Piss Easy Electric Ignitors

[Anthony]

I'm making a Special Effect for an uncle's themed birthday, and for it needed a bunch of electric ignitors. Estes ones are good but expensive.

My usual method for homemade ignitors was to solder a length of nichrome wire between two pieces of copper wire, then squash it flat and wrap it up in tape to try and prevent shorts.

They usually worked, but were big, messy, prone to shorts, and fiddly to make. I don't know about other people, but in my experience, nichrome wire is difficult to solder properly to copper wire.

So I fiddled about and came up with the following method for creating electric ignitors. No soldering, gluing or taping is required. It's quick, easy and uses few materials.

We start with the components:

<img src="http://www.roguesci.org/images/bw1.jpg" alt=" - " />

A short piece of figure 8 bell wire, a piece of nichrome heating element cut from a hairdryer and a small loop of nichrome cut from the element.

Next, hold the top of the loop of nichrome in a pair of pliers with the "legs" poking out. Hold the pliers in one hand and the bellwire in the other. Simply push the end of the bellwire onto the legs of the nichrome loop. Each leg will force itself down one of the conductors in the bellwire.

The finished piece:

<img src="http://www.roguesci.org/images/bw2.jpg" alt=" - " />

A close up with scale:

<img src="http://www.roguesci.org/images/bw3.jpg" alt=" - " />

These literally take a minute each to make, maybe less if you get a production line going. One knackered hairdryer a reel of cheap bellwire will make a couple of hundred of these things.

They're quite robust and will stand squashing and forcing through small holes. They're quite compact and size is largely dependant on the size of the bellwire. Some ones I made before used thinner bellwire and fit nicely into a 3mm hole.

I know it's a pretty basic idea, but it might be of use to someone :)

[DBSP]

I've had this idea too, never gotten around to it though. I saw something similar to this a couple of years ago, well actually exactly the same but the nichrome wire was coated with laguer and dipped into mealBP a couple of times. That produces very effective ignators.

At the moment I'm using single wires from from wires similar to the on you have in the pic. I then tie them to each wires and tape it together. (I know this sounds really strange) The reason is that I'm using my blastingbox and it isn't capable of burning off a nichrome wire unless I charge it a long time which I hane't got time to do. When using single wires from normal wires it workes great but it's a pain in the ass to make them, scince theay are really thin.

I'm currently putting together a new one with better power and shorter charging time. If it will be good enaugh to burn nichrome I'll definately start using this type of ignators.

Do you think it would be ok to make a new topic about blastingboxes?
This one I'm making right now and the old one is really simple to make and really easy to get materials to and has good power. It might be good for some people to see a that it doesn't have to be that hard to make one, cheap too.

[Anthony]

I've just been inserting these directly into powder charges, so no priming required. Dipping in laquer/BP is a good idea though.

I see no reason why you can't create a new thread about blasting machines, you're not exactly a newbie <img border="0" title="" alt="[Wink]" src="wink.gif" />

[Mr Cool]

A dab of epoxy to hold the nichrome in place would make it even more reliable, to prevent the bridge from falling out if you fancied swinging the charge around your head or anything.
Next time I have £5 to buy a disposable camera I'm going to try something similar for an EBW. Take a strand of multi-core wire (like a single length of that bellwire, for example), strip the insulation from a patch in the middle, roughly equal in length to the diameter of the wire, cut all wires in the core except one in this length, and fold the wire in half at this point. Then tape the wires together to hold everything where it should be. The result should be two parrallel wires, joined at the end by a short length of thin wire to act as the bridge. Quick, cheap and easy to make, should be rugged, and hopefully will work.
Damnit, where did all my camera circuits go?! A while back I went to a Boots photo developing place and walked out with a sack of disposed disposable cameras to take the flash circuits out, and now they're all gone. Now they won't give me any, because I must be doing something weird with them.

