Ejection charges.

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John Taylor

John Taylor

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Been out of rocketry and DD for 16 years. What are you all using for your charges? Used to use xxxx black powder. Can I get it legally and easily nowdays? What else is used nowdays, I've heard something about Pyrodex being used in place of BP. Does it perform compairably to BP?
If so, how would one use it compaired to BP?
Thanks, John
 
Yes, you can get black powder legally. Easily? Matter of opinion. It can be bought online in bulk, or you can find a local gun store that caters to muzzle-loader enthusiasts.

Legally, it is a low explosive and thus is regulated by the ATF. Requires a LEUP and a safe to store/transport it in.

There may be forum members here who forego the LEUP and/or the safe, but that would not be for me to comment upon.

There are those who use pyrodex, but I have not, and thus can't comment on the efficiency of that. However, I think the standard is "use in the air whatever you ground tested with." Pyrodex and BP do not behave the same, and it is not a simple one-for-one substitution.
 
John Taylor said:
Been out of rocketry and DD for 16 years. What are you all using for your charges? Used to use 4F black powder. Can I get it legally and easily nowdays? What else is used nowdays, I've heard something about Pyrodex being used in place of BP. Does it perform compairably to BP?
If so, how would one use it compaired to BP?
Thanks, John
Click to expand...
 
John Taylor said:
Thank you very much!
Click to expand...

I was originally going the route of Pyrodex P, but it was “underwhelming” in my opinion. Has to be packed very tightly to get remotely close to decent performance, and you need to use 15 percent more Pyrodex P per an ejection charge calculator I found.

Have you looked around locally for shops that specialize in black powder shooting and/or weapons? I found one that was a bit of a drive(90 mins away), but picked up a pound of FFFFg black powder. It was a bit of a hike, but I got it same day and avoided the HAZMAT fees (which was honestly less than the gas I used for the drive).

The first time you use FFFFg you will see a huge improvement over the performance of Pyrodex P. All my objections to black powder were immediately dismissed.
 
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Triple7 works much better than Pyrodex in my testing. Make sure you get FFFG Granular Powder. It does need to be packed tightly, but then so should BP. It is easy to clean up and far less corrosive than BP. But make sure to test as you may find you need a bit more volume (do not measure by weight) to get the results you expect.

Or get BP.


Tony
 
manixFan said:
Triple7 works much better than Pyrodex in my testing. Make sure you get FFFG Granular Powder. It does need to be packed tightly, but then so should BP. It is easy to clean up and far less corrosive than BP. But make sure to test as you may find you need a bit more volume (do not measure by weight) to get the results you expect.
Tony
Click to expand...
I've been using Triple7 exclusively for several years, it works just fine. It doesn't make nearly the mess that BP makes, and the residue cleans up very easily... one pass with a baby wipe and it's gone.
 
cerving said:
I've been using Triple7 exclusively for several years, it works just fine. It doesn't make nearly the mess that BP makes, and the residue cleans up very easily... one pass with a baby wipe and it's gone.
Click to expand...

I've had very good results with Triple 7 as well. It leaves much less corrosive mess behind, compared to BP. It seems to be more energetic than BP. Based on my ground testing, I end up with less Triple 7, compared to BP. For containment, the centrifuge containers taped shut seems to work very well, it make for a neat, clean package.

Two of my rockets use BP, and the rest use Triple 7. For various reasons I'll use one or the other, but I prefer the Triple 7. So much cleaner.
 
You guys are going to make me research Triple7, aren't you? Sounds too good to be true.
 
What is the weight to weight ratio for using the 777 for charges opposed to BP?

People say "don't measure by weight, measure by volume" but I've been measuring BP by weight exclusively so far.
 
Nytrunner said:
What is the weight to weight ratio for using the 777 for charges opposed to BP?

