1569 replies to this topic

[karlfoxman]

It is possible its two shells with a passfire but i believe this can be done with one shell. If you look the comets have traveled much further out than the star pattern. This indicates a break from one end as i see it anyway. I am no expert on shell design but i am applying what i already know. We need to speak to the guy who made it, if anyone knows please please let us know....although this is a very interesting discussion and i like a good puzzle.

[paul]

You?re right. It?s fun and I always try to improve my english skills to get a clearer articulation in a way.
I mean that I can make clear to others what I mean


So, getting into contact with this guy would be great. Any Idea to archieve that?!


with best regards,

paul

[Mortartube]

I think that the stars are placed in one end of a cylinder shell (around formers), as described. Imagine them to be like an aerial mine without the surrounding mortar tube. If the sides and one end of the shell casing are very strong whilst the other end is weaker, it would theoretically be possible to get a burst like the one shown. A very short mortar tube gives a wide spread to a bag mine. I believe that the stars are coming out of the end of the shell in a cone, but towards the camera. Look at his photo and you will see one break side on and it is conical and not blown out from the middle like a traditional ring shell would be.

http://freakpyromani...=4124&si=Mqabba

[paul]

You are right! Thanks very much for picking out that certain picture! The two shells in the center of the picture really show what you mean.

I don?t know why, but I allready have a kind of drawing in my head how to produce such an effect with a cylindrical shell.

But only a ring and not such difficult shapes like the blue/yellow star with the ring around.

[karlfoxman]

I think that the stars are placed in one end of a cylinder shell (around formers), as described. Imagine them to be like an aerial mine without the surrounding mortar tube. If the sides and one end of the shell casing are very strong whilst the other end is weaker, it would theoretically be possible to get a burst like the one shown. A very short mortar tube gives a wide spread to a bag mine. I believe that the stars are coming out of the end of the shell in a cone, but towards the camera. Look at his photo and you will see one break side on and it is conical and not blown out from the middle like a traditional ring shell would be.

http://freakpyromani...=4124&si=Mqabba

Good one mortartube, this is the only way i think it can be done. And yes one end would have to be weaker, must be very hard to 'dial in' break charges for this shell. I am thinking it can be done with 6" shells, maybe a 5 inch if the stars are kept small. At the moment i am preparing the cases for a sun and planets shell while all my burst charges/stars dry. I will photo the cases and post tomorrow.

[italteen3]

I guess its possible as long as there is some balance to the shell casing a burst. I, like I said before, always thought that the equal burst charge from each hemisphere is what made spherical shells much superior for pattern effects. But leave it to the Maltese to break that "rule".

And I stand corrected....kinda

[JamesH]

Could it be a compartment shell, One shell containing the star pattern and the second containing the comet rings. Since there seems to be a great many stars in that star pattern, if all were in one shell wouldn't there be a large compromise in burst volume?

[Mortartube]

It could be a compartment shell. But I believe that the ring effect stars are probably placed around the burst charge in a cylinder shell ( much like a spherical shell), whilst the pattern is at one end, so the one burst charge does both jobs at the same time. Video would be more helpful than stills in trying to analyse the method of construction.

Edited by Mortartube, 21 November 2005 - 12:43 AM.

[karlfoxman]

It could be a compartment shell. But I believe that the ring effect stars are probably placed around the burst charge in a cylinder shell ( much like a spherical shell), whilst the pattern is at one end, so the one burst charge does both jobs at the same time. Video would be more helpful than stills in trying to analyse the method of construction.

Took a while but here is a link to some videos....truely amazing pyrotechnics guys!

VIDEOS

It becomes less of a mystery....

Use Innternet Explorer to get them, i had problems with Firefox

Edited by karlfoxman, 21 November 2005 - 09:24 AM.

[JamesH]

Heres a 2.5" cylindrical shell i made over the last couple of days.
The stars i used were 8mm pumped D1 glitter. The burst charge was 3FA black powder in a central 7/8" cannule. Flax twine was used for spiking the shell with 12 verticals and 5 horizontals. The lift was 18g of 3FA black powder.

A few photos of some of the construction:

After spiking
http://i11.photobuck...22/3df89c26.jpg

After pasting
http://i11.photobuck...22/69a4bad4.jpg

Prior to lifting
http://i11.photobuck...22/8859109f.jpg

Completed shell
http://i11.photobuck...22/d43261c5.jpg

Heres the video clip:
http://media.putfile.../25in-can-shell

[Maineiac]

Nice work James! What paper did you use for the case and paste wraps? Strange looking stuff. Have you tried 24 verticals and 6 or 7 horizontals on the spiking? Remember the headers photo on the bench? They use those numbers and are only slightly larger than your shell. No paste wrap either on those so the break is modified a bit. Was the D1 regular formula or the modified we discussed? Again, nice work! A few more like that and you'll be moving on to multi-breaks.

[JamesH]

Nice work James! What paper did you use for the case and paste wraps? Strange looking stuff. Have you tried 24 verticals and 6 or 7 horizontals on the spiking? Remember the headers photo on the bench? They use those numbers and are only slightly larger than your shell. No paste wrap either on those so the break is modified a bit. Was the D1 regular formula or the modified we discussed? Again, nice work! A few more like that and you'll be moving on to multi-breaks.

Eric, thank you for the encouragment!
I used 4 turns of 90gsm (0.004" thickness) virgin kraft paper for both the case and the paste wrap. Most of the kraft paper we have this side of the pond tends to be the machine glazed ribbed type. 70lb virgin kraft is not available here as far as I am aware.

I have not tried using more verticals, I will do so to see if I can improve the break radius and symmetry. Will 24 verticals be to much in combination with the 4 turns of paste wrap? The 4-ply flax twine I am using has an ultimate tensile strength of approximately 44lbs.

The D1 glitter used -200 mesh atomised aluminium. It was the batch I had over incorperated, hence the short delay.

[sasman]

I like how you finish your shells they look very tasty... Nice burst .. was it big in real life? its very hard to judge how big the burst is from video?..when you mention about the D1 glitter what do you mean over incorperated? hence the short delay? .. Nice job with filming ... have you got a video with sound?..

Lets see some more please!!!

[JamesH]

Cheers Rob, the burst was fairly large but I would like to improve on it. The camera was about 100m from the mortar.

What i mean by over incorperated is, I ball milled the ingredients (minus the Al) for too long. This tends to drastically shorten the glitter delay.

The video should have sound!?

[Richard H]

How did you cut your end discs James? Looks well constructed to me.