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How many hours do you ballmill your BP?


Ubehage

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As Caleb mentioned, using a "real world" test is usually the most telling. Besides a baseball in a 3" mortar, the other common way to test is the FPAG shuttle BP tester. http://pyrobin.com/files/pvc%20bp%20tester%20pdf.pdf This is Ned's build of it, but the parts list is the same as the real FPAG one sans the weight and sponge and stuff at top.

 

Granulating is easy, but it's one of those things where everyone has their own opinion and method. I like 5% dextrin and straight water wetted into a clay-like lump and granulated through a 4 mesh screen. Spread thin on a piece of paper or lined screen and allow to dry in a well ventilated warm area. In the sun in a breeze is ideal. Stir every 30 min or so, and it can dry in a couple of hours.

 

In truth, using good quality dextrin will allow you to drastically reduce the amount you need. 1-3% is often sufficient. The stuff from Phil at www.ihaveadotcom.com is awesome, but I'm sure other suppliers are also offering great product too. Using homemade dextrin, which I don't really recommend anymore, will require a little more. You may also hear suggestions about using straight alcohol, which I do not like as it tends to give softer grains. Some have rediscovered that 70% isopropanol will somehow also activate dextrin. I've never understood that in the 10+ years I've known and tried it, but it works. If I can already dry my powder in a few hours I've never really felt the need to add alcohol to the mix just to shave a little bit of time.

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I used the shuttle tester quite a few times. When I tested balsa BP with it, it shattered on some hard summer ground. What I didn't like about the shuttle was that it can only be reliably used on a perfectly windless day. Otherwise, even a slight wind can cause it to wobble in the air. The shuttle is oblong and unevenly weighted. I don't see how such an object was designed as a black powder tester, but I followed the herd. Now I use baseballs and I feel they are much better suited to the task.

 

I don't know that the 70% isopropyl activates the dextrin. I don't know that it doesn't either. After nothing but failures to make good grains with any kind of pure alcohol with any kind of black powder, I resorted to 70% isopropyl alcohol. It makes fairly hard grains without using dextrin. There is a guy on FW that uses an alcohol solution to make match bound with dextrin. He says it works great. My thinking is that the much of the alcohol evaporates before the water does, thereby increasing the percentage of water in the remaining liquid enough that the dextrin then binds. I don't know that to be true either. But it works somehow!

 

I think that most people overlook the fact that potassium nitrate itself can (and does) act as a binder for black powder. Anybody that makes pucks or knows how commercial powder is made knows this. The sulfur is also said to plasticize under pressure and bind the powder, but in my simple tests, I saw no evidence of that. I also never saw the slightest hint of binding from the volatiles in the charcoal. I believe that the rapid drying of screen-granulated black powder is what makes the hardest grains, and that water must be present for that to occur. Straight alcohol-granulated powder is uselessly fragile for anything other than making rockets. It's dusty even for that, and the rockets will most likely CATO. Alcohol is expensive too.

 

I have done experiments where I proved that pure alcohol or acetone do not bind potassium nitrate to itself, and that adding water to those same solutions did cause binding. I'll see if I can find those results.

 

I've also found some dextrin to be noticeably less sticky than other seemingly identical dextrin. From experience, I would also never recommend making dextrin at home.

Edited by DavidF
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...

 

I don't know that the 70% isopropyl activates the dextrin. I don't know that it doesn't either. After nothing but failures to make good grains with any kind of pure alcohol with any kind of black powder, I resorted to 70% isopropyl alcohol. It makes fairly hard grains without using dextrin. There is a guy on FW that uses an alcohol solution to make match bound with dextrin. He says it works great. My thinking is that the much of the alcohol evaporates before the water does, thereby increasing the percentage of water in the remaining liquid enough that the dextrin then binds. I don't know that to be true either. But it works somehow!

...

I've also found some dextrin to be noticeably less sticky than other seemingly identical dextrin. From experience, I would also never recommend making dextrin at home.

 

That is my best guess as well. It works for stars too. Rock hard 1/2 color stars overnight. Still can't wrap my head around it.

 

The point about dextrins is good. I haven't had enough experience with various suppliers to have a good feel for what's bad, good, and outstanding though.

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I agree on the home made dextrin.. pretty crappy was the best i ever did. I got some from Phil and it's like super glue. Everything you touch when you get it out gets all sticky. :)

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Caleb,

I never had that problem! I made dex pretty much from the beginnings of my pyro exploration, until I finally got into circles where I could obtain the commercial product.

