nater Posted October 8, 2011 Share Posted October 8, 2011 I'm curious how many of you mill your fuel, or just screen it. With your method do you prefer a more reactive coal? When Steve LaDuke talks about the BP fuel for his U/H spindle, he says it works with screen mixed fuel using commercial air-float. I've had terrible luck with this method. At a recent shoot, I tried a new batch of fuel, ball milled for a couple hours using alder coal, and had CATOs. I think I'm going to try milling commercial airfloat for my next batch and see how that goes. Link to comment Share on other sites More sharing options...
TheArchitect23 Posted October 8, 2011 Share Posted October 8, 2011 (edited) i personally screen once, then mill for maybe 1 hour, with commercial air float. what size rockets you making? are you ramming or pressing, if ramming make sure you are on a hard surface, any crack or loose spot in the grain will cause a CATO.also, what ratio are you using? full 75-15-10? most of the time with standard tooling that is to hot.try 65-25-10.remember, to hot add more charcoal, to slow, more KNO3.( re-mill after making adjustments. ) Edited October 8, 2011 by TheArchitect23 Link to comment Share on other sites More sharing options...
nater Posted October 8, 2011 Author Share Posted October 8, 2011 (edited) I'm making 1/2" and 3/4" rammed core burners right now. I've tried 60:30:10 fuel on standard tooling 70:20:10 on U/H tooling and 75:15:10 for nozzleless. The best flights I've had were using screen mixed 75:15:10, with a nozzle on standard 3/4" tooling. The other combinations I've tried have either stayed in the rack, made a nose dive into the field, or flown to an acceptable height, but slow enough I don't think they'd lift anything. I'm making small batches of fuel while I get everything dialed in to my tooling, but I'm just curious what seems to work for most people. I'm planning on building a press this winter. I'm coming up with a design that I hope will work with a bottle jack and allow an upgrade to an electric power pack in the not-too-distant future. Edited October 8, 2011 by nater Link to comment Share on other sites More sharing options...
Mortartube Posted October 8, 2011 Share Posted October 8, 2011 (edited) Try coffee milling your KNO3 first and sieveing, and use airfloat. The fuel I use is as fine as Talcum powder for a 16mm ID (roughly 3/4") core burner with an 8mm choke. I don't have a very fine commercial sieve, so I use a very fine small homemade sieve using material from a pair of womens tights. DO NOT SCREEN MIXES through these. But it is good for making sure you only get very fine KNO3 from the coffee mill. I do not ball mill the fuel for these core burners. I only ball mill fuel for endburners of the same size. Standars 75:10:15 with a 3mm choke. Edited October 8, 2011 by Mortartube Link to comment Share on other sites More sharing options...
pyrokid Posted October 8, 2011 Share Posted October 8, 2011 (edited) Nater, For my one pounders, I simply screen the fuel (6-3-1) and screen granulate it with water and no binder. This is using homemade white pine charcoal passed through a kitchen sieve, so I have a range of airfloat and coarse grades of fuel in there. These will lift 150 gram payloads. The potassium nitrate is very fine. Good luck! Edited October 8, 2011 by pyrokid Link to comment Share on other sites More sharing options...
drthrust Posted October 8, 2011 Share Posted October 8, 2011 (edited) i mill for three hours when making willow nozzle-less motors, i have the mill on a simple household timer, to get consistent as possible propellant Edited October 8, 2011 by drthrust Link to comment Share on other sites More sharing options...
Peret Posted October 8, 2011 Share Posted October 8, 2011 I always ball mill rocket fuel, after this experiment. http://www.youtube.com/watch?v=FzeXiaAlLmY Link to comment Share on other sites More sharing options...
nater Posted October 8, 2011 Author Share Posted October 8, 2011 Peret, that first rocket is about how my screen mixed fuel performs. Without a header, I don't get a round trip. Guess I'll try milled fuel with my commercial airfloat instead of the more reactive coal next. Link to comment Share on other sites More sharing options...
allrocketspsl Posted October 11, 2011 Share Posted October 11, 2011 try screening three times then wet then knead it for say 5 minutes then granulate on a 1/4 inch mesh thats all i do works great!Although mine has to set 3 weeks before I can use it cause my formula is weingarts 57/34/09(lots of charcoal for my red tails)yeah yeah everyone thinks I crazy but it works for me Link to comment Share on other sites More sharing options...
drthrust Posted October 11, 2011 Share Posted October 11, 2011 what size motors are you using the 57/34/09 in? Link to comment Share on other sites More sharing options...
WonderBoy Posted October 11, 2011 Share Posted October 11, 2011 (edited) Ballmilling is not essential to making a good nozzled BP rocket motor. Yes, ballmilled fuel is going to be faster(hotter) than screen mixed fuel. You simply have to allow for this when developing(or choosing) your formula. If you are not going to mill your rocket fuel, then you may need to use a hotter composition, one with a higher ratio of KNO3 to charcoal. I do not mill my fuel for nozzled BP rockets and they lift 3" cylinder and 4 1/2" ball shells with ease. I use a mix quite a bit hotter than 60-30-10, it is closer to 75-15-10 with a few percent of KNO3 replaced with coarse charcoal. I use commercial lump charcoal, most any other charcoals would CATO a motor with this comp. But ballmilling or using airfloat individual chemicals is a must. Using a coffee grinder doesn't cut it. A coffee grinder alone will not grind the chemicals near as fine as they need to be. Edited October 11, 2011 by WonderBoy Link to comment Share on other sites More sharing options...
dagabu Posted October 11, 2011 Share Posted October 11, 2011 Ballmilling is not essential to making a good nozzled BP rocket motor. Yes, ballmilled fuel is going to be faster(hotter) than screen mixed fuel. You simply have to allow for this when developing(or choosing) your formula. If you are not going to mill your rocket fuel, then you may need to use a hotter composition, one with a higher ratio of KNO3 to charcoal. I do not mill my fuel for nozzled BP rockets and they lift 3" cylinder and 4 1/2" ball shells with ease. I use a mix quite a bit hotter than 60-30-10, it is closer to 75-15-10 with a few percent of KNO3 replaced with coarse charcoal. I use commercial lump charcoal, most any other charcoals would CATO a motor with this comp. But ballmilling or using airfloat individual chemicals is a must. Using a coffee grinder doesn't cut it. A coffee grinder alone will not grind the chemicals near as fine as they need to be. I made a single 3# BP rocket with riced 75-15-10 and then added 15 parts 80 mesh charcoal three years ago on a BP spindle lifting a 500g shell to about 200'. The tail and sound was amazing so I tried time and again to duplicate that rocket to no avail. I think it had more to do with hot charcoal at the time and less with the airfloat nature of the chems. -dag Link to comment Share on other sites More sharing options...
Algenco Posted October 11, 2011 Share Posted October 11, 2011 I made a single 3# BP rocket with riced 75-15-10 and then added 15 parts 80 mesh charcoal three years ago on a BP spindle lifting a 500g shell to about 200'. The tail and sound was amazing so I tried time and again to duplicate that rocket to no avail. I think it had more to do with hot charcoal at the time and less with the airfloat nature of the chems. -dag hmmm, need hot charcoal Link to comment Share on other sites More sharing options...
allrocketspsl Posted October 12, 2011 Share Posted October 12, 2011 what size motors are you using the 57/34/09 in? 1lb,2lb and 3lb size Link to comment Share on other sites More sharing options...
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