[blacktalon]

I have never had success soldering nicrome wire. :-) When I need squibs and I am out of factory electric matches, I go to a dollar store or Wal-Mart and get myself a bunch of 12v operated Christmas lights. (If I can find them, I stock up around Christmas.) I have seen them several times at dollar stores for 50c each. They are short strands of 12, but each one would be good for 12 squibs. Pull the bulb out of its socket, and then remove the plastic base. Straiten out the wires at the bottom and remove the little glass nipple at the tip of the bulb with a small file. If you do this right, it won't break the filament. Then gently fill the bulb with some FFFFg black powder and seal the hole with some epoxy. These things work great and they are cheaper than hell. 5 cents each!

[PyroTech]

Anthony, what kind of battery do you use?
A little while ago, I made some electric igniters. They were from a resistor, looked really nice, but I needed a larger battery.

[Anthony]

I use either a nicd pack or a lead acid gel cell, plenty of amps either way. I don't believe in punny 9v batteries :p But they might work with these - I've never tried. Buying some thinner nichrome wire would certainly be a good idea.

[Tuatara]

You can get really fine nichrome wire out of 10W wire-wound resistors - the sort with the rectangular ceramic body. Be careful what you by as you can also get power film resistors in the same style case. I was lucky enough to find a couple of 1/2kg rolls of fine (like hair!) nichrome at a surplus electronics shop.

IIRC nichrome can be soldered with Duzzall flux (brandname - in a dark green plastic bottle) , and a lot of heat. Duzzall is just a mix of zinc chloride and HCl (I think). My grandfather used to make his by chucking a lump of zinc into some HCl when ever he needed a bit!

[EP]

That's a pretty tricky way of doing it, never thought of that! Would you mind if I copied the text and pics for my section on ignition? (giving you full credit of course) <a href="http://krimzonpyro.com/ep/projectsdevicesdir/homemadefuseignition.html" target="_blank">http://krimzonpyro.com/ep/projectsdevicesdir/homemadefuseignition.html</a>
I've been using the christmas lights lately, but that looks a lot faster!

[DBSP]

I became ill at noon yeasterday and didn't have anything to do while staying in bed, so I decided to make some ignitors.

I bought 10m of 220V wire a couple of days ago for this purpose.
I made 11 regular(to me) with a single "wire" from the cable as bridgewire. And I made one of the nichrome wire thingy. I covered the wires around the bridgewire with hotglue as insulation.

<a href="http://dbsp.sensorystatic.com/pictures/blastingbox" target="_blank">http://dbsp.sensorystatic.com/pictures/blastingbox</a>

btw I hope to be able to put my new blastingbox together within a few days.

[Anthony]

No problem EP, as long as there's credit to Roguesci too :)

[kvitekrist]

here is a picture step by step on how i make mine..: http://home.no.net/gjalring/sp/ign.jpg

the nicromewire is 0,1mm (or thinner) and it glows/burns easly with my 12v blastbox.

[blindreeper]

Anthony those ignightors are the best thing since this forum :p
I use 0.325 mm nichrome wire. I find the hard part gettting with wire into the err other wire. Pushing it into the copper wire I mean. It's a bit fiddly. I get pliers and crimp the ends of the bell wire to loosen the copper strand and it's easier to stick in. If you have rockets with cores you can use a longer piece of nichrome wire to make it longer so it will fit up the nozzle.

[RDX*]

Here's how I do mine. http://www.geocities.com/rdxgames/Ignitor.jpg

I use film canisters with nichrome wire at the bottom “corner" and fill the canister with desired amount of AP. Then to stop the AP to shake around I fill the rest with toilet paper.
The only negative about the design is that it uses 4-8 cm of nichrome wire to every ignitor. But at a price of 3 $ /10m I think I can afford it:cool:.

[edit: if the link dont' work cut it and place it in another window]

[DBSP]

Blindreeper, if you are having trouble getting the nichrome into the ends of the bellwire you can use a needle to make a small whole in the ends, that makes it a bit easier to get it into place.

Why do you have to use so much nichrome? you don't need more that a cm or two at the most with your design. somply attache the nicrome to one of the wires put it through the canister and fasten it to the other wire, you don't need very much nichrome to do that.

[Mendeleev]

This sounds like a good idea, will these things detonate mercury fulminate?

