Charge Canister Options

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Kruegon

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I've read about people using .38 casings for charge canisters. I dont have access to them. What I do have is .223, .45, .40, 9mm, and 7.62x54R. I have polished steel in a few, brass in most, and the 7.62x54R I believe are copper washed steel. Which would you recommend as my best option? I can and am willing to cut down the necks of the .223 and the 7.62x54R.
 
I've used sections of SU motor casing, cut down. I've also used copper pipe caps. I think you could pick from a number of different brass casings with equal results.

I haven't flown HPR for quite awhile, so things have probably changed alot, but I used to cut a small square of Saran Wrap, pour BP into the center of it, set an e-match in the BP, form a small tight ball around the BP, and seal it with a nylon quick tie. It was then placed into the "charge cannister". I usually had a small hole in the bottom, that the twin lead fed down through, but others I know just draped the twin lead over the edge and down into the cannister.
 
Any of these would work. For convenience (depending on your av-bay bulkhead layout) I would go for a larger diameter casing as it is just easier to add the BP and pack appropriately. Also pay attention to the length vs dia ratio as you will get better burn at any altitude with a higher ratio (longer vs same dia.), e.g., in the chart below although the 9mm and 357 magnum are essentially the same diameter select the 357 mag as it has a length 3X+ the dia.

22-to-50.gif
 
Just cut the 7.62x54 off to about 1 inch long and you have a good charge cannister for smaller HPR and all the Estes PSII kits, the .45ACP will do the same job just as well. Knock the primer out, drill the flash hole to whatever size screw you want to fasten the casing to your AvBay cover with.
 
Thanks guys. Glad I asked. For the PSII kits I was considering the 9mm.
 
Is there any reason why I shouldn't use cut down, spent, Estes 18mm motor cases for canisters?
I'm planning on securing them to the bulk plate with epoxy then placing the igniter inside with wadding on top.
I'm only planning to fly the rocket a couple of times at most so providing they survive the first flight, no problem.

From what I read I'm guessing this is not the best way to go? Something stronger and metallic maybe?

Thoughts and advice welcomed. This will be my first time using duel deploy and charge canisters.

SO.

PS. Good advice on the length/dia. Ratio. Is 3:1 a good starting point?
 
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They don't have to be super strong. Like electricity, an explosion will always take the easiest path, in this case, straight out of the open end. People use PVC, plastic wells (like Doghouse sells), aluminum (Blastcap and MAC Performance), syringes, etc.

As far as length vs. diameter, obviously too wide is no good. You want to maximize the pressure going forward and not out the sides. 2;1 or 3:1 is probably reasonable. And remember to pack the BP with dog barf on top so that it is as compressed as you can get it, and tape it down with masking tape.
 
Another method is finger tips of surgical gloves. Cut the tip off, insert powder, e-match and tape up with masking tape. It's a practice used by many and it's quite cheap.
 
Another method is finger tips of surgical gloves. Cut the tip off, insert powder, e-match and tape up with masking tape. It's a practice used by many and it's quite cheap.

True. Didn't mention that because I've never tried it.
 
True. Didn't mention that because I've never tried it.

Its used by many indeed, its also by some not recommended for use in lighter weight Estes types tubes due to the fact it can if the charge gets against the side blow out the tube wall.
 
I was told the glove tip or the tape package method was good, but put it into the charge canister to direct the blast the direction you need it to face. I just needed to know what size casing to use.
 
I was told the glove tip or the tape package method was good, but put it into the charge canister to direct the blast the direction you need it to face. I just needed to know what size casing to use.

I guess bottom line is: can you fit the igniter, all the powder and all the packing material in there? If so, it works.
 
I was told the glove tip or the tape package method was good, but put it into the charge canister to direct the blast the direction you need it to face. I just needed to know what size casing to use.
I couldn't disagree more. With a canister/tube you're "directing" that charge right up into your recovery gear. Having it directional doesn't help that much - you're pressurizing the tube not shooting the end off.

I have NEVER used or recommended to anyone that they use a directional charge holder. Ever. Parachutes are far too expensive for me to tolerate blasting holes in them.

YMMV, --Lance.
 
Glove tips are a good method. The key is to pack them correctly. You can tape them to the bulkhead and if there is a concern about blowing out the tube then make sure there is tape on that side. Do not completely cover the glove tip with tape when taping to the bulkhead though. The charge will take the path of least resistance.
 
I started DD using duct tape and just laying the match on the tape, pouring the powder on the match and folding the tape to hold the charge. That worked very well. I then started using pipe caps and packed dog barf over the powder and taped it all in place. My impression is that, although you don't need to contain BP like you do BP substitutes, containing the BP by packing dog barf over it and tightly taping it in resulted in stronger ejection charges than the same amount of BP that was less contained in the duct tape.

Using the duct tape method allowed putting the charge at the top of the motor in a standard DD rocket which pushed the shock cord and drogue out of the lower tube instead pushing it into the tube when using the canisters attached to the av-bay. What I found is that since the charge is only pressurizing the tube, it didn't really matter which method was used, they both worked equally well.

I don't know which caliber brass would work better, but I use 1/2" pipe caps for 4" or smaller av-bays and 3/4" caps for larger. The 3/4" caps will hold about 6g or 7g of BP which is quite a lot.
 
The last several I made used toilet paper or paper towel tubes rolled and raped with making tape. It creates an expendable canister that is dirt cheap and will not put a hole in you body tube.
 
I ended up using the .45 casings. Worked very well. I like the directional shaped charge effect. It was very successful. Two flights. Two successful deploys. One successful L1 cert.
 
It's hard to get people to pass off those cases. They tend to reload them. Plus I'd think they would be better on 4" or higher diams.
 
It's hard to get people to pass off those cases. They tend to reload them. Plus I'd think they would be better on 4" or higher diams.

I was joking. The amount of powder a 50 BMG can hold would be a lot.
 
If you go with charges that large, just use 12 gauge shot gun shells.
 
Well, you can only reload 50BMG cases so many times before it has to be tossed... so I'm sure someone will let them go if it's no longer good for reloading. Seriously though, it would hold enough powder to pressurize a very large airframe.
 
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