823 replies to this topic

[BigBang]

P.S. I would love to see a long train of flash burn though ! ( like 100 feet or more long), with a goodly pile of the stuff laid out, maybe a few inches high in cross section. Would it confine, or just race at several 100 ft/sec ? Hrmmmm.....

The simple answer is that it depends on the type of flash used. If you use standard 70:30 flash it just burns EXTREMELY fast, with a blinding white light, and a dull thud. A 1metre trail, approx 0.5" wide and 0.5" high, goes up in about 1second or so, but if you use the type of flash i use in my "flash demo" video, you get a defeningly loud bang, and 1metre goes up in micro-seconds!! Its actually very interesting to watch...from a distance i might add

Standard flash, doesnt need much confinement, but it does need some, albeit not very much, otherwise the burn rate is relatively slow. (i mean relative to other flash types, but still much faster than say fast BP).

[pyrotrev]

An old old topic for endless argument I guess it depends on your specific definition of detonate vs deflagrate. I have never seen studies proving that the burn front and shock wave in flash was greater than mach 1 though.

I seem to remember that Shimizu quotes 1100m/sec or so - and he and his Japanese mates seem to be so rigorous in their method I have little reason to doubt it's true.

Edited by pyrotrev, 19 February 2007 - 07:11 PM.

[cplmac]

I've gotta think that is contained to some extent. Not necessarily confined, but more like quick match. As we all know the blackmatch get's exponentially faster when wrapped in just one layer of paper tube. For all intents and purposes I think it is only fair that we use 70/30 as the standard for flash since it seems everyone agrees that this is the most common, easy, best bang for the buck flash around. Not saying there isn't better flash, just that 70/30 seems to be the accepted formula for flash.

[BigBang]

I seem to remember that Shimizu quotes 1100m/sec or so - and he and his Japanese mates seem to be so rigorous in their method I have little reason to doubt it's true.

I dont know how this test was carried out or the amounts used, but for it to burn that fast, it would either need to be confined to some extent, or the amount tested was large enough for it to self-confine.

[cooperman435]

Ok safety check

As a last ditch attempt to aid the report and break for my smaller shells Im resrting to some very small experiments to the dark side of flash.

I didnt really intend to but Ive tried so much already that I am prepared to make and use very small batches of flash to get my desired results.

I have alu powder but am unsure of its actual grade so am dubious of its use for flash it is dark in colour but still silvery in a pile. Is it possible to actually use mesh to establish its grade for something that needs to be this fine?

Potassium Perchlorate is hard to find but is it worth the effort?

I have a reasonable amount of 50 50 magnelium which is extremely easy to grind with a mortre and pestle would this be useable for flash or are the partice sizes needed so small I can forget the idea?

Thanks guys

Edited by cooperman435, 07 March 2007 - 01:23 AM.

[Wyvern]

Due to still not recieving my latest order from Keten i have also been making more exotic flash mixtures.

i have settled on

Potassium Chlorate 50

Magnalium 50:50. -250 mesh 30

Antimony Trisulfide, Dark Pyro 20

i have extensivly tested this comp for friction/shock sensitivity and i havn't found it to ignite i have also kept a small amount ~1g in storage for about 3 weeks now and still works as well as the day i made it.

Edited by Wyvern, 07 March 2007 - 07:52 AM.

[cplmac]

That mix will definately work. Is your antimony antimony trisulfide? If so be careful as chlorate and sulfurs don't play well together. Also, on their own each makes flash more sensitive, especially antimony.

[Wyvern]

That mix will definately work. Is your antimony antimony trisulfide? If so be careful as chlorate and sulfurs don't play well together. Also, on their own each makes flash more sensitive, especially antimony.

Yeah it is trisulphide, although i havnt seen any evidence of interactions between it and the chlorate. And i only make about 1-2g of it at a time depending on how much i need for a perticular shell and have done vigourous testing of it before using it in live applications.

[pyrotrev]

Ok safety check

As a last ditch attempt to aid the report and break for my smaller shells Im resrting to some very small experiments to the dark side of flash.

I didnt really intend to but Ive tried so much already that I am prepared to make and use very small batches of flash to get my desired results.