[blindreeper]

Of bloody course they will set off MF! MF is primary = heat sensative! These things produce a great deal of heat. Put 2 and 2 together :rolleyes:

[spydamonkee]

another way of doin it is like this:

http://www.boomspeed.com/spydamonkee/FireWire.jpg

Cut the wire so it looks like the 1st section then take a small peice of steel wool from a common "goldyllocks" or other brand of steel kitchen pot scrubber and wrap it around the base of the tall strand of copper wire then bend the wire over to hold it inplace then wrap it down the insulator and then the lower copper wire bending that over also.

once you get good at it you can make 1 under a minute and they cost bugger all as a length of wire and the steel wool should last you a life time. In about 15 minutes i made over 40 of these ignitor's.
the gap between the two wires should be enuff to prevent shorting via the two main wires.

A simple 9v cell makes the steel wool go red hot and a 12v makes it go red,white then burn out very fast.

[Mendeleev]

In the first post Anthony stated that the wire he used was #8 bell wire. It bore a close resemblance to speaker wire so I was wondering if speaker wire would work because I have a 250 foot spool at my house.

[grendel23]

Mendeleev,
Here's what to do, go to your local radio shack, or other electronic supplier, and tell them you want a roll of detonator wire. Be sure to bring in one to show them so they can get you the right gauge.:rolleyes:

Any wire of sufficient gauge and with insulation good for the voltage will do fine.

I think we have a winner in the race for the title of "Mr. Obvious".

[Rosco Bodine]

grendel23 ,

In another thread you mentioned having made the azo-clathrate and
I made reply with a solution for fine tuning the rate of an addition funnel .

Anyway , if you like the azo-clathrate , you should also try any of the following
as a flash igniter which gives excellent performance with electrical or fuse firing .
I think you will like what you see , particularly the first , but all three are good .

Igniters :

US2175249 See example 2 for one of the best "first fire"
low order detonating flash igniters , a superbly useful
and easily made compound .
US3293091 See example 4 for a similarly useful different compound .
US1478429 See example 1 for the most simple and third variant which is the
parent compound for the two above compounds .


BTW , thanks for the feedback and confirmation on the 4 / 12 azo-clathrate .

[grendel23]

Rosco,
I did see your suggestion for the addition funnel. That is a great idea, my funnel has a PTFE stopcock and it will be easy to make that modification.

I will check out your other references when I have more time, I have to get some sleep before I go to work.

It is refreshing to see a new forumite who makes it worth wading through all the cognitively challenged Kewls lately.

Thanks for the info.

[Bert]

I went to the official US gov't. Patent & Trademark Office (http://www.uspto.gov/patft/index.html) and checked the numbers given- all came up with no content. Any thoughts?

[Microtek]

Old patents aren't viewable in fulltext, so you have to press the "images" button to view a scan of the document. It requires a viewer which can be downloaded free of charge.
Recently, I haven't been able to view the scans because I'm apparantly missing some activeX gallery component.

[Rosco Bodine]

The European Patent Office has original document full text viewing as PDF .
The server is down for times of maintenance? nearly every day it seems ,
but here is the link for one of the gateways for the old version ESPACENET .

http://ep.espacenet.com/espacenet/ep/en/e_net.htm

Just paste in the patent numbers complete with the country prefix letters US
into the number search box and follow the links to the original document .

The US patent office uses a TIFF file format for original documents and
you have to install the TIFF plugin to see the image files on older patents .

[Mendeleev]

I meant to follow this up a while ago, but anyway, nobody having confirmed or denied the effectiveness of speaker wire, I tested it myself, and frankly I don't think you need bell wire or detonator wire, but just any sort of double wire. I hooked up one end to a torn off Christmas light, and the other to a 6V flashlight batter, and it worked perfectly, lighting the bulb just as well as the socket. I then proceeded to take of the tip of the plastic light and creater a cap using brainfever's method with the epoxied straw. Filled this with 1.5 grams of acetone peroxide, and connected it to the battery. Nice loud crack, good, cheap, easy blasting caps.

