26 replies to this topic

[The_Djinn]

Alany,

Maybe a nose cone might help, lots of drag with the nice large flat surface.
Will be interesting to see how this works as there is no reason for it to not to perform.

Charge the video cam up

[alany]

Well I shot it last night, the videos are here:

http://www.vk2zay.ne...vice.php?id=157

It royally sucked. I think I over-broke it blowing most of the stars blind. Those primed KP/Zinc stars have never been hard to ignite before, so I am thinking the flash scattered the guts of the shell before the flame front made it to them.

I'll definately give it another go in the future.

The other shell wasn't too bad though, but I wasn't happy with the pattern, I need to use jute for spiking in the future. This cotton/polyester blend was purchased for match making (labelled as pure cotton - bugger!), and I've been trying to get rid of it.

[Phoenix]

Nice work. I love that glitter. I think I'll try one of these ring shell rockets ASAP. I'll make it my pyro thing for next weekend (I make something every weekend - just had a great result from a 40mm can shell of 10mm flash cored tiger tail).

[alany]

Friday's shoot cleaned me out of BP so it will be a while before I can try again. I think next time I won't glue the stars down, I'll hold them in place with a paper ring until I pack in the burst. The canister walls should be thicker next time too I think.

Bernie mentioned a different construction technique that I might try too.

[Phoenix]

Just fired it. The shell was about 55mm outside diameter by about 15mm outside height. Vertical spiking only. It used a BP on vermiculite break charge, and 10mm flash cored charcoal stars, which were just seated around the edge and held in place by the burst. Stuck it proudly atop a 1/2" rocket with an empty cone on top, and one with the top cut off on the bottom (around the motor), to make it super aerodynamic.

And...it didn't work. The stars seemed to head up from the rocket, rather than out. I think the top disk just blew off. I recovered the stick and motor casing with the bottom disk still stuck to them, and after a bit of hunting around found the cones and most of the wall of the shell, which seemed to have just split, rather than fragmented. Couldn't find the top disc, as there was snow everywhere anyway so it didn't really stand out. It was great fun anyway though. That was the largest rocket I have made to date, and it had a brilliant tail.

[alany]

Sounds a lot like the way mine broke.

In fact most of my canister shells on rockets seem to blow out the top and sides with very little directed down. I am not sure if the passfire tubing and inertia of the motor attached to the bottom disk is making any difference. In fact it seems to happen to devices where the shell has been blown clear of the motor before the break. Unlike larger shells the passfire volume is significant, but even when I just had a hole in the bottom disk (igniting the break from one end) it did largely the same thing. I guess that doesn't apply to these disk shells because they are only as deep as the star size.

I've been blaming the forward motion of the rocket too, because my current designs have virtually no delay.

I'll try again, I have one motor left before I need to make another batch of propellant, and I just made a batch of benzolift hulls which I want to try out for break. Now if only I had some timefuse I could avoid 'spoulette hell' and make test shells a whole lot faster sans the rocket motor.

[dfk]

These ring shells sound interesting, and I like the disk idea better than a using a ball shell and wasting all that space.
How would the fusing work for a multi break, disk shell rocket header?

[alany]

A single long spoulette or piece of timefuse cross matched at the middle of each shell might work.

Construction would be complicated mechanically by the cross matching, maybe just a spoulette with a hole drilled at the right place for each shell, however you'd need to seal the disk to spoulette penetrations well or else it will chain fire.

[LadyKate]

Well I shot it last night, the videos are here:

http://www.vk2zay.ne...vice.php?id=157

It royally sucked.  I think I over-broke it blowing most of the stars blind.  Those primed KP/Zinc stars have never been hard to ignite before, so I am thinking the flash scattered the guts of the shell before the flame front made it to them.

I was reading over these posts and decided to make one myself. I had a failure, too. I think my problem was too little flash/whistle or poor packaging - it was a weak break. You can see the project at: http://www.wichitabu...works/ring.html

It does seem like a fun project - I'll try again later.

[Yugen-biki]

I have found that makeing a ring shell in a cylindrical shell is harder than in a sperical.

Why I'm not quite sure. But the stars has to be fitted tightly and the burst needs to be strong.
It is possible though. There is an article in best of AFN covering the subject of ring shells made in cylindrical shells.


Here is a 3" sperical ringshell from my pyro page. The stars were not fitted very tightly and H3 were used. It was not very hard to make.
http://www.a0tu.com/...r/Ringshell.avi

Edited by Yugen-biki, 23 July 2005 - 03:43 PM.

[LadyKate]

I have found that makeing a ring shell in a cylindrical shell is harder than in a sperical.
Why I'm not quite sure. But the stars has to be fitted tightly and the burst needs to be strong.
It is possible though. There is an article in best of AFN covering the subject of ring shells made in cylindrical shells.

Where in best of AFN? I have them so I guess I could just scan them but I'm lazy today.

I've made a successful small ring shell using a plastic refillable Easter Egg - and a small amount of BP/Flash. However, I think you are right about the cylindrical shells - the breaking charge has to be stronger rather than weaker. Also, after looking at Alan's pictures and comments, it might be necessary to spike it a bit to stop the top from blowing upwards too early and spoiling the ring.

Update: I secured the top of the shell to the bottom with a middle column and added in some flash to get the break better. I used some Bleser #1 stars that lit very well. I overdid the flash by a bit but the whole thing did come closer to a round break... sort of. See it at: http://www.wichitabu...works/ring.html

Edited by LadyKate, 24 July 2005 - 03:32 AM.

[Yugen-biki]

This was my first ringshell in a cylindre:
http://www.a0tu.com/...er/RedSrNO3.avi

But after makeing a spherical a few days later with much less effort, I gave up the cylindrical one.

AFN II page 156