114 replies to this topic

[LadyKate]

I've been experimenting with flash cores embedded in the comet

 

BTW (and to drift towards the forum topic ): Putting strobing stars into the comet would seem to be a waste of stars. IMHO the comet is going to start peeling them off right away and the effect would be wasted. However, if a larger strobing star is somehow timed to ignite at apogee then it might be kind of cool. The strobing star formula on United Nuclear works great and would be what I would try first:

Barium Nitrate 51 grams
Potassium Nitrate 7 grams
Sulfur 19 grams
Magnalium 60 to100 mesh 18 grams
Dextrin 5 grams

(which is the Bleser strobe formula - not quite sure if they credit him on that)

Edited by LadyKate, 11 August 2005 - 02:13 PM.

[Yugen-biki]

Adding ordinary stars (flash cores) to a comet will not create the effect of a flash at the end. Maby useing strobe stars, but then you limit your self what kind of chemicals you can use. NH4ClO4 has some chemical incompabilities as you all know. A BaNO3 based comp. is probably the choise if you consider strobe.

Why not make a twinkle composition? They have bright flashes in the end of the tail.

Another way might be to put a delay composition on the flash cores...
I use a BaNO3 based flash core comp. by Shimizu, and it works great. But if the stars are larger then about 2-3mm they will not flash, but rather become white stars swimming around in the sky.

[LadyKate]

I use a BaNO3 based flash core comp. by Shimizu, and it works great. But if the stars are larger then about 2-3mm they will not flash, but rather become white stars swimming around in the sky.

 

Two questions... what is the Shimizu formula (or point to it in his book - I have a copy) and is it hard to light (do you just wrap it with star comp?)?

The Bleser formula is difficult to light and I'm looking for something a bit more reliable.

[broadsword]

I was hoping for the comet to flash at the very end, so i thought about pumping a normal bright star then putting that inside the center of the comet. Like this...



Or to replace the star with a small 'star' (sort of thing) made out of KNO3:Mg, would this be unsafe?

I wasnt looking for a report, just a quick flash.

Broadsword calling Danny Boy??? Where Eagles Dare?

Yes

[LadyKate]

I was hoping for the comet to flash at the very end, so i thought about pumping a normal bright star then putting that inside the center of the comet.
I wasnt looking for a report, just a quick flash.

 

Well .. I haven't tried that but I don't think my comets would cooperate. The size of the comet is big enough to allow lots of variables to develop fully as the burn progresses. The burn rate would vary from front to back on the comet. Rushing through the air would probably have various effects - all the way from blowing the leading flame out to oxygenating and causing the comp to burn quicker. The composition itself would have at least some variability and the fact that the comet is not round would mean a non-uniform ignition of the center sphere. However, as I said, I haven't tried it. Heck, it might work!

EDIT: Having thought about this another microsecond.... A larger metallic fueled star of some sort might work. A bigger one would stand a chance of surviving the comet burn long enough to make a stage presence. The reason for the metal fuel is to contrast it with the rest of the burn. An easy one to make might be the white antimony based star - it lasts a medium amount of time and is easy to ignite.

Source: Davis
KNO3: 62
Antinomy (III) sulphide: 17
Sulfur: 17
Dextrin: 3

Edited by LadyKate, 11 August 2005 - 03:58 PM.

[broadsword]

I have found a video that shows what I wanted to create.

I found it on ACP and it shows a 3 inch shel with Tiger Tail to D1 glitter stars.

Click Me

[adamw]

If you want a flash at the end, why not just create a pumped star with a cavity, and insert a small twist of tissue paper with a bit of flash in the middle, and then just seal the cavity with some more comet comp. This should not create a report, just a mere flash. (an effect sometimes created with a bad crossette)

[broadsword]

Good idea, thanks.
The only problem may be that the denesity of the comet will be diferent to the stuff that has 'bunged' the hole up, so would make different burning rates.
I could just use a slower BP or add more charcoal though.
Anyway thanks for the advice, any other ideas are welcome though.

[Mumbles]

The only problem with the stars in the shell you posted is that they are rolled. I know the person who made it, and he definatly rolled them. Anyway, you could always try something called a stacked comet(I think that is the name at least). You press one comet. Score the top, and press a different composition on top, in a thin layer. You would then have to place an end disk on top, and paste over most of the sides to ensure burning only from the bottom. Once it reaches the second layer it would switch.

The pasting provides two things. First is confines burning to the bottom of the comet only, which could slow the burn rate. Secondly it holds the two layers together incase they don't adhere together. As always, you should check for compatibility issues between the two compositions.

[Yugen-biki]

I dont think flash cores are what you are looking for. They will work as in the movie broadsword posted.
The flash cores doesn't really flash in the true sense. If made small they will just blink one time in the end of the star they are put in.
And the effect comes to it?s best when they are used in a star that is good in contrast to the white blink, like chrysantemum.

They are found in Shimixu?s book on page 219 under the name "Brilliant core". A good prime for them is found on page 220 as "core coating composition".
But I have used them in twinkle stars found on page 222 in Shimizu wtih 100% ignition. But the coating is reccomended.
Here is a 4" shell with the twinkle stars I'm thinking of:
http://www.a0tu.com/...inchtwinkle.avi

adamw has a good suggestion. Mumbles?s migh be of interest to because it sounds easier.

The risk you take by using a "white star comp" and use this as a core or finish of a star, is that it migt not me noted if the comet has a white tail. The comet itself will burns white, and the effect would be a comet wich loses it?s tail at the end.
I would have tried adamw?s suggestion and make a "bad crossette".

#An important note on "brilliant core":
They have to dry very long if water is present in the solvent as suggested by shimizu. If they contain any ammount of water they will be very hard to light. And They have a tendensy to dry very slowly because of the high Al content.
Chrysantemum will most likely not light them on it?s own.

#A note on flash:
An Al based flash like 60:40 would be quite sufficient to make a flash inthe end of the comet.

Edited by Yugen-biki, 12 August 2005 - 01:53 PM.

[GBthriller]

Here is a 4" shell with the twinkle stars I'm thinking of:
http://www.a0tu.com/...inchtwinkle.avi

YB- That is a beautiful shell, was it your handi-work?

What is the formula? How much lift? How did you get such a nice large break? Please please share.

Thanks! GB

P.S. for the next month I'll be signing Merry Christmas, before it's illegal to do so here in the U.S.

[Yugen-biki]

GBthriller
Thanks!

Star formula from Shimizu?s book, originally from Winokur. 5 different similar formulas are listed in the book and I don't remember which one I used. But I was something like.

KNO3 40
S 10
C 10
BaNO3 16
Al 12
Fe(III)O 7
Dextrin 5

I did not really like this formula because the effect was to concentrated to the burning star.
Lift was 30-35g BP.
I used H3 with 1-2g 70:30 flash.
1,5s time fuse.
15 layers of kraft paper.

[GBthriller]

Thats a very complete answer, many many thanks!!

I'll try it! If its anything like yours, it will be a personal best!

Edit: Which Al would you use?

Edited by GBthriller, 06 December 2005 - 06:18 AM.

[Yugen-biki]

<77?m atomized Al.
A finer Al would work better I think. I have had better results with <63?m atomized Al in other glitter compositions. I don't know how this glitter would work with finer Al though.

[Bluehawk]

Anyone have any good formulas for small strobe pots in the .75"x1" or so category?