Fuses

[nath0r]

Yeah, that's no problem.  You'll need to measure and average the burn-rate of a a few precisely cut pieces using a digital camera in movie mode or some other video device. After you've figured out the proper length for your specific timing, you'll need to add a 1/4" or more on both ends to allow for priming (cross-matching or splitting and dipping into a prime). You'll also need to cover the outside of the fuse with a wrap of some sort to prevent the side spit of sparks from prematurely igniting your burst...I use a few wraps of aluminum HVAC tape because it molds very closely to the outside of the fuse.

 

Thanks for the reply, when my flying fish arrives ill wrap it in AL tape and try it out on some smallish shells.

 

@ Bonny - I'm guessing that if you find your shells are working fine with uncoverd visco, then there is no need to change your method of construction.

[crazyboy25]

My trick was to use a few wraps of Al foil before masking tape. Some sort of fireproof layer is totally essential in my experience. Using pasted kraft worked, but just masking tape failed on occasion for me.

would that create crappy quick match and ruin the timing?

[Mumbles]

Well, visco isn't supposed to light from the outside, so no it doesn't make a crappy quickmatch. I think mostly what happened with the masking tape were just air bubbles, or folds or something like that that allowed fire all the way up too soon. I was having a muzzle-break type problem, where they would have some timing, but go off far too soon.

 

The purpose of the paper, tape, and Al foil is two fold. One is to get it up to the normal 1/4" size. This allows it to properly fit in premolded plastic shells and just makes transitioning over to/from fime fuse easier. It also contains all the sparks, so the fuse can actually be burning within the shell without setting them off. Too long of a fuse on the outside could potentially be sheared off by spinning in the mortar, or may endure some occasional side-lighting to give a much reduced delay. It's also just part tradition.

[qwezxc12]

I originally posted this in the Random Thread, but it appears to be relevant to the conversations here, so sorry for the duplicate post:

 

...I use visco for timing exclusively, and I thought I'd post a picture of how I cross-match it. I used to split and prime with slurry, then I tried cutting at an angle and priming. Cross-matching with black match is easy and so far it's been 100% reliable and consistent when using masking tape to prevent side spit.

 

This is important - I use a 3in length of the timing width of the fuse as it gives 10-12 wraps around the visco, absolutely preventing side spit while the fuse is burning through the tape "tube". I then wrap an additional 3in of narrower tape to build up the neck that gets hot-glued into the cup. If you want, you can use 6in of the full width, as I did at first,but it makes the fuse harder to roll up neatly. I do not use an inside wrap of foil...just tape.

 

The width of the tape sets the desired time increment: When using American visco that burns at 1/2in per second, a 1-1/2in wide strip = 3sec delay for both 3 and 4in shells, 2in wide tape = 4 sec for 6in shells. I then use little strips of high-tack masking tape instead of dental floss to secure the cross-match both inside and outside the shell.

 

The picture shows the outside cross-match and the top portion of the 2in masking tape that creates the time delay (it's a 6in shell). The slightly darker tan tape just sticking up through the glue is the additional 3in of tape to build up the fuse to 1/4in diameter. The inside is cross-matched similarly and the black-match is folded up into a plastic drinking straw to pipe fire to the center of the shell.

http://www.apcforum.net/files/IMG_0947.jpg

[lnstantkarma]

Hey I just tested out my first quickmatch that I produced in large quantities and I was wondering if it was possible for it to burn too fast? When it lit it instantly produced a report and actually moved the dummy shell it was attached to a couple inches across the ground. I don't know if this is bad but I definitely wasn't expecting it. My quickmatch is made from medium kraft with a 1/4 inch inner diameter with two strands of blackmatch.

[Mumbles]

No, the quickmatch is fine. It preforms just how it should.

[asilentbob]

Very thin copper wire will heat up enough in a couple seconds to light BP. Especially with something like a 6V lantern battery. Hell a small 9V battery will... it will just take longer... I made the mistake of shorting the terminals of a 9V battery when i was like 10 with some copper wire that i had wrapped around both terminals... i didn't think that it would heat up that much... but it ended up burning me and i ended up throwing it into the trash nearly and running away because i thought it would blow up or something. Remember, i was like 10...

 

You should really use a wire that doesn't conduct electricity as well where you have the pyrogen. Thin steel for instance... some people sware by steel wool.

[psyco_1322]

Hay just what is that little white plastic thing that you get with bigger plastic shells for? I think it what you have around your fuse there. Thats the only thing I can figure it to be for, but whats its purpose?

[qwezxc12]

You usually get two items with 4" and larger plastic shells:

 

A lifting ring, which is glued into the hole on the non-fused hemisphere. It allows you to lower the shell into the mortar without straining the leader. On my 4" & 6" shells, I use 1.5" re-enforced gummed tape for QM pipe, folded lengthwise in thirds - it's really strong this way instead of spiral wrapped. I just run it through the lifting ring and use it for lifting the shell as well.

 

You also get the re-enforcing ring that goes around the 1/4" fuse hole...Spherical shells are bottom fused so the fuse hole sees a lot of stress during firing. It's glued in place with whatever solvent you're using to assemble the hemis. I use Xylene. One side is cupped to match the shell's curvature. The other is stepped and allows you to fill the cup with hot glue to seal around your time fuse / spoulette after the ring is attached.