[s25]

Hey what about the filament in the bulbs reacting with the AP (it is obviosly metal sensitive)

[Sonny Jim]

(it is obviosly metal sensitive)
No it aint, you're thinking of HMTD.

[tiac03]

I read through quickly but i didn't see anyone talk about just taking a regular piece of multi-strand copper wire cut off a piece of the covering in the centre then cutting all but one of the strands and then folding the wire onto itself (so it looks like the first one {one in the pic i reposted}) . wouldn't this work since the wire will heat up because the current is forced to go through that single strand?

[braegler]

To let the wire not react with the HMTD or AP, you can dissolve NC in Acetone and coat the wire.
This will reduce the risk of accidents.
The lake will burn and ignite almost all flameable substances.

Greeting
braegler

[Zappy]

Any of you guys ever try using strands of steel wool? This is what I used to use, before discovering the trick with miniature Christmas light bulbs. Not the best method but it will do if you have nothing else. When initiating multiple steel-wool ignitors, you must always wire them in parallel. No two strands of steel wool are the same thickness, and this means that when wired in series, one or more of the ignitors will burn out before the others have a chance to heat, thereby opening the circuit and creating misfires.
On the topic of blasting machines; try looking around on Ebay. You won't find any newer, push-button types but there are plenty of the old plunger-style machines to be found. Not cheap though; average prices range from $150 - $300. The old plunger-style machines are really neat to see in action, or even just to put on display. Typical voltage output for a 50-cap machine is about 150-200 volts - depending on how hard you push the plunger down. Current however is much lower than a capacitor-discharge type machine, so these are only capable of firing in series. For this reason, only Christmas-light ignitors can be fired with an antique blasting machine.
The blast box I came up is a rather fancy little thing. It uses two 9-v batteries for the power source, these feed an AC inverter circuit which steps the voltage up (through a small transformer) to about 200VAC. This is then rectified by two diodes and used to charge a 200V, 1000uF filter capacitor. When the fire button is pressed, a relay connects this cap to the output terminals. This thing will vaporize a small strand of steel wool with a bright flash and a loud bang.
You can also take the circuit from an old electronic camera flash, and build a blast box from it. Be careful of that capacitor though (typically 300V @220 uF) - it can give you a very bad shock! Just discharge it by shorting the terminals with an insulated screwdriver, before touching.

[Mendeleev]

Even if it would have reacted with the filament, there was a thick layer of pressed, ground up match heads. I know I'm cheating, you're supposed to use BP but I am to lazy to make it, messy charcoal, sulfur dust makes you sneeze, waste of good nitrate salt for nitric acid, need for long grinding or ball mill construction, basically too much crap. Although with AP you probably don't even need it, its a nice measure to have. Sort of had an idea. For christmas I got this little whistle key chain which beeps if you whistle or make a lound noise, so you can always find your keys. While I was making caps today, I was whistling a tune and the damn thing started beeping. Well, I got to thinking if you hooked up a 9 volt battery to it, and hooked up the beeping terminals to a cap you could have an explosive detonated by whistling. This probably isn't practical because you probably can't whistle loud enough to be a safe distance, but its a fun idea to play around with.

[nuclearattack]

Those nichel/chrome igniters work perfectly also with a small 9V battery.
I tested two AP detonators yesterday with this kind of igniters, i detonated them from a distance of 10 meters with a 9V battery and it worked perfectly.
So you don't need big and heavy batteries, and if you want more power you can use two 9V battery to have 18V output.

[Mendeleev]

I have a couple of pictures of my caps here, they aren't packed with primary, but I tested them out this saturday, with 2.0 of AP, very loud, despite ear plugs. I personally find the horror stories of AP sensitivity a bit inflated. I heated half a gram on a spoon over a torch, it took a while for it to blow, and pressing it into the caps with a stirring rod was no problem. The AP was made at -12 C, so perhaps I got the trimer form is responsible.

