Granulated vs. Meal in Rockets

[dagabu]

Well, I granulate mostly to keep the dust from floating around. I think it was from one of the Skyligther newsletters I saw it first; a o-ring on the rammer keeps the dust from shooting up when using mill dust in drivers.

 

The one issue I have with granulating it is that each batch differs depending on the boiling water. It seems that just a few degrees makes a huge difference in burning rate. Its OK with rockets but it makes a 50' difference on lifting a 5" shell.

 

I have stayed with the red-gum and alcohol method but really dont like the extra cost associated with that method.

 

D

Edited October 6, 2009 by dagabu

[Aquarius]

I get your point on the different batches dagabu.

My way of getting around it is to make a batch or two and mix it with the previous made batches. That will keep things kinda average.

If all things are the same, a "baseblend" of say three or four batches will not differ much if another batch is added with a slightly different burn rate.

 

But then again, I focus more on cosistency than super hot and fast. My powders are never hotter than they need to be...

[drtoivowillmann]

In my experience, the graphite adds nothing to the compaction when pressed. The fuel grain of the same weight is exactly the same length. It makes for easier spindle removal but they become a little harder to light and have an effect on the tail, albeit small.

 

I tried a small amount of baby oil in my last comp to keep the dust down and found that as long as I added 5% Willow to the mix, the thrust remained the same and the tail was just as nice. I just added drop by drop until I saw some clumping and screened it all. I will clump lightly when squeezed.

 

D

 

You are completely wrong.

 

Graphit gives a dry lubrication. If material is well pressed or not, does not only depend from

the pressure used but also from the friction of the material, which inhibts good compression.

 

An empiric fact is, that many granulated black powder based or black powder like rocket driver

mixes, without it, make your rocket explode, but with exactly 4% work properly.

 

All industry make their end burning rocket drivers with graphitated granulated "Soft Grain"-Black-Powder 75:15:10 !

With no graphit they usually explode, with only 2 % instead of 4 % they still tend to explode.

 

Don't make philosophy ! Try it and you will see. Careful: your grains must not be too hard or even

graphite will not help.

 

Greetings from Brazil:

Toivo

[drtoivowillmann]

Interesting on the graphite. My last BP batch was created as a dedicated rocket fuel using 65:25:10... would the addition of graphite reduce the power too much in this ratio?

 

Dear Swede:

 

I do not see any problem.

Simply try it. This will not be so complicated.

 

Careful: your powder granulate must not be too hard

or even graphite will not help.

 

Greetings:

Toivo

[Mumbles]

I wouldn't be so quick to say "all industry". You're not the only one here with commercial manufacturing experience. We never added graphite to any of our drivers, gerbs, or rockets, and they preformed just fine. I can't go too deep into formula, but it was all based off of strong fast BP.

 

If you are showing empirical data that graphite prevents them from exploding, I think it's pretty obvious that the powder is slowed, if only slightly. Otherwise, the same issue could be remedied by increasing pressing force.

[dagabu]

You are completely wrong.

 

Graphit gives a dry lubrication. If material is well pressed or not, does not only depend from

the pressure used but also from the friction of the material, which inhibts good compression.

 

An empiric fact is, that many granulated black powder based or black powder like rocket driver

mixes, without it, make your rocket explode, but with exactly 4% work properly.

 

All industry make their end burning rocket drivers with graphitated granulated "Soft Grain"-Black-Powder 75:15:10 !

With no graphit they usually explode, with only 2 % instead of 4 % they still tend to explode.

 

Don't make philosophy ! Try it and you will see. Careful: your grains must not be too hard or even

graphite will not help.

 

Greetings from Brazil:

Toivo

 

I will have to email my source from Estes but I am almost certain that they do not use graphite in their mix. And I do know several industry members as well as Mumbles (Hi Mumbles!) and the 75 : 15 : 10 mix is seldom used at all.

 

I know that I am splitting hairs but I believe that 74.5% of KNO3 is the true peak for BP. 65:25:10 is pretty common as are a hundred other mixes made especially for the casing, charcoal, nozzle diameter, spindle length, etc.

 

I am sorry that I somehow offended you with what you call philosophy, Philosophy is the study of general and fundamental problems concerning matters such as existence, knowledge, values, reason, mind, and language. We all make philosophy every day and as a human it is an inalienable right of mine to do so as I please.

 

And while you are jumping around trying to indite me, I clearly wrote "In my experience".

