kpknd Posted July 5, 2014 Posted July 5, 2014 (edited) I made some granulated 60-30-10 BP rocket fuel as per instructions in the Skylighter publication and was not impressed. I used 4oz and another motor size that behaves well and both burst imedatly after takeoff. I will stick to my tried and true fuels rather than trying to figure out a new one. The screen mixed 60-30-10 worked perfectly. in the same rockets. Edited July 5, 2014 by kpknd
MrB Posted July 5, 2014 Posted July 5, 2014 I made some granulated 60-30-10 BP rocket fuel as per instructions in the Skylighter publication and was not impressed. I used 4oz and another motor size that behaves well and both burst imedatly after takeoff. I will stick to my tried and true fuels rather than trying to figure out a new one. The screen mixed 60-30-10 worked perfectly. in the same rockets.Sounds like it either got to hot, or you hadn't compacted it properly leaving cracks. But there isn't anything wrong with using a known good setup. Stick with what you know works, unless you have reasons to try and diversify.B! 1
kpknd Posted July 5, 2014 Author Posted July 5, 2014 My thaught has been that this fuel can leave small voids between compacted grains leading to a CATO.
pyrokid Posted July 5, 2014 Posted July 5, 2014 What were the specifications of the motors? How was the fuel compacted? I rammed about ten one pound rockets last summer with granulated 6-3-1 without binder and had no issues.
MrB Posted July 5, 2014 Posted July 5, 2014 My thaught has been that this fuel can leave small voids between compacted grains leading to a CATO.If you cant compact granulated BP enough to avoid small cracks and voids, then you need to hit harder, or use a larger press. Granuals aren't dense enough to make this an issue. Corned stuff i suppose you should press with more force / square then it was compacted with before corning it. Never played around with that, so no idea. I use my BP as powder for rocket-engines.B!
hindsight Posted July 6, 2014 Posted July 6, 2014 kpknd, You don't say whether you press or ram. The same question occurred to me, and I press at 9000psi. It seemed to me that when pressing at that pressure, the granule size (for example, meal versus FFG) used for BP rockets would not affect the CATO rate, but I lack the experience to make that statement empirically.
jessoman Posted July 6, 2014 Posted July 6, 2014 (edited) Also, if you suspect that "cracks and voids (in between grain)" is the case. How does the outside of the motor look? If your hand ramming you may have stuffed things up. Which tubes are you using? Edited July 6, 2014 by jessoman
kpknd Posted July 7, 2014 Author Posted July 7, 2014 I am ramming with a rawhide mallet like I alwas do, the tubes are 1/2" I.D. from firefox. I'm not going to worry about it since granilating just involves more steps and screen mixing or ball milling is what I'm more familiar with anyway.
nater Posted July 7, 2014 Posted July 7, 2014 I have found that granulated fuel compresses easier and much cleaner than unprocessed screened or milled fuel. For rocket fuel, you do not need a binder. If you dampen, granulate and dry the fuel, these steps will make soft grains which compress nicely and are not dusty. The grains are not as durable as using a binder, but will work just fine for rocket fuel.
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