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franklyn
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Stocking stuffers
http://www.harborfreight.com/3-lb-rotary-rock-tumbler-67631....
http://www.harborfreight.com/dual-drum-rotary-rock-tumbler-6...
http://www.amazon.com/Diameter-Chrome-Steel-Bearing-Balls/dp...
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Armistice19
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Wow, I wish I hadn't bought my materials already. Those are really good prices, it seems I've been overspending. That rock tumbler looks exactly like
my ball mill. Perhaps I've been severely ripped off 
“Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire
world, and all there ever will be to know and understand.” -Albert Einstein
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Armistice19
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I tried once again to synthesize aluminum powder with the new information and suggestions from all of you. The experiment went as followed...
VARIABLES:
Aluminum granules and stearic acid were placed in a neoprene air tight ball mill with chrome plated steel media. The ratio was 10/1 media to filling
by weight. The filling was 97% Aluminum and 3% Stearic acid by weight. Mill was run 24 hours at a time, then turned off. Once turned off the
containers were removed from the mill and allowed to sit for 2 hours. After this the containers were opened and allowed exposure to the air for
another 2 hours before being resealed and put back on the mill for another 24 hours. This process was repeated for 4 weeks without any problems.
RESULTS:
A semi-fine bright reflective powder was obtained. This Aluminum powder was mixed with finely powdered store bought potassium perchlorate in a plastic
container that had been sprayed with "Static Guard". The ratio was 30% Al to 70% KCLO4. Batches of 1gram, 5grams, and 30grams were ignited separately
with American Visco waterproof fuse. All of the tests had the same result. A very bright, slow burning, thick smoke producing lameness.
HYPOTHESIS:
Too much stearic acid caused lack of sufficient friction in the ball mill to create a fine enough aluminum powder for rapid deflagration. Experiment
will be repeated with the exact same variables except a 0.5% to 99.5% ratio of stearic acid to AL by weight.
...Thoughts comments?
“Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire
world, and all there ever will be to know and understand.” -Albert Einstein
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hissingnoise
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Results might be better using thin aluminium foil and hardened lead media!
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Armistice19
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I was using hardened lead antimony in my previous batch, and I actually am using thin aluminum foil. It had been cut into very small pieces and then
put through a blender and ground into fine granules. Anyway, I was told that using chrome plated steel would be an efficient media because of its
hardness compared to aluminum, where as lead is softer than aluminum. I expected better results this time. It seems that I have gotten rid of the
spontaneous ignition problem, but only at the expense of the aluminum itself. I still think it was the stearic acid concentration.
“Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire
world, and all there ever will be to know and understand.” -Albert Einstein
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Armistice19
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This morning I used a cheap 200 mesh brass sieve to sift through the previous "lame batch" of aluminum powder. After sifting I obtained ~24g of 200
mesh aluminum. This was then mixed with ~55g store bought powdered KCLO4. The result was a majestic "WOOSH" that closely resembled store bought black
powder which I had handled in the past. This further supports my original hypothesis that the aluminum was not fine enough due to the lubricating
effect of having too much stearic acid in the mill. I am hoping that this new batch containing only 0.5% stearic acid by weight will reach a much
higher mesh and possibly even produce an report whilst uncontained.
CHEAP LAB SIEVES!! ---> http://www.sheffield-pottery.com/SearchResults.asp?Search=si...
“Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire
world, and all there ever will be to know and understand.” -Albert Einstein
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hiperion42
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I found the use of tin snips or scissors to break the foil
down one level to be quite inefficient.
So i started using a paper shredder with confetti cut to
produce 4 x 23mm rectangles which works good.
Getting it down further to 1 x 1mm stage i introduced the
confetti into a blender which i turned on for about 2min at max speed.
The resultant product is a great starting point for introduction into
the ball mill for milling with alumina media.
The only problem is that after blending 1 role of aluminum foil confetti the
blender is fatally injured and has to be replaced.
Does anyone else have blender woes?
[Edited on 7-5-2011 by hiperion42]
.....ejuu....................................................................Ffg..............................g.............
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quicksilver
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Cut prior to putting it in a blender. When I played with that it was OK on the blender IF I cut them up 1st. Basically what you're doing with the
shredder.
The concept is to get them in a position where the ball mill can have a object to tear into. The blender should produce a size that's damn near
perfect for that.
It's the final result that counts however and if you're getting a good result w/ a shredder; so be it. A "lab-level" blender is a great deal better
designed than one from a kitchen. It's not worth you ruining your stuff.
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hiperion42
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The blender was a cheap one so i am curious how a more
expensive one will hold out.
On the picture from foil to confetti to 1mm level using paper
shredder and blender.
