38 replies to this topic

[Mumbles]

The dextrin may play a role with the extreme slowing. I have the same type of plastic shells that you do, and I have never gotten a good break off them with just BP. From my experience flash bags or whistle bags give a harder break that simply mixing it into the burst. Mixing it in helps to give better symetry IMO, but the bag just gives a harder break.

[Artopunk14]

The dextrin may play a role with the extreme slowing. I have the same type of plastic shells that you do, and I have never gotten a good break off them with just BP. From my experience flash bags or whistle bags give a harder break that simply mixing it into the burst. Mixing it in helps to give better symetry IMO, but the bag just gives a harder break.

How do I make a bag for my whistle? Does it go on the end of the fuse? Does it have to be tight?

Thanks for all the replies so far.

[GBthriller]

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'.

I'm fairly sure that much dextrin would cause a driven-in moisture problem. It might take three months to fully dry that burst mix.

GB would also appreciate any bag building tips from the experts here.

Thanks

[BrightStar]

For my last batch of 3" plastic shells, with satisfactory but not very hard breaks, I used BP + 10% dextrin on corn cob, with BP alone used for the last coating, giving a 3.5:1 BP to cob ratio in total. 20% dextrin as above is too much. 2g 70/30 perc/benzoate whistle boosters were added in the middle in a cling film (saran wrap) packet. Drinking straws full of grain BP were used to carry fire from the time fuse to the centre of the shells and the whistle bags.

The shells were spiked with a couple of layers of fibreglass tape and gave reasonable symmetry, but I intend to paste them properly with 8-10 layers of kraft next time for a bigger burst. Also, the BP coated corn cob creates big granules that are light weight and probably more suitable for bigger shells. I'll be trying grass seed or similar next time to try to get a greater mass of BP in the shell.

Edited by BrightStar, 24 October 2006 - 10:56 AM.

[Frozentech]

I'm fairly sure that much dextrin would cause a driven-in moisture problem. It might take three months to fully dry that burst mix.

GB would also appreciate any bag building tips from the experts here.

Thanks

Holy crap ! That is a *huge* amount of dextrin !!! burn that up and start over, sorry. Add 5% dextrin to your BP to coat the burst carrier. Dried corncob works fine if you can't get rice hulls or puffed rice.

One way to make a good flash bag is to use a paper coin wrapper, one that is narrow, in the US, a dime wrapper is good, or wrap 2 turns of 30# kraft paper on a 1/2" former and make a small paper tube with thin walls, about 1 inch long. Tie the bag over the end of the fuse, add 2 grams of whistle or flash and tie off the end of the bag with a clove hitch. ( I learned there is a name for this, a 'coupette' ) The bag should be at the center of your ball shell. You may have to make an internal passfire tube to extend the length of the timefuse to the center for best symmetry...

Another method, used by Tom Rebenklau, is to make a small 'bubble' of saran wrap filled with a couple grams of flash and set it in the center of the shell. I have made a shell this way, but not fired it yet. It's a 4" ring shell that I was trying to improve the symmetry of...

[Artopunk14]

Holy crap ! That is a *huge* amount of dextrin !!! burn that up and start over, sorry. Add 5% dextrin to your BP to coat the burst carrier. Dried corncob works fine if you can't get rice hulls or puffed rice.

One way to make a good flash bag is to use a paper coin wrapper, one that is narrow, in the US, a dime wrapper is good, or wrap 2 turns of 30# kraft paper on a 1/2" former and make a small paper tube with thin walls, about 1 inch long. Tie the bag over the end of the fuse, add 2 grams of whistle or flash and tie off the end of the bag with a clove hitch. ( I learned there is a name for this, a 'coupette' ) The bag should be at the center of your ball shell. You may have to make an internal passfire tube to extend the length of the timefuse to the center for best symmetry...

Another method, used by Tom Rebenklau, is to make a small 'bubble' of saran wrap filled with a couple grams of flash and set it in the center of the shell. I have made a shell this way, but not fired it yet. It's a 4" ring shell that I was trying to improve the symmetry of...

I will make some new BP coated corn cob. Does 187g of BP to 9g of dextrin sound good? I was using 10g of whistle sprinkled in the shell and was still getting puff breaks.

[Jerronimo]

10 gram?????! this amount of whistle should've turned your stars to dust!
What whistle formula are you using?
I normally use 2 gram in 3'' and 3 gram in 4'' shells and they give nice breaks.

[Artopunk14]

10 gram?????! this amount of whistle should've turned your stars to dust!
What whistle formula are you using?
I normally use 2 gram in 3'' and 3 gram in 4'' shells and they give nice breaks.