 

Mine was always "like glue"... really.

 

Lloyd

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Making decent dextrin is not all that hard. My stars were fine, the grains came out plenty hard. Compared to commercial stuff though it's like Elmer's vs. Titebond.

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The dextrin I got from HCS a year or so ago must suck then because I can't get the "hard grains" you guys describe whether I use 100% water or 50% Water & 50% Denatured Alcohol or even 80%/20%. Maybe my definition of hard glossy wax grains relies too heavily on the small 4FA Chinese grains I cannibalized on small commercial products.

 

Don't get me wrong the method I use produces some hot 2-4FA grains but they aren't as pebble grain hard as what I picture when I read your guys' posts.

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Well, there's two of us that didn't make it right ;) Anyhow- I think dextrin is too important, cheap, and readily available to try again to make it.

 

Nickmaslo, I only said 'fairly hard'. Fair is just above fail! Also, the weather is very important to perfect drying. Right now I'm going through the laborious process of making, corning and grading black powder pucks. Those are some hard grains. I'm only doing it for testing purposes, but geez, I'm getting a lot of other 'stuff' I can use from it! I may just keep making all my black powder this way. As a hobbyist, I don't need huge amounts.

 

The beauty of the pucking process is that it makes durable grains that are clean to handle, and are very predictable in performance. The PITA factor seems like it might just be worth it. This is the direction I'm leaning toward. I already have a press for rockets, and making pucks is really quite easy, using it.

 

For me, making screen-granulated powders with water or water/alcohol mixtures has always been a bit of a crapshoot. Even coating rice hulls with the same mill dust, some batches have a bigger 'whump' factor. The nearest I can tell, it's from the drying conditions more than anything else.

 

If I take mill dust and screen-granulate it with 2% wax in naphtha, I get 'grains' that are soft and dusty, pretty much. But, for making rockets, it's ideal in texture and hardness. The performance of batch to batch is consistent. The drying conditions are not that important when using waterless solvents.

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I mill 4lb batches for 18hrs. with 5% Dextrin. When i granulate it with 25/75 91% alcohol/water i dry it as fast as i can, if it is cold or not at least 80 deg.F sun shining i put it under a heat lamp. As long as i stay with the same charcoal i get pretty consistent powder. I cant see where i need to be corning. You are right David i think the faster you dry it, less KNo3 that leaches out.

Mumbles how can you beat testing it the way you are going to use it? Oh i forgot David i can make a 2" comet and when it dries i drop it on the floor and it doesn't break.

Edited by dynomike1
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Hey Nick, good to see you posting again!

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I will prove that my screen-mixed powder method using supermilled charcoal is better than using milled powder. People will ultimately see that they never need to mill complete black powder to get a superior product.

 

Yesterday, I took my pre-milled willow charcoal, pre-milled potassium nitrate, and rubbermakers sulfur, and screened them twice through 40 mesh. I sprinkled 3% additional dextrin onto it, and worked it in, as an afterthought. The powder was blended by hand with 70% isopropyl rubbing alcohol. Then, I forced it through a 4 mesh screen. The powder was dried and graded.

 

Today, 10 grams of the coarsest grade (2FA) gave a baseball flight time of 11.5 seconds. This seems incredible but it is true.

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I will prove that my screen-mixed powder method using supermilled charcoal is better than using milled powder. People will ultimately see that they never need to mill complete black powder to get a superior product.

 

Yesterday, I took my pre-milled willow charcoal, pre-milled potassium nitrate, and rubbermakers sulfur, and screened them twice through 40 mesh. I sprinkled 3% additional dextrin onto it, and worked it in, as an afterthought. The powder was blended by hand with 70% isopropyl rubbing alcohol. Then, I forced it through a 4 mesh screen. The powder was dried and graded.

 

Today, 10 grams of the coarsest grade (2FA) gave a baseball flight time of 11.5 seconds. This seems incredible but it is true.

This is not impossible, however in my experience ballmilled powder has always been better than my screenmixed.

Ned Gorski have also said that screened BP wetted with alcohol (no binder!) should perform very good as well.

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This was just a test to get a better feel for the different preparation methods.

 

10 grams, pucked, corned, and graded to 2FA gave a baseball flight time of 8.9 seconds

 

Pucked, corned, graded to Fg (12-16 mesh) gave a time of 11.2 seconds.

 

The above-mentioned powder, with the 3% dextrin, gave 11.5 seconds, the highest of all.