People say "don't measure by weight, measure by volume" but I've been measuring BP by weight exclusively so far.
Click to expand...
I watched a video comparing FFFg BP to FFFg Triple7. The Triple7 is more energetic, and the host recommended less. But there was no direct ratio given. Would require ground testing all over again. And then, I have no idea how FFFg Triple7 compares to FFFFg BP. The cleaner burn is appealing, though.
 
Nytrunner said:
What is the weight to weight ratio for using the 777 for charges opposed to BP?

People say "don't measure by weight, measure by volume" but I've been measuring BP by weight exclusively so far.
Click to expand...
If you read the literature for all of the BP substitutes, they say to measure by volume, not by weight. So you're on your own if you want to go by weight. Personally, I don't understand why you would want to use weight over volume. You can buy a set of BP volume measures that will allow you to get what you need a lot more easily and quickly than messing with a scale. Wind isn't nearly as much of a factor if you are measuring at the field using volume dippers.

Watch a video of someone shooting a BP firearm. They reload by volume - that's how a powder horn works. It would be pretty hard to weigh out powder in the middle of a battle.


Tony
 
Bat-mite said:
I watched a video comparing FFFg BP to FFFg Triple7. The Triple7 is more energetic, and the host recommended less. But there was no direct ratio given. Would require ground testing all over again. And then, I have no idea how FFFg Triple7 compares to FFFFg BP. The cleaner burn is appealing, though.
Click to expand...
Was that for shooting or for ejection testing? There is a big difference burning powder in a barrel compressed under a bullet than the way we use it for parachute ejection. In my personal testing, BP was more energetic that any of the BP substitutes.

You can't compare using powders the way we do to those using it for it's intended purpose as a bullet propellant.


Tony
 
mbeels said:
I've had very good results with Triple 7 as well. It leaves much less corrosive mess behind, compared to BP. It seems to be more energetic than BP. Based on my ground testing, I end up with less Triple 7, compared to BP. For containment, the centrifuge containers taped shut seems to work very well, it make for a neat, clean package.

Two of my rockets use BP, and the rest use Triple 7. For various reasons I'll use one or the other, but I prefer the Triple 7. So much cleaner.
Click to expand...
manixFan said:
Was that for shooting or for ejection testing? There is a big difference burning powder in a barrel compressed under a bullet than the way we use it for parachute ejection. In my personal testing, BP was more energetic that any of the BP substitutes.

You can't compare using powders the way we do to those using it for it's intended purpose as a bullet propellant.


Tony
Click to expand...
Thanks for your response.
 
manixFan said:
If you read the literature for all of the BP substitutes, they say to measure by volume, not by weight. So you're on your own if you want to go by weight. Personally, I don't understand why you would want to use weight over volume. You can buy a set of BP volume measures that will allow you to get what you need a lot more easily and quickly than messing with a scale. Wind isn't nearly as much of a factor if you are measuring at the field using volume dippers.

Watch a video of someone shooting a BP firearm. They reload by volume - that's how a powder horn works. It would be pretty hard to weigh out powder in the middle of a battle.


Tony
Click to expand...

Several reasons actually;
-I'm a rocketeer, not a reloader.
-I use BP calculators that give required mass of 4F, so I use mass/weight to pack charges (at home not at the field)
-Weight and volume should be directly proportional if material density is constant
-If I could know something more concrete than "a bit more" than I can work out the rest myself
 
manixFan said:
Was that for shooting or for ejection testing? There is a big difference burning powder in a barrel compressed under a bullet than the way we use it for parachute ejection. In my personal testing, BP was more energetic that any of the BP substitutes.

You can't compare using powders the way we do to those using it for it's intended purpose as a bullet propellant.


Tony
Click to expand...
Shooting. Good to know. I'm not a chemist and have not done any testing. I am pleased to know there is a BP substitute that leaves less residue. If I ever run out of BP, I may look into it. And I would need to retest all my ejections.
 
