AzoMittle Posted May 25, 2014 Posted May 25, 2014 In homemade motors how can you make an ejection charge for the recovery system? What I mean is for low to midpower rockets (subsonic / small diameter) how much 'oomph' do I need from my motor to push a parachute? I'm using r-candy with paper tubes, concrete bulkheads and nozzles. I treat the paper with high heat paint (1200F) glue and roll it, pour a bulkhead, attach motor mount/centering rings, this is glued into the body tube; the nozzle is poured separately and the fuel is cast into long BATES grain (simulated in BurnSim) making a lightweight reloadable motor.I was thinking of putting a nozzle on each end or drilling a small hole in the bulkhead, while using a slower fuel for the appropriate delay; is this a good design? Would it be more appropriate to leave the nose-cone end as an end burner essentially? I could also build a baffle directly into the motor tube in place of a motor bulkhead/retainer. Is fuel rich r-candy okay for a delay charge or should I use bp? Is delay/ejection normally cored or end? I've been looking around but I can't find any articles. I haven't downloaded RockSim yet and didn't see how to do it in OpenRocket. Thank you, Azo
nater Posted May 25, 2014 Posted May 25, 2014 The delay is not cored. The ejection charge is typically a small amount of loose, granulated BP. You can test the ejection charge in the rocket on the ground to see if it will pop the chute out. I highly recommend David Sleeter's book "Amateur Rocket Motor Construction" if you want to learn more about delay grains and ejection charges. Another great site is James Yawn's site: http://www.jamesyawn.net/rcandy/index.htm
schroedinger Posted May 25, 2014 Posted May 25, 2014 Just keep building them like you do, and drill a passfire into the bulkhead. For the ejection charge about 3g bp should be god to too much.
WSM Posted May 30, 2014 Posted May 30, 2014 Just keep building them like you do, and drill a passfire into the bulkhead. For the ejection charge about 3g bp should be god to too much. I think it better to go lighter on the grained BP. See if 0.5g-1.0g will do. There's no sense blowing the nosecone and parachute so hard they separate from the rocket body . WSM
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