27 replies to this topic

[MDH]

The problem is very likely the prime and not the stars. A very hot prime containing thermitic mixtures or silicon should ignite just about anything. The problem is that the prime is not catching alight. It is not uncommon in commercial practice to lightly coat stars with overfueled or overoxidized greenmix when the prime is still damp. Highly smooth prime surfaces can prevent flame from impanting hot particles of dross into the composition. Uneven, granulated meal powder and overfueled greenmix might be needed.

And yes - binding with acetone to make "rubber" stars can sometimes cause them to be harder to ignite (though, I must stress not hard enough to resist strong thermitic primes). You can try binding it with water, but wouldn't that introduce another inhibitor into the picture?

[pyromaniac303]

Have you considered step-priming?

On high-magnalium fuelled stars which are proving hard to light this is useful:

Layer        Ratio (meal / star composition)

Outer                100 / 0
Penultimate           70 / 30
Middle                50 / 50
Inner                 30 / 70
Star                   0 / 100

And for good measure you can add +5% silicon to the meal. This is definitely overkill for the veline system, but certain stars, generally those containing 20% metal content or greater require a very hot prime. It does add a small amount of extra labour, but it is worth the effort to guarantee ignition, and also uses only 2 compositions that you will have to hand.

You can reduce or increase the number of steps depending on the composition. The layers needn't be very thick.

In most cases though 5% silicon + meal will do the trick without any of this additional work.

Edited by pyromaniac303, 27 October 2010 - 02:00 AM.

[Atom Fireworks]

Cheers fellas food for thought, though if what most of you are saying then i should not be having any problems really? Digger i dont use anything but bp burst in my shells, the rocket was an experiment as i was trying to burst a 50gram payload with a decent enough bang and not a measily pop plus lift it with my experimental motor.

Anyways so the things i shall now try is as follows,

1, Step prime
2, Also slow my prime down as ime using the meal powder i make my lift out of which is extremely fast as you can hear by the thunderous boom as the shells leave the tube ( it was actually alot louder than the video suggests)

What do you think of the shells in general? The first one had colour changing stars from red to blue some of which worked and some did not but the inner sphere all the stars seemed to ignite fairly well. The second shell was just all the stars i had lying around and wanted to get rid of them so thought ide chuck them into a shell . Did the burst look to hard? i didnt think so as the stars did not spread far, well not as far as commercial shells of the same calibre.

[Peret]

The only Velines I have trouble with are the barium nitrate greens - all the perchlorate stars ignite every time. The greens are very slow getting started and it's an unusual shell where they all light up and burn at the same time. I found it helps greatly to poke a hole through the stars with a skewer, after cutting, while the comp is still damp, and making sure the holes are well packed with prime. I use Veline prime, btw, with the evil dichromate everyone is so terrified of these days. I substitute silicon for the MgAl to reduce the white priming flare.

[Potassium chlorate]

I primed Lancaster chlorate silver stars with magnalium/German Black inner prime and H3+10% silicon outer prime. They worked very well despite the high metal content, >30%, though then I used my home-made NC-lacquer made out of high-nitrated cotton and acetone to bind it with. Shame there's nothing left of it.

[Creepin_pyro]

2, Also slow my prime down as ime using the meal powder i make my lift out of which is extremely fast as you can hear by the thunderous boom as the shells leave the tube ( it was actually alot louder than the video suggests)

l
Sounds good - save your fast meal for things other than primes. Slower (green and slightly overfuelled) meal gives a little time for things to get going, and the more time you have molten dross surrounding the star the more likely it is going to light properly.

[starseeker]

I have just watched the videos dumper and the break looked to be fairly weak,how many pasted layers did you give them?I was wondering if maybe they were breaking prematurely before everthing has time to get going.

[Atom Fireworks]

I have just watched the videos dumper and the break looked to be fairly weak,how many pasted layers did you give them?I was wondering if maybe they were breaking prematurely before everthing has time to get going.

