small comet bomb problem

[superspike23]

hi all

I tried to make a small comet bomb 7g of bombs but the result was an explosion on the ground. Yet I used black powder 2g lift. The shell is just out of tube to explode on the ground. here is the video:

 

http://www.youtube.com/watch?v=kI5O622Phlg

[Mumbles]

What do you mean by comet bomb? It's not a term I'm familiar with.

[californiapyro]

crosette? or aerial salute? either way, your lift powder is way too slow. you need to ball mill it and granulate.

[superspike23]

comet bomb is http://www.pyroguide.com/index.php?title=Bombettes_and_Comet_Bombs

[Lance]

7g ? what size is it ?

 

Anyway, like californiapyro said your black powder is very slow, won't give much of a good lift.

 

Nice report though.

 

 

[Xtreme Pyro]

I think what he means by comet bomb is bombette (I didn't look at the definition on PyroGuide because it comes up as a virus). Anyways as others have said you need better lift...

 

 

 

• What ratios?
• What kind of charcoal are you using?
• How long are you milling it for?
• Are you granulating your powder? If so what mesh?
• How pure are your chemicals?

 

- XP

[superspike23]

the height of the launch tube is 10 cm id of launch tube is 1.5 cm shell height of 5 cm is id of shell is 1.2 cm

[Lance]

Indeed, even the name of the video is "Test bombette"

[superspike23]

charcoal for bbq's, bought in supermarkets. it is reduced to a fine powder before moving to the ball mill with sulfur and KNO3. the ball mill works about six hours. I use the finished product directly without granulating. Other chemicals are from laboratory and are of good quality

[nater]

Granulated BP will work better than mill dust. Good charcoal will work better than BBQ briquettes, which have clay in them.

[superspike23]

here video of my black powder:

 

http://youtu.be/AV_AMO1O1vw

[Lance]

The kind of charcoal has an enormous effect on the speed of burn of your BP. Bbq charcoal is not suitable for good BP.

 

Try using a softwood charcoal like Willow.

 

 

 

 

Edit: seen the video. Your black powder is slow, it won't do for a good lift. Try using a better charcoal and Granulating it.

 

 

Edited July 22, 2012 by Lance

[californiapyro]

superspike: balsa, willow, or paulownia are all very good for charcoal. commercial airfloat will work fine as well.

off-topic: why does pyroguide come up as a virus?

[Lance]

Heard it is infected by malware

 

Here

 

 

Edited July 22, 2012 by Lance

[superspike23]

superspike: balsa, willow, or paulownia are all very good for charcoal. commercial airfloat will work fine as well.

off-topic: why does pyroguide come up as a virus?

 

 

I do not know. At home it is not recognized as viruses. I use internet explorer 9 as browser

[Bcorso85]

I highly reccomend willow. The Charcoal Bricketts are loaded with clay and other fillers that give them the slower burn for grilling. This is slowing you down. Danny Creagans website has an excellent page on the quality and comparrisons of MANY wood types for B.P. VS Sparks. You want a nice hardwood that is very pourous. This will help the oxidizer integrate or be obsorbed by the charcoal. Which is what actually makes the powder hot (the absorbing of the oxidizer into the fuel). By granulating the powder the water is helping this happen. Hence making the product MUCH more powerful. The granulating also increased the surface area which helps the burn rate significantly.

 

 

 

Ben

[yvariro]

hi,

 

Oh un francais! tu doit granuler ta poudre c est obliger si tu veut avoir une belle ascension,et pour de la poudre noire granulée met la plus longtemps au moulin a bille il faut avoir une meilleure vitesse de combustion possible,sinon c est un bel essais,le delais etait reussi!

 

 

(this is not a traduction lol ) Personally i use BBQ charcoal but i'm planning to make some willow charcoal soon,but i have no problems with my black powder, for a good result i ball mill it 20H and it make a good "wroof" so i can lift all sort of shell with this !

but i must ball mill it 20H for a goods results....

[bob]

if you take some old cottan shirts and cut them up to make patches you might be able to get your lift to work

just use a lot more bp and use the patches to make what ever your are shooting hard to get down the mortar

using a diffrent charcoal is deffinitly the way to go and granulat it will be WAY better

I know a lot of people are not going to like what I said about the patches getting you black powder burning better is way better then using patches but patches do work I got a little cannon working using green mix

bob

[Col]

If it had lifted, the timing would`ve been about right. Its always a good idea to test with a dummy shell of equivalent weight to make sure it can lift it reliably.

[psyco_1322]

I like how everyone assumed he was using briquettes, they do make actual charcoal for use of cooking in your grill. Royal Oak and Cowboy Charcoal are two major ones you see in the stores. They will work fine, it's just not the most reactive charcoal.

 

You have to granulate the black powder with some sort of binder added in, I use 5% dextrin. That dust that comes from the mill will not lift anything, regardless of how good it burns.

[superspike23]

I have my black powder granulated using 5% dextrin. I think I have just too wet. It looked like a piece of wet clay. I let it dry before putting it in my sieve but how well the wet? Like a wad of chewing gum or just moistened?

[Col]

Granulate the wet bp ball through a screen onto a sheet of kraft or newspaper. It will look a bit like heaps of worms Let it dry and then screen it again to seperate the different grain sizes.

Something like 4FA or 5FA would probably be about right, you dont want big chunks of lift for a 15mm shell.

[Col]

Comet bombs are tricky beggars to get right as the tail comp acts as the time fuse. Bombettes generally use a traditional fuse like visco or CTF which makes it a bit easier. Here`s a 5/8" id comet bomb timing test, the burst was pitiful as i used bp with fe-ti just for a visual indication. According to the "Pffft" at apogee, the timing seemed spot on.

https://www.youtube....h?v=Mwffn7nYQdk

 

I added 10% fe-ti to the C6 for a whiter tailled option and pressed 20 of each type to the same spec. The next test was to judge how much burst charge it would take to get a decent break, i used with D1 glitter stars (rolled 1/8" - 3/16").

 

https://www.youtube....h?v=1sbB8P7_SYk

 

The test didnt go quite as well as expected but the break was surprisingly good for a small insert. I guess either the tail comp wasnt quite dry or the added fe-ti slowed the burn rate to provide a 4 second delay instead of the 2 seconds i got in the previous test using straight C6 for the tail.

As the timing is fixed by the tail comp, the worst case scenario is i`ll have to increase the amount of lift to compensate.