823 replies to this topic

[cplmac]

The way you wrote out your mix it seemed like you used 70 german / 30 perch, which is backwards and would definately cause the symptom you are describing. You might also want to try using the flash as a delay rather than making a header, this would give you the benefit of the strong rocket walls for confinement.

[karlfoxman]

Post a picture of the aluminium powder, you can tell from the colour if its Dark German.

[cooperman435]

I too suspected it might not be Dark German but it was bought from hobbychem so guess it is.

Hobby chems page states its 30micron spherical ali so thats far from ideal for flash.

[Creepin_pyro]

They don't currently have the flash grade Al up on their website.

[BrightStar]

treefingers, One test for real flash I have seen in the past is to pour a little into an upright 5mm id cardboard 'firecracker tube', perhaps 1.5" long and only a third to half filled, fused with thin visco. The base of the tube should be closed, the top open. If this reports rather than jets then you most likely have decent flash powder and hence good Dark Al.

Edited by BrightStar, 17 March 2007 - 05:01 AM.

[treefingers]

I've been rummaging around and finally managed to find my close up filter, so heres a photograph my Aluminium. The first is a small 0.5 gram pile of my flake compared with the same weight of 350mesh spherical.

http://s85.photobuck...nt=PICT0001.jpg

http://s85.photobuck...nt=PICT0002.jpg

As you can see the flake takes up a greater volume than the spherical which from what I gather is a rough sign of the smaller partical size. Also I find when opening the container of flake, a fair amount of dust escapes and there is a quite a distinct smell (not sure why it smells?)

The way you wrote out your mix it seemed like you used 70 german / 30 perch, which is backwards and would definately cause the symptom you are describing. You might also want to try using the flash as a delay rather than making a header, this would give you the benefit of the strong rocket walls for confinement.

Sorry I am using 70 perchlorate/30 Al not the other way round. Also I thought about using a delay and flash in the tube but as the tubes are so small, I expect being only 3/4 full of propellant the rocket wouldn't gain so much height. Once I sort out my flash i'll give it ago though as I could be wrong.

treefingers, One test for real flash I have seen in the past is to pour a little into an upright 5mm id cardboard 'firecracker tube', perhaps 1.5" long and only a third to half filled, fused with thin visco. The base of the tube should be closed, the top open. If this reports rather than jets then you most likely have decent flash powder and hence good Dark Al.

I gave this ago using the tubes that im using for my bottle rockets which are 1/4'' ID with fairly sturdy 2mm thick walls. Anyway the result was the end plug at one end being blown out with a thump and quick flash emmiting from the open end. With both ends sealed off with paper plugs and super glue I managed to get a report but it was more of a deep thud then a sharp crack that I would have expected from real flash.

[Wyvern]

Well, thats definetly not dark german flake, it looks granulated might be the picture quality though.

[MMMMMM Pyro]

I've been rummaging around and finally managed to find my close up filter, so heres a photograph my Aluminium. The first is a small 0.5 gram pile of my flake compared with the same weight of 350mesh spherical.

http://s85.photobuck...nt=PICT0001.jpg

http://s85.photobuck...nt=PICT0002.jpg

As you can see the flake takes up a greater volume than the spherical which from what I gather is a rough sign of the smaller partical size. Also I find when opening the container of flake, a fair amount of dust escapes and there is a quite a distinct smell (not sure why it smells?)
Sorry I am using 70 perchlorate/30 Al not the other way round. Also I thought about using a delay and flash in the tube but as the tubes are so small, I expect being only 3/4 full of propellant the rocket wouldn't gain so much height. Once I sort out my flash i'll give it ago though as I could be wrong.
I gave this ago using the tubes that im using for my bottle rockets which are 1/4'' ID with fairly sturdy 2mm thick walls. Anyway the result was the end plug at one end being blown out with a thump and quick flash emmiting from the open end. With both ends sealed off with paper plugs and super glue I managed to get a report but it was more of a deep thud then a sharp crack that I would have expected from real flash.

If I may ask is your 5mic. Flake from Hobbychem? If so, thats where I got mine from and mine makes fine flash, not as potent as the German Dark I have, but definately comparible.
I believe that the smell may come from the Al's coating, which IIRC is Stearic Acid...

Regards,

Mike

[BigBang]

That pic is definately not german dark. It is 'light' flake aluminium, and yes the smell is the steric acid coating. It does make fairly good flash, but it doesnt come even close to the proper stuff - I have both - Also dark flake doesnt have a coating, making it more reactive. If hobbychem is selling this stuff as german dark, then he's lieing.

Dark pyro ali powder is a matt dark grey colour and not shiney or silver. The stuff you have will coat most things and give them a bright silver appearance.....am i correct??

[treefingers]

Well, thats definetly not dark german flake, it looks granulated might be the picture quality though.

Its certainly not granulated I think its just the picture. It tends to almost or at least look clumped togther but when you touch it with something i.e. spoon it deposits a fine dust that gets everywhere ( i mean everywhere).

Anyway as it was bought from hobbychem and the same aluminium works for 'MMMMMM Pyro' i'm sure the problem lies else where. I've been avoiding it but i'm going to grind down some Chlorate and give it ago.

That pic is definately not german dark. It is 'light' flake aluminium, and yes the smell is the steric acid coating. It does make fairly good flash, but it doesnt come even close to the proper stuff - I have both - Also dark flake doesnt have a coating, making it more reactive. If hobbychem is selling this stuff as german dark, then he's lieing.

Dark pyro ali powder is a matt dark grey colour and not shiney or silver. The stuff you have will coat most things and give them a bright silver appearance.....am i correct??

Off hand I couldn't say what it was llisted as under hobbychem but as it was certainly described as 'fine flaked and porous' I generally assumed that a fine flaked Al would be Dark German.

[BrightStar]

Treefingers, through friends I've been lucky enough to test 'Hobbychem Bright Flake Al' (stearin coated), 'Hobbychem 2 micron Dark German Al' and 'Eckhart 5413 Super-H' from a professional supplier. The latter two were comparable in brissance, but for certain uses the Bright Flake is actually preferable.

A well confined 6mm ID * 45mm * 3mm insert with the Bright Flake Al will burst with a 1m radius ball of bright white light, and is sometimes more impressive visually than a dark Al salute.

I think you might be expecting too much from your 70/30 flash in <1g unconfined batches. It's not the hottest or most sensitive mix - there are more violent comps, as per BigBang's Coke Can demo, but these are wisely avoided...

Edited by BrightStar, 21 March 2007 - 06:32 PM.

[cplmac]

I've always said that bright flake aluminum smells like crayons. I hate working with that stuff because it airfloats, gets on everything and is a mess, smearing silver all over the place, but I do love the smell of crayons!

Edited by cplmac, 19 March 2007 - 08:41 AM.

[Caramanos2000]

Im gonna try mixing 70/30 with Mg and Dextrin and make small balls with fuses see wut happens. Will also do the same but instead of dextrin I will use vaseline. Any ideas of the results?

[Frozentech]

Im gonna try mixing 70/30 with Mg and Dextrin and make small balls with fuses see wut happens. Will also do the same but instead of dextrin I will use vaseline. Any ideas of the results?

A bright white star with a lot of white smoke.

[Mumbles]

I actually kind of wonder if the stars will even light. The vaseline may inhibit ignition. Also if used in a shell or mine, I suspect that the stars would melt in short order, and possibly burn up pretty fast, or make some long drips with a potential fire hazard.