FFG vs. FFFFG

[iter]

My local retailers only stock FFG Pyrodex. I wonder how far that is from FFFFG powder that regular ejection charges use.

Ari.

[troj]

More Fs = smaller grain size = faster burn

Have you asked about FFFg or FFFFg? FFg is normally used for rifles; as I recall, pistols normally use FFFg, and FFFFg is what is used in the pan on muskets.

If asked, the retailer may be able to get you FFFg or FFFFg.

Otherwise, ground test to figure out how much of the FFg you need.

-Kevin

[amarillo_rocket]

You can order 4F powder online from Graf and Son's. http://www.grafs.com/ . When I purchased from them 3 years ago they required the purchase of 2lbs not sure if that is still a requriement.

[rockets4kids]

I've had no problems using 3F (true) BP, but I'm not sure you would want to drop back to 2F. I got mine at the local Bass Pro shop. Perhaps one of your local retailers could order you a can?

[tightwad]

I have used 2F for ground testing and have had no problems with it. (I like to save the BP for flight.) I have not used 2F in flight yet, but in a pinch I would use it (only in an old rocket, that is beat up and if it prangs I wouldn't cry) and if it passes flight testing, then I would use it.

[iter]

Thank you for your responses guys. I like the emphasis on ground testing.

Ari.

[xenon]

I've used everything from cannon grade to meal d/4FG, no problems on either end of the size spectrum. Fireworks shells are commonly lifted with 2FA, which is basically equivalent to cannon grade and it's much gentler, but still produces the same volume of gas. Personally, I like the cannon grade stuff better as it's gentler but still fast enough to get the laundry out. I also think it passes fire faster among grains since there's more space between them, which eliminates worry about containment like smokeless powders. YMMV

Ground test or blow it out or blow it up (or both...), but ground testing is a better idea.

[powderburner]

iter,

I don't know how to try to make this not sound like I am being a smartie, because just as soon as I post it that is exactly what it is going to sound like, but-----there is a collective ton of info already posted here on TRF on this subject (blackpowder substitutes, forms of Pyrodex, how to make Pyrodex work effectively, etc) in the old links and also in the archive from TRF 1.0

Probably worth some time trying combinations of search terms.....

[Zeus-cat]

Just to be safe I have to say that you can't use Pyrodex like "FFFFG powder that regular ejection charges use". If you would put Pyrodex into the ejection well of any RMS motor it would just burn. Black powder will explode and produce enough force to eject a parachute. Pyrodex will just burn unless contained. I'm hoping you know this, but better safe than sorry.

[powderburner]

Z-C makes an important point: Pyrodex (and all the non-blackpowder blackpowder "substitutes") have significantly different combustion properties than plain old gunpowder.

Continuing the just to be safe thing, and at the risk of over-explaining what has already been posted probably two dozen times, Pyrodex ejection charges have to be contained more strongly to get them to combust completely. A lot of people who use Pyrodex-type materials put them into a small plastic vial and tape over the open end with several layers of tape. If the Pyrodex ejection charge is not properly installed, the first bit of Pyrodex will burn and push out the rest of the ejection charge without igniting it, setting up a problem situation where insufficient gas is created to deploy all the recovery gear. Keeping the Pyrodex contained inside the ejection charge well is necessary to get it all to burn and to create the necessary ejection event.

You don't have nearly the same problems with real blackpowder.

[iter]

I make some tests today. I use coat-hanger tube, 3/8" poplar dowel plugs with yellow glue and a tantalum capacitor for initiation.

The first tube I make holds about 1 gram of FFG Pyrodex. It blows a 3" nosecone 10' into the air.

The second tube has 2.0 grams (my measurement is more precise on that one). It blows the same 3" nosecone 50-60' into the air and breaks a 3/32" bulkhead in the tube. The experience most resembles firing a mortar.

I'm hesitant to test the 2.2 gram tube :=)

Now, where do I buy blackpoweder blackpowder?

Ari.

[o1d_dude]

Are you by any chance Ari K of L.U.N.A.R.?

If so, I've seen your big boost glider at a launch recently and we chatted.

[iter]

I am him. Embarrassingly, I cannot associate your name with your face or your rockets. Perhaps you can remind me the chat--was it Moffett or Snow Ranch?

I have a thread on the SkyFun in the boost glider section: http://www.rocketryforum.com/showthr...-Foamie-SkyFun . Sadly, I crash it over the weekend while fiddling with the autopilot. I'm building a new, simpler version of the glider for my L1 cert attempt.

Ari.

[UncleVanya]

I make some tests today. I use coat-hanger tube, 3/8" poplar dowel plugs with yellow glue and a tantalum capacitor for initiation.

The first tube I make holds about 1 gram of FFG Pyrodex. It blows a 3" nosecone 10' into the air.

The second tube has 2.0 grams (my measurement is more precise on that one). It blows the same 3" nosecone 50-60' into the air and breaks a 3/32" bulkhead in the tube. The experience most resembles firing a mortar.

Improperly contained Pyrodex will fail to reliably eject. Properly contained Pyrodex will create a heck of a bang if you use it by weight and base things off the online calculators. BP is much heavier for the same volume and consequently you don't weigh Pyrodex and substitute it in for BP - you have to either measure by volume or just create your own charts based on results.

[iter]

Properly contained Pyrodex will create a heck of a bang

I'm noticing just that :=)

Ari.

[iter]

I have a separate thread on it here <http://www.rocketryforum.com/showthread.php?37422-R-C-deployment> but I feel this video is relevant to the Pyrodex topic of this thread. This is 1 gram of Pyrodex:

[karlbaum]

I use pyrodex in 1/2 inch vinyl tube with the ends hot glued. You can also attend a Tripoli Central California launch and purchase BP from What's Up Hobbies.

[iter]

I worry about using hot glue on pyrodex.

Ari.

[karlbaum]

I have made dozens of ejection canisters and never had a problem with hot glue. I used to apply the hot glue directly to the pyrodex but now I insert a piece of foam rubber so that hot glue never touches the powder. I actually do this so that I can keep the powder tight in the tube.

[Tarasdad]

Pyrodex is a direct replacement for black powder on a strictly VOLUME-FOR-VOLUME basis ONLY. Going by weight can easily lead to an overload and damaged gear - or serious injury. Proceed with EXTREME caution.

[iter]

Tarasdad: Thank you for your warning. I use purely experimental means to derive the necessary amount of powder to use in my application. "No black powder formulas were used in the production of this movie."

Karl: Thank you for sharing this bit of experience. Even though a hot glue gun's temperature is lower than Pyrodex ignition temperature, I'm reluctant to experiment with this. Now that I know that you are using hot glue safely, I'm much more comfortable sing it myself.

Ari.