[psyco_1322]

Ok thats what I figured it was, put one together and thats just what I did with it. Thanks for the comformation on that.

[Nightstalker]

I think I may have discovered a viable alternative for those of us that have trouble acquiring visco.

If you are able to make blackmatch, it can then be sheathed in heatshrink tubing.

Provided the blackmatch is decent, it will burn similar to visco. Another advantage is that it is completely waterproof.

 

I only discovered this about five minutes ago so I am yet to test specific burn rates, waterproofness and reliability/ignitability but I believe I will be using this fuse for a number of future projects.

[WarezWally]

That should burn as fast as quick match

[Nightstalker]

I initially thought that it would quickmatch, however the heatshrink I used is a special type I use for marine wiring, it consists of a standard heatshrink tube with a thermoplastic glue on the inside it, causing it to glue itself when heated. I think this sealed the blackmatch in it's entirety, preventing quickmatching.

 

I have currently burned several feet of the stuff with no quickmatching and a very stable burn rate. I will try and get some photos and maybe a video of it burning tomorrow.

[Sylar]

They are quite reliable (I tested it a few years ago) but also quite costly.

To me at least because heat shrink tubing is not all that cheap ...

 

I can however verify that it does not have a quickmatch effect, so if you really can't get anything else, it might be a good visco/timefuse alternative.

[Nightstalker]

I am using this because I have been able to find visco only once, and then it cost $8/meter. I am rather limited with regards to supplies where I live so the heatshrink blackmatch appears to be a rather attractive alternative.

[Achtung]

hello all, I'm new in APC this is my visco machine:

http://pl.youtube.com/watch?v=nB4CsTG3aU4

 

in my account there is a lot of tutorials, and pyro compilations.

 

i hope i learn something, from you,

 

sorry for my english,

[50AE]

Hello,

 

I'm new in this forum, so my first question will be about fuses, if you don't mind .

So, for fuse I make blackmatch. It burns well, but I can't normally use it, beacause if I flex it, the meal powder falls and the fuse becomes inusuable.

There is one thing that doubts me - if the cotton string is not good, beacause it's already painted and it can means the paste can't glue well on the string.

 

So I ask if is natural for every blackmatch to have is powder falling when flexed, or not, and then should I change the string, and put a NC laquer or something ? I really want to have a good flexible fuse, beacause sometimes I make small firecrackers, like polumnas with BP.

 

I'm sorry, if my english level is low.

[WarezWally]

Add more dextrin and pre-soak the cotton in a kno3 solution and allow it to dry before using it.

 

Makes perfect blackmatch every time

[Mumbles]

Yes wally, but that will in no way affect the crumbling.

 

You don't give many details of manufacture, so it's a bit hard to help. If you are just running the string through a slurry and coating the outside, yes crumbling will be detrimental. Try rolling up the cotton into a coil, and actually kneeding the BP slurry into the string, working it between the individual strands. This will greatly improve reliability, and will allow it to continue to burn if some of the product flakes off.

 

Another thing you may want to look into is a different binder. Dextrin is fine for stars as it dries ridgid, but this same property isn't ideal for blackmatch. Adding some CMC gum will keep all the BP in suspension, and make the slurry more viscous, and adhere better. The addition of something like guar gum will improve plasticity, and allow for less flaking. They should each be added at around 1% by mass.

[crazyboy25]

yeah mine flakes too but it works i recently used some commercial quickmatch and the blackmatch inside was think heavy and had a very very thin layer of BP it burnt purplish so i know it was black powder but its was also very flexible i liked it and was curious how they made it.

[qwezxc12]

If you don't have CMC or Guar or Gum Arabic, you could try adding some blended paper pulp to your BP slurry. It's been recommended by some to soak some pulp (paper towels, recycled craft) in water and run thoroughly through a blender to make a suspension of pulp fibers about as thick as gravy. Add a small amount (5-10% IIRC) of this to the BP slurry to reduce the BPs tendency to flake off when the match is bent...sort of like adding fiber-glass strand to resin.

 

I've never done this, only read accounts.

[pudidotdk]

Is CMC really that hard to come by, I found it as wallpaper paste in granules. I've not used it for any purposes yet, since I've got 'nuff commercial blackmatch. The CMC takes some time to dissolve completely in water though.

[50AE]

Thank you for your replies. I will try something like @Mumbles idea. I will get a tooth pick, and roll fine strands into it, to make a coil. Then, I'll put it in the paste. It will be a hard fuse , but i don't need flexible one for firecrackers.

 

Something like this but fuse, not electromagnet. The con is, that the manufacture of the fuse will take some time

 

[Mumbles]

I didn't mean a tight coil. I meant a loose coil. It is really only to keep the string from getting tangled during kneeding. Try rolling around a soup can or something. I make around 200 feet at a time, and use a 4" mortar to roll around.

 

For stronger fuse, you may want to use thinner string, such as for crocheting, and place multiple strands into the same "string" of black match.

[50AE]

So you think, that rolling will help ? I will try it then. Thank you.