PVC as a ball mill tumbler

[EWBTus]

I built my own ball mill and built PVC tumblers (see pic) out of 4" PVC tube and fittings that I use for oxidizers (mostly Potassium Nitrate), Charcoal, and BP - 1 tumbler for each. I use lead balls for milling. My issue is not very good BP. I have tried a lot of different way to mix it - red gum, dextrin, etc. but still get nowhere near the performance of commercial BP on lift (breaks seem to be fine but I think that is because the BP is contained better). My question is about the tumbler - is it possible that PVC is being ground off by the milling and contaminating the ingredients? I have made small batches with a coffee grinder and don't see the issue.

Thx 

[PyroGb]

My first thought is the quality of your charcoal that plays a big role in the quality of the bp Lastly and possibly the culprit may be the size of you container This is just a thought but if your mill is too narrow in your case 4’ than the balls may not be able to roll corectly. If that is the case try maybe puting Less of everything in it or useing a bigger pipe do you have a vid of the bp?

[EWBTus]

I don't but I can try and make one using different batches of BP compared to commercial BP. I test by launching comets out of a 3/4" mortar. Small but when they don't go very high I would rather deal with a little comet than a big one. I saw a video where a guy tested BP with golf balls but somehow waiting for a golf ball to land seems more dangerous than little comets.

 

[cmjlab]

Are you not able to mill all 3 components together?  It's hard to make. b.p. when you first start that compares to commercial B.P. when you aren't milling all 3 chemicals together.  

Personally I don't think you would be knocking much PVC off your mill jar with lead media - it's pretty soft, and you would likely be able to see marking from it if there was enough to significantly alter your B.P.... but I don't know that for a fact.

If you can't due to safety factors, space considerations, or are just not comfortable with that, I am certainly not pushing you to do it, I have immense respect for someone who has established safety parameters, and will not cross them.  However, there is a gentleman on here who did some testing to show that you can make useable B.P., I believe he states "it just takes a bit more of it" to accomplish the something a good hot B.P. would .

Edited January 6 by cmjlab

[FieryCreations]

Do you have lifters in there?

Everyone told me charcoal is important. I did not understand to what degree until I made some using Cottonelle Ultra Comfort. Holy hell what a difference from Skylighters stuff...

[EWBTus]

Sorry for the delay in responding; have had a very bad cold. So, I ball mill the oxidizers in one container and then ball mill the BP mix in another. The components are inexpensive so making separate containers is cheap. I have a third for ball milling charcoal. I have every thing set up for a comparison test and will hopefully get a video tonight. As an aside, I made a small batch of Benzolift as a test - wow! I used the raw BP mix from my ball mill with Sodium Salicylate and Potassium Perchlorate in a 30%/70% ratio.  With a 30g 1.75" test ball 2g was too much (we lost sight of the ball and only knew it landed when it hit the roof of my greenhouse) and outperformed commercial BP significantly. As a comparison Benzolift had a TOF of 9.6 seconds while commercial BP was only 7.1 seconds. I have read about the many dangers of Benzolift so would rather use BP.

[EWBTus]

I was curious about the height of the previous test with a 30g 1.75" test ball on 2g of Benzolift that had a time of flight of 9 seconds. Did some ballistics math and the answer came out to 1300 feet. Seems high for a little test ball. 30g may be heavier than typical so it may be an inertia thing. Thoughts?.

Edited January 16 by EWBTus

[EWBTus]

So, finally was able to make a video of my not so good BP. #1 is commercial BP, #2 is BP made in a coffee grinder with Skylighter Airfloat, #3 is balled milled BP made with Skylighter hardwood charcoal (36 mesh balled milled), and #4 is balled milled BP made with same airfloat. All are consolidated with alcohol and screened through a 20 mesh screen and I used the finer than 10 but courser than 20 cut from the mix. As you can see they all suck. I use the same mix as #4, mixed to a slurry and coated on rice hulls as a break and it works fine. At $30 a pond commercial is expensive. As you can tell my wife is quite unimpressed. 😄

Thoughts

 

 

[Pyrogeezer]

On 1/4/2024 at 10:49 AM, EWBTus said:

I built my own ball mill and built PVC tumblers (see pic) out of 4" PVC tube and fittings that I use for oxidizers (mostly Potassium Nitrate), Charcoal, and BP - 1 tumbler for each. I use lead balls for milling. My issue is not very good BP. I have tried a lot of different way to mix it - red gum, dextrin, etc. but still get nowhere near the performance of commercial BP on lift (breaks seem to be fine but I think that is because the BP is contained better). My question is about the tumbler - is it possible that PVC is being ground off by the milling and contaminating the ingredients? I have made small batches with a coffee grinder and don't see the issue.

