17 replies to this topic

[Grey Area]

OK, so not actually pyrotechnics, but I'd like to know where I can get a safe, reliable fuse that I could use to detonate hydrogen/oxygen balloons in my science lessons (I'm a trainee teacher).

I know I could use a lighted splint on a stick...but the fuse adds a nice bit of drama for the class!

Any suggestions? I orginally made my own chlorate fuse but I see from all the posts that this is not recommended.

Thanks!

[digger]

OK, so not actually pyrotechnics, but I'd like to know where I can get a safe, reliable fuse that I could use to detonate hydrogen/oxygen balloons in my science lessons (I'm a trainee teacher).

I know I could use a lighted splint on a stick...but the fuse adds a nice bit of drama for the class!

Any suggestions? I orginally made my own chlorate fuse but I see from all the posts that this is not recommended.

Thanks!

Why not make black match. It is easy and will provide the archetypal fuse to the ticking round black B@mb. Visco is available but can have some problems as it can become self propelled.

[MDH]

He could try falling leaf. Grey area, where are you located?

[CCH Concepts]

who sells falling leaf. i've read it can be quiet effective in short lenths in small shells.

[Grey Area]

Don't want to get into making my own. School would have to store it and they'd be happier with a "manufactured" product.

Had one recommendation for Visco, but it sparks WAy too much - one spark on my balloon and it'll go up before I've legged it.

Falling leaf? Never heard of it...I'm in the UK (Yorkshire).

Again, it needs to be something that bruns with a minimum of pretty sparks - so I guess kind of contrary to what you guys would normally want.

[CCH Concepts]

you could do it remotely to that could be impressive to a class. simply some nichrome wire taped to the side of the balloon, maybe an added pyrogen if your allowed. you could do it with a battery from a safe distance or remotely if you can spend a few quid of a transmitter/receiver.

[phildunford]

If you can make/ buy some pyro match heads, that's not a bad idea.

All the stuff I've done with kids has been on the end of a long wire (blowing up boxes etc) and they will kill to be the one who presses the button!

Thinking of it, you could get something very similar from hobby rocket suppliers. They are not as robust as the ones we use in pyro, but they will do the job and they are buyable and a commercial product if your school is fussy about that...

Edited by phildunford, 24 November 2009 - 10:09 PM.

[CCH Concepts]

i was thinking some bp slurry on the nichrome to give an effect. but for simplicity I'm sure a slurry could be made from just common match heads ground up.

[Arthur Brown]

Chinese Time fuse is a like time fuse, BUT it does not spark out of the sides, it just burns up the inside.

The mass that a small balloon can carry is very small, so a short length of fuse is essential.

An Electric igniter is a product available to legitimate users, which is instant and needs bell wire and a PP3 or like.

[CCH Concepts]

yer can just be brought from a local model shop for armature rocketry.

[MDH]

Don't want to get into making my own. School would have to store it and they'd be happier with a "manufactured" product.

Had one recommendation for Visco, but it sparks WAy too much - one spark on my balloon and it'll go up before I've legged it.

Falling leaf? Never heard of it...I'm in the UK (Yorkshire).

Again, it needs to be something that bruns with a minimum of pretty sparks - so I guess kind of contrary to what you guys would normally want.

Falling leaf fuse does not produce any sparks at all. It produces a coloured flame for some time and burns incredibly slowly.

The place I use in pyroplanet.co.uk, but that is because they ship internationally. Their fuse prices are very expensive, but they have falling leaf fuse.

By the way, I don't think you should be concerned about making chlorate fuse if you are simply dipping cotton string in a solution.

Edited by MDH, 24 November 2009 - 11:06 PM.

[fruitfulsteve]

Magnesium ribbon.
Cupboard in the chemistry lab, i would hope !!!

[mike_au]

I know I am being pedantic, but as a teacher I'm going to hold you to a higher standard than the man on the street

Hydrogen & oxygen doesn't detonate (a supersonic reaction propagated by a shock wave) , it deflagrates (a subsonic reaction propagated by heat).

On topic (although everyone else has already said it) falling leaf would seem to be the way to go. The only problem I can see is that it burns *very* slowly, so (assuming you are letting these balloons float away) you will need a very short length of fuse to make sure they go before they get too far away. You will need to be careful when lighting the fuse that whatever you use to light it doesn't ignite the balloon.

[CanadianPyro]

Hydrogen & oxygen doesn't detonate (a supersonic reaction propagated by a shock wave) , it deflagrates (a subsonic reaction propagated by heat).

The deflagration can transition to a detonation given sufficient run-up distance. A stoichiometric Oxygen/Hydrogen mixture has a very high flame front velocity, so the distance is quite small. I seem to recall a test in which DDT was achieved in an open-ended pipe just 10" long and a few inches in diameter.

[Mumbles]

If you are doing this indoors, just make a flame thrower out of the methane gas line. A wand can be made long enough to be at a safe distance. Given that you are are a trainee teacher, I'd imagine this is not in a large college lecture room. I'm not sure if a traditional sized primary school lecture room is large enough to do safely.

If doing outside, use an e-match. I you have to be too close to light the fuse, and any sort of open flame or sparks near the balloon would be dicey.