5 replies to this topic

[Flashy]

Hi all,

I made a fountain this evening, it was a 1 inch diameter with a half inch rammed clay nozzle. It was made with two compositions, The first half was BP with 20% added aluminium powder, the second half was BP with 20% added Ti powder. I seperated the two comps with 0.5g of milled willow BP, i did this to clear the dross from the nozzle before the Ti kicked in. The BP i used for the two comps was made with BBQ charcoal and was not milled.

When ignited the intial Al comp was great, giving some blueish sparks that faded slowly. The burn time was around 20 Seconds with a height of around 3.5m. The problem came when the straight BP was reached, at this point the fountain just exploded. The case was not ruptured but the clay nozzle was destroyed. The salute was very deep and VERY loud, I really didn't want this on a sunday though.

Has anyone ever experienced this?

[Richard H]

Only where the effect was intentional, commonly referred to as a 'bounce' in the texts.

[Flashy]

It would have been great if this effect was intentional, as a finale to a set piece. But it somewhat ruined my fountain really, as once the straight bp was reached the Ti BP must have gone up with it.

[Chaz]

I expect it's just because the burn rate increased as it hit the BP, which burned too fast and caused the explosion. I can't make fountains any more, because my BP is too fast. To make them I have to purposely make 'rocket grade' or 'fountain grade' BP, with BBQ charcoal, so that they dont explode.

[Flashy]

I expect it's just because the burn rate increased as it hit the BP, which burned too fast and caused the explosion. I can't make fountains any more, because my BP is too fast. To make them I have to purposely make 'rocket grade' or 'fountain grade' BP, with BBQ charcoal, so that they dont explode.

Thats what I do, its fairly easy just to keep a seperate container full of milled BBQ charcoal just for the purpose of slow burning BP. If anyone else uses the technique of a layer of straight BP to clear the nozzle, could you tell me if you use fast BP or meal powder.

Just an added note, the comps were consolidated well. So there were no airpockets.

[alany]

Gerb compositions generally only need be screened together, or perhaps a quick mill to make them homogenous before you screen in the metal or microstars. This is especially true if you are using traditional compositions like those in Lancaster or Weingart which specify meal or grain as a major component.

A changing relay between the Al and Ti effects was probably not required at all, your compositions are high in BP and probably aren't that drossy. If you wanted a definate buffer then greenmix might have been better, or 6:3:1 rocket propellant.