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Ejection Charge Design?


AzoMittle

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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

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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
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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.
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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 B)

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