Jsweimer Posted October 1, 2017 Posted October 1, 2017 I seem to have a consistent problem with my attempts at BP rockets, in that they simply explode rather than fly. Some research brought me this- Core depth to be approx. seven times the inside diameter.Core diameter to be 33% of inside diameter. That said- if I had a body that was .75 i.d. x 7.5" in length, my core would be .250" X 5.25". Cannot figure out why I am making big firecrackers rather than rocket motors. Any help would be greatly appreciated! Jeff
Mumbles Posted October 1, 2017 Posted October 1, 2017 Those dimensions sound right. We can't give much more help if you don't provide more information. Type of tube, formula, how you're ramming/pressing, what sort of tooling, etc. I'm going to take a total stab in the dark, and say it's probably the propellant you're using. You can't use full strength BP in nozzled core burning rockets. If you made them without a clay nozzle they'd probably fly fine. 60:30:10 nitrate:charcoal:sulfur is probably the most common core burner fuel.
Mortartube Posted October 1, 2017 Posted October 1, 2017 You could try nozzleless rockets. Use hot milled BP in small increments and make sure it is well rammed or pressed. I always rub the rammers and spike with a candle. This helps to lubricate things a little. This process will get some good motors flying. In the meantime you can experiment with nozzled rockets. I suggest this as it can be very frustrating if you can't get ANYTHING to fly properly at all.
OldMarine Posted October 1, 2017 Posted October 1, 2017 I've quit putting nozzles in my rockets I use for lifting headers altogether and just use nozzleless using the hottest BP I can make. With my nozzled core burners I'd still get the occasional CATO even with weaker fuel and I got tired of premature erockulation taking out a header I'd spent hours building. My core burners are standalone devices that give a pretty tail and a salute at the end.
Maserface Posted October 3, 2017 Posted October 3, 2017 I seem to have a consistent problem with my attempts at BP rockets, in that they simply explode rather than fly. Some research brought me this- Core depth to be approx. seven times the inside diameter.Core diameter to be 33% of inside diameter. That said- if I had a body that was .75 i.d. x 7.5" in length, my core would be .250" X 5.25". Cannot figure out why I am making big firecrackers rather than rocket motors. Any help would be greatly appreciated! Jeff I am not surprised that you are gettin catos with those tooling dimensions, a more traditional design would use a 50% nozzle opening, that is, 0.375" opening in a 0.75" ID rocket. The difference between a 0.375" nozzle and a 0.25" nozzle is actually pretty huge, as far as performance goes. you could reduce the length on the taper to 2.25" for a more reliable rocket
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