I began using "gun barrel" type charge holders in 2010 when I designed the Space Cowboy 54mm for the fastest to 10,000ft. drag race at LDRS. The rocket would easily go over 20,000 ft.& did.
That's the altitude generally accepted where deployment can get wonky without proper containment.
These were the first iteration of the design. Rocket had a payload so there was room for 2 on each end of bay. Really not needed for main as it fires under 1000 ft.
Current day version with hex bottom removed, I still have them tapped for #6 all thread so I can just screw them on the tie rods and eliminate nut. Even on larger size BP's 3-4inch. I just use #6 size screw to hold on BP as tie rods are usually #10 or 1/4-20 size.
No need for them on both sides as I mentioned, main deploys at low altitude & no room in NC when deploying with H.E.D. [out of cone]
dimensions are approx 1/2 in. diameter & 1.75 long.
I use 1 on 38 minimum with 2 matches in same holder for redundancy.
Here is an interesting test article/pdf done by Jim Jarvis.....[the other Jim] explain how all this works. Shows how when test 1 gram charges at equivalent altitudes pressures with his chamber were done, only 1-2 tenths of charge burns leaving 8-9 tenths, unburnt in chamber.
Jim Jarvis high altitude testing & results: I was the "other flyer" who sent the plastic vials. I was doing some testing of my own 'caveman' style. After placing plastic vial's into airframe on ground, I was amazed at the sharp, jagged pieces of plastic remaining and knew there had to be a better solution. {same plastic as vials that so many use now with flip lock lids, scares me}
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This validated what I already knew, [not to that extent however] but shocked us with how little actually burns, due to cold & pressure non transfer of heat between BP particles.
If any of you who live in the cold North, ever lit a plain ole strike match below freezing, has seen how slowly the head burns with very little flame. Translate this same phenomena to our ejection charges at higher altitude where temps can be in the -30 to -75 range and lower.
Yes for normal sport flying a NON-ISSUE.....BUT many of the non initiated, are beginning to fly these 2-stagers & minimum diameter projects over 20,000.
My mate Nic's version used inside a 7-1 cone [3ft long]for his 63,000 ft flight.
Av-bay is in tip of cone with barrels pointing back. 12in. long if memory serves. Screws hold sled in place going through NC in 3 points. There is an aluminum ring where screws attach. See post down bit with side view of assemblies.
Quite Xtreme & not needed, [by me] but they work for him and that's what he uses on everything he does.
Just trying to make folks aware of some of these issues they will encounter. No vendor I know of is making these available, so they would serve those doing these type flights if they were.
I suppose a poll maybe in order to sort out the demand.
I do know many, in the same boat as myself, make & use them.
They work....we use them...'nough said. :smile:
Edit: almost forgot...there are other methods [as always] but this one works for me!