Poor man's Tiger Tails

[Infragreen]

Okay, here goes...

I'm a noob here, I've read tons of good stuff and I'd like to return the favor.
I think I've done my homework (search and test) AND that I have a novel idea for any remote-ignition buffs out there.

I heard of a product named Tiger Tails (igniters for model rocket engines), that consisted of a single strip of conductor-isolator-conductor sandwich, with a blob of electrically sensitive pyro compound at one end.

The strip would be connected via a single clip, like a clothespin with a contact stud in each jaw.

This led me to figure out this dirt-cheap, kitchen-table-workshop igniter system.

You will need:
Cardboard (light, pizza boxes work fine),
aluminum foil (light kitchen type),
glue (stick, spray or spread-it-yourself),
adhesive tape
matches
something marginally heavy
scissors

First, cut a rectangle of cardboard (maybe 3x4"), then a rectangle of alu foil double one side of the cardboard (say 6x4").

Second, cover one side of the cardboard in glue, place it glue-down on the end of the aluminum and press/squeeze to ensure a good cohesion.

Third, cover the other side of the cardboard in glue, fold over the alu foil and carefully press/smooth over (rub with cotton, if you're a stickler for detail; makes for a fine gloss).

Fourth, cut into strips PERPENDICULAR to the side where the aluminum folds over (1/8 - 1/4").

Fifth, cut off the CORNERS ONLY of the ends with the bends. Go for a remaining alu strip of about 1/2 - 1 mm (.05" or as wide as a push-pencil lead, the thinner, the better).

Sixth (I hate this word; it makes me sound like Daffy Duck), crush matchheads (with heavy-ish object), place 2-3 heads worth on a strip of adhesive tape and wrap around the tip of each strip.

And there we are. I've had these thingies fire from a single D cell, 4 if on long leads.

The clip should be equally easy. Just wrap some unisolated wire around each jaw of a clothespin, hook up the wires to your firing leads and hey presto.

And there's my first contribution to the forum, not to mention my first post and my first topic.

I had hoped my spike-tube-concealing ping-pong-ball caltrops would qualify, but "someone" beat me to it with a plaster version.

Well, I hope this passes the scrutiny of the elder gods of nasty stuff B)

I'll pour myself a drink, light up a fag and wait for the fireworks.

Cheers!

[CACO3]

Why don't you use aluminum tape instead of glue and foil? You can buy it cheap at any hardware store. It would make the process much easier than trying to glue foil. Great idea though!

[Alexires]

Infragreen - Good first post. It took me a little while to work out what you were getting at, but after puzzling over it for a bit, it seems like a good idea.

Perhaps by soaking the whole cardboard card in a saturated KNO3/Sugar solution, you could increase the chances of a successful ignition. You could also possibly wax coat it, in an attempt to make it water resistant.

The main problem I can see with this is that the aluminium might burn out too fast, resulting in UXO if that is what you are using it for. You might be better suited using a thin piece of aluminium plate (I mean really thin) and doing what you have done here. But if you are in a jam, you certainly could probably find a D cell battery, some Al foil and some cardboard.

Also another problem you might have with it is incompatability with some primaries (HMTD comes to mind). You need to screen what you are planning to use it with before you jump right in and lose some fingers or worse.

If you changed the insulating material, you might even be able to embed the ignitor in a cast block of something (I'm thinking KNO3/Sugar here)

I've always wondered what would happen if you had a couple of kg of fused KNO3/Sugar mix and ignited it from the inside....

[Infragreen]

Thank you, guys.

CaCo3:
I haven't had any problems glueing (?) alu foil to cardboard using stick or spray.
The aluminum tape from our hardware stores (Denmark) tends to be of a heavier gauge, requiring more current to heat the "bridgewire", but making the tape more useful for other endeavors (e.g. liners for "candy" fueled rocket motors).

