Ideal pyrodex charge?

Discussion in 'Recovery' started by ArchitectOfSeven, Apr 17, 2019.

Help Support The Rocketry Forum by donating:

  1. Apr 17, 2019 #1

    ArchitectOfSeven

    ArchitectOfSeven

    ArchitectOfSeven

    Well-Known Member

    Joined:
    Dec 26, 2017
    Messages:
    85
    Likes Received:
    11
    Hi all,

    I'm trying to set up some pyrodex ejection charges in 2ml centrifuge vials and want to know how well I should try to contain the powder. With the vial completely full (~1.8g), and sealed with quite a bit of masking tape it went off with a sound a lot like a gunshot in a preliminary test outside of the rocket. Is that ideal or does that risk blowing holes in things?

    Thanks! :)
     
  2. Apr 17, 2019 #2

    timbucktoo

    timbucktoo

    timbucktoo

    Well-Known Member Staff Member Global Mod

    Joined:
    Jun 13, 2014
    Messages:
    5,677
    Likes Received:
    442
    Gender:
    Male
    Location:
    Cocoa Beach
    Personally I wouldn’t bother with Pyrodex. You’ll get more reliable results with Goex 4F black powder. Most people here will agree.
    As far as the amount of powder to us, that really depends on the volume of airspace in airframe.
     
  3. Apr 17, 2019 #3

    cwbullet

    cwbullet

    cwbullet

    Obsessed with Rocketry Staff Member Administrator TRF Lifetime Supporter Global Mod

    Joined:
    Jan 24, 2009
    Messages:
    21,832
    Likes Received:
    1,185
    Gender:
    Male
    Location:
    Glennville, GA
    Tightly wound in the tape is fine. Centrifuge tubes also work. Watch the lids in cardboard rockets. I usually use multiple layers of tape if I am using it alone. ;
     
  4. Apr 17, 2019 #4

    swfa

    swfa

    swfa

    Active Member

    Joined:
    Feb 2, 2017
    Messages:
    38
    Likes Received:
    1
    Gender:
    Male
    Location:
    Moundridge KS
    In my experience, residence time is just as important as containment. I use aluminum "gun barrel" type canisters, sized so that the charge fills up no more than half of the length of the canister. For example, my canisters for 1.0 g and under are 0.25" by 2.875" internal dimensions.

    I also always use three layers of electrical tape over the end. If more layers are needed to prevent un-burned powder, then I use a longer/bigger canister. I completely fill the void with bits of fiberglass insulation. Cellulose insulation would probably work too.

    In my testing, when there is no place for the powder to go, and it is very tightly contained, you just get a bang and lots of unburned powder. The initial combustion ruptures the containment, and throws un-ignited powder everywhere. YMMV
     
    Last edited: Apr 17, 2019
  5. Apr 17, 2019 #5

    ArchitectOfSeven

    ArchitectOfSeven

    ArchitectOfSeven

    Well-Known Member

    Joined:
    Dec 26, 2017
    Messages:
    85
    Likes Received:
    11
    I'd totally do black powder but this is California and I basically gave up on that dream. Best I could realistically do was 3F pyrodex :/

    I just ordered some 5ml capsules to give me more room for larger charges and a little head room for longer burn time. I don't really have much more room in the rocket so I'll just have to test with that and see how it goes.

    Thanks for the advice everyone! I'll do my first round of testing with an old shirt or something instead of the chute to prevent damage and analyze what it does. Also I'm lucky in this case to have an aluminum body tube but I really wanted to know if this would hurt any of my other rockets or their chutes.

    Thanks again!
     
    timbucktoo likes this.
  6. Apr 17, 2019 #6

    manixFan

    manixFan

    manixFan

    Well-Known Member

    Joined:
    Feb 15, 2009
    Messages:
    1,115
    Likes Received:
    191
    I've tested both Pyrodex and Triple7 and had better results with Triple7. But Pyrodex works just fine. However, I found that I needed more volume than with BP due to its slower burning. (All of the BP substitutes say to measure by volume and not weight.)The advice SWFA gives is important - you want to use a long tube to help the powder completely combust. Just be sure to pack the empty space with flameproof wadding to keep the powder down around the e-match. It will be loud if it's not in a body tube - a tube will muffle it quite a bit. One advantage to non BP powders is a lot less nasty residue to clean up.

    Just do plenty of testing until you know how the Pyrodex works and you'll be fine.


    Tony
     
  7. Apr 18, 2019 #7

    Banzai88

    Banzai88

    Banzai88

    Lvl 1,Wallet....Destroyed

    Joined:
    Jul 15, 2015
    Messages:
    1,942
    Likes Received:
    225
    Try Blackhorn 209, it's closer in burn rate and performance to real black powder than any other BP substitute.
     
  8. Apr 18, 2019 #8

    manixFan

    manixFan

    manixFan

    Well-Known Member

    Joined:
    Feb 15, 2009
    Messages:
    1,115
    Likes Received:
    191
    That's true if you are shooting an actual black powder firearm. Blackhorn is a very good powder, but it is harder to ignite than other powders. It won't work in some black powder firearms that don't have a strong ignition source. Triple 7 and Pyrodex are less sensitive to that issue. Like anything new, it requires testing to make sure it will work with your setup.

    The point is there are several very good substitutes to BP, but all should be tested prior to use.


    Tony
     

Share This Page