 

This just goes to show that density and particle size are very important considerations when evaluating black powder. I'm not suggesting everybody use rubbing alcohol. We should be trying to avoid the use of solvents, IMO. I wanted to try it 'just because'.

 

I am now of the belief that 3 component milling limits the potential of black powder by limiting the fineness of the grind of the charcoal component. It's not just the simple tests above that lead me to this conclusion. Giving the most attention to the most critical component- the charcoal- is where I'm at in my thinking. If I did side by side tests with one component vs. 3 component milling with the same charcoal, I think the one component powder would win.

 

I think Roger O 'Neill's ground-breaking black powder study in Pyrotechnica 17 scratched the surface but didn't quite 'get there'. My results have been achieved with far less time and effort. I believe the weak area in O 'Neill's work was to use large ceramic media to do the milling. He acknowledges that in the article. My use of small stainless steel media is what makes all the difference. O 'Neill's work was my inspiration, and the happy accident of receiving 6600 5/16" 304 S.S. spheres- for FREE- put me on this path. The media chose me :)

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I have a lortone 15lb. Barrel and a homemade roller assembly w/ variable speed control and this is how I do mine, I put in the mill 450 grams kno3 90grams b.p and 60 grams of sulfur. The jar has a couple hundred .490 lead balls to fill to the jar half full I then dump all ingredients in and run at 70 rpm (approximately) for around 3 to 3.5 hours. It's now like talcum powder. I now add roughly 5 to 6% water by spraying, just enough to keep the dust down I then press at 10,000lbs of force on a 1.75" die. Let dry for few days then crush the heck out of em. Sifting out 3 and 4fa granules. No dextrin at all and they are hard as rocks sound like glass clinking them together, iv lifted 4" shells WELL Above where they should be broken at using 7 to 8% of the weight of the shell.. Edited by MudDuckPyro79
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I have a lortone 15lb. Barrel and a homemade roller assembly w/ variable speed control and this is how I do mine, I put in the mill 450 grams kno3 90grams b.p and 60 grams of sulfur. The jar has a couple hundred .490 lead balls to fill to the jar half full I then dump all ingredients in and run at 70 rpm (approximately) for around 3 to 3.5 hours. It's now like talcum powder. I now add roughly 5 to 6% water by spraying, just enough to keep the dust down I then press at 10,000lbs of force on a 1.75" die. Let dry for few days then crush the heck out of em. Sifting out 3 and 4fa granules. No dextrin at all and they are hard as rocks sound like glass clinking them together, iv lifted 4" shells WELL Above where they should be broken at using 7 to 8% of the weight of the shell..

This sounds like the same process i use, except for I grate mine instead of pucking it. I was using 10% wt for lift and my shells were going to high so this year i will be using 8% wt. Ive tried milling longer than 3 hours but did not ever notice a difference in the power that came from the lift so i stop right at 3 hours and make 500 gram batches.

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The only reason I puck them is it gives consistent results (for me) and when I separate mesh sizes the granules are of a consistent size. And it just plain looks better
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MudDuck

 

You may try breaking your pucks when they are still 'wet'. Letting them fully dry makes them tougher and harder to break up. They are still plenty hard with the few percent of water but they take a lot less effort to break apart right after pressing than letting them dry.

 

Dave F - I would be really interested in hearing what kind of flight times you got with the FPAG shuttle, even if it wasn't your favorite tester. I like the concept of being able to compare BP but never found many people sharing their results, even as a member of FPAG (though I'm not the most social butterfly in the world). I did notice the shuttle would 'wag' a bit but don't remember anything too extreme and I always averaged multiple shots to get a result and didn't notice to many large time variations and didn't think much of it. But if you still have your longest flight time using 4g of BP I would love to know assuming you have them and not too hard to track down.

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This is what comes of pucked and corned. If it's clear enough look at how the grains are all pretty consistent thus is why I do it thus way.

post-20978-0-29031100-1491526911_thumb.jpg

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FlaMtnBkr, here are my results from the original BP testing I did with the shuttle tester. I got it from Ned. It was called a 'dongle' at the time. I don't know if it was identical to the FPAG tester or not. All my tests used 4.0 grams of powder or friable granules. I realize now that the mill dust tests were pretty much useless, but I included them for posterity.These results are years old and my note-taking stinks. When I first started out, I was using ceramic media. The media for all these tests was probably .780" diameter cylinders. It's possible I switched to mixed sizes by the time I got done this round of tests. I don't recommend ceramic for this purpose.

