theinkdon Posted August 12, 2015 Posted August 12, 2015 Thanks for the responses, Mumbles and pyrokid. After I posted that I went and read the link that tradami posted in message #22, and it put my mind at ease about my BP efforts. Everyone says that the charcoal makes the difference, so I'm confident that by getting the results I did with the commercial airfloat then when I get my hands on some better charcoal I'll be set. Thanks again.
tradami Posted August 12, 2015 Posted August 12, 2015 Hi all, new here but thought I'd share something and ask some follow-on questions about it. I'd bought some "airfloat" charcoal (probably hardwood) from one of the pyro places before I knew anything about BP besides the basic formula. Mixed up a batch of 75/15/10 +1 dextrin in my new Harbor Freight rock tumbler with 1/2" ceramic media, milled for 3.5 hours, wet with water, made a lump, screened it through 4 mesh, let it dry two days, ran through the 4 again, then sorted it with 12 and 20 screens. Made some little 1/2" and 3/4" mines with it, just shooting a star or two, and some flying fish fuse bundles, using 10% of the weight of each payload as a lift charge, using the -4+12 granules (equivalent to 2FA, yes?). The results were disappointing to say the least. Doubled and then tripled the powder charges, and it was only then that the effects got high enough to burn out before coming back down, but even then they weren't satisfying. So today I did some more experimenting. I had some 1.125" ID tubes, 8.5" long, I'd salvaged from a commercial cake, so I hot-glued four of them to a base. Then I made four dummy shells from some 3/4" ID tubes, 1.75" long, filled with sugar and capped with rammed clay on each end. I wrapped them with some magazine paper and blue painter's tape till they barely fit in the tubes. They weren't jammed in, but mostly slid down under their own weight. Each weighed 27 to 28 grams. Now mostly I've read that 2FA size grains are used for lift, so that's what I used yesterday. But today I was thinking that finer grains ought to give a bigger oomph for the same weight, so that's how I set up my four tubes. In the first I put -10+12, 30% of the weight of the shell, about 8 grams. In the next I used -12+16, in the next -16+20, and in the last, whatever passed my 20 screen. (These are stainless steel woven screen fabric from Grainger, so probably similar to what others use.) So guess what? The second shell went higher than the first, the third higher still, and the fourth went highest, probably to a height I'd feel comfortable with breaking stars at. So my questions: this is probably really slow powder, right? I probably needed to mill it longer, and I haven't yet done the mod to make the HF mill drums turn at 80-90 RPM. That's okay, it was only a 200g batch, and I have some willow charcoal coming in the mail. But now that I've proved to myself that it works better in smaller grain sizes, is it okay for me to use it like that? More generically, if you made up a batch of BP and it was a little slow, is there any harm in using smaller particle sizes of it in order to "speed it up"? You probably wouldn't want to use -20 to dust like I did here, but could you use -16+20? Does it get into the "hardness/violence" of the lift charge damaging shells or something? Is it okay to use 4FA as lift? Thanks in advance for any insights.Mike A couple things to add here. I was in your exact same position doing the exact same thing as you. You can look into my above linked thread to see my journey. You are going to be amazed at how much faster your BP is with willow. Here's my comparison between airfloat and willow. Everything was exactly the same for these two BP's except for the charcoal used. One was airfloat the other was homemade willow. https://www.youtube.com/watch?v=h88veIHX3UMhttps://www.youtube.com/watch?v=rpB9RVOyL90 Also, you should reduce your mill comp a bit. Your drum should be half full and then you should add 1/4 comp to your drum leaving 1/4 open. This is around 130 grams ideally. I would recommend to do this especially since your mill isn't optimized. You can optimize your mill by adding a piece of tubing over your existing roller. This article details it: http://www.skylighter.com/fireworks/how-to/ball-mill.asp Basically you just need to purchase a 1/2" I.D. x 3/4" O.D. tube to slide over the existing roller. This is available at home depot.
schroedinger Posted August 12, 2015 Posted August 12, 2015 For this tube size -20 +30 is a very good granulation. These tubes are short, 2 FA will burn longer then the insert need to exit.From 2 - 4 " 4 FA is a good lift after that 2 FA. If you wan't to play more with the granulation 3 FA in 4 and 5".
