability to actually get the right parts for a end result that is actually better then a cheap, bought unit. Also, when i consider building it my self i want variable speed, brush-less, and maintenance free, and when i consider pre-fab units, i'm happy with whatever they opted for. Weird, i admit, but...

Oh, and having someone in the shop make it for me, would mean he has to take time of from his actual job, so i'd be paying for that, as-well as the material. With salaries what they are here in Sweden, i would end up paying as much or more, as for a cheap junk unit, and the end result might not be any better.

 

I do like the PVC jars, but it seams we don't have the rubber cap, and sealing of a BP milling jar with a screw cap... No. No, i think not. But i DO like the idea of the rebel jars.

B!

[lloyd]

I just checked against the 'industry formula' in Imperial, and that's correct.

 

Optimum speed is around 65% of the critical speed (which is calculated by the i.d./media formula), although with some combinations, it can be slower than somewhat faster speeds, so your constant could be from 0.65 to 0.80.

 

Lloyd

Edited January 14, 2016 by lloyd

[lloyd]

Oh... just to be clear, that formula as you expressed it only works for jar and media diameters expressed in cm, not mm. Change the 2.54 to 25.4 for mm.

 

LLoyd

[lloyd]

Patrick and others... see this, if you wish.

 

 

http://www.pyrobin.com/files/the%20explosion%20of%20a%20ball%20milling%20jar.pdf

 

Lloyd

Edited January 14, 2016 by lloyd

[OldMarine]

Hey Lloyd, that tutorial is the main reason I waited until I could use my brother's acreage for milling!

[MrB]

Optimum speed is around 65% of the critical speed (which is calculated by the i.d./media formula), although with some combinations, it can be slower than somewhat faster speeds, so your constant could be from 0.65 to 0.80.

 

I'm using lead for when the milling matters. (BP) So i guess the .65 is fair. I'm also using positively "tiny" media, at 12mm. Looking for a 1" mold, but none so far. Anyway, the figure should be reasonably close to real world. I would like to find some cheap ceramic media, and use it for "other" things, saving my lead for BP, and BP based live compositions. Given that ceramic media is a fair bit lighter, i assume it should spin faster. But i think reality kicks in and says that the drum will spin ever so slightly faster due to being lighter, and with that tiny increase, it's going to have to do well enough.

Also, since hexagonal shapes "lift" the media more effectively, does it affect the constant?

 

Oh... just to be clear, that formula as you expressed it only works for jar and media diameters expressed in cm, not mm. Change the 2.54 to 25.4 for mm.

 

Indeed. It's intentional. Well, at least on my part.

 

Patrick and others... see this, if you wish.

 

 

http://www.pyrobin.com/files/the%20explosion%20of%20a%20ball%20milling%20jar.pdf

 

I've seen that one before somewhere. Ended up being a lengthy talk about if using HDPE barrels would be better or worse, and, to what extent. Nobody did the obvious reality check, and blew one up. I'm on the fence. Most HDPE barrels use a screw on lid, and while that might be fine after filling, and closing the jar, at some point you are going to open it... Screw on lids provide rotary movement and friction. Small risk, but still a risk.

 

Neat test.

 

Hey Lloyd, that tutorial is the main reason I waited until I could use my brother's acreage for milling!

 

Makes sense. Leave lead spread around on someone elses backyard, instead of your own. ;- )

I got a industrial lot where i do the bulk of my pyro. At this point i got 3 20' containers for storage, and shielding. It's not as remote as you'd like, but on the upside it's completely dead in the evenings, and on the weekends. Nothing but pests, cats, seagulls (well, they are pests to...) and me out there. The closest structure is our secondary workshop, in which i have a few tools, presses and such, as they are a part of the workshop equipment. I've added lexan shielding and such, which i couldn't if it was our primary workshop. Lucky, i guess.