 

1) 8 hour milled willow-based red gum BP, per Ned's instructions- 7.0 seconds

2) 3 hour sumac BP with 1 1/2% wax- 6.6 sec.

3) 3 hour willow BP with 2% wax- 6.5 sec.

4) 3 hour willow BP 7:1 on rice hulls, 6.4 sec. I may have used more than 4 grams to account for the rice hull weight.

5) 3 hour alder pellet BP with 1 1/2% wax- 5.4 sec.

6) GOEX Fg- 4.9 sec.

7) 3 hour willow BP milled with 2% wax as fine shavings, tested as powder- 4.5 sec.

8) Same powder as above, granulated with water- 5.5 sec.

9) 3 hour willow BP with 2% shaved wax, then riced with lacquer thinner- 6.4 sec.

10) Same powder as above, riced with water- 5.5 sec.

11) Same powder as above, after drying more- 5.9 sec.

12) Willow BP, 2 hour mill, granulated with alcohol only- 7.2 sec.

13) -20 mesh red oak, pre-milled 4 hours, then milled as BP 3 hours, granulated with alcohol- 6.6 sec.

14) Same powder as above, but the BP mill time was doubled to 6 hours- 7.1 sec.

15) -20 mesh balsa charcoal milled 1 hour, then milled as BP 4 hours, riced with alcohol- 6.9 sec. Shuttle wobbled in flight.

16) Same powder as above on a very still day- 7.7 sec.

17) -20 mesh clear white pine charcoal milled 4 hours, then milled as BP 4 hours- 4.9 sec. Probably mill dust was used.

18) -20 mesh Castor plant stalk charcoal milled 4 hours, then milled as BP 4 hours- 5.4 sec. Probably mill dust was used.

19) Old willow charcoal, milled as BP 4 hours- 8.2 sec. No other details. Charcoal was likely milled 4 hours, BP was likely riced with alcohol.

 

These mill times are excessive, and the media used was the least efficient also.

Edited by DavidF
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I'm following along with my own variations on Dave's experiments. I don't have free, magic stainless media, even though I'd really like to :).

I have a Rebel 17 jar with 35# of 1/2" spherical lead media. I mill 500g of my ERC pet bedding charcoal for one hour, stopping once in the middle to clean the area around the lid.

 

I mill 882.4g of greenhouse grade nitrate and 117.6g of slightly gritty sulfur together for an hour, again stopping once in the middle to clean the grit out from under the lid. I screen that sulfur/nitrate mix through a 100 mesh and toss what little refuses to pass through it.

 

I take 85% of the sulfur/nitrate mix, and 15% of the charcoal, add some dextrin (still playing with amounts there), then sieve everything twice through a 40 mesh and once through a 100 mesh. Wet with 7:3 isopropyl alcohol until very soft dough, then granulated through a 4 mesh. Graded -4 +8 mesh "2FA." The results speak for themselves.

These first tests were with no binder. I'm now working on slowing it back down and hardening the grains up, since they are quite fragile.

 

https://www.youtube.com/watch?v=3ApZg0X5mY4

 

And here are some tests with dextrin. All 10g shots.

 

https://www.youtube.com/watch?v=rPTpQfmq6NA

 

Keep in mind that the "old stock" and "6hr milled" powders have served me well for lifting all of my cylinder shells up until this point. That's the power level I'm shooting for.

 

So, I guess the point is that if you make 3 component milled powder, but don't care for the inherent danger of it, you don't need anything different from what you already have to make screen-mixed powder. You'll probably want a 100 mesh screen if you don't have one already, but those are cheap: https://www.amazon.com/SE-GP2-14-Patented-Stackable-Sifting/dp/B00BP2I77U/ref=s9u_simh_gw_i1?_encoding=UTF8&fpl=fresh&pd_rd_i=B008B0T5Z2&pd_rd_r=17SDWDA1NJPYH77D8YY0&pd_rd_w=QfCds&pd_rd_wg=yQvRI&pf_rd_m=ATVPDKIKX0DER&pf_rd_s=&pf_rd_r=G6BEYNC5M8F24952FRTS&pf_rd_t=36701&pf_rd_p=781f4767-b4d4-466b-8c26-2639359664eb&pf_rd_i=desktop&th=1

Edited by Wiley
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This is what comes of pucked and corned. If it's clear enough look at how the grains are all pretty consistent thus is why I do it thus way.

Can you give a few more details of your methods please? I mean about the process to obtain the granules out of pucks until they are granulated.

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