The 4" had approx 10-12 layers of 70gsm craft gummed tape in the 3 strip method. and allowed to dry for a week, they were that solid i physically could not squeese or depress any part of the shells surface, bear in mind on the video them shells went very high, if you imagine the highet of a power cable pylon times that by around 5 or 6 and you get the picture, i put far too much lift under them because my 4" tube is a little small in length i must have gone abit overkill.

I thought about your point however my 3" shells have over 20 layers and they still dont ignite all the stars.

[starseeker]

The 4" had approx 10-12 layers of 70gsm craft gummed tape in the 3 strip method. and allowed to dry for a week, they were that solid i physically could not squeese or depress any part of the shells surface, bear in mind on the video them shells went very high, if you imagine the highet of a power cable pylon times that by around 5 or 6 and you get the picture, i put far too much lift under them because my 4" tube is a little small in length i must have gone abit overkill.

I thought about your point however my 3" shells have over 20 layers and they still dont ignite all the stars.

It was just a thought,it certainly seems to be suggesting that it is the prime then.

[Atom Fireworks]

It was just a thought,it certainly seems to be suggesting that it is the prime then.

Thanks for the suggestion though matey, it really is strange. After ive tried and tested the ideas we have come up with i will post the results hopefully with some lovely fully ignited stars

[Creepin_pyro]

I would expect veline stars to blow blind if primed with mill dust - just use a proper prime (like the one veline suggests) or use step priming as already suggested and your stars will be absolutely fine.

[Atom Fireworks]

I would expect veline stars to blow blind if primed with mill dust - just use a proper prime (like the one veline suggests) or use step priming as already suggested and your stars will be absolutely fine.

Will do CP, hope it works out fine as its makin me wanna give up and call it a day !!

[drtoivowillmann]

The problem is very likely the prime and not the stars. A very hot prime containing thermitic mixtures or silicon should ignite just about anything. The problem is that the prime is not catching alight. It is not uncommon in commercial practice to lightly coat stars with overfueled or overoxidized greenmix when the prime is still damp. Highly smooth prime surfaces can prevent flame from impanting hot particles of dross into the composition. Uneven, granulated meal powder and overfueled greenmix might be needed.

And yes - binding with acetone to make "rubber" stars can sometimes cause them to be harder to ignite (though, I must stress not hard enough to resist strong thermitic primes). You can try binding it with water, but wouldn't that introduce another inhibitor into the picture?

Many friends will send to you their single-layer primes. Some will work, other not.
Takeo Shimizu uses primes of 7 or even more layers upon his coloured stars. And that guy is not crazy, but knows exactly, why.

I (I am a professional) have developped a 3-layer prime.

First a little bit of prime-theory:

* Compositions based on Magnalium need quite high temperatures to ignite.
* Compositions based on Potassium Perchlorate ignite slowly, so your prime has to maintain heat for some instances.
* Compositions based on Magnalium and P. Perchlorate have quite low Critical Speeds in the very moment they ignite. So your stars should slow down, before being
ignited. This means that your prime must be also a delay composition.
* Modern shell break, using flash powder. So a single spark must be sufficient,to ignite your prime.

It is very hard to fulfill all theese criteria in a single composition. Therefore I use 3.

1 Kg of coloured round star core + 200 g layer "A" + 400 g layer "B" + 400 g layer "C".
Prime like making your round stars. Use (best destilled) water, adding 10 % of acetone to it.

Here the exact formulas:

Layer "A":
46 % Barium Nitrate (not too micronized)
22 % Potassium Nitrate (not too micronized)
14 % Magnalium
14 % Red Gum (Acaroides)
3 % White Arabic Gum (not Kodorfan)
1 % (basic) Magnesium Carbonate

Layer "B"
1st version:
50 % Potassium Nitrate (well micronized)
22 % charcoal
15 % Dark Aluminum
8 % sulphur
4 % Dextrine
1 % Boric Acid

2nd version:
raise charcoal up to 24 %
exchange Dark Aluminum by 13 % of finest Atomized Aluminum

Layer "C":
99 % Meal Poder (75/15/10 or 70/18/12)
1 % White Arabic Gum

That's all.
Greetings from Brazil:

Toivo