I also had a machinist swing by and dig me a hole, put 2 cement "rings" down on each other, and back-fill the outside. That's my milling pit. Anything that goes boom, will end up in the concrete, or quite high in the sky. The return to earth "should" place the solids inside our fence. Should. I'd like to leave that a theory. When i'm not milling, it's closed of with 2 sheets of half inch marine plywood, and 4 sandbags. Mainly to keep said pests from moving in, but also to keep someone, or something from falling in.

B!

[lloyd]

"Also, since hexagonal shapes "lift" the media more effectively, does it affect the constant?"

------------

Not by its 'lifting' action: The hexagonal jar does affect the 'critical speed', because the mean i.d. of a hex jar is different than that of a round jar of the same o.d.

 

Also, that formula has all to do with the acceleration of gravity, and the acceleration of gravity does not change with media density choices.

 

The 'critical speed' is that speed at which the media begins to centrifuge to the outer wall of the jar as it goes 'over the top'. For a given i.d. and media o.d., that speed is the same regardless of the density of the media. Ceramic or lead would behave exactly the same in that regime.

 

Hex jars DO help prevent slippage of the body of the media/charge, but that helps most with 'wet' grinding. With most dry ingredients the charge won't slip, even in a smooth-walled vessel.

 

Lloyd

[Col]

B, I dont see any difference in jar speed between lead and ceramic (53.75rpm), if your motor can turn lead wirhout bogging down it`ll turn ceramic at the same speed. I use 12mm lead too, its not tiny compared to 3/8 ceramic.

 

 

[lloyd]

Split-phase, switched-auxiliary induction motors vary in speed little with load, until they start to slip badly (at which point, they're near stalling). They normally run in the ~98% (no load) to ~90% of synchronous speed (full load without excessive slip).

 

Shaded pole motors can slip a bit more without stalling -- about 100% to 75%.

 

Likely, the little 1/8HP motor on the hobfir unit is a shaded pole variety, so speed could be an issue with load.

 

Lloyd

[OldMarine]

The frame on this unit is large/sturdy enough that I can upgrade later if I don't build one myself. It's worked so far but I've not trusted it unattended. I'm having to power it with a generator so I tote the whole shebang up the hill and enjoy a tasty adult beverage while it tools away. Even with the generator running you can still hear the lead clacking in the pvc jar from a couple hundred feet away!

[Arthur]

I've no problem with having a small mill, 1/ for beginners it saves on chems while getting things wrong, 2/ they are ideal for test batches and odd compounds, 3/ drums are cheap and there is not much media if you want to have one mill for chlorate comps.

 

However for bulk comps and especially BP a big mill well built and designed is essential. One friend had a 200litre plastic drum on rollers with a three phase motor with soft start. I like ceramic media, a cheap mill will spin a drum full of ceramic balls when it will not spin a full drum of lead balls.

 

Some research done in the UK suggested that small drums milling BP made little mess if deliberately ignited but much over a kilo of BP mix would behave badly if ignited. I wonder if the pics are still available, I'll ask -they were not mine.

[MrB]

Not by its 'lifting' action: The hexagonal jar does affect the 'critical speed', because the mean i.d. of a hex jar is different than that of a round jar of the same o.d.

 

So, to calculate target rpm on a hex, you'd ideally measure over the corners, and over the flat faces, and use a number right in the middle of the two?Or do you calculate on the corners, to prevent that the media gets airtime?

 

B, I dont see any difference in jar speed between lead and ceramic (53.75rpm), if your motor can turn lead wirhout bogging down it`ll turn ceramic at the same speed.

 

Weight should make it turn slower with lead. Unless you use a motor that has active RPM controls to increase torque with heavier loads. Which of course is possible. More expensive i suppose. Needs a feedback-sensor to give a RPM signal, and some logic to give it more voltage when the load is higher. Or PWM control, which pretty much does the same thing, but provides short bursts of the full voltage, instead of changing the input voltage.

B!