Thx 

Hi EWBTus, Great looking jar! I had access to a good amount of PVC stuff on a construction project I was consulting on and built a few dedicated 8" mill Jars with 5-3/4" high half round PVC lifting bars. I use one for BP charcoal exclusively. It has been in operation intermittently for the past 4 years, (15 to 20 times a year). I use 3/4" hard lead balls for the media and it can comfortably mill 5 pounds of powder per batch. We use it for R&D samples of powder for our American Visco Safety fuse. I used PVC primer and cement to bond the bars inside the schedule 40 PVC pipe body and they have held up great. You can expect a good long life out of your jar. 

About the particles from the PVC. We did notice the same issue on our jars but it disappeared after a few operations, but they were few and far between.   

Edited January 26 by Pyrogeezer

[cmjlab]

I'm still confused..... Is the OP ballmilling all 3 components individually,then ballmilling them together to make B.P.? Or is he ballmilling them individually,and screen mixing them together?  

As for the PVC particles, I used a 6" PVC mill jar (homemade) for 2 years before switching to the Rebel mill jars. Not as big as PyroGeezer, but bigger than. The one shown, so I would think the PVC particles would have shown for me as well.   I didn't notice any PVC in any of my batches using Lead / Antimony milling media, then stainless steel media for the 2nd year of the PVC mill jar use.  I had square lifters in my jar, because I was too lazy to sand them down. I'm not a physicist, but I've read some information in several places that the media grinds by cascading action causing particles to be ground up between the surfaces of the media.  Since they shouldn't be falling from the top of the mill and smashing into the sides of the PVC jar, I'm not exactly sure how you would get that much PVC into your B.P.  again, I'm not saying anyone is wrong, since I don't have the knowledge to argue otherwise.

Either way, I would assume that a small amount of PVC would not be responsible for the performance reflected in the video above (the bits I could view of the video anyways, maybe I'm the only one, but the only videos I can really watch are YouTube videos.  The videos like the one above just buffer, play a few frames, then buffer for quite a while till I give up).  

[cmjlab]

Now that I re-read that, it may come off a bit "asshole-ish", sorry, I have COVID and my brain may not be functioning at 100% just yet.

[Arthur]

Sulphur and potassium nitrate are chemicals of commercial purity, charcoal is a natural mixture, with it's own structure (from the cells of the tree). Charcoal is the ingredient that needs most care. Willow and red alder are the classic timbers for British BP from history. Eastern red cedar (apparently found retail as pet bedding!) is highly regarded. Old demolition lumber may also offer some well dried pine for little or no money. 

Does your mill have enough media of a reasonable size? IMO you need a mill jar half full of media, and the media should be 8 to 16 balls to a internal diameter of the jar.

Sometimes it helps to reduce the size of the charcoal lumps to pass 2 or 4 mesh with a hammer or rolling pin (of your own!).

[EWBTus]

So, I decided to count my balls - I use 150 1/2" lead balls which weigh about 5 pounds. It fills the tube to a little less than 1/4 of capacity. My mill setup uses swamp cooler parts so it has no problem turning with 5 pounds of BP mix and the 5 pounds of lead balls. I mill the oxidizer separate and sift it into >160 mesh, >100 mesh but <160 mesh, and <100 mesh. I put the middle fraction in with the charcoal and sulfur and mill for 4 hours typically.

[AustralianPyromaniac]

It's not the PVC. The mill, milling procedure, or charcoal is going to be the issue. 

The mill should be half-full, not a quarter. 1/2" lead is a good size. Your RPM may be too low. Jar is too small for proper media cascading. Charcoal may be bad. The mill may be overloaded. Probably all of the above.