 

Do what you will, slow your fuel, over compact your grains, as long as it lights and we all say Ohhh, Ahhhh, Ooooo! Its all good with me.

 

D

[drtoivowillmann]

Dear Friends :

 

Are you really Pyros ?

Then try it or forget it !

Nothing more to say about it !

 

Greetings:

Toivo

[dagabu]

Dear Friends :

 

Are you really Pyros ?

Then try it or forget it !

Nothing more to say about it !

 

Greetings:

Toivo

 

Done it, sucked, DONT do it, does not work. Period!

[dagabu]

Back on the thread:

 

It all comes down to the hardness of the BP grain and its size. I have a box of Mil Spec 7 powder that is equivalent to 7FA powder, very fine. That will compact nicely if lightly spritzed with water and left to dry after pressed. MS 7 is very energetic and seems to do well even in the presence of Graphite.

 

Dave

[Swede]

Lucky guy! Where the heck did you find that BP? I have never seen any commercial powder finer than 4F offered for sale. The better sites have all the "F" grades and some cannon grades, but rarely finer stuff.

[dagabu]

Lucky guy! Where the heck did you find that BP? I have never seen any commercial powder finer than 4F offered for sale. The better sites have all the "F" grades and some cannon grades, but rarely finer stuff.

 

Easy Peasy!

 

http://www.addictedtoblackpowder.com/2.html

 

Jon Blackert is a really nice guy. His fuse powder is nice too, you can press rockets directly with it. At a $ a pound and at $101.00 for 44# delivered, its hard to resist. I am going to Va Beach Va in November and will be rolling by his place so I am going to pick up a box of fuse powder and the 140# keg bulk keg. Its full of felt doughnuts filled with salt and 2FA BP. You have to separate it but it looks pretty easy. You end up with 35# of 2FA for $50.00!!

 

Dave

 

PS, not to rub it in but I have the day off tomorrow to press rockets for the fall club shoot here in MN. Expecting snow

 

All you BATFE spys out there: I will be getting less then 50# of BP total

Edited October 8, 2009 by dagabu

[Mumbles]

Swede, you have to remember the difference between FA and Fg. 7FA is 4Fg, which I have seen around. It's common for pistols I think. 4Fg can be substituted for meal D in a pinch. The only difference is the lack of a bottom screen cutoff on Meal D.

 

Approximately:

 

2FA = Cannon Grade

4FA = 1Fg

7FA/Meal D = 4Fg

[drtoivowillmann]

I wouldn't be so quick to say "all industry". You're not the only one here with commercial manufacturing experience. We never added graphite to any of our drivers, gerbs, or rockets, and they preformed just fine. I can't go too deep into formula, but it was all based off of strong fast BP.

 

If you are showing empirical data that graphite prevents them from exploding, I think it's pretty obvious that the powder is slowed, if only slightly. Otherwise, the same issue could be remedied by increasing pressing force.

 

Dear Sir:

 

I beg your pardon. In Germany, where I learnt, before I went abroad, nearly everone uses graphit powder

(about 18 microns). I do not have any right to applicate these facts necessarily on the USA.

I myself assisted a test in NICO-Pyrotechnik Trittau (nearby Hamburg): 0 % = bang !,

2% = still many bangs; 4% = no bang at all. I did not pick up any xerox from the test protocol, to give to

other people, otherwise I would have been fired.

I know that competitors of us, who do not use graphite powder, simply press with higher pressure. This

also works. But this is just, what I talked about: any tabletting, any compacting is relieved by solid lubricants. Other solid lubricants, like the known stearates, really slow down any composition. Graphit

does not do so.

 

My question about your products: do you use your compos in a powdered form (in this case graphit really

does not make any sense or effect) ? Only, if you granulate your compo, before pressing, graphit will make your job easier.

People, who do not like to use aluminium tubes within their rocket end-burning drivers, but only purely cardboard tubes, and use Soft-Grain Black Powder (Hard Grain, even with graphit, will never work) go right to use graphit, because compacting pressure may be less, in order not to stress too much the inner part of the paper tube's wall.

You are right, in gerbs and fountains there is no need at all for it. But the gas pressure of them, when ignited is also smaller than that within a good end burning rocket driver (generally core burners work with less gas pression).

I myself use graphit even in core-burning drivers:

# the dosage of grain powder is easier,

# I like quite high gas pressures in them, when ignited, in order to make them more powerful.

 

Thanks for your informations,

yours truely:

Toivo

[dagabu]

Swede, you have to remember the difference between FA and Fg. 7FA is 4Fg, which I have seen around.