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quicksilver
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It appears appropriate to me; it should mill quite well. I should add that I used a variety of medium in the mill and did get some fairly excellent
results. But it is something that is best done outside and with a ground on the motor or metal frame of the mill. There's less chance of static
outside and the "puff" of sub-micron Al won't hover above the opened container. I found it was optimum to work with as large as weight unit as was
feasible at one time due to the time element in milling. The one issue I had was with Mg becasue that material granulated finer and finer; it didn't
flake. It needed a well thought out means to work with it once it past a certain point (about 8um) it would settle into a near solid, it was so fine.
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hissingnoise
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I assume you mean that the inside of the jar was neoprene-coated since a neoprene jar would be too soft for powdering metals.
An airtight jar would mean that minimal oxidation would occur and a lubricant would be unnecessary.
In this case grounding too, wouldn't be required . . .
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Armistice19
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Here is the ball mill that I purchased, http://www.pyrocreations.com/inc/sdetail/11955/11959
Note the description:
"6 Lb capacity DOUBLE Barrel ball mill. Perfect size for milling 2 different comps at once in separate drums. (2 barrels measures 4.75" high x 4.5" in
diameter).
Grind most materials into a fine powder in just a few hours. Includes 2 single 3 lb. Neoprene barrel with quick-seal, leak proof closures (spark
resistant) Heavy construction and easy to use and built to last a lifetime. Liquid can be used in the barrel without any worry of leakage.
Continuous-duty fan-cooled motor that should never give problems. If used on 220 volt a power converter must be used."
Also for everyone having trouble with their blenders if you have several hundred dollars to spare you might want to waste it on one of these.... WILL
IT BLEND? "BlendTec" the indestructible blender----> http://www.willitblend.com/
“Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire
world, and all there ever will be to know and understand.” -Albert Einstein
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Armistice19
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Good news folks. Excellent results were acquired with the new variables introduced. Very fast burning flash powder was synthesized after the stearic
acid content was changed from 3 wt.% to 0.5 wt.%. Instead of a slow "woosh" a nice quick "POOF" and the flash powder was instantly gone. For those who
would like to know here are the variables to my successful experiment.
Media to filling ratio:
-10/1
Filling composition by weight:
-AL 99.5%
-Stearic acid 0.5%
Milling time:
-4 weeks with breaks every 8-24 hours to allow open exposure to oxygen.
Sieve size:
-200 mesh brass
Conclusion:
-These variables make a nice fine aluminum powder for flash compositions but in my opinion 4 weeks is too long for most milling projects, and on top
of that it is very very difficult to sift through a 200 mesh brass screen. Next time I will be using a 15/1 media to filling ratio in order to speed
up the process, also I will be using a 120 mesh sieve.
“Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire
world, and all there ever will be to know and understand.” -Albert Einstein
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Refinery
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Does fine aluminium react with acetone? This is because I want to remove the paraffin/stearic acid from the powder. What would be best method to dry
the powder after purifying? Would heating it in container with back-pressure valve over hot water bath allow acetone vapors to escape but prevent air
from entering?
But 900 grams of balls for 100 grams of aluminium powder and 4 weeks milling time to produce only fair results? Oh god, I was aiming for something
like 60:40 filling rates at maximum of 1-3 days.
[Edited on 1-3-2014 by Refinery]
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Bert
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It's the necromancer!
The ball mill chosen was far too narrow. Mill efficiency goes up dramatically with increased jar diameter- That "6lb. ballmill" is actually just two
3lb. (tiny!) mill jars on a double length roller system.
Charge is not determined by WEIGHT. Charge is determined by VOLUME. Mill jar should have been exactly 1/2 full of media, charge to be ground should
fill up the interstitial space between the pieces of media, no more. Overfilled jar makes for a much slower grind-
Cheap acetone isn't too pure, acetone is also hygroscopic and needs to be dried before use in several pyrotechnic applications I know of, particularly
where it contacts Mg or high Mg alloys. Molecular sieves work for that, so would various anhydrous chemicals that take up water as they hydrate and
aren't soluble in acetone.
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Refinery
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Hmm, but does it actually matter if there is 3% of paraffin in aluminium if it is used in pyrotechnics?
Btw, does anyone have any ideas of cheap and easily available grinding media? I've been thinking of cutting cylpebs from 10-15mm steel rod, but the
steel is obviously pretty soft and it might be consumed in the process. I might also get carbon steel which I could temper into good hardness but the
rods are pretty expensive. Any sources of ceramic balls that would be tensile enough for milling?
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Dornier 335A
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Yes it matters. Even small amounts of oil or similar will slow down flash powders considerably.
I have used glass marbles as grinding media in a small ball mill. They work surprisingly well and look like new even after 50 hours in the ball mill.
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Refinery
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Well, that's bad.
Any ideas how to dry acetone moisten aluminium powder without igniting it? What if I mix a small amount of carbon with it at the begin of milling,
would it protect the aluminium enough or would it be washed off the surface by acetone? Best way would be to use inert atmosphere with argon, but darn
I dont have the welder(yet) as a reason to buy a cylinder.  My best idea so far
is back-flow valve and hot water bath to allow acetone evaporation but prevent air letting in.