70/30 Potassium Perchlorate/Sodium Benzoate. I ballmill the benzoate for about 10 hours then mix it with the perchlorate through a screen.

[GBthriller]

70/30 Potassium Perchlorate/Sodium Benzoate. I ballmill the benzoate for about 10 hours then mix it with the perchlorate through a screen.

Jerronimo is right! That much whistle...ugh. You better review a few things before you go on amigo. Seriously, I dont mean to sound like I'm preaching but thats nuts. Did you build up to that trying to overcome your soft break problem?

Sodium Benzoate is likely the problem, here again combined with your wet burst. The dextrin and sodium would war for the moisture. Did you steam up the whole block when you fired up your shells?

Thanks all for the bag building tips. I have built all my shells with the intent to break only w/ BP on hulls. It's been o.k. because I build hard, (dry) shells. But the spread is just adequate, and they lack THUMP. I will try some bags. Will report results as they come. Frozentech's shells are impressive, I could use some of that noise!!!

[Artopunk14]

Jerronimo is right! That much whistle...ugh. You better review a few things before you go on amigo. Seriously, I dont mean to sound like I'm preaching but thats nuts. Did you build up to that trying to overcome your soft break problem?

Sodium Benzoate is likely the problem, here again combined with your wet burst. The dextrin and sodium would war for the moisture. Did you steam up the whole block when you fired up your shells?

Thanks all for the bag building tips. I have built all my shells with the intent to break only w/ BP on hulls. It's been o.k. because I build hard, (dry) shells. But the spread is just adequate, and they lack THUMP. I will try some bags. Will report results as they come. Frozentech's shells are impressive, I could use some of that noise!!!

I know how strong whistle mix can/should be. I tried 5g first with no succsess and then 10g and the break wasnt any better. When my new corn cob is done ill keep the whistle under 4g. Its just very aggravating wasting the chemicals and time on puff breaks.

[Artopunk14]

I just ballmilled my perc for a day and WOW my whistle burns alot faster now. I also made some new Bp coated corn cobb with 5% dextrin. I think ill be ready to shoot on sunday, ill report back what happend. Wish me luck.

[Artopunk14]

Well I just tested my new 4" shell, it broke with a little bang and more stars lit but still way short of a 2" inch consumer shell! I used new Bp coated corn coob with 5% dextrin and I made a whistle bag from a dime wrapper with 4g of whistle at the end of the time fuse. Then i wrapped the hell out of it with fiberglass tape. There is still something wrong on the inside of the shell. I think it was a little better only because of the tape I added. Any more ideas??

Thanks for the info so far.

[BrightStar]

Well I just tested my new 4" shell, it broke with a little bang and more stars lit but still way short of a 2" inch consumer shell!

Hi Artopunk14, helping out with a show last night, I realised that my 3" plastic balls with fibreglass tape (BP on corn cob with whistle boost) also have much softer breaks than the commercial shells, so we are in the same boat here...

I tried an experiment a few weeks ago with a couple of small MDPE plastic pepper pots. Each had about 10g of slow-ish BP meal and were fused and glued shut with solvent cement. One was wrapped with a couple of layers of fibreglass packing tape. The first one went off with a 'putt', the second (with the fibreglass tape), went off with a marginally louder 'phutt' but still not a real bang. The fibreglass tape just snapped at the join with the lid and made little difference to the confinement. By contrast, a previous experiment with paste-soaked twine spiking resulted in a solid salute.

My conclusion was that it might be the pasting and spiking that is hampering our shell performance. The low density of the corn cob burst (ie less BP per unit volume) might also be an issue. I'll try 8 or 9 layers of pasted kraft on a plastic shell ASAP and report the results here...

Edited by BrightStar, 06 November 2006 - 02:14 PM.

[Artopunk14]

I just tested a new shell out with BP coated corn cobb and 60g of super fine BP(ballmilled 4f powder) and fiberglass taped it. This was the best one i've done so far, had a allright boom and my first roundish break, the break was small but it gives me hope. For my next shell im gona add a whistle bag and shorten the time fuse. Hopefully this will give me the break i desire.

If it doesnt work out I was wondering if anyone could tell me how to paste kraft paper over the shell?

Thanks

[RegimentalPyro]

I use a method of hemi pasting that was detailed on passfire.

You need strips of the following dimension

width= 1/16 of the circumference of the shell
length= 1/3 of the circumference of the shell

The first strip is pasted from one of the poles, across the equator.
The second strip overlaps the first by half and lies 50:50 across the equator
The third strip overlaps the second by half and runs from the other pole across the equator.

You then repeat the process round the shell until it is covered. Each complete turn of pasting round the shell counts as 2 layers as all the strips overlap by 50%