38 replies to this topic

[Artopunk14]

Hello, I have been trying to make my 4 inch shells work for sometime now and I just cant figure out whats wrong. I've been doing exactly what this artical says to do: http://www.unitednuclear.com/shell.htm. I get the shell to lift good but the break is just a little puff, less than a firecracker! I think my problem is my 70/30 Potassium Perchlorate/Sodium Benzoate whistle mix. I bought a ball mill to grind down the benzoate and I have gotten the whistle mix to produce a loud report realitivly unconfined, but when sprinkled in the shell it still just has a puff break. This is very aggravating and if someone could help me out I would really apreshiated it.

Thanks in advance

[Richard H]

How do you construct your shells exactly? What is the casing made of? If you paste the shells, how?, what with?, how many layers of paper?. How is the burst charge configured? Are you using a flash-style bag to contain the whistle in the centre of the shell?

The more specific you can be the more we can help.

P.S. Welcome to the forum!

[Artopunk14]

How do you construct your shells exactly? What is the casing made of? If you paste the shells, how?, what with?, how many layers of paper?. How is the burst charge configured? Are you using a flash-style bag to contain the whistle in the centre of the shell?

The more specific you can be the more we can help.

P.S. Welcome to the forum!

Plastic shells put together with pvc cement, i use black powder coated corncob with whistle mix sprinkled in it.

[sizzle]

How fast is your BP, is it the same stuff you use for lift, is it Willow based or a slower charcoal like Pine?

[Artopunk14]

How fast is your BP, is it the same stuff you use for lift, is it Willow based or a slower charcoal like Pine?

I ballmilled 2f black powder for 10 hours, its finer than 4f now.

[sizzle]

Are you pasting your shells after sealing them?

[Artopunk14]

Are you pasting your shells after sealing them?

no, just sealing the 2 plastics halfs together

[karlfoxman]

Corn cob depending on its size maybe stopping the flame from making progress through the shell, if I was you I would use rice crispies for my carrier with a 2:1 coating of fast willow powder + 5parts dextrin. Then for whistle I would use fine milled ingredients (never milled together) and well mixed. This I would add to the break at 10% the weight of the burst charge. I sprinkle half the whistle in one hemi and the other half in the other hemi, just loose on the break. Ensure your break is also fully dry as theis will turn the whistle into crap!

As for gluing the shells I have always used paint thinners, just let a few drops into the gap before fully closed. Where are your hemispheres from? I use the Plasticos Gamon ones but they hare made quite thick so I never need to paste to get round breaks.

Just my 2 pence

[RegimentalPyro]

If you have commercial 2F blackpowder then just use that to break. It should be fine without Whistle in a four inch shell.

How much to use is a different matter. Completly filling the shell with 2F could be overkill, and cause your stars to blow blind. You might consider mixing with [not coating!] a filler [cotton seeds mebbe] in varying proportions [80:20 75:25, 66:33]

[Artopunk14]

Corn cob depending on its size maybe stopping the flame from making progress through the shell, if I was you I would use rice crispies for my carrier with a 2:1 coating of fast willow powder + 5parts dextrin. Then for whistle I would use fine milled ingredients (never milled together) and well mixed. This I would add to the break at 10% the weight of the burst charge. I sprinkle half the whistle in one hemi and the other half in the other hemi, just loose on the break. Ensure your break is also fully dry as theis will turn the whistle into crap!

As for gluing the shells I have always used paint thinners, just let a few drops into the gap before fully closed. Where are your hemispheres from? I use the Plasticos Gamon ones but they hare made quite thick so I never need to paste to get round breaks.

Just my 2 pence

I got the shells from http://www.pyrocreat.../plastic_shells. I had the corn cob dry for 3 days, when I lit one piece of corn cob it would burn for a sec and stop leaving most of it unburned. Im not sure how good corn cob is supposed to burn.

[skipjack]

the corn cob doesnt fully burn down to ashes, since its only the carrier for the blackpowder... so thats ok.

BUT one second of burning time sounds very long to me.
if you test-light a little pile of BP-coated corn cob, you shouldnt even see it burn. it simply goes "woooosh" in a blink of an eye!!

thats why i think there's either something wrong with your BP or the burst charge simply isnt dry yet.
my advice is to check your BP before you put it onto the corn cob.

Skipjack

[Jerronimo]

What ratio of BP to corncob did you use?
I normally use ricehulls and use a ratio of 6:1.

You could also add a layer of fibreglass/filament tape to the outside of the shell, this will improve the break.

[Artopunk14]

What ratio of BP to corncob did you use?
I normally use ricehulls and use a ratio of 6:1.

You could also add a layer of fibreglass/filament tape to the outside of the shell, this will improve the break.

I didnt really use a ratio , i used a half cup of corn cob with 180g of BP and 37g of dextrin. I was thinking of picking up some fiberglass tape but wasnt sure if it would help.

edit: I just did a little pile of corn cob and it burned VERY fast and went "woosh'.

Edited by Artopunk14, 23 October 2006 - 07:29 PM.

[Pretty green flames]

Whoa, slow down on the dextrin a bit, 37g is WAAAY to much. Use a maximum of 5%. The ammount you used will slow down your BP when 5% should have very little impact on the burn rate.

[Artopunk14]

Whoa, slow down on the dextrin a bit, 37g is WAAAY to much. Use a maximum of 5%. The ammount you used will slow down your BP when 5% should have very little impact on the burn rate.

allright, i just cut everything in half that united nuclear said to use.