resistor for ball mill earth stake

Hi
I have made a ball mill using orange waste pipe, I am fairly sure its PVC. I have made a couple of ball mills and had a couple of interesting experiences opening them up after milling! Mostly its just been charcoal etc that I have milled but now I am milling some more erm 'lively' materials, I have the milling machine at the bottom of the garden out the way. I want to try and reduce the static as much as I can so thought of adding a earth stake tied to the various parts of the machine frame and stuck in the ground.
Any idea if I need a resistor? if so would 10meg do it? I had charcoal catch light on my last tube when I opened it (more of a flash) and the stuff I want to mill now is a bit more touchy.

Not knowing what a "ball mill" is, I went to google satellite view of the earth and looked at your back yard to see.
**broken link removed**

I built a ball mill for my brother to mill charcoal for his fireworks so to prevent static issues I made it out of steel and the drum is directly on the output shaft of the gearbox that the motor is connected to which in itself is grounded through both the mills metal frame and power cord.

That's what I would recomend however as a cheat for a plastic one I would say just put a ring of aluminum foil tape on the inside that goes to a screw that connects it to the outside and a second aluminium foil tape ring and have that ground through a brush of sorts like a small wire that drags over the drum that's connected directly to the earth ground.

ronsimpson said:

Not knowing what a "ball mill" is, I went to google satellite view of the earth and looked at your back yard to see.
**broken link removed**

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LOL nah thats the old one!! I can not get my head around using something that big!! Man a small 10cm one made a mess when it went off!
They are a nightmare, you have to judge the time just right. Not long enough and the powder isnt fine enough and a couple of mins too long and it become pyphoric. I am using lead coated with antinime shot, so a metal container was considered on the no list, also with a metal container WHEN they go bang you get high velocity steel shooting about.
PVC isnt great to use but its pretty tough with a inbuilt weak spot. I have a copper collar on the tube and all the metal bits are connected by wire bonds, I wasnt sure if I needed a resistor before the ground stake. I wont be doing much of this mix but I want to watch static with it, once this lot is done I am back to charcoal and plant material. A bit safer but I still keep the quantity down to a couple of grams tops.
Those things in the picture are asking for a big bang! I have a stainless steel tube for doing iron powder for a catalyst but I dont use much. This one is going to mainly be for plant material and willow charcoal for a chemical scrub tube, the trouble with the charcoal is you need it really fine but just before it gets to the burn in air by friction stage. The number of people on the chemistry sites that have ball mills go bang is pretty scary, I have around 250g of potassium perchlorate to powder in batches. I dont like messing with it in lumps let alone a fine powder.
I also want to mill down some acid washed diatomaceous earth for a chromatography column, i am fed up paying ridiculous money for florasil powder for the columns.

Interesting pictures

And I have a (mildly) interesting story, vaguely connected.

Near where I grew up was a monument, called Earl greys Tower:



Since I was a very small child, along with others of my friends, we'd tried to climb it - it's 50 feet high, and the door was bricked up well before our time.

From 4 or 5 years old, to probably 20 odd?, I'd always managed to get about half way up, then started shaking so never managed higher than that.

So we applied 'technology' (bearing in mind there's no way to get there, other than by walking).

Back then I was a caver, and I owned 110 feet of SRT rope and 50 feet of wire caving ladder (two 25 foot ladders that clip together).

So the problem was how to get the ladders to the top of tower.

Enter ball mills

One of my friends worked at a local brickworks, they had a ball mill - and threw the balls out when they were reduced to about tennis ball size - so our friend Roger got one of these steel balls and welded a small metal hoop to it.

We then bought a ball of string, and tied it to the steel ball, threw the ball over the tower, tied the string to the rope, and pulled the rope over the tower. Finally we tied the rope to the ladders, pulled the ladders up the tower, and tied the end of the rope to a nearby tree.

We then climbed up the ladders (me first!) to get to the top of the tower - this was when I discovered that it was a VERY idea I'd never managed to free climb it, as the stones round the top were all loose - and trying to support your weight on the top stones would have resulted in a rapid 50 foot descent closely followed by a large heavy piece of stone

Needless to say, good view from the top, and we obviously climbed down the spiral staircase to the back of the bricked up door at the bottom.