I have alu powder but am unsure of its actual grade so am dubious of its use for flash it is dark in colour but still silvery in a pile. Is it possible to actually use mesh to establish its grade for something that needs to be this fine?

Potassium Perchlorate is hard to find but is it worth the effort?

I have a reasonable amount of 50 50 magnelium which is extremely easy to grind with a mortre and pestle would this be useable for flash or are the partice sizes needed so small I can forget the idea?

Thanks guys

Phill - It's difficult to say definitely what your Al is, since fairly fine flake is halfway between silver and dark grey, but so are some atomised grades, which is much more available and likely. A possible test is to rub some on your fingers - flake will tend to make your fingers go more silvery than atomised, but the best test is to look at it with a microscope and see whether the particles are rounded/sausage shaped (=atomised) or plate-like (flake). Alternatively where did you get it from? most sources of Al are documented on this forum. Perchlorate is worth the effort finding - try Inoxia for instance , MUCH safer than chlorate and extra bang for your buck . Magnalium makes good flash (the Chinese use it a lot), but unless very fine apparently increases sensitivity due to the hard sharp splintery fragments. It's splintery brittle nature does however lend it to milling down quite easily I would guess. If I wanted to add flash bags personally I would be tempted to use whistle mix, phlegmatised (love that word) with some petroeum wax/jelly and granulated I feel it's slightly safer option than flash.

[cooperman435]

I agree with your reluctance to use flash but unfortunately it seems the easiest composition to aquire the neccecery components for.

I think Im going to have to be going down the route of signing up for inoxia but hate the idea of any web companies because of big brother and because I realy dont want a Kg of the stuff when Ill be using less than a gram at a time.

If you can sugest a whistle comp that is going to be as accesible I would really apreciate it but I am also concerned with ordering fuel and oxidisers in a single order and or from the same company.

[pyrotrev]

I dont know how this test was carried out or the amounts used, but for it to burn that fast, it would either need to be confined to some extent, or the amount tested was large enough for it to self-confine.

He doesn't say the exact conditions only that "the loading density was 0.65", and it was initiated with a No.8 detonator . I was wrong it was actually 1200 m/sec for 70/30 flash, add a bit of sulphur and it goes faster at 1450 or so.

[pyrotrev]

I agree with your reluctance to use flash but unfortunately it seems the easiest composition to aquire the neccecery components for.

I think Im going to have to be going down the route of signing up for inoxia but hate the idea of any web companies because of big brother and because I realy dont want a Kg of the stuff when Ill be using less than a gram at a time.

If you can sugest a whistle comp that is going to be as accesible I would really apreciate it but I am also concerned with ordering fuel and oxidisers in a single order and or from the same company.

Here's a link for making granulated whistle http://www.jackerypy...m/whistles.html. Toluene is available as thinners for some types of paint I believe, though petroleum spirit would also work - obviously watch the fire risk!!! For NaBenz go here: http://www.aromantic...t...?category=5

Edited by pyrotrev, 09 March 2007 - 12:01 PM.

[treefingers]

After a few succesful lauches with dummy headers, I've been looking into making reports for my 1/4'' bottle rockets but i'm having a few problems with the flash and was wondering if any of you guys could help.

Anyway I'm using 70/30 '5 micron Dark German Aluminium' powder and Potassium Perchlorate mix. I screened the Perchlorate with 120 mesh screen then diapered in the aluminium but im still finding it too slow for a decent report. Confined loosley in 2-3 layers of paper the sound is hardly audible. I would imagine more confinement would help but with the amount needed I would expect it to affect the performance of the rocket.

Can any of you think what the source of the problem could be?

[karlfoxman]

At a guess your aluminium is not German Dark type, where did you get it? Real flash is deadly, when you have just 1g light it will make a deep thump noise. Just be careful when using it.

[treefingers]

I too suspected it might not be Dark German but it was bought from hobbychem so guess it is . I also thought it could be a problem with my perchlorate but it seems to be work well in coloured stars so its left me confused.

Does anyone know anything about the stability of Barium Nitrate/Aluminium flash? I thought testing different oxidisers with my Al might shed some light on whether the problem lies in the metal itself?