[matjaz]

These work best in my dreams. They are made from thin steelwool strands, connected to a double insulated wire, cut from a PC-type multi-wire flat cable.

step 1 (see attached figure).
Cut some 5mm of insulation away and bend the two metal cores apart. This will neatly slide the steel wool turns right down to the insulation as you wind them, providing better mechanical support to the wool.

step 2
Start winding the steel wool in figure-eights on the bare ends of the terminal wires. This is better as opposed to just wrapping it around both wires in that it works as a spacer and will keep the two wires from touching each other. The more turns, the more reliable. The fewer, the more sensitive (if you only have a weak source of electricity to fire it). I usually wind around five "eights".

step 3
Fold over the stripped ends of the terminal wires to lock the steel wool turns in place. Fold to the opposite sides of the insulation to prevent shorts.

step 4
Once you're done, dip the last few mm in your favourite lacquer to cover all exposed metal and fix the wires mechanically.

It is almost impossible for this design to fail since the turns of steel wool work a bit like a spring, ensuring good contact of at least some of the turns. Also, there's no worry to damage the filament since there are many of them in parallel and all work like spares. Talk about redundant engineering! ;)

It works great with a camera-flash CD box like this one: http://www.roguesci.org/theforum/showthread.php?p=51896#post51896.

[hobojojo]

Hi all, I am new to the forum but not new to pyrotechnics. I use Xmas lights with the top broken off and filled with fffg black powder and a piece of tape put over the end of the bulb and the fuse you are trying to light. These can be lit with a simple 9 volt, I've had success lighting them with telephone wire from over 300 feet. When I have some time I will post some pictures.

[hot04wrx]

This might have been mentioned already but here goes anyhow:

Go into radio shack and pick up singles or three packs of the small clear silicone diodes. Straighten the 2 wires in opposing directions so they are not touching each other. Place a match head on the diode and wrap the wires in opposite directions trying no to touch the wires together around the match head and diode as to hug the head to the diode. Keep the end exposed so you can hook leads + and – to with solder or more easily lead clips and hook to a 9v battery.

There are different diodes but if you get the same level of diode each time the ignition times are with a 10th of a sec. from each other.

You may also substitute a powdered charge with epoxy directly to the diode instead of a match head. Both are quite easily made, cheap, and most importantly effective.

[Azido]

The way I see it, if you use anything but a christmas light ignitor, you're making a mountain out of a molehill. they work fantastically, are cheap, versatile, and require very little energy to ignite the beginnings of a det-train. they can be epoxied anywhere and are coonveniently made in pretty colors. What could be better.

[totenkov]

You may want to see my post about making simple wire/detonator at DRO:

http://www.dererumomnis.org/bbs/index.php?topic=287.0

I have used christmas lights however they are not durable. The thin wire is easily pulled away from the contacts and can be faulty. 38 gauge wire is incredibly tough and durable, made well, they will take anything.

[Azido]

Good point. When my christmas light detonators are full of acetone peroxide however my detonators aren't subject to particular mistreatment.

[-=HeX=-]

I have used the christmas light ignitors for years as ematches and out of 100 or so I have only had one dud and that was due to shoddy making.

What powder do you all use to yours in yous igniters and how much powder?

I use 15 match heads of powder in mine and seal with wax to make it all OTC. They are very effective.

[Azido]

I use a less than a gram or so of bp in my ignitors, the rest is ap. sealed off with some epoxy, they've done me well.

[Charles Owlen Picket]

There is a technique of wrapping the bridge-wire on an unevenly cut length of duplex that will work quite well will no soldering for immediate dipping into a pyrogen or other material. Actually there several techniques for this but they all make use of a bear section of insulation or a wire wrapping tool.

I used the Ruby-fluid flux for nichrome a few times and it really did work very well. It's really the only way to solder nichrome; I think it's zinc chloride solution.

[Azido]

I was pondering what the advantages of ignitors like matjaz provided were, and it came to me. the simplicity. You can simply run a length of wire from power to detonator, trim your ends, and wrap them with some steel wool. No connections that could be ripped out or disconnected, no possibility of shorts, no taping needed, and the ignitor is resilient as. I still like christmas lights though. :D

[c4goesbang]

For the leader wire I use 20 ga. Duplex shooting wire. You could also use thermostat wire from an HVAC supply store.