Fun things you do when young and stupid

Most people run a bare copper wire threw pvc to keep it from shocking you. If you could fix a piece inside some how and slip ring on the outside to ground it You'd end your problem.

Nigel Goodwin said:

Fun things you do when young and stupid

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Some of us lived and some did not.

be80be said:

Most people run a bare copper wire threw pvc to keep it from shocking you. If you could fix a piece inside some how and slip ring on the outside to ground it You'd end your problem.

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I have copper tape on the outside, for charcoal I would put a hole in it but for perchlorate I fill with Butane and seal it shut. Oxygen is a bad idea inside a ball mill with some mixtures, lucky enough I dont intend to do many batches of this. Charcoal makes a huge woosh when it meets air after its been milled too fine, I might try an acrylic tube one day (well grounded) so I can see how fine the powder is. Normally I only do plant material and it dosnt have to be any finer than flour, it just makes extracting the compounds easier with a soxhlet extractor if you have a fine powder.
Apart from the perchlorate which is for bonfire night the plant stuff is for an insecticide I am working on. I normally plant Marigolds around my carrots (dont laugh), this year I didnt and had really bad root fly. I cant find out exactly what it is in marigolds that stops the flies, all the literature seems to contradict which components are responsible. So I am extracting marigold flowers with pet ether and chloroform and then separating the fractions with column chromatography.
Whats really odd is even with very high quality whatman TLC plates I only get 7 peaks, yet when I put a sample through the gas chromatograph I get 11. The books name 5 components in marigold, so somewhere there are a few missing in the books and they seem really hard to isolate.
The plan is too powder the dried flowers by first freeze drying carefully then powder and extract, its a bit of a distraction really and I should be concentrating on the other experiment. But my reactor has gone a bit quiet at the moment, the culture is alive still but seems to have slowed right down. I wish there were some decent Biology forums about, but most are either really snotty or more a help with your homework thing!
There is a distinct lack of decent science forums these days. As a side note I have a visit next week to Dumfries University, I emailed a lecturer there asking for a copy of a paper he did (I didnt want to pay £35 for it!). He emailed me the paper and asked if I would like a tour of his lab, I expect he thinks its the first time I have been in a pro lab . But I figure it dosnt hurt to network and is a day of school and a chance to cadge some reagents or microscopy stains if I am lucky

I have copper tape on the outside

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That don't help the inside. The copper on the inside keeps the charge from happening one on the the outside doesn't do anything if it's not hooked to the inside. Think of it like a capacitor one side is inside one is outside where you short the pins the cap can't charge. And the power is being applied on the inside. So you short both to ground they use this in pvc to keep from starting fires. When you move dust in the pipes.

But the same Idea would work closed up and spinning you build the charge but it has a piece of copper running the from end to end and grounded there be know build up or leave it ungrounded make lightning bolts LOL and a fire

be80be said:

That don't help the inside. The copper on the inside keeps the charge from happening one on the the outside doesn't do anything if it's not hooked to the inside. Think of it like a capacitor one side is inside one is outside where you short the pins the cap can't charge. And the power is being applied on the inside. So you short both to ground they use this in pvc to keep from starting fires. When you move dust in the pipes.

But the same Idea would work closed up and spinning you build the charge but it has a piece of copper running the from end to end and grounded there be know build up or leave it ungrounded make lightning bolts LOL and a fire

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Burt it never occurred to me! Yeah makes sense when pointed out. I could use metal end caps and have that connected to a short wire inside and the copper band on the outside. Having seen alot of these homemade ball mills for pyro powder I am starting to see why so many go bang! Nothing I have seen so far has an earth inside, very few are metal because many of the powders are shock sensitive so plastic and soft balls are preferred. Maybe the missing link is the inside earth!!
I will remake the one have, I dont actually ball mill anything that bad but the perchlorate isnt something I want going off while holding the tube.
I will pass this on to the chemistry lot as some of them ball mill flash powders etc pre mixed (utter madness).

A 10 meg will help prevent a flashover spark and therefore a source of ignition, a conductive tube to make the mill might be better too, metal is probably a no no, if it went bang then it'd make thing much worse.
If you nuke certain types of drainpipe in a microwave it'll get hot, indicating the presence of metals, some brands seem to use it, I've done this when I've made radomes.