Nytrunner said:
Several reasons actually;
-I'm a rocketeer, not a reloader.
-I use BP calculators that give required mass of 4F, so I use mass/weight to pack charges (at home not at the field)
-Weight and volume should be directly proportional if material density is constant
-If I could know something more concrete than "a bit more" than I can work out the rest myself
Click to expand...
Weight = Volume with black powder. So 1 CC of BP = 1 gram = 15.2 grains. So the value given by a BP calculator could just as easily be labeled CCs as grams. A good set of scoops is just as accurate as we would ever need to be for a typical ejection charge. So there isn't any real advantage to weighing vs. using volume. Reloaders risk serious death or injury if they miscalculate or 'mis-measure' a load, certainly they need a high degree of accuracy. If scoops work for them, I think they should work for us.

A web search turns up this chart:

https://www.curtrich.com/BPConversionSheet.htm

Which gives you the information you are looking for, the equivalent weights of BP substitutes. You'll see that 1cc of Triple7 weighs 12.2 grains or .8 grams. But I would still use volume as that's what the manufacturer recommends.

Bottom line, if you don't feel comfortable or see a compelling advantage to using a BP substitute, stick with BP. No reason to complicate life unnecessarily.


Tony
 
David Schwantz said:
I ground tested with 777 several times and I got several burn holes with it. Not sso much with 4f.
Click to expand...

777 is like 3Fg BP so it has slightly larger particles. Those particles take longer to burn and if your chute isn’t protected can burn holes. 4Fg BP has smaller particles which burn faster and thus have less opportunity to burn the parachute. Better protect your chute and you should be good.
 
manixFan said:
web search turns up this chart:

https://www.curtrich.com/BPConversionSheet.htm
Click to expand...

Thanks for the reference table Tony!

Humor an engineer that has his own preferred methods. (plus I don't have powder scoops, but I do have scales)
You mentioned "a bit" more volume of 777. That seems imprecise. From the weight/volume relationship in that table, I see triple 7 is 20% less dense than BP, so when I run out of my bottle of 4F, I'll start ground testing with +20% calculated mass of BP and see how she blows.
 
Nytrunner said:
What is the weight to weight ratio for using the 777 for charges opposed to BP?
Click to expand...

I haven't tried to establish a weight or volume equivalency, I use them in different ways. My HP rockets get the normal charge cups, BP, and ematch. So far I've used Triple 7 in my mid power rockets only. I suppose I decided to stick with tradition in HP, but I like to experiment in mid power.

For what it is worth, here is my experience based on ground testing. If you just stick Triple 7 in a charge cup instead of BP, the results will be poor. It doesn't burn completely so you get smoldering bits that char things and unburned Triple 7 coating the insides of your rocket. My best and most consistent results have been with this:

PA011030.JPG

It is a centrifuge container with less than 0.5 cc of Triple 7. I fill to the 0.5 cc line, but the ematch is taking up volume inside. I fill to the top with dog barf, glue the lid shut, and then tape over everything with Scotch 88. With this, I get complete combustion, it burns cleanly, and it is more than sufficient for my BT-55, BT-60 and BT-80 mid power rockets.

I've found that trying to use less than that volume of Triple 7 has been less consistent, some times the ejection is pretty anemic. When I use more, the charge is extremely energetic. Once I compared Triple 7 and BP in a HP rocket, and 1 cc of Triple 7 was way more energetic than 1.3 grams of BP. With the Triple 7 the rocket nearly catapulted itself across my back yard.

I think what is going on is that BP will just burn quickly when lit, so you get linear results that can be extrapolated and interpolated predictably. With Triple 7, my results seem to be more quadratic, I suspect that is due to the dramatic increase in combustion efficiency with increased pressure. But I haven't done testing any more scientific than putting it in my rockets and watching the results.

So I have one tested quantity and use of Triple 7 that has given me very consistent results, in a few dozen mid power launches. I can prep a couple of canisters in advance and get my rockets ready to fly quickly and easily at the field. Probably with more testing I could find a combination that works well for my HP rockets, but I'm content with BP for those, at least for now.
 

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