For the bridge wire, I use stranded picture hanging wire. Cut to proper lengths and unwind the strands. One small roll makes several igniters.

Bag ties also make good bridge wires. Just strip the plastic/paper off of a bag tie and you have a bridge wire.

I fire these igniters with a cordless drill battery 12-18 volts.
I have also fired them with a battery from a discarded 600 Polaroid film pack. This is a hot little battery for its size.

http://s168.photobucket.com/albums/u166/mortarfire/?action=view&current=2ematch011sz1Rouge.jpg

Here is what I use to make the pyrogen.

KClO4 (2 Parts) by weight
German Black Aluminum (1 part) by weight
Nitrocellulose Lacquer (4 drops per gram of mix)
Acetone (As needed)

I usually make a 4 gram batch. .

Add 12 to 14 drops of NC Lacquer to 3 grams of KCl04 (fine powder, no lumps)
Add enough acetone, a few drops, and stir with a wooden stick, to form a thin slurry. I use a pop sickle stick available at kraft stores. Wetting the KCl04 first reduces the chance of accidental ignition.

When mixed well add 1 gram of aluminum powder. I use German Dark. Mix well, adding drops of acetone if needed to form a slurry. I use a small, 3” diameter ceramic bowl for mixing.

Dip igniter in the slurry. I usually let it dry, this stuff dries very fast, and dip it a second time. You can dip it more times if you want. Stir often and add acetone as need, to keep mixture from drying out.

When completely dry you can dip in NC Lacquer to waterproof the match.

http://s168.photobucket.com/albums/u166/mortarfire/?action=view&current=4ematch014sz2Rouge.jpg

Firing with a 12 volt cordless battery.
http://s168.photobucket.com/albums/u166/mortarfire/?action=view&current=ematch.flv

[Charles Owlen Picket]

I was working with electric igniter's the other day for a friends son and noticed a few things. The dependencies of construction reflect what the power source is and what overall level of reliability is required. If you have a high-end power source available, you have much more flexibility as to what you use as a bridge-wire. If that power source is fixed at a simple 9v battery or something similar; you had better plan ahead.

If the power source has consistently strong amperage, the bridge-wire can be almost anything. If that is NOT the case; you need it to light up from a 9v battery or something.....you better get a resistance wire of quality construction. What's more, if something important is on the line like an expensive rocket or your arms and legs, you had better get that thing constructed in a manner that it will light up 1st time, every time.

Just from a personal perspective, I am a firm believer in doing things like this in a very thoughtful manner (the "hard way") with nichrome or other resistance wire and actually soldered to the leads. I've seen too many problems arise with substitutes and lack of soldering (even though I've certainly done it myself). Without proper soldering, the pyrogen/NC lacquer material can get between the lead and bridge and you're suck with no connection. Additionally a nichrome wire is rust resistant and actually has resistance to a measurable extent, etc, etc.

I simply get tired of the frustration of not knowing if the thing is going to light up and get sick of approaching a dud. Five minutes of soldering and five cents of nichrome is worth the effort. The reason I even bring this up is that I was using substitutes and having trouble until I broke down and got out the soldering iron and the nichrome...

[-=HeX=-]

Charles: I know where you are coming from there with the 'Do it once, do it right' ethic because I have had countless nerve wracking flops in rocketry, all because of shoddy ignitor bridge wires or under powered batteries.

Therefore I have a 'Piss easy = Piss poor' ethic when I am making pyrotechnics. (Despite being a lazy teenager, I like to just do it right).

Remember, never stinge on the bridge wires connections and never be stingy with the battery. If you are stingy on the pyrotechnic, it will be stingy to you!

I hope you all shunt your wires, and is it true that a cell phone can set an ematch off?

[Charles Owlen Picket]

Quite frankly, I've been around this stuff a great deal (mostly when younger) and I have not personally ever seen EMR or radio waves set off anything. But it's been common knowledge that it happened. - I just can't site a situation that DIRECTLY has a radio transmission knocking down any squib.

