Ideal pyrodex charge?

[ArchitectOfSeven]

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!

 

[tim cubbedge]

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.

 

[cwbullet]

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. ;

 

[swfa]

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

 

[ArchitectOfSeven]

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.

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 :/

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

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!

 

[manixFan]

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

 

[Banzai88]

Try Blackhorn 209, it's closer in burn rate and performance to real black powder than any other BP substitute.

 

[manixFan]

Try Blackhorn 209, it's closer in burn rate and performance to real black powder than any other BP substitute.

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