 

Sorry, my fault,

 

0.420 to 0.149 = Class 7 = 7Fa, = Meal-D = 4Fg

[dagabu]

I myself assisted a test in NICO-Pyrotechnik Trittau (nearby Hamburg): 0 % = bang !,

2% = still many bangs; 4% = no bang at all.

 

Tovio,

 

In my opinion:

 

A dusting of graphite on the inside of the tube accomplishes this task easily without adding another element to the mix.

 

As far as pressing BP, I wholeheartedly agree that hard grains will not compact enough to allow for a solid grain but Meal D will compact nicely as long as the pressure is held steadily for 30 seconds. As the pressure is applied to the grain, the BP crushes, shifts and compacts filling voids in the grain but will not do so if you were to bring the press to pressure and then bleed the pressure off and add another increment to press.

 

If a continuous pressure is applied over a period of time, a much more compact grain can be achieved. Adding a dusting of graphite inside the tube can help a lot with accordioning but all ingredients change the fuel characteristics.

 

Your quote says it all, 4% will significantly lower the thrust of BP due to its refractory nature (help me out here Swede) as it will not burn and will absorb energy as the fuel burns. It adds nothing to the comp. Dusting the spindle and the tube walls works just fine and I will do some testing on thrust after the Pyro season is over.

 

D

[Mumbles]

Everything was granulated prior to compaction. It does not make sense to shoot all the unnecessary dust into the air in a commercial environment if you do not have to. Everything I can think of went into very strong cardboard tubes, heavy steel reinforcing sleeves. I do not recall specific details as far as pressure used.

 

I still may give the graphite a shot next time I make a batch of drivers/rockets, so I can compare back to back. It seems intriguing that it can prevent CATO without drastically effecting performance.

[dagabu]

Everything was granulated prior to compaction. It does not make sense to shoot all the unnecessary dust into the air in a commercial environment if you do not have to. Everything I can think of went into very strong cardboard tubes, heavy steel reinforcing sleeves. I do not recall specific details as far as pressure used.

 

I still may give the graphite a shot next time I make a batch of drivers/rockets, so I can compare back to back. It seems intriguing that it can prevent CATO without drastically effecting performance.

 

Why do you think that is?

 

D

[FrankRizzo]

That it wouldn't impact performance is impossible. That it would help case-bonding or void removal is understandable, *BUT* you also lose that 4% of fuel, so performance *has* to take a hit.

[dagabu]

That it wouldn't impact performance is impossible. That it would help case-bonding or void removal is understandable, *BUT* you also lose that 4% of fuel, so performance *has* to take a hit.

 

Actually, I was thinking that it made the case walls slippery so that the tube didn't accordion.

 

D

[FrankRizzo]

Right, that was the case-bonding issue I was referring to. As the comp is crushed, the layer most near the rammer face will tend to grab the tube wall, pulling it with the increment, and causing an accordion of the tube. As you said, graphite will help prevent this.

 

I *believe* the intended effect was/is to help the granules crush and flow under pressure, eliminating inconsistencies of void removal during the pressing operation. Damping the power also has this effect, which is why you can press BP comets to a higher density with a few percent moisture added.

 

Both problems/solutions are valid. The contention that there's no lose of power is what I don't understand. It's still missing 4% of the BP, replaced with an inert ingredient. Maybe the increase in loading density somehow makes up for this?

[drtoivowillmann]

Right, that was the case-bonding issue I was referring to. As the comp is crushed, the layer most near the rammer face will tend to grab the tube wall, pulling it with the increment, and causing an accordion of the tube. As you said, graphite will help prevent this.

 

I *believe* the intended effect was/is to help the granules crush and flow under pressure, eliminating inconsistencies of void removal during the pressing operation. Damping the power also has this effect, which is why you can press BP comets to a higher density with a few percent moisture added.

 

Both problems/solutions are valid. The contention that there's no lose of power is what I don't understand. It's still missing 4% of the BP, replaced with an inert ingredient. Maybe the increase in loading density somehow makes up for this?

 

Tank You:

 

You are the first, who really understood. This is exactly the way graphit works.

I use graphit, inorder not to damp the powder, because damp drivers I have to dry afterwards, made

with graphit I can test and use imediately.

 

Greetings from Brazil:

Toivo