Be carefull messing around with nasty stuff.

A mate of mines brother is a chemist, and has been known to make rockets and other dangerous things.

With my brothers mill we just put rubber sewer pipe end caps on them. Easy on easy off and guaranteed to blow off before the metal blows up.

So far he has been running that way for years and has done hundreds of pounds of charcoal without a single incident so obviously the design works here.

BTW with your over milling issue once you get your charcoaling process worked out to produce consistent charcoal material you can time you milling down to within minutes of knowing exactly when you are going to go over the edge of over pulverizing it and thus can put a simple timer on your mill to make perfect batches every time.

Hers what we do around our farm to entertain ourselves.
https://www.youtube.com/results?search_query=mum+pyrotechnics

I have tried timers and they work to a point, the main problem is charcoal type, we have alot of different willow growing here and as willow is the worlds greatest ever charcoal thats what i use .
I built a stainless steel tube for pyrolising the charcoal and it works well, I use methane or butane as the initial filler gas and then heat until no more gas is evolved then add 5 mins. The milling time depends on the thickness of the twigs used and type of willow, this is where I come unstuck with timers . If I wasnt lazy and if I could afford a decent brass gauze I would use an inner brass mesh of appropriate size for the powder I am making and just let the powder fall out the way of the balls.
The pipe I use is common in the UK and is orange, its predominately PVC but fairly hard so gives very good results. I use 3 different types of ball depending on what I am powdering, I use ceramic for hard powdering of mainly charcoal and I use antinomy coated lead shot of different sizes for medium risk stuff, then I have lead shot coated with PTF for anything thats nasty (chlorates mainly). I am always very careful and the mill is a good distance away from building and people, I still get a tingle when approaching for the uncapping though . I only mix powders using the paper transfer method and do it nice and slow to reduce friction.
I dont use the same tubes for different powders I would rather make and use a new tube for each different compound I powder.
One of the ptro forums I use has a thread on a really experienced pro firework maker, he was powdering a mix (a no no for me) and on taking the mix out it deflagrated and took his hand off and part of his arm. His mistake was being in a rush and making sure he had a cotton suit on, I learn from others mistakes!
In the UK there are tough laws on most of the chemicals so I have to be careful anyway, lucky I live well away from anyone else so bangs and flashes dont draw attention .
I have seen a very thick borosilic glass tube for sale but the price is very high! A glass tube would be cool because at the moment I have to stand there and listen for a couple of mins to make sure I have the best speed.
My next make project is a 2 axis Clinostat, but at the moment I am only at the design stage. I have a single axis one but they are limited in value for what I want

Little Ghostman said:

the main problem is charcoal type, we have alot of different willow growing here and as willow is the worlds greatest ever charcoal thats what i use .

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Are you sure about the 'willow'? Always read that grape vine was the best pyro charcoal.

Why not use copper or bass pipe and the rubber end caps that TCMtech was suggesting for the ball mill. Non sparking using copper or brass and conductive to the ground brush.

for most things Brass is great, my concern with this is impact, its not really risky like a chlorate but I prefer a softer material to metal. The other problem is some the mixtures reactor in a bad way with metals, as you mill tiny particles come off and can cause problems later.
Nothing beats willow , never tried grape but willow has a great structure when char coaled and to be fair i have got used to using it lol, most of the pyro guys have favorite that cant be beaten, but as a general rule most agree that willow is good. Grape isnt easy to come by here so it isnt an option. Beech is too fine a grain and oak is too coarse, hazel is medium but like hazel willow you can copice so you get a good choice of size and age and it grows quick. One other minor point most of my charcoal isnt used for pyro, most gets used for reactions and catalysts and a few other things like biological beds. So to be fair my claim that its the very best should come with a disclaimer that its the best for what I use it for and have access too .
The perchlorate I am using is for pyro and I made it myself in a electrolysis cell, I also make chlorates but mainly for weed killers and other non exciting projects.
Brass would be a good choice for charcoal but it costs a fortune and like most metals is something goes wrong you have shrapnel flying about, My very first ball mill was some old steel scaffold pole, I used it twice until it was pointed out I was playing with what is essentially a pipe bomb waiting for an excuse to go off.
If this pipe goes bang I dont have to worry about it going through me.