From a design perspective, if the bridge wire is very thin (like a 40 or thinner) then I would imagine that it may be vulnerable to radio waves. Thick stuff (28-30) would have a less of a degree to act as a receiving antenna I imagine. There must be one or two people here who really know this stuff who could set the record straight. I just haven't seen it. But that's empirical observation and really doesn't mean a thing.

I wanted to edit this but was too late. I did a very quick experiment and cooked up a squib with the thinest nichrome I had (40) and could solder with these bad eyes. I then made a very sensitive material with chlorate, aluminum, and Realgar in a Matrix of NC lacquer.

I placed this next to various radios transmitting at 2-10 watts. I moved off and tried it at 2, 10, 15, & 30 feet. No go.... I am NOT saying radio transmission is safe by any means! I'm simply saying I could not reproduce this type of ignition.

[-=HeX=-]

Thanks Charles for testing that. I had read about it happening somewhere, but cannot find the .pdf it was in. I had that backed up by the fact that on Richard Nakkas site it says to always shunt the leads in case one acts as a ground, and the other as an antenna.

I had a unusual dud today actually, an Estes ignitor failed to ignite, even from a car battery! And they go off from 6 volts. I wonder why? Maybe it was a dud but it passed the continuity checker test. I wonder why?

[Charles Owlen Picket]

There is actually some written material on this in various electronic magazines; dealing with the concept of "power" and available energy coming off a transmission antenna. There were apparently a lot of misnomers and although it is NOT SAFE (caps exposed to radio transmissions) and it's unpredictable, the level of transmission power needs to be pretty unique.

One of the biggest safety features to come along in industrial blasting was the EBW & Nonel concept in detonators. But most people don't have the materials to achieve the amperage necessary and many mining concerns actually don't want to spend that on the machines themselves (most costing upwards of $1500 each). As an aside, a good quality CD unit for standard caps are now easily over $500 each. In addition Nonel is, of course, not re-usable. Not only the line but the linkages and all active Nonel systems materials are a 1-time use item, costing thousands of dollars each shot.

The most reliable course of action is actually soldering a real bridge wire to the leg wires. The wrapping without soldering is an attractive concept but it also opens the door for the development of a more effective "antenna effect" in the fuse bulb. Basically the thinner the bridge wire the more effective for lower current. But it also makes for a more effective antenna configuration.

It is only opinion that the more reliable fuse bulbs are made via soldering connections; I'm sure someone has made a reliable free-wrap fuse bulb, however it opens the door to the pyrogen to act as an insulator. The absolutely most reliable fuse bulbs are made through well soldered connections and if that bridge wire is really resistance wire (copel, nichrome, etc) the chances of antenna formation recede a bit. Especially if the bridge wire is above .036 thickness.

No one likes taking the "long road" but the absolute necessity of the functionality and reliability of the bridge wire is foremost in anyone's mind. ...Personally I would solder that thing and use high quality resistance wire.

I have built rockets that I put literally hundreds of hours into. I would NOT take a chance on malfunction at that stage of the game. If someone is experimenting with energetic materials the loss is not only money and time but arms legs and eyes.

I have become very adept at micro soldering residence wire and can say honestly that it's not that tough or time consuming. You need a simple "holding & magnification" setup, a quality very fine soldering iron and "Ruby Fluid" flux (nichrome is NOT hard to solder IF you have the right flux - without it, it's a real pain in the ass).

The "holding & magnification" setup can be as simple as a $5 set of alligator clips & magnifying glass (the shit made in China that looks like a little statue & holds the leg wires while allowing for easy viewing of the soldering element). A high quality soldering iron can be bought surplus for a few bucks and the "Ruby Fluid", if you can't find it can be made from zinc chloride. It is sold at some hardware stores & really works so well, I can't praise it enough!

If you can solder at all, in a few hours you will become a champ! My bridge wires are damn clean and with that simple setup I can choose the resistance wire of my application and matching power source. Real resistance wire is an improvement because it is resistant to oxidation and you have complete control over the diameter of the wire. When you start to weigh these issues, it all makes sense to take the high road, use quality, and expend the time. It really IS easy to do it right the 1st time.