Based on that load of media, it should be charged it with maybe 150g of BP, no more. Mill it for 12h, maybe longer if your RPM is low. 4 hours is fine for a well-tuned mill but likely not nearly enough for what you have built. 

Probably the result will be acceptable. Then you can start eliminating variables to get a better process. If that does not work, the jar you have made is the wrong dimensions and will not work at all. Build a new one. 

Did you design this ball mill by calculating its specs, or just wing it? 

Edited January 29 by AustralianPyromaniac

[cmjlab]

2 hours ago, EWBTus said:

So, I decided to count my balls - I use 150 1/2" lead balls which weigh about 5 pounds. It fills the tube to a little less than 1/4 of capacity. My mill setup uses swamp cooler parts so it has no problem turning with 5 pounds of BP mix and the 5 pounds of lead balls. I mill the oxidizer separate and sift it into >160 mesh, >100 mesh but <160 mesh, and <100 mesh. I put the middle fraction in with the charcoal and sulfur and mill for 4 hours typically.

So based on what you said  in this post, I would agree with everything AustralianPyro said.  

Mill should be half full of milling media, your B.P. charge when in the jar with media that fills 1/2 a jar, should be a total of approx. ~3/4 full; leaving 1/4 empty space.

Id also suggest throwing a small black marker mark (or a piece of tape) on the bottom edge of the jar and count how many RPM your jar rotates at (also like AustralianpPyro said).  If it spins too slow, then you lose the milling efficiency that allows to mill for a shorter time.  If it spins to fast, your media sticks to the walls from centrifugal force and you lose the milling action of a substantial portion of your media.

Edited January 29 by cmjlab

[Arthur]

The media should IMO JUST be covered by the the ingredients.

Unless you have a really good reason do not skimp on mill time even though milling ingredients means three times the milling time.

[Mumbles]

Just chiming in well after the fact here.  A mill underloaded (within reason) with media, can still make good BP.  It just takes longer.  Same thing with the RPMs of the jar.  A 4" jar with 1/2" media should be spinning around 90 RPM I believe to get optimal cascading efficiency.  I ran a Harbor Freight rock tumbler for a number of years with far from desirable conditions.  It was underloaded with media, it spun way too slow, and I was overloading the amount of BP in it by about 50%.  It took 8-12hr to get what I needed, but it eventually got the job done.  

I would say your charcoal source is another area to look at.  Commercial hardwood is far from optimal in terms of speed or lifting abilities.  These sorts of factors are amplified in smaller shells and smaller scale tests.  Hotter the better for this scale of testing.  

As far as the PVC, I doubt it would be much of an issue.  I upgraded to a 6" mill with PVC jars based on Lloyd Sponenburgh's design.  It consists of a piece of 6" PVC, an end cap, and a 6" to 4" reducer and a rubber cap.  Over the years the initially crisp cut corners of the PVC pipe wore down a bit and were rounded off.  The various pieces had some dings, scratches, etc. but the general integrity was maintained.  

[MadMat]

This is a very late post, but... My first ball mill was a home built and I used 4" pvc for the tumbler and it made great black powder! I used 50 caliber lead musket balls for media. I never milled single components. I would just measure out my chemicals, throw them in and start it rolling. My mill spun at approximately 93 RPM. After 3 hours, I had very good grade mill dust. If I added my KNO3 in its prilled state without any pregrinding, I would mill it for four hours just to be sure. As for charcoal, I made my own from either black willow or cedar, since I have both trees growing around my farm.

 

 

Edited May 18 by MadMat

[Arthur]

Try for a mill jar that's say 8+" diameter and 3" to 4" long, yes I'm sure PVC pipe that size is available wherever you live, but finding a short piece may need friends or contacts, fill the jar 1/3 full of media -probably ceramic balls, and run it for 12 hours.

Go for the classic fast charcoals -Willow and Red Alder, or something available locally to you that's known to be good (even soft paper!). If the incorporated powder is not good after 12hours of milling then mill for another 12 hours!

Rock tumblers usually run too slowly to make powder in a short time, if you try to speed the rotation then usually it will stall or the drive will slip -which is why you use ceramic media - it's lighter so easier to turn. If you have to consider neighbours and noise then find a rubber mill jar, they are seriously quieter than rigid plastic jars.