theinkdon Posted August 13, 2015 Posted August 13, 2015 tradami: you're right, I seem to be following exactly in your footsteps. My first batch of commercial airfloat BP caught the paper on fire just like yours did. Yesterday I received an order of willow charcoal artist's sticks I'd bought on ebay, ground those up, milled a 75/15/10 (no binder) batch overnight, wet it with denatured alcohol today, riced it through 10-mesh, let it dry for maybe an hour under a fan, then did the flash test again. WOW, is all I can say. A 2" line of BP flashed almost instantly, didn't burn the paper, and didn't leave much if any residue behind. That by itself made me a believer, but I was pounding up some 3/4" (1 lb) sugar rockets tonight, so I used some of the new granules as a little salute header, maybe a half-teaspoon, and again, WOW! Doing the same thing with the old powder only made a jet out the top of the rocket, but this one made an oh-my-gosh BOOM. I'll repeat my testing with the 1&1/8" mortars and dummy shells in the next day or two and post the results, but I can already tell they're going to be good, more in-line with what you more experienced guys are used to. For anyone reading this later, JUST BUY (or make) THE WILLOW (or similar) CHARCOAL **NOW**, at the beginning of your journey. Don't fool with the commercial hardwood airfloat stuff. It makes THAT big a difference. (Today I received a 1 lb order of willow charcoal from Phil's General Store, so that'll be this weekend's project. After that I'll be making my own from the cedar pet bedding.) Schroedinger: thanks for the granule-size tips for these smaller tubes. I figured +20 was as low as I'd want to go, but you're saying -20+30 so that's good to know. I don't have a 30-mesh screen but I've got a 40 so I'll use -20+40 in my experiments. Thanks again guys!
tradami Posted August 13, 2015 Posted August 13, 2015 tradami: you're right, I seem to be following exactly in your footsteps. My first batch of commercial airfloat BP caught the paper on fire just like yours did. Yesterday I received an order of willow charcoal artist's sticks I'd bought on ebay, ground those up, milled a 75/15/10 (no binder) batch overnight, wet it with denatured alcohol today, riced it through 10-mesh, let it dry for maybe an hour under a fan, then did the flash test again. WOW, is all I can say. A 2" line of BP flashed almost instantly, didn't burn the paper, and didn't leave much if any residue behind. That by itself made me a believer, but I was pounding up some 3/4" (1 lb) sugar rockets tonight, so I used some of the new granules as a little salute header, maybe a half-teaspoon, and again, WOW! Doing the same thing with the old powder only made a jet out the top of the rocket, but this one made an oh-my-gosh BOOM. I'll repeat my testing with the 1&1/8" mortars and dummy shells in the next day or two and post the results, but I can already tell they're going to be good, more in-line with what you more experienced guys are used to. For anyone reading this later, JUST BUY (or make) THE WILLOW (or similar) CHARCOAL **NOW**, at the beginning of your journey. Don't fool with the commercial hardwood airfloat stuff. It makes THAT big a difference. (Today I received a 1 lb order of willow charcoal from Phil's General Store, so that'll be this weekend's project. After that I'll be making my own from the cedar pet bedding.) Schroedinger: thanks for the granule-size tips for these smaller tubes. I figured +20 was as low as I'd want to go, but you're saying -20+30 so that's good to know. I don't have a 30-mesh screen but I've got a 40 so I'll use -20+40 in my experiments. Thanks again guys! Take a look at this chart for mesh sizes for grades of BP. http://oi60.tinypic.com/33eppu9.jpgSource
theinkdon Posted August 15, 2015 Posted August 15, 2015 Just wanted to post my results after repeating the tests with my new willow BP. I've seen people recommending that the weight of lift powder be in the ballpark of 8-10% of the weight of the shell, so with the same 1.125" tubes and the same dummy shells from the other day I set one up with 6% by weight of 4FA (-12+20), the next with 8%, then 10% and 12%. I figured the 10 or 12% would be the sweet spot for my non-optimized Harbor Freight milled willow charcoal artist-pencil BP. So, expecting the 6% tube to not do a whole lot I lit it, and WOW, the shell went higher than 30% of the -20 commercial airfloat ballmilled BP tested in my first post. ONE-FIFTH the weight in willow BP, and larger grains to boot, performed way better than the commercial airfloat fines. Incredible! I lit the 8% tube and of course it went even higher, surely high enough for a shell break, but I didn't think to time it. After the thump that one made I didn't even light the 10% and 12%. If I find later after breaking my first shell that more height is needed then I'll bump it up. So again, thanks to all for the great info on this forum, and the specific advice in this thread. To any other newbies looking for help with your commercial airfloat, give it up and get or make some GOOD charcoal. It really is the key to good BP.
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