My only intent to use paraffin is because one journal found that by mixing 3% of it with aluminium will decrease the particle size from coarse
(0.5-2mm) to 20-50um in 6 hour period and without paraffin the flakes were reduced only to 500um. This time saving is so high that it becomes even
fundamental.
[Edited on 2-3-2014 by Refinery]
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Bert
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If you live in the USA, get enough nickles to 1/2 fill your ball mill jar. Non sparking, fairly non reactive (better than steel, anyhow!) and they
work pretty well. If you get different media later, clean them and return to the bank!
If you want ceramic media, it's a common industrial item. Google is your friend!
Hint: It's often used by people making glaze for ceramics.
http://m.ebay.com/itm/400301684295?nav=SEARCH
Stearin wax was the lubricant of choice for milling flake Aluminum. Parafin? Do you mean the wax, or what is called kerosene in the USA?
[Edited on 2-3-2014 by Bert]
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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DubaiAmateurRocketry
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Talking about the ignition,
I find the color of a propellant has a effect on the burn rate, maybe largely. If you have a transparent binder(PU/HTPB/GAP), it will burn fast. I am
unsure of the reason but I came up with one. And if the propellant is dark colored (adding 1% carbon power/ asphalt/ pen ink) it will burn much
slower(few mm/s) for some reason. Modern energetic composite propellant's burn rate is too fast, sometimes few centimeters per second. Too fast for
many application(a half meter wide rocket/missle will finish its fuel maybe in less than 10 seconds). Therefore I wonder if there are any dark colored
liquid energetic materials.
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Bert
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Quote: Originally posted by DubaiAmateurRocketry  | Talking about the ignition,
I find the color of a propellant has a effect on the burn rate, maybe largely. If you have a transparent binder(PU/HTPB/GAP), it will burn fast. I am
unsure of the reason but I came up with one. And if the propellant is dark colored (adding 1% carbon power/ asphalt/ pen ink) it will burn much
slower(few mm/s) for some reason. |
If a solid propellant is transparent to infrared and/or visible light, energy will be transmitted into a fuel grain's interior by light from the
burning surfaces in addition to the energy transfer by conduction from the burning surfaces. Increaseing the energy fed back into a grain will
obviously increase burn rate, and in extreme cases can cause a grain to catastrophically fail. (KABOOM!)
Carbon black is commonly used as you describe to reduce light penetration into fuel grains. It's cheap and has some fuel value.
As far as dark colored liquid propellants: The infrared absorption profile of liquid fuel droplets sprayed into a combustion chamber certainly MATTER
in regard to their speed of reaction. But unless the combustion chamber and tankage are transparent, light energy can't pre-heat propellant before it
enters the combustion chamber in a way analogous to solid fuel.
If you WANT your fuel/oxidizer pre-heated, route it through a cooling system built into the walls of your combustion chamber & expansion bell
(regenerative cooling).
,
[Edited on 2-3-2014 by Bert]
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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DubaiAmateurRocketry
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Yes thats my explaination for this phenomenon too. A dark colored binder should reduce the large amount of radiation from the combustion to penetrate
the transparent binder and pre-heat the next layer of propellant so it will be easier to ignite. Therefore ending in slow burn rate.
In my opinion, bitumen/asphalt is better than carbon black since it is a liquid and is miscible with most liquids, such as PU.
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Bert
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You know of the original asphalt based "composite fuel", GALCIT 53 propellant?
For well characterized, storage stable mil spec propellant, carbon black is likely going to be a cheaper & easier material to obtain in consistent
quality than asphalt. Uniform performance is KEY with solid propellant- Every oil field is different and lots of odd things rode along with those
hydrocarbons we wanted.
Have you got Richard Nakka's books on composite fuel & engine design?
http://www.nakka-rocketry.net/#Quick
Re-inventing the wheel is fun, and good training-
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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DubaiAmateurRocketry
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| Quote: Originally posted by Bert | You know of the original asphalt based "composite fuel", GALCIT 53 propellant?
For well characterized, storage stable mil spec propellant, carbon black is likely going to be a cheaper & easier material to obtain in consistent
quality than asphalt. Uniform performance is KEY with solid propellant- Every oil field is different and lots of odd things rode along with those
hydrocarbons we wanted.
Have you got Richard Nakka's books on composite fuel & engine design?
http://www.nakka-rocketry.net/#Quick
Re-inventing the wheel is fun, and good training- |
GALCIT53, yes thats some old stuff, but yeah. Potassium perchlorate's burn rate wont be slowed down by any other binder.
The reason I said asphalt so that there is more binder content. even 1% liquid can help with the viscosity a bit and allow more mixing and higher
density in the end  For uniformity of performance, just get the same asphalt
product from same supplier hehe.
Nakka's site is very useful and some of his sites on theories are very useful for calculations. His book should be a lot of help on motor designs,
however I have been concentration on the fuel and not the motor, ill eventually study that.
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