633 replies to this topic

[digger]

Hi,
please can you help me ?
i need "snow gold" composition.
thanks

Are you sure it is "snow gold" and not the very beautiful "slow gold" if the latter it has been posted here a few times before, it will come up on a search.

[citron vert]

oh sorry ^^
slow gold yes
kno3, 36
charcoal airfloat, 29
charcoal 8i0 mesh, 14
sulfur, 9
titanium Sponge 40-8i0 mesh, 7
Dextrin, 5

bye and thanks ^^

[MDH]

Snow gold, or snow ball?

You know, the simplest way to make a quite dense gold tail is just to mix -200 atomized aluminum with black powder and charcoal....

[citron vert]

Hi,
i've some twinkling formulas, and i would like to know what'll happen if i use magnalium 200 µm (about 70 mesh) instead of magnalium 250 µm (60 mesh) and 177 µm (80 mesh) ?

i use the occasion to give you the formulas :


twinkling white stars

Magnalium, 80 mesh (treated with potassium bichromate).....25
Ammonium perchlorate..............................60
Barium sulfate....................................15
Potassium dichromate (as a stabilizer)............+5%

twinkling yellow stars

Magnesium, 60 mesh (treated with potassium bichromate).....40
Ammonium perchlorate..............................50
Sodium sulfate....................................10
Potassium dichromate (as a stabilizer)............+5%

thanks and bye

[digger]

Hi,
i've some twinkling formulas, and i would like to know what'll happen if i use magnalium 200 µm (about 70 mesh) instead of magnalium 250 µm (60 mesh) and 177 µm (80 mesh) ?

i use the occasion to give you the formulas :


twinkling white stars

Magnalium, 80 mesh (treated with potassium bichromate).....25
Ammonium perchlorate..............................60
Barium sulfate....................................15
Potassium dichromate (as a stabilizer)............+5%

twinkling yellow stars

Magnesium, 60 mesh (treated with potassium bichromate).....40
Ammonium perchlorate..............................50
Sodium sulfate....................................10
Potassium dichromate (as a stabilizer)............+5%

thanks and bye

It will change the frequency of the strobing slightly. By the way the potassium bichromate is a catalyst.

Edited by digger, 04 July 2010 - 10:34 PM.

[citron vert]

but, the effect should be beautiful isn't that so ?
if a use a ball mill, can i reduce the magnalium 200 µm to 177 µm ?
if it's possible, how long to do that ?

[MDH]

I vastly prefer coarser grades when I make strobes, since it makes the effect more distinctive and less "Spammy" in appearance. However I tend to use sulfur based strobes since AP is rather expensive.

I would say, prepare a small amount of test composition first and make "Demonstration stars". If you don't like slower flashing, then yes, you can mill the magnesium or magnalium, but ensure that the mill is opened to oxygen every fifteen minutes. The magnesium will take several days of milling. I haven't ever milled magnalium but I'm sure it would take less time.

Edited by MDH, 05 July 2010 - 02:08 AM.

[citron vert]

"but ensure that the mill is opened to oxygen every fifteen minutes"
with magnalium too ?
and why ?
where did you find your magnalium/magnesium ? my producer only do 200 µm
thanks for the rest

[digger]

"but ensure that the mill is opened to oxygen every fifteen minutes"
with magnalium too ?
and why ?
where did you find your magnalium/magnesium ? my producer only do 200 µm
thanks for the rest

Do not expose the magnalium to air when milling. I have heard of a fire caused by milling with air still in the jar. It is a hard metal prone to sparking when milling. The best way is to replace the air in the mill jar with Argon. Once finished loosen the lid and leave it a little while before fully opening to expose it to the atmosphere. It will only take a couple of minutes to reduce your mgal to a finer mesh. It mills very quickly due to its hardness/brittleness.

I would not be too concerned about the difference in the mesh sizes. The formula should be tunable by changing the ratio's of course to fine MgAl

[portfire]

Mmmmm. Rolled up some Veline Magenta the other day, the strange thing is, I can hear the lead core rattling around I understand how this could happen but will the star be weaker? Anyone else had this happen?

[CCH Concepts]

thinking from a mechanical point of view the strength comes from the binding, the core is just there to get it rolling.

are for being hollow, there is very little difference between a solid and a hollow structure, the only real difference is the hollow one is lighter. look a car chassis, H-beams for houses, i think this should be the same for the sphere as long and there no weakness in the outer layer, such as cracks.

[portfire]

Makes sense. Yeah the outer layer is fine, I'm not worried, just wonderd if anyone else has had the problem (not that it's a real one)

[digger]

as for being hollow, there is very little difference between a solid and a hollow structure, the only real difference is the hollow one is lighter. look a car chassis, H-beams for houses, i think this should be the same for the sphere as long and there no weakness in the outer layer, such as cracks.

I do not want to sound rude, but that is utter bunkum

The difference in strength between a solid beam and a hollow beam may not be so significant in bending (look up the bending moments). BUT this is not what happens when a shell explodes. The issue is external pressure. If you take the analagy of the hollow beam, actually lets take a tube to make the maths easy then:...

Hoop stress

σc = [(pi ri2 - po ro2) / (ro2 - ri2)] - [ri2 ro2 (po - pi) / r2 (ro2 - ri2)]

where

σc = stress in circumferential direction (MPa, psi)

r = radius to point in tube or cylinder wall (mm, in)

pi = internal pressure in the tube or cylinder (MPa, psi)

po = external pressure in the tube or cylinder (MPa, psi)

ri = internal radius of tube or cylinder (mm, in)

ro = external radius of tube or cylinder (mm, in)
maximum stress when r = ri (inside pipe or cylinder)

Now given the strength of the material you can see that wall thickness has a dramatic effect on the stress within the material.

So a solid tube is massively stronger than a hollow tube when exposed to external pressure.

The lesson is that you want to avoid rattling stars.

The reason for this is that they were probably over wet when they were rolled.

[CCH Concepts]

Well your reasoning seems alot more solid than mine. Lol

[Mnemotron]

Who is the author of this composition. It looks as though it was intended for use with KCLO3 not KCLO4 as there is no chlorine donor in it. Try adding 10% - 15% of parlon to your composition and it it will be transformed.

Yep the velines are generally pretty good in colour saturation except for the blue. (hint 70/30 magnalium helps with the colours). Yes you can bind them with pure alcohol.

Hello,
Can I replace Parlon with Chlorowax?