My brothers choice for pyrotechnics charcoal is a local type of red willow that most everyone else sees as almost being a nuisance plant around wet areas. So far at the national competitions they are making some of the top grade stuff with it.

As for the shrapnel effect PVC is not much safer than common low carbon steel. PVC and similar hard plastic piping tends to shred under certain conditions whereas steel tends to peel open. Also with steel unless it's very thin just having one end of a container open makes it very difficult to blow it apart into shredded pieces.

Now for purposely blowing things up in a pipe for launching tube he prefers to use either the heavy rolled paper tubes that bulk rolled materials like newspaper stock are delivered on or to use heavy wall poly pipe which is very stretchy when exposed to high pressure shock loads.

IF i ever wanted to launch something up into the sky I would use the cardboard rolls like you describe, they are great but in the uk you have to pay for them , well worth the money though.
Charcoal milling yes steel or metal isnt a problem, chlorates and perchlorates I just wouldnt trust the powders. Call me chicken but that stuff is hair raising enough without flinching every time a ball drops down in the tube , I dont do open ended normally I normally use butane or nitrogen depending on what I want the powder for. Most my uses are not pyro so sometimes I need an inert atmosphere, especially if the powder is for the reactor experiment, I have no idea why but the charcoal works better if milled under butane. A rough guess I would say the pores pick up the butane so the microbes dont get an oxygen overload, but I dont know the real answer just that it works for me.
Thanks for the tips.

You do know that two things happen here one the PVC can charge two you heat up the mill it's getting hot if you keep the heat lower you'll be a lot safer.
And for god sakes I hope you can turn this thing off from more then a 100 feet away . I would monitor the temp too cooler is better. Oh and do all this at 100 feet plus.
PVC would be like standing and letting someone throw knifes at you.
And don't use a PVC cap use a rubber cap like a test cap that can pop off easy then you just get a little fire not a bomb going off.

be80be said:

You do know that two things happen here one the PVC can charge two you heat up the mill it's getting hot if you keep the heat lower you'll be a lot safer.
And for god sakes I hope you can turn this thing off from more then a 100 feet away . I would monitor the temp too cooler is better. Oh and do all this at 100 feet plus.
PVC would be like standing and letting someone throw knifes at you.
And don't use a PVC cap use a rubber cap like a test cap that can pop off easy then you just get a little fire not a bomb going off.

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No I didnt think of heat! heat is never a problem with charcoal but with the perchlorate it could well be! So point noted and a water bath will be installed under it, end caps are actually now silicon (RTV) I molded them myself they will pop off easy enough.
The controller is a decent distance away even for charcoal I dont switch on or off anywhere near the thing. I have a roll of cat5 cable that runs to the frame so I have about 300m if needed, currently I am around 200' from it for charcoal but it will be further for the other mixtures. I am looking at casting a RTV silicon sleeve to fit inside a metal tube, I double checked and metal and chlorates are not good friends. Perchlorates dont seem so bad but I cant guarantee my perchlorate is 100% chlorate free so I have to treat it like chlorate mix.
The motor is 8' feet away from the mill and is powered by a belt to the drum rollers. I doubt I will be making much more of this stuff so mainly I am looking for upgrading the ball mill for charcoal.
The willow has started to turn now and the leaves are falling , I have a few more weeks to get some decent twigs processed. The winter wood is great for pyro but not so good for the bio beds, when you heat the green woods quickly and the steam explodes it makes the pores bigger, not too sure it matters for pyro mixs but for bio beds it hold the bacteria better.

I saw first hand the results of a PVC pipe blowing up at work. They were building a large vacuum reservoir for a rubber molding press line. 60 feet of 12 inch double strong PVC pipe. Solvent welded joints. The "engineer" of the project told the pipe fitters to use air pressure to check for leaks, so they hooked up the air hose. The air rushing in and the static it caused set off the solvent fumes in the pipe. Sent big, sharp chunks of PVC hundreds of feet across a big building. The pipe was under a catwalk of 3/16" steel trad plate which was ripped in to more big chunks, but stayed in place because it was welded to its frame work.

Luckily no one got hit or hurt, but many of the people needed to change their underwear. This was in a fully working factory at the time.