Alexires:
I specifically went for a low-current igniter, thus having to accept the short, wimpish burn time of the bridge.
I tried a couple of compositions (BP, BP-NC, "Candy"), but the best turned out to be matchheads. Of course, the more finely ground, the better (smaller particles more likely to be ignited).
(Added) Oh, it just hit me after writing the whole reply, you mean not ONLY KNO3-dipping the tip, but in addition!? Assuring ignition of the charge, not the igniter!? Yeah, that might be a useful just-in-case'r. Mostly, I was just thinking about putting some booster in a second tape packet around the matchhead packet. (Added end)

As for the incompatibility issue, by all means insulate the igniter from any aggressive materials it might come into contact with.
I like your idea of a quick wax dip.
I'm also thinking of boosting the composition (ingredients and amount) and slipping it into a commercially available sheath of latex.

My primary thoughts about improving on the composition would be addition of fine charcoal (as the matchhead burn is only a short, sharp spit - PFT!)

Any more ideas will be very welcome.

[nbk2000]

A small plastic tube, like that used to hold the ink in ballpoint pens, could be useful to concentrate and direct the brief flame into a jet, rather than a more diffused flame, increasing the likelyhood of ignition.

[Alexires]

Infragreen - If you are thinking about using a condom, they don't burn well.... especially if they have been used *grin*....also they are better used for other things.

Seriously though, a good one for a slow burning mix is a KNO3/Sugar in INCORRECT ratios. For instance, more sugar than KNO3 or visa versa. By using more sugar, you can melt it down and dip the whole thing in the ensuing toffee like substance. Maybe while its still cooling, you could kneed a little KNO3 into the outside of the mix to ensure a fast/hot flash of flame at the end.

Another idea might be to incorporate the silicon fuse that is being talked about around here. Make the mix up and coat the outside in that. This should make it waterproof as well as making it better than an inert barrier.

[Infragreen]

Nbk2000:
Yes, with a bit of redesign, this should definitely work. The "shot" from the matchheads tend to penetrate the tape at just one random weak spot.
Your version could provide a rather powerful, forward jet.
Design table time...

Revision 1. Ballpoint tube and hot-melt glue. Gotta try this one.

Alexires:
I only have these reservations about KNO3-sugar mixtures, because i find them particularly difficult (not hard) to ignite. Especially when melted.
Quoting an elder: They need a bit of roasting.
I'm rather partial to the matchheads by now, but would like to prolong the burn time just a bit. Maybe alu, ferro or titanium fines added.
But as earlier stated, there would be no problem in adding a booster-igniter in a second adhesive-tape wrap on top of the other.

And yes, condoms were my choice of commercially-available latex-sheath.
They don't burn well, but due to composition and thickness, they BURN-THROUGH well, and that's what I'm after.

[nbk2000]

Polyurethane condoms would burn better, or use fingers from gloves. They're thicker so they'll hold pressure longer until bursting.

[Infragreen]

I'm wondering if the thickness mightn't be a drawback, as the igniter is already a bit wimpy (whaddya expect from a single AA cell?)

I figure the addition of charcoal will provide a longer burn time plus sparks aplenty.

But, Nbk2000, you have just provided a valuable addition to the "poor man's" angle on the bent-foil igniter.

Plastic gloves can be had for zero dollars at our gas stations.

Just cut off a finger (glove, duh), pour some booster powder in and slip the sheath over the nasty thing. Oh, and tighten up, of course.

Off-topic: Regarding the hemispherical caltrops we both thought up...

I have a use in mind... Grumble...

Did you ever think of rolling a ball of clay, cutting it in half, shoving the steel "syringe" through the half-balls, poking out the "cork" and just letting them dry?

Providing they don't crack, There's Poor Man's for ya.

[Microtek]

Not to belittle your idea (which is good), but it isn't exactly novel. Both Mr Cool and myself experimented with that very setup some years ago on this forum. We used them for EFIs ( exploding foil initiators ) with a camera flash cirquit for power. It works quite well when the wires aren't too long; the "bridge" goes with a very sharp report, and can cause confined MHN to go DDT.
Anyway, it's nice to see a fellow Dane on the forum.