1569 replies to this topic

[paul]

karlfoxman: Why do you use such a heavy prime in your inserts? I made about 20 of them as well and did only prime the 2mm visco sticking out of the inserts with bp slurry...

Now I´m unsure about if thats enough...

[karlfoxman]

Paul,

These beraq dont use visco, I use the slurry delay paste that i push into the fuse hole. Doing this makes a big lump of slurry that is over the casing. Then just after filling the delay hole I dip the sticky prime into fine granulated BP. So the mess on the side is caused by the making the delay process.

Hope this helps.

Karl

[paul]

Now that technique is interesting!

Would you mind describing, what diameter holes you use and what
formula the delay paste is?! I guess its a low-KNO3/charcoal mixture with
added aluminium or something to aid ignition?

Edit: how thick are your tubes?

Just a thought

Edited by paul, 12 April 2007 - 10:21 AM.

[karlfoxman]

Ok heres what I use:

Tubes:

I hand roll them from 250gsm paper, 420mm long strip by 40mm wide. Rolled tightly and pasted all over. Former is 3/4. Then I paste normal printer paper over it, 40mm wide and 210mm long.

When dry I seal with either hot glue or sawdust/pva mixture. A 2mm hole is drilled in the side slowly and I use soap to lubricate the bit to stop it messing up the inside of the casing.

The formula is as follows:

Standard BP 75 Potassium nitrate, 15 Alder charcoal, 10 Sulphur.

This is milled to make it fast, I mill 100g for 1.5 hours as this makes fast powder in my mill.

Once milled I add 5% Gum arabic, this can be changed to alter the speed of the burn but I would not go below 4% as it may not make the paste strong enough. The paste needs to look like black treacle so add enough water to do this. The paste is the pushed into the hole using a knife, you want to see a 2mm 'pooh' start to come out the delay hole on the inside. Now paste a bit more over the hole and dip the prime into grain powder.

Once the paste has dried you can feel hoe strong it is! Now fill with flash and seal the other end.

One note, I add pasted paper to either end of the casing to stop flame getting inside the beraq before it should.

[pyrotrev]

So to alter the delay you change the amount of gum in the mix? or use a thicker tube?

[karlfoxman]

Thats right Trevor, normally you would just make a thicker case. When I have got the timing good enough I will make a beraq 6" shell with 5 rings.

[pudi.dk]

Made my first comet that I fired today.

30 mm TigerTail Comet - Split

Used activated charcoal for the TT.

[paul]

Thats a great one. What I especially like is the professional look (e-match, description whats inside, nice wrapping!).

Never thought (tried it myself ) that someone can get such a nice tail out of activated carbon!
Even the break into two pieces worked flawlessly. Impressive for your first comet!

Keep your videos coming!

[pyrotrev]

A lot of people dismiss activated charcoal because it doesn't burn fast enough to make good lift, but I've found it useful in various star comps and delay mixes to give an enhanced tail or to make them burn longer. And it seems to be a very consistent product (if a little pricey), at least the stuff I got from Wragg.

[leosedf]

Hi!
I wanted to share with you a small 3 inch ball shell (paper) i've built for easter.

The star formula is a nitrate flash:
50 KNO3
30 -325 bright flake Al
20 Sulfur.

The burst used is only BP made with white poplar charcoal (actually i use it for lift but didn't had time to do anything else)
Here it is : http://www.apcforum....iles/wshell.wmv

Edited by leosedf, 16 April 2007 - 05:00 PM.

[Wyvern]

Iknow, not the ideal place to post my spherical shell video but its the closest i can find to put it lightly the launch was crap, my 3" mortars are about 7mm bigger than the shells i use so i usualy paste then a constderable amount, but this time i tried a different way of fiting it to the mortar but failed miserably and blew on the floor. The one thing i am very pleased with is the golden tail stars (my own formula, as far as i know), the shell was half golden tail, half veline blue here it is

http://tompearceltd.co.uk/goldblue.wmv

[maxman]

How much lift did you use? and what burst charge?

[Pyromaster2003]

Them charcoal stars were spot on mind sharing your comp im about to make some myself! Did you roll them or just cut?

[paul]

The break looks and sounds impressive though! Would you mind sharing that composistion?

[Wyvern]

The lift was 12hr milled bp granulated through a sieve the problem was i think is that i skimped on the pasting and just used tape around the centre to make it fit the mortar properly, the break was a 2g 70:30 flashbag with bp on crispies around the stars. As for the comp it was quite a job to make and was pumped into 14mm stars.

40g Potassium nitrate
10g Barium nitrate
10g Antimony Trisuphide (400 mesh)
20g Willow charcoal (bag ranges from airfloat to 40 mesh)
5g AL flake (40-120 mesh)
5g Al Sherical (325 mesh)
7g Willow charcoal ( same as above but added post milling)
3g Mg (170 mesh)(coated)
10g Sulphur
5g boric acid

Mill the 40g Potassium nitrate, 10g Barium nitrate, 20g Charcoal, 10g Sulphur, Boric Acid and Dextrin for 4 hours, then mix in the rest of the ingredients through mesh screen until thoroughly mixed wet with a 50/50 water alcohol and pump