AboutJames Bell Expertise I am a member of Tripoli Rocketry Association, and am certified to fly hi power rockets. I can answer questions anyone may have about design, materials selection, stability calculations, motor selection, altitude and performance predictions, and parachute and recovery options.
Experience I make my rockets from existing kits or parts readily made through commercial channels. I do NOT make my own motor propellants (they are challenging enough even for the companies that do this for a living), and I do not advocate making rockets using "typical household item" such as paper towel rolls.
Question Hi James. I did some more searching last night and finally came across my answers about how to set up the black powder ejection charge. I don't recall what I finally used as search terms in "Google", but I got to Info-central.org and Rocketry Planet and learned about how to make the charge and how to wire it to be triggered.
There were basic ideas like making a cup out of plastic wrap (with an electric match taped and taped really tight), PVC cups with tape on top, to reuseable items like the "No Match ejection system".
I read that the black powder comes in different qualities (3Fs - 4Fs, etc), and that it's better to make a charge a little too strong than not enough (damage to the former can be mitigated by a longer shock strap... to a degree).
So, I think I got enough basics that I can go from here on my own: purchase BP at a gun store or something, figure out a containment device, ignition method attached to the containment device, timer/altimiter connected to ignition method...
If I'm off target with this stuff, let me know.
Thanks. --Glenn
Answer Glenn -
You are pretty close on your solution. I prefer FFFg (3Fg) powder, but 4Fg works well also. I used an altimeter that charged a capacitor, releasing all its energy at once. I used a large flash bulb with long leads. I take the charge of black powder and wrap it in a small piece of plastic cling wrap. Just enoug to hold it, but not too thick. I wrap and tape the powder package around the flash bulb. I would imagine an electric match would also work. All you need is to have the black powder contained so the match can ignite all of it at once. I've never experimented with reusable plastic PVC cups. The match/bulb goes off, the powder burns and expands through the plastic wrap and the expanding gases blow off the nose cone.
If you don't have any electronics for your altimeter, I would suggest you look at one of the Adept systems (http